Fibreoptic bronchoscopy in thoracic anaesthesia

3 Fibreoptic bronchoscopy in thoracic anaesthesia CHARLES

B. W A T S O N

Anaesthesia for surgery in the thoracic cavity is one of the more challenging areas of anaesthetic practice. Aside from the technical and physiological problems posed by the lateral position under anaesthesia, and the open chest cavity, the minute to minute threat of cardiorespiratory homeostasis during surgical manipulation of the heart and lungs requires constant vigilance and active participation during the surgical procedure. Endobronchial tube placement for one-lung anaesthesia (OLA), selective lung ventilation or bronchial blockade is commonly practised in North America and Europe. The primary indications for this are surgical technique and convenience, but there remain a number of situations in which patient safety and protection of lung tissue provide strong arguments for lung isolation. Endobronchial intubation is taught in anaesthesia education programmes although practitioners in the United Kingdom and the United States have simplified their practice to the extent that double-lumen endobronchial tubes modelled after the Robertshaw tube are more commonly used than any other type of endobronchial tube or blocker. Examination and auscultation of the chest are time-tested means of ensuring lung isolation and confirming appropriate endobronchial tube placement. Nevertheless, despite repeated examination of the chest during and after endobronchial tube insertion, one sees unsatisfactory lung isolation at thoracotomy or during manipulation of thoracic viscera. The less obvious problems of secretion or blood drainage into dependent bronchopulmonary segments during lung surgery often present postoperatively as unexpected hypoxaemia or atelectasis. Thoracic surgery patients often have significant disturbances of the normal lower airway anatomy or chronic inflammatory and degenerative changes. These may alter the physical examination so that lung isolation is difficult to verify clinically. In addition, anatomic abnormalities occasionally deflect and misdirect endobronchial tubes during insertion so that lung isolation is extremely difficult. The flexible intubating bronchoscope is a versatile instrument which is the logical successor to the rigid intubating bronchoscope as a tool for precise positioning of endobronchial tubes and blockers. Direct visualization of the anatomy substitutes certain knowledge for the educated guesswork which Baillibre's Clinical Anaesthesiology

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skilled clinicians have had to employ in the past. A new generation of more slender, flexible fibreoptic instruments combines satisfactory directional control with suction capability and an adequate field of vision. A smaller external diameter offers increased utility with decreased risk of airway obstruction. Thus endoscopy before and during surgery is safer than in the past. Mastery of flexible fibreoptic endoscopy is less difficult than rigid bronchoscopy and thus more likely to achieve wide use in thoracic practice. The major barriers to the anaesthetist's use of the flexible instrument are expense and inexperience. Fibreoptic instruments are now less expensive and ubiquitous in medical practice. Techniques involved in airway endoscopy using a tracheal tube are straightforward and safe. This chapter is intended to introduce the flexible endoscope to those whose thoracic practice has not included it in the past and to provide useful guidelines for monitoring and patient management during endoscopy. It is the author's contention that recent advances in fibreoptic technology has placed a powerful tool in the hands of the anaesthetist. It is logical that the thoracic anaesthetist, with his knowledge ofcardiorespiratory function and the pathophysiology of pulmonary disease, should master fibreoptic instruments as adjunctive means for precise definition of the dynamics of lower airway pathology, for direct control of endobronchial tube placement, and for the maintenance of airway patency in the perioperative period. HISTORICAL CONSIDERATIONS The evolution of thoracic anaesthesia as a concentrated area of practice is closely tied to the development of lung isolation techniques since the problem of secretion aspiration and asphyxia during surgery was a concomitant of both lateral and dorsal thoracotomy approaches in patients with suppurative pulmonary conditions (White, 1960; Mushin, 1963; Bjork et al, 1953). With the increased ability to control infections following the introduction of antituberculous and bacterial chemotherapy, lung isolation became somewhat less important for the anaesthetist and more a matter of surgical preference and convenience (Kleine et al, 1980) (see Table 1). Techniques designed for lung isolation and secretion removal have evolved more slowly in recent years although they have spread extensively throughout the world (Newman et al, 1961; Lunding and Fernandes, 1967; Tarhan and Moffitt, 1973; Black and Harrison, 1975; Read et al, 1977; Hazrati, 1978; Jutner et al, 1984). A rigid intubating bronchoscope was developed by Magill in the UK in the 1930s in order to allow precise placement of the endobronchial tubes and blockers introduced prior to that time (Magill, 1936). The rigid ventilating bronchoscope was also modified for this purpose by Mansfield with the expectation that safer tube placement would be possible if oxygen insufflation or controlled ventilation were possible (Mansfield, 1957). Other instruments which have been used for the purpose of endobronchial tube or blocker placement include the paediatric ventilating bronchoscope and the Storz rigid fibreoptic bronchoscope with Sanders injector (Vaughan, 1985). It is generally

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Table 1. Indicationsfor OLA. Essential Endobronchialbleeding Bronchopleuralfistula Vascular procedure--anticoagulation Bronchiectasis/pus Tracheobronchialobstruction Tracheo-oesophagealfistula

Surgical convenience Partial/completeresection Pleural stripping Closed cardiac procedure Thoracicvascularprocedure Chest wall procedures Oesophagogastrectomy Oesophageal surgery Chamberlain procedure Closure PDA Coarctational repair

agreed that the modern practice of thoracic anaesthesia less frequently involves the chronic suppurative lung cases which were predominant in the pre-antibiotic era. This, in addition to the difficulty of tube placement, is occasionally cited as the reason why endobronchial anaesthesia is not universally practised (Black and Harrison, 1975). Although the practice of endobronchial anaesthesia and various other lung isolation techniques has been reported repeatedly in the world literature and is evidently commonplace in many major medical centres, the practice of rigid bronchoscopy for accurate lung isolation appears to have fallen by the wayside. The introduction of the flexible fibreoptic bronchoscope into the practice of thoracic surgery by Ikeda et al in 1968 was an important advance in thoracic practice because it was easier for the surgeon or chest physician to complete a thorough review of the lower airways during the preoperative period. Certain knowledge of the structural and functional properties of the airway obtained with greater patient comfort and safety replaced educated conjecture based upon indirect studies and rigid bronchoscopy under anaesthesia (Sackner et al, 1972; Harrel, 1978; Landis, 1978; Credle et al, 1974; Suratt et al, 1976; Feldman and Huber, 1976; Lindholm et al, 1974). After Murphy described use of a fibreoptic choledochoscope for a difficult tracheal intubation in 1967, a number of others reported the fibreoptic instrument's utility for securing, reassessing, and changing the tracheal tube perioperatively (Watson, 1982). With continued evolution and increased medical utilization of flexible fibreoptic instruments, rigid bronchoscopy became largely unnecessary for most preoperative assessment and is now, for the most part, a surgical technique whose indications are confined to the removal of large foreign bodies in the airway and, occasionally, the support of a critically compressed airway. After the mid 1970s, a newer generation of thin ( < 5 mm) flexible fibreoptic instruments made it possible for the anaesthetist to perform endoscopic intubation and intraoperative therapeutic bronchoscopy for most adults and children (Watson, 1982; Wood and Fink, 1978; Vigneswaram and Whitfield, 1981; Rucker et al, 1979). Several groups reported use of the paediatric flexible instrument as an intubating bronchoscope for endobronchial tube placement in the early 1980s and the technique has subsequently been popularized with

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Figure 1. Intubating bronchoscope.

numerous citations in medical journals, in refresher course lectures pertaining to thoracic anaesthesia, and with semi-annual workshops in fibreoptic bronchoscopy for the anaestbesiologist (Watson, 1982; Wood and Fink, 1978; Vigneswaram and Whitfield, 1981; Rucker et al, 1979; Shinnick and Freedman, 1982; Shapiro et al, 1981; Raj et al, 1974; Aps and Towey, 1981; Watson et al, 1983; Ovassapian et al, 1983). Ovassapian, in 1983, and Smith et al, in 1986, have suggested that fibreoptic endoscopy is a skill which should be routinely taught in anaesthesia training programmes. Indications for endoscopy in the thoracic surgical setting continue to evolve with increasing experience of these instruments and the recent introduction of a less expensive, full length intubating bronchoscope. The flexible intubation bronchoscope, shown in Figure l (Olympus LF-1), was designed for tracheal intubation of children and adults and for the use in the thoracic surgical setting in consultation with the author and other anaesthetists in the USA. The progressive development of direct visualization techniques is summarized in Table 2. INDICATIONS FOR FLEXIBLE FIBREOPTIC BRONCHOSCOPY (FFB)

The flexible fibreoptic instrument is used in thoracic anaesthesia for preoperative assessment of the airway, for tracheobronchial tube or blocker positioning prior to surgery and for immediate evaluation and therapy of postoperative atelectasis which is probably due to secretions. Although some

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Table 2. Endoscopy in thoracic anaesthesia historical notes. Date 1920M0s 1936 1940s 1956 1960s 1967 1968 1975 1978

1979 1981 1982 1985 ??

Key events Lung isolation techniques evolved Magill--Intubating bronchoscope Use of paediatric ventilating bronchoscopes Mansfield--Ventilating intubation bronchoscope introduced Storz--Rigid fibreoptic endoscopes Murphy--First flexible fibreoptic intubation Ikeda--Flexible fibreoptic bronchoscope for thoracic surgery Raj et al--First FFB placement endobronchial tube for OLA PVC double-lumen endobronchial tube widely used in USA Full length FFB ( < 5 mm) available (Olympus, Machida) Paediatric ( < 4 mm) FFB with suction (Olympus 3C4) Watson et aI--OLA in two-year-old using paediatric FFB PVC double-lumen endobronchial tube colour-coded for FFB (Mallinckrodt) Flexible intubation bronchoscope (Olympus) FFB routine for lung isolation in thoracic anaesthesia

would question the instrument's use for routine placement of double-lumen tubes, most would agree that significant distortion o f tracheal or bronchial a n a t o m y by intrinsic obstruction, extrinsic obstruction or progressive scarring presents an absolute indication. A dynamic airway evaluation can only be obtained by direct visualization o f the structures in question during breathing and other respiratory manoeuvres prior to anaesthesia and surgery. The F F B is less c o m m o n l y used intraoperatively to verify tube placement, successful closure o f segmental bronchi, absence o f tracheobronchial trauma, secretion clearance and haemostasis, and the patency o f adjacent bronchi following segmental resection. We have found the F F B to be helpful both in defining pre-existent laryngeal problems prior to the placement o f e n d o b r o n c h i a l tubes and for atraumatically assessing laryngeal function in the postintubation period. We have more rarely used the F F B in the case o f suspected tracheooesophageal and bronchopleural fistulae following t r a u m a due to chronic or acute causes. Indications for F F B in the thoracic surgical setting are listed in Table 3.

ENDOBRONCHIAL INTUBATION Most anaesthetists who perform O L A use double- or single-lumen e n d o b r o n chial tubes with considerable success. F r o m time to time there are particularly

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c.B. WATSON Table 3. Indications for FFB. Most important Define surgical pathology Dynamic assessmentof obstruction Establish progression of disease Documentpreoperativelaryngealfunction Useful Endobronchial tube placement Guided suction intraoperatively Verify postoperative anatomy Rule out aspiration episode Assess 'intubation' injury Evaluate postoperative atelectasis

difficult patients in whom a tube will not advance or repeatedly passes into the wrong bronchus or, for whom, despite apparently adequate tube placement, lung isolation remains incomplete. At the University of North Carolina, routine endoscopy was performed for teaching purposes on almost all patients having OLA in 1980. The patients were anaesthetized and positioned following satisfactory placement of double-lumen endobronchial tubes of one sort or another as judged by clinical examination before and after positioning. In accordance with the prevailing practice at that institution, the majority of tubes were left-sided. Surprisingly, a large number of tubes were found to have the bronchial cuff either just at or above the carina. Thus, these were in a position where dislodgement would be probable with minimal manipulation and obstruction of the opposite bronchus would be a likely event if air were added to the bronchial cuff in hopes of obtaining a better seal for lung isolation. Another c o m m o n observation was that a number of tubes had been advanced too far into the left bronchus and required re-positioning lest obstruction of either the upper or lower lobe divisions ensue during OLA. In two cases it was noted that hyperinflation of the bronchial cuff caused a concentric constriction of the endobronchial lumen which reduced the internal diameter to less than that of the bronchoscope (i.e. < 3.7 ram). In line with these unpublished observations, other groups and case reports have reconfirmed the risk of deep penetration to the level of bronchial divisions with double-lumen tubes patterned after the Robertshaw tube, and the ease of placement into the wrong bronchus (Black and Harrison, 1975; Brodsky et al, 1985; Watson, 1986). In 1986, Smith et al, have reported that 48% of doublelumen tubes which they placed and later examined the placement of with the flexible fibreoptic bronchoscope were in suboptimal locations. They also reported herniation of the bronchial cuff in 22% (6/23) of their patients and noted concentric constriction of the bronchial lumen in one patient. The tubes employed by this group at Yale University were polyvinyl chloride (PVC) Robertshaw tubes (Bronchocath, Mallinckrodt, Inc.). A study of tracheobronchial tube placement and subsequent trauma following intubation with PVC (Bronchocath) and red rubber (Carlens or White) tubes was reported by Watson et al from the University of North Carolina at Chapel Hill in 1984. Both left- and right-sided tubes were placed.

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More difficulty was encountered placing right than left endobronchial tubes. Trauma to tracheal and bronchial mucosa was more severe and more common after intubation with red rubber tubes. These findings have since been corroborated by Clapham and Vaughan (1985) working in the United Kingdom. An unexpected finding which was noted in the former study was that the Carlens tube could be suboptimally located with the hook twisted into the left bronchus, partially obstructing the right bronchus, or everted into the tracheal orifice of the tube as it was advanced too far into the bronchus with the hook at or below the carina. Surprisingly, the hook of both new and used Carlens tubes could easily be twisted and dislocated from its ideal location engaging the carina of a lung model (Zavala Lung Model) and dogs. The author's unpublished findings during pilot work with a newer hooked PVC double-lumen tube (Mallinckrodt) introduced in 1985 also demonstrated that it was not difficult to manoeuvre the hook too far into the bronchus. H o o k herniation or eversion could not be demonstrated in a lung model (Zavala Lung Model). These latter observations suggest that tube misplacement problems noted with the Bronchoeath and other PVC double-lumen (Portex, Inc.) tubes patterned after Robertshaw's design are not unique to that design. Although tube misplacement may be more common with the newer, more flexible and thin-walled designs, it is not a phenomenon which results from an inappropriate choice of endobronchial tube. Many experienced anaesthetists prefer to avoid placement of right endobronchial tubes because of the high probability of right upper lobe occlusion and subsequent atelectasis during endobronchial anaesthesia (Alfrey and Benumof, 1981). The major problem with use of a left tube during surgery in the left chest is not the uncommon problem of having it sutured into place or clamped in the bronchial stump even though this can present life threatening complications. More commonly the tracheal lumen is forced against the tracheal wall or the carina during manipulation of the lung at surgery, thus causing direct occlusion or a ball valve mechanism and intermittent obstruction with hyperinflation of the dependent lung. The logical solution--a cage protecting the tracheal lumen like that on the BryceSmith tube--is bulky and adds to difficulty during translaryngeal placement. It is not available on the less tiraumatic, more flexible PVC tubes now in use. Not uncommonly, one sees carinal compression due to mediastinal shift and narrowing of the dependent bronchus in the lateral position. These are most effectively stented open by use of an endobronchial tube. From time to time one encounters a patient whose distorted anatomy due to scarring or compression makes left-sided intubation unsuccessful (Watson, 1986). For these reasons I prefer to place a right endobronchial tube during surgery in the left chest. The rather narrow clearance between the tracheal carina and the right upper lobe orifice makes right tube placement without direct visualization of the anatomy notoriously unreliable (Wilson, 1983). A number of right-sided tubes have been developed in the search for a tube which is more likely to achieve satisfactory right lung ventilation during endobronchial anaesthesia. In an unpublished pilot study conducted at the University of North Carolina, using various prototype PVC bronchial cuff designs for right endobronchial tubes in a lung model (Zavala Lung Model)

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and anaesthetized humans, bronchoscopic examination demonstrated that no single design was ideal in the sense that it would always effectively isolate the right lung without occluding the right upper lobe bronchus. Anatomic variation also makes sizing of the right-sided tubes more difficult (Watson et al, 1984a or b). Although the length is not often a problem, the diameter of the bronchial lumen and subsequent 'fit' of the cuff to the bronchial wall is a problem which can best be appreciated under direct vision. The current eccentric cuff design which is used on one model of right endobronchial tube (right Bronchocath, Mallinckrodt, Inc.) appears most likely to achieve right lung isolation without occlusion of the right upper lobe orifice when used blindly and with fibreoptic control (Watson and McGrail, 1983, unpublished observations). The right upper lobe bronchus and bronchus intermedius can be directly visualized during and following intubation by use of a fibreoptic instrument for accurate endobronchial tube placement. With the increased utilization of computerized axial tomography in the USA, a number of patients present for segmental lung resection or mediastinal exploration without a recent screening bronchoscopy. This has posed a new problem because a dynamic assessment of tracheobronchial anatomy was part of the preoperative routine. Most radiographical studies obtain a static view of the airway. Direct visualization of the airway during respiratory manoeuvres via a fibreoptic instrument gives the best appreciation of the dynamics of airway movement and compression.

Endobronchial intubation--single-lumen tube From time to time it is necessary to place a single-lumen tube in an endobronchial position. E1 Baz et al have advocated the fibreoptic technique as the optimal means of obtaining endobronchial isolation for OLA in 1986. Since a number of thoracic cases are scheduled for screening fibreoptic bronchoscopy immediately prior to lung resection in some centres, the advantage offered by use of a single-lumen endobronchial tube is that the larger lumen of a (6.07.0 mm) single-lumen tube will permit bronchoscopy with a 5 mm fibreoptic instrument and allow OLA without requiring a second intubation procedure. Advocates of the single-lumen tube have also cited the difficulty encountered with translaryngeal passage of large double-lumen tubes and the fact that double-lumen tubes are not acceptable as long-term airways in case a patient requires ventilatory support postoperatively. The single-lumen tube is the only option for endobronchial intubation of infants, children and smaller patients. Although a number of techniques have been employed for blind placement of single-lumen tubes, including manipulation of the tube via an open thoracotomy by the surgeon, the bronchoscopic technique is somewhat more reliable (Watson et al, 1983; Ovassapian et al, 1983) and has been shown to provide lower pulmonary shunt fractions during endobronchial anaesthesia (El Baz et al, 1986). The latter finding is not surprising since occlusion of either the upper or lower lobe bronchus on the left or the middle or lower lobe bronchus on the right should be less likely when endobronchial intubation is performed under endoscopic control. The newer, thin bronchoscopes offer an

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Table 4. Intubating and paediatric bronchoscopes contrasted. (Olympus) Immersibility Tip deflection Suction channel Working length Flexible Insertion tube Angle of view Resolution

LF- 1

BF-C34

Yes 120/120 1.2 mm 60 cm Stiffer 4 mm 75 ~ Adequate

No 150/60 1.2 mm 55 cm Very 3.7 mm 55 ~ Superb

immediate advantage in the paediatric patient. These ensure better ventilation via a small tracheal tube during diagnostic bronchoscopy as well as during endobronchial tube placement. Endobronchial blockade

Recently, surveys of practising anaesthetists in the U K (Pappin, 1979) and the USA (Watson et al, 1984a or b) have shown that OLA is rarely performed with endobronchial blockers. Both flexible fibreoptic and rigid endoscopes are used for endobronchial blocker placement. In the USA and abroad, techniques most commonly reported use small diameter balloon-tipped catheters (e.g. urinary, embolectomy and pulmonary artery catheters) for endobronchial blockade while ventilation is managed with a single-lumen tracheal tube (Vale, 1969; Dalers et al, 1982). Precise placement of a blocker in the specific lobar bronchus involved during wedge resection Or lobectomy will allow ventilation of the adjacent lung without secretion drainage from the involved area and, thus, provide the least pulmonary shunt fraction even though a quiet operative field is not possible. Bronchial blocking tubes can be placed using clinical criteria alone; however, since there is no way to ensure a precise bronchial seal short of observing a quiet lung during surgery, use of the FFB for blocker placement was advocated by Aps and Towey in 1981. A new PVC single-lumen endobronchial blocking tube was introduced into American practice by Kamaya and Krishva in 1985 (Univent). Once the tube is positioned in the lower trachea, a retractable 2 mm balloon-tipped extension is advanced into either bronchus under endoscopic control. The tube can thus be used for blockade of either lung and allows fibreoptic endoscopy with larger bronchoscopes (5 mm). The blocker extension has a central lumen which can be used for secretion removal, oxygen administration or high frequency ventilation as well as a balloon inflation lumen. The blocker is more versatile than earlier 'bronchus-specific' designs and is somewhat easier to place translaryngeally than double-lumen tubes (Hultgre et al, 1986). Like earlier blockers, this innovative design is not available in smaller sizes: the smallest is 8 mm. It can be employed for lobar blockade with fibreoptic control although the blocking

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extension itself may partially obstruct other lobar bronchi on the same side. Unlike endobronchial tubes which stent open the dependent bronchus while blocking the surgical bronchus, this tube will allow partial compression of the dependent bronchus. In the author's view, bronchial blockade attempted under circumstances which do not involve a direct visualization technique--whatever the system employed--is likely to fail. It is not possible with the Univent tube and is best attempted with a smaller double- or single-lumen tube which can be placed blindly into one bronchus when tamponade of the other is critical. Airway bleeding is less commonly encountered in this era of effective antituberculous chemotherapy. Nevertheless, it is the most common situation where asphyxiation can be prevented by blind intubation for bronchial blockade. Given control of the situation and less tenuous oxygenation, fibreoptic endoscopy can guarantee the precise location of an endobronchial blocker, whether an improvised or commercially available one is chosen. D E S I G N OF F I B R E O P T I C I N S T R U M E N T S

All flexible fibreoptic instruments have common features, although design characteristics such as outer diameter, control of flexion in one or several planes, suction or air feeding channels, and flexion control determine the most suitable settings in which the instruments can be employed. The operator's hand and eye are located at the optical head. Light fl'om a remote source, suction, oxygen insufflation, biopsy channels, etc., must all tie in through the optical head and pass down the narrow cylindrical instrument to the working tip. The brightness of the image seen is a function of the power of the light source and the diameter of the instrument, since the latter determines the number of optical fibres which can be packed within the flexible working end of the instrument. Depth of field and resolution are partly defined by the number, diameter and 'overlap' of fibreoptic strands and the light available, but the optical design of the working tip and optical head is the major determinant of visual field, given a critical mass of fibres. Fibreoptic strands are flexible and, hence, conduct light around corners, but they cannot be kinked, stretched or twisted without snapping. Older instruments which have received heavy-handed use frequently present an image which has a number of small black dots caused by the 'dropout' of fibres which have been lost as light conduits. Bundles offibreoptic strands are tied into the umbilical cord from the optical head to the working tip along with the suction channel, stiffening elements and flexion cables surrounded by a water-tight coating. Repairs thus require violation of the instrument's integrity and are both time-consuming and costly. The light source connects via a fibreoptic cable to the light conducting bundle which provides light at the working tip. One or two bundles serve to carry the image from the tip to the optic head and objective lens. Most instruments provide a final focus adjustment at the optic head which allows for the operator's variable focal length. Distortion of the image is limited by narrowing the field of vision. Modern FFBs can provide a >75 ~ range,

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depending upon instrument diameter and optical design. An excellent lens system wilt provide a larger field of vision if the instrument is larger. The image quality, given any lens system, is greatly dependent upon fibre 'overlap', a property of bundle design. Inadequate bundles leave a very grainy image with multiple dark areas due to the non-light conducting space between fibres. Fibreoptic bronchoscopes are by necessity thinner than gastroscopes and other flexible instruments which can be used for direct visualization of larger channels than the airways. Therefore, even with the newer high resolution light bundles composed of smaller strands, the area in each instrument which is available for accessory channels for suction and steering is limited. The practical result of this is that bronchoscopes can only be flexed in one plane. Up or down flexion requires strands or cables which pass through a separate conduit on opposing sides of the instrument. Flexion cables on the top or bottom of the instrument are pulled alternately by movement of a lever or rotation of a wheel, thus deflecting the tip of the instrument in one direction or the other. The angle and radius of tip deflection are controlled by careful placement of retaining joints which constrain the flexion cables. Some instruments possess a locking mechanism which allows the operator to lock the working tip into position and free his dominant or operating hand for manipulation of suction, air or oxygen insufflation, and an array of brushes and biopsy forceps. If an instrument is withdrawn or advanced with the tip locked or manually deflected in a fixed position, considerable stress is placed on the flexion cables themselves, or their constraining linkage. A reduction in the angle of deflection or total loss of deflection often results from blind or heavy-handed manipulation of the FFB. Since optical resolution and control of tip flexion are key determinants of the space available for any given diameter, early instruments had to be quite large if an additional channel was to be provided for suction or lavage. Large diameter instruments like the colonoscope can have several such channels but FFB design has tended to include one multi-purpose channel. Instruments like the early fibreoptic laryngoscopes (AO-Riker) characteristically had larger ( > 6 mm) outer diameter, limited tip deflection, poor optical resolution, and no suction channel. These were reasonably priced in order to make them available to the anaesthetist. Unfortunately, this combination enabled most anaesthetists to experience, first hand, the frustration caused by inferior optics, a significant size limitation, and the inability to obtain topical anaesthesia or clear secretions with the instrument. The first intubating fibreoptic scope of small diameter (3.5 mm, Machida) had a very small suction channel and limited tip deflection. Larger FFBs (5-6 mm outside diameter) now have suction channels which range up to 2.7mm while smaller instruments have more limited suction (1-1.2 mm) or no suction. Until the mid-1970s the bronchoscopist needed assistants to control his suction and alternate irrigation with lavage solutions or injection of local anaesthetics. This greatly limited the operator's independence of action. Multipurpose adaptors have been designed which allow the operator to have suction continuously applied with an external bypass, until he occludes the bypass port and suctions via the lumen of the FFB (Olympus, Pentax, USCI, etc.). It is also possible to load a syringe into a central adaptor and, without

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removing one's eye from the optic head, alternately occlude the suction port for external suction and inject a small volume of drug or lavage solution under direct vision. Biopsy or brushing still requires a knowledgeable assistant; otherwise the operator must remove his eye and hand from the optical head in order to connect and control external devices. Light source designs can vary from a light bulb powered by hand torch batteries to an air-cooled electric arc source on a large floor-mounted unit. Most institutions have a more portable multipurpose light source which provides high intensity light with an air-cooled bulb and conventional wall current for a number of the flexible endoscopes in use. If still or moving photography is to be effective, fast film and very high power light sources are particularly useful with smaller instruments where the available light is limited by the size of the conducting bundle. If one employs a teaching head in day-today practice (a lens system which splits the mirror image so that one can see an image at a remote lens head as well as from the instrument's optical head) the power of the light source also becomes critical. Commercially available handheld battery sources are so weak as to be useless with full length bronchoscopes of any diameter. For a detailed description of light sources, the reader is referred to manufacturer's literature (Olympus, Pentax, etcetera). A broad range of acceptable sources is available at prices which inflate as much as tenfold from the price of an entry-level, portable, air-cooled DC transformer pack and bulb powered from wall current.

W O R K I N G W I T H A FLEXIBLE F I B R E O P T I C E N D O S C O P E

Two key features follow from endoscope design and these determine overall technique. First, the instrument flexes. It is necessary to hold the optic head next to the eye with one hand (the dominant, preferably) while advancing or withdrawing the flexible tip with the other. The optic head has been designed so that one can manipulate tip deflection with the thumb while a forefinger intermittently occludes the suction channel adaptor without the necessity of removing the eye from the lens. Most conventional FFBs place the tip deflection control and suction ports on opposite sides of the instrument in the plane of tip deflection. Thus an aspiration line, syringe for injection of biopsy forceps is manipulated on the side which points away from the operator's face. Also the plane of tip deflection is always easy to identify in reference to the position of the hand holding the optical head. The second key feature of fibreoptic systems is that they will not twist or corkscrew. Thus the plane of tip deflection is fixed, and the instrument must be rotated as a unit around the central light conducting axis in order to obtain tip deflection in another plane. One cannot rotate the working tip without rotating the optic head. It is, therefore, easiest to rotate the optic head and allow the tip to rotate passively. Again, since the tip deflection control and suction port are conventionally in the same plane as tip movement, the operator can determine the location of the deflection plane around the instrument's central axis from the position of these markers and his hand.

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Table 5. Clinical use of the fibreoptic endoscope: guidelines for practice. Obtain informed consent Practice preventative maintenance Ensure airway/ventilation first Monitor oxygenation/ventilation Monitor patient haemodynamics Limit duration suctioning/FFB Never force the instrument Resist the temptation to biopsy Document clinical findings

Insertion, withdrawal and rotation should not be forced with the instrument's tip deflected since these movements can damage the fibreoptic bundles or flexion cables. The non-dominant hand actively withdraws or advances the instrument with the tip deflection guided gently by the thumb of the dominant hand so that undue traction is not exerted. The dominant hand rotates the instrument around its central axis while the flexion control defines the plane of tip flexion and the non-dominant hand allows the working tip to rotate passively. The operator must master two-handed control of the instrument from the fixed vantage of his eye and position himself so that this is convenient over a wide range of motions. As is common with other manual techniques that require hand-eye coordination, rotation of the operator's head or flexion of his body as the instrument is rotated, advanced, and withdrawn, serves no function and can only be wearing to the operator. Also, since the advantage offered by a flexible instrument which can be steeled is that it can conform to a patient's anatomy, there is no reason to attempt to lift tissues or force them into position as with rigid instruments. The working tip is manipulated and advanced so that it follows the most convenient, least resistant path to its goal. Once there, it can provide information, direct drug application or suction, or perform as an optical stylette to guide something into place. The FFB has only a very limited ability to force itself past an obstruction or foreign body. Nevertheless, it can scrape, erode and damage airway mucosa or cause extensive bleeding from vascular malformations, tumours and friable tissue when it is forced against tissue blindly or inconsiderately. Inexperienced operators are particularly frustrated by some features of airway endoscopy. A narrow field of vision makes it easy to get 'lost' in the anatomy. A magnified view of one section of the larynx or of the trachea can be quite disorienting. This is generally resolved by withdrawing the FFB a bit, rotating the instrument, and examining the area with gentle up and down tip deflection so that a more complete picture can be obtained. When the working tip is forced against normal tissue one sees a pink fog or haze. The initial response to this should, again, be to withdraw the FFB for more optical perspective. 'Fogging' of the tip is easy to resolve with suction. It can be prevented with anti-fogging agents but tends to be less of a problem when the instrument warms to body temperature. A white haze of indistinct images

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could be an out of focus objective lens (a problem prevented by focusing the instrument prior to insertion) or secretions which are adherent to the tip. Irrigation via the suction channel usually washes secretions off but may not work if the channel is plugged when they are tenacious or clotted. When the image is indistinct, one withdraws the FFB, suctions gently or irrigates and suctions, and, finally, withdraws the instrument from the patient in order to examine and clean the tip or brush an occluded channel. Any instrument which has not been cleaned properly may have a residual surface coating on either of the lenses which will also fog or distort images until it has been cleaned. Smaller diameter instruments are particularly frustrating for the beginner since the suction channel plugs easily. It is wise to limit suctioning and direct the instrument around secretions, if possible, when first examining the airway. Lavage and suction may be time consuming operations. Therapeutic lavage is best left until the operator is familiar with the anatomy. It is often confusing when one advances a fibreoptic endoscope directly below a tube or airway and notices a number of small divisions. Since the angle of view and image resolution creates a magnification effect, image size alone may not clarify which division is being visualized. Additionally, placing patients in supine or lateral positions or visualizing airway pathology can distort the 'normal' appearance of airway structures. As with any maze, it is best for the bronchoscopist to retrace his steps and, after clearly recognizing trachea with right and left main divisions, begin again by counting and identifying the configuration of major bronchial segments. Since circumferential tracheal rings and the posterior membranous portion of the trachea are not continued down below the second division airways, these are good landmarks which, together with length of the trachea, clearly define the location of the major carina between right and left main bronchi. The angle of the right bronchus generally directs tracheal tubes, endoscopes and suction catheters into the right. One can usually identify the trifurcation of the right upper lobe bronchus opposite the carina on the cephalad aspect of the right bronchus but, if anatomical distortion and patient position confuse the bronchoscopist, the length of the major bronchi before they divide enables one to differentiate right from left. Also, inspection of the preoperative chest x-ray and discussion with another endoscopist who has evaluated the airway before surgery can provide valuable information when the anatomy is likely to be abnormal.

ADJUVANTS FOR ENDOBRONCHIAL INTUBATION

If an endoscope is small enough it can be used for endobronchial placement of any tube and provide room for adequate ventilation around it or, simultaneously, via the adjacent lumen of double-lumen tubes. One useful adjunct for this is a ventilating adaptor. Several types are now commercially available. Most are swivel adaptors to which a standardized connector from an anaesthesia or ventilator circuit can attach. The female end receives the standard 15 mm tracheal tube connector. A side hole with partially occluding flap valve or 'o' ring allows passage of the flexible instrument without loss of

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ventilator pressure. The most widely available connector has different sized 'o' ring adaptors with occlusive plugs for 5-6 m m and 3-4 m m bronchoscopes (Portex). Prior to the availability of this connector, one had to either manufacture a rubber diaphragm by perforating a sheet of rubber or the finger tip of a disposable glove and securing this to the side port of a T-connector or occluding the port manually with a wet gauze or tape. Other versions are available from several equipment manufacturers as of this writing. Newer transparent tracheal tubes made of medical grade plastic offer clinical advantages. It is easy to see secretions which reflux in one or another lumen and, in a system which uses dry gases, one can appreciate the character of misting during exhalation due to airway humidity. Thus, one can inspect both lumens of a double-lumen tube and characterize ventilation or gas return with exhalation and p r o m p t clearance of humidity with inspiration. A change in compliance and direct obstruction or 'ball-valve' obstruction can thus be differentiated by inspection alone. Also the endoscopist can quickly inspect the larynx, trachea and carina through the transparent walls of a clear tube during endoscopy. One disadvantage with transparent tubes and cuffs is that it is difficult to recognize the cuff at times or identify one's position within a tube. Because of the former problem, the newest models of NCC-Mallinckrodt double-lumen tubes introduced in 1981 (Robertshaw design) and 1984-85 (versions with carinal hooks) have colour-coded connector tubes, cuffs and pilot balloons. This makes it easier to distinguish the tracheal tube and its cuff from clear secretions fogging the working tip of the FFB. An additional feature of these tubes with carinal hooks is that the hook is also coloured blue so that it can be readily visualized from the tracheal lumen. Radio-opaque markers are also useful to the endoscopist because the ring placed for radiographic determination of best location of the tracheal lumen, vis-fi-vis the carina at x-ray, can also be a depth indicator when the blue tracheal cuff appears to be advanced well below the carina. Double-lumen catheter mounts which divide the ventilation from a single circuit are helpful, especially if they permit occlusion of one limb while allowing suction or FFB access from a more distal port to the occluded lumen of the tube. It is also easy to adapt a high frequency ventilation or oxygen insutttation system for unilateral CPAP (continuous positive airway pressure) through such a connector. A disposable system, including a forked transparent adaptor with double, compressible tubes leading to angled swivel adaptors with locking suction side-ports, is available with the disposable PVC Bronchocath (Mallinckrodt, Inc.). With use of these catheter mounts, one can easily examine the non-dependent lung via the open suction port of the tracheal limb when it is occluded proximally for OLA. The equipment necessary for fibreoptic endoscopy in the operating r o o m - light source, suction adaptors, Luer slip-tip syringes, topical anaesthetic, water soluble lubricant, sterile gauze, sterile gloves, brushes and 70% methyl alcohol or denatured ethanol--is so routine that it is convenient to store the instrument, the light source and accessory equipment on a portable cart. Since quality of wiring access varies so greatly from one physical setting to another, it is useful to have a socket from a fused circuit with an extension cord and/or

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transformer mounted on the cart. Similarly, an extension tubing and receptacle for suction is useful. Some institutions may require a portable suction compressor as well which can be powered from the same system as the light source. A wheeled cart can move adjuvant equipment from one site to another without loss of key items. One can place the fibreoptic instrument in a padded drawer or receptacle which will protect it from damage during transport. Finally, one can use the cart for a work area. Space is required for the recommended alcohol/saline wash disinfection before and after each use. It is particularly important to have a supply of appropriately sized brushes and a work area for cleaning potentially obstructive materials from the suction channel so that the instrument can be formally sterilized at a later time without fear that the suction channel and optics will remain coated with blood, inspissated secretions or protein coagulum.

MONITORING DURING ENDOSCOPY

Airway obstruction, with consequent hypoventilation or air trapping and barotrauma, excessive suctioning with resultant hypoxaemia, and disturbances in ventilation/perfusion balance with hypoxaemia and hypercapnoea, are well documented complications of fibreoptic bronchoscopy. Hypoxia is widely acknowledged by thoracic anaesthetists to be the most common and significant complication of OLA (Gothard and Branthwaite, 1982). This is also the case with fibreoptic bronchoscopy (Credle et al, 1974; Suratt et al, 1976) and the preventative monitoring concept is widely practised in clinical anaesthesia. The anaesthetist commonly monitors ventilation and oxygenation, both intermittently and continuously, when endoscopy is performed by another physician using anaesthesia. It would also seem prudent for another to monitor these when the anaesthetist performs endoscopy using anaesthesia. Oxygenation is ordinarily monitored by intermittent observation of the colour of blood or skin during routine cases. Many anaesthetists routinely place all patients on a high inspired oxygen fraction in order to diminish the impact of hypoventilation and abnormal ventilation/perfusion balance upon systemic oxygenation during endoscopy. Intermittent arterial blood gas monitoring, like intermittent observation of the colour of the blood, can be helpful but is certainly not effective in identifying transient hypoxaemia such as that which occurs during suctioning. In some centres, transcutaneous oxygen monitoring has become a recommended routine during thoracic and endoscopic procedures (Chubra-Smith et al, 1986). Transcutaneous oxygen tension provides an index of end-organ function and involves a number of variables in addition to arterial oxygenation. The monitor is an extremely helpful perfusion indicator but demonstrates a delayed response to steep increases or decreases in arterial tension in adults as demonstrated by Brown et al in 1984, and, later, by Tremper et al in 1986. Additionally, the time and difficulty involved in membrane stabilization, skin preparation and electrode placement limits the monitor's usefulness in the operative setting. The pulse oximeter, in contrast, is a self-calibrating arterial oxygen saturation monitor which is simple to employ. The device possesses a response time which allows

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immediate identification of significant hypoxaemia. Since the introduction of pulse oximetry, it has rapidly become recognized as a key monitor in thoracic practice as suggested by Brodsky et al in 1985, and Viitanen et al in 1986. A proliferation of products has decreased monitor costs significantly in the USA in recent months. Clinical monitors of ventilation include direct observation, monitors of mechanical ventilatory parameters, and physiological monitors. During airway endoscopy, branches of the lower airway are intermittently occluded, and the lungs are transiently evacuated by suction. One should, therefore, assess the adequacy of tidal exchange and evaluate the physiological and haemodynamical response to its intermittent impairment. Bronchoscopy causes dramatic alterations in ventilation, but these are usually transient. No preset alarm mode can function by itself to warn the endoscopist. In the author's view the best monitor is another skilled anaesthetist who can continue to focus his attention upon the patient's ventilation while the endoscopist works. Direct confirmation of the tracheal location of an endobronchial tube or blocker should always be made on clinical grounds prior to attempts at lung isolation. In the rare circumstance of a doubtful clinical examination, a rapid inspection with the endoscope, or detection of carbon dioxide in exhaled gases by infrared capnometry or mass spectroscopy provides unequivocal evidence of tube location (Birmingham et al, 1986). Acute, asymmetrical air-trapping by a partially malpositioned endobronchial tube is always a possibility which should be ruled out prior to bronchoscopy by inspection and auscultation of the chest, manual assessment of gas return, the presence of asymmetrical misting of condensed water on the internal lumina during the exhalation phase after inflation with dry inspired gasses, and by measurement of breathto-breath exhaled tidal volumes. Acute obstruction of one of the lumina can be detected in similar fashion and by dual capnography (Balagot, 1986). During endoscopy, direct and continuous monitoring of breath sound by a precordial or oesophageal stethoscope is the best way to identify ventilator circuit disconnection or significant obstruction to inhalation. Since leakage around the bronchoscope is common, especially in view of the increased proximal pressures required for ventilation around the instrument, a spirometer in the exhalation limb of the anaesthesia circuit and a proximal pressure gauge are useful monitors. Continuous transcutaneous carbon dioxide monitoring has been suggested but, like transcutaneous oxygen monitoring, the transcutaneous carbon dioxide level responds to a number of complicating variables and is difficult to use in the operating room setting. We have found the capnometer with oscilloscope display, or continuous capnogram to be a most useful monitor. By examining the slope of the carbon dioxide level during exhalation, one can qualitatively assess the magnitude of obstruction to exhalation. Additionally, one can intermittently withdraw the FFB into the proximal airway and obtain an expiratory carbon dioxide plateau which will approximate arterial and document effective ventilation. Although the capnometer has long been utilized as a research tool, its utility as a clinical monitor which can provide earlier and more specific information regarding ventilation has become evident only recently (Waterson et al, 1986).

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Indwelling arterial and tissue carbon dioxide and pH monitors have been introduced for clinical trials, but despite their promise as acute monitors in the operative setting, no data have been reported and the cost-benefit ratio of these has yet to be established. Since the early and late complications of disordered ventilation, transient hypoxaemia, and the 'auto-PEEP' effect of uneven air-trapping during fibreoptic endoscopy are ultimately manifest as haemodynamic derangements, it is essential to provide continuous haemodynamic monitoring. Most centres follow the surface ECG and intermittent Karotkoff blood pressure determinations, and continuously listen to heart sounds throughout thoracic anaesthesia as a routine procedure. A number monitor arterial pressure continuously during major thoracic cases (Watson et al, 1984). An additional advantage afforded by continuous, beat-to-beat, arterial pressure display on a calibrated oscilloscope is the acute change in arterial pressure associated with an extreme Valsalva manoeuvre such as that which occurs with significant air trapping or 'auto-PEEP' distal to the FFB during endoscopy. Acute wheezing followed by muffling of the heart sounds and an acute drop in systolic arterial and pulse pressure suggest tension pneumothorax during bronchoscopy. Occasionally a patient with significant cardiopulmonary disease requires chest surgery. Some disagreement exists over whether pulmonary artery catheterization has a place in monitoring such patients as noted by Watson et al in 1984. The major concern is that the catheter will become lodged in a pulmonary segment which is destined for resection. Additionally, movement of the pulmonary artery is more likely to cause catheter perforation and endobronchial haemorrhage or exsanguination. The oximetry catheter (Oxymetrix, Mountain View, California or Edwards Laboratory, Santa Anna, California) can be placed quite proximally in the pulmonary artery and signal significant haemodynamic changes without greatly increasing the risk of mechanical complications since the pulmonary artery occlusion pressure is not required so often. The pulse oximeter, when combined with an oxygen saturation pulmonary catheter, provides a significant level of monitoring discrimination since the arteriovenous oxygen saturation difference is continuously displayed (Norfleet and Watson, 1985). Thus, acute changes in arterial oxygenation can be differentiated from haemodynamic and metabolic reasons for arterial desaturation from an on-line display during bronchoscopy as well as during thoracotomy and OLA.

DOUBLE-LUMEN TUBE PLACEMENT When endoscopy is planned for double-lumen tube placement it is wise to have a light source, sterile saline for irrigation, suction, and Luer slip-tip syringes at the bedside. Since an increasing number of other monitors, the anaesthesia machine, and an additional equipment cart is frequently present in the operating room it is often difficult to keep the bronchoscopy cart out of the way during the process of anaesthetic induction, intubation and positioning. The endobronchial tube, whether single- or double-lumen, is first

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.\

Figure 2. Endobronchial tube is passed into appropriate bronchus over FFB as guide. From Watson (1982), with permission.

an endotracheal airway. It is wise to verify this first by conventional means before becoming involved in airway endoscopy after tracheal intubation. Once the patient is positioned for thoracotomy, it is convenient to move the bronchoscopy cart into range and proceed with verification of tube placement. The patient receives a high oxygen concentration and automated monitoring while the double-lumen tube is positioned. If the trachea is long enough, a double-lumen tube placed with the tracheal cuff just below the vocal cords will have its tip just above the carina, and the FFB can be advanced via the endobronchial lumen into the appropriate bronchus. At this time, the tube can be advanced over the FFB until its tip position allows ventilation of all segmental bronchi but secures the bronchus (see Figure 2). Note is taken of the distances by measuring them roughly by use of graduated markings on the FFB. Ventilation can be continued via each lumen during this and should be confirmed following withdrawal of the FFB by mist appearance within transparent connectors and use of tidal volume, minute ventilation and exhaled carbon dioxide monitors. When a safe clearance for the bronchial tip has been defined, the FFB is withdrawn. The ventilation adaptor is changed to the tracheal lumen and the FFB is passed into the trachea until the carina can be clearly seen. This allows visualization of the endobroncbial tube as it passes into the bronchus. Inflation of the bronchial cuff is observed and either the cuff, itself, visualized or the fact that secretions and gas do not leak back around the carina with the cuff inflated (see Figure 3). If ventilation is directed entirely via the bronchial lumen, the presence of an air leak is generally easy to recognize. It is useful to estimate clearance of the cuff below the carina so that, should lung isolation become ineffective due to surgical traction, the anaesthetist can predict the

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Figure 3. The FFB observesthe carina to ensure that the bronchial cuff has not occludedthe opposite main stem bronchus. From Watson (1982), with permission. best means of regaining control. After examining the airway from both within and without the bronchial lumen, one can tell how easily the tube will be dislodged from an acceptable position by gently manipulating the tube or, alternatively, by flexing and extending the neck. At the same time, one can clear secretions from the endobronchial lumen, dependent bronchus, and major segmental bronchi before one-lung ventilation is required. If patients are monitored carefully, it is possible to perform endoscopy a number of times during the procedure. We tend to place the tube orotracheally in the supine position, confirm tracheal placement clinically, and position the tube during surgical preparation and draping unless bronchopleural fistula, bleeding, deformed anatomy, or a particularly wet case requires tube placement awake or in the supine position. Regardless of the timing of the endoscopy it is essential to ensure safe levels of anaesthesia, ventilation and oxygenation prior to and during the procedure.

RIGHT E N D O B R O N C H I A L I N T U B A T I O N

The unique problem associated with right endobronchial intubation is isolation of the right bronchus without occlusion of the right upper lobe (RUL) bronchus. As noted before, ideal isolation may not be possible with any endobronchial tube design. The anaesthetist should first identify the R U L bronchus and establish its position vis-/t-vis the carina from the endobronchial lumen. Next, it it important to identify the orientation of the slot or orifice in the right endobronchial tube which will be lined up with the RUL. Often, the endobronchial tube is twisted out of alignment as it is rotated

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Figure 4. Bronehoscope verifies right upper lobe ventilation as right endobronchial cuff is inflated. From Watson (1982), with permission.

following passage via the larynx and the slot for the R U L may lie in a different plane from the upper lobe orifice. Some rotation is often required to place the slot in the correct position. After the tube orifice or slot is placed in line with the upper lobe bronchus, the FFB visualizes the junction of the upper lobe bronchus as the endobronchial tube is advanced over the FFB into the bronchus. The instrument is then angled so that the R U L bronchus can be seen via the R U L slot in the endobronchial tube as the bronchial cuff is inflated (see Figure 4). Occasionally the endobronchial tube must be repositioned so that the R U L orifice is not partially occluded by the endobronchial cuff. With the eccentric cuff design of the Right Bronocath the orifice need not be precisely in line with the R U L bronchus as cuff inflation ordinarily will not seal the bronchus if the bronchus and the orifice in the endobronchial tube are on the same level. In the unlikely event of a varient R U L bronchus, the eccentric cuff can be wedged at the carina and allow ventilation of the R U L unless the bronchial division is well above the tracheal carina. In all cases, the anaesthetist would do well to perform endoscopy via the tracheal lumen in order to assess the position of the endobronchial cuff vis-fivis the carina since there is rarely more than 1-2 cm of clearance, given an endobronchial tube of appropriate size. If it is impossible to achieve a satisfactory right endobronchial tube placement, the bronchoscope is again passed via the bronchial lumen, the tube withdrawn, and rotated for left endobronchial placement and lung isolation. Left endobronchial intubation remains the most likely approach to succeed. In the case of an aberrant R U L bronchus which is truly derived from the main trachea, it is the only way to succeed without ensuring obstruction of the bronchus whether one employs a single- or double-lumen endobronchial tube.

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S I N G L E - L U M E N TUBES A cuffed or uncuffed single-lumen tube can be wedged in either bronchus to allow OLA (see Figure 4). The recent introduction of 35 Fr PVC doublelumen tubes makes this less often necessary for small adults and large children. I f a single endotracheal tube is used, it should be longer than average to allow for tracheal length. An intubating bronchoscope or paediatric fibreoptic bronchoscope allows effective blockade with 4.5-5 mm tracheal tubes. When a single-lumen tube is chosen for adults, it is often possible to pass a suction catheter or FFB into the trachea via the larynx next to the endobronchial tube at initial laryngoscopy. These can be left in place for intermittent inspection or for secretion clearance when dual ventilation is again desired. The bronchoscope can be used for placement of other bronchial blockers when endobronchial intubation for OLA is not possible or desired. The bronchoscope is passed via or next to the tracheal tube and assists in guiding the blocker into place. One technique which has been described for paediatric orotracheal intubation can also be employed for placement of a bronchial blocker. A 160-170 cm, paediatric flexible spring-wound vascular guide wire is passed into a segmental bronchus under anaesthesia during endoscopy. The endoscope is withdrawn and reinserted. Then a pulmonary artery catheter or other balloon-tipped catheter is passed over the guide wire into the bronchus under direct visualization by the adjacent endoscope. The guide wire must be quite long to allow exchange of a 50-60 cm endoscope and a long catheter. The endoscope thus guides precise placement of the blocker and confirms that the balloon effectively seals the segment. The fibreoptic endoscope is not useful for initial endobronchial blockade of massive haemorrhage. Blood obscures the visual field and requires copious irrigation and suctioning time if any anatomical structures are to be recognized. In this situation, blind techniques are most likely to be life-saving and both ventilation and oxygenation are so tenuous that an additional obstruction caused by an endoscope may be lethal. We prefer the new generation of tubes with radio-opaque markings which allow use of radiographical or fluoroscopy control after blind tube placement. When the clinical situation is more stable, it is possible to clear secretions and confirm or improve tube placement using the FFB. THERAPEUTIC ENDOSCOPY The smaller suction channel of the flexible intubating bronchoscope and paediatric bronchoscope place these at a disadvantage in contrast with larger (5-6 mm) instruments. The 5 mm bronchoscope available from several manufacturers will effectively pass through 6.5 7 mm tracheal tubes and large Robertshaw or 39 and 41 French Bronchocaths. These are best for secretion clearance under direct vision unless smaller tubes are necessary for small airways. Two clinical settings commonly associated with trauma would make the thoracic anaesthetist preferentially select the smaller instruments for this

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purpose. With blunt chest trauma and pneumothorax or possible tracheobroncheal rupture, a smaller endoscope will reduce airway obstruction during exhalation and prevent further barotrauma due to air trapping. Effective blockade of a bronchial leak or balloon occlusion of a tracheal tear may be life-saving if achieved when the patient is stable and awake prior to emergency surgery. A second common problem in trauma is closed head trauma. The smaller instruments improve ventilation by obstructing the airway less and enhance exhalation, thus minimizing hypercapnoea and the effect of a sustained Valsalva manoeuvre upon central venous pressure and intracranial pressure. Additionally, since a smaller suction channel is less effective, it is more difficult (although possible) to cause transient suction hypoxaemia.

L E G A L AND PECUNIARY C O N S I D E R A T I O N S When perceived or actual injury has been sustained by a patient, many clinicians believe that they should counsel the patient and attempt to relieve his distress or minimize his actual injury. In the USA, patients who complain of injury have direct access to potentially large financial settlement through litigation in a modified common law system. In recent years, malpractice litigation in the USA has become so common that it has been estimated that within the past decade the incidence of legal actions brought against physicians has increased from 1:4 to 1:2. It is widely perceived that the potential for lawsuit is so great that each new or modified medical procedure must raise questions concerning associated medicolegal risk. Since many American anaesthesiologists have not employed the FFB in training and dayto-day practice until recently, it could be argued that they are unskilled or 'uncertified'. This objection to mastering the technique in one's practice is not tenable. Almost all anaesthetists have learned the indications, complications and safe management of fibreoptic bronchoscopy under anaesthesia during basic anaesthesia education. Thoracic anaesthetists, in particular, have experience with endoscopy in day-to-day practice. In contrast, the American Board of Pulmonary Medicine only requires fifty procedures for 'certification' of its diplomates as endoscopists while thoracic anaesthetists and well-trained generalists have most certainly managed many more procedures in the upper and lower airways. One could argue that well-trained anaesthetists are better qualified to assess and manage problems associated with endoscopy than their pulmonary medical counterparts in the USA. In the UK, the incidence of complaint regarding substandard practice is much lower and the financial incentive to pursue malpractice litigation is limited because the solicitor's fee contingency arrangement is more limited. Those European countries whose legal system is based upon the Napoleonic code have also not experienced such a dramatic increase in concern over the issues of standard and substandard practice, possibly because the threat of unpredictable financial awards by a jury is not present. Thus, outside the USA, it is difficult to envision any medicolegal impediment to more widespread practice of fibreoptic bronchoscopy by experienced personnel.

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Regardless of the legal position of the practitioner vis-fi-vis his patient, it is wise to inform the patient in full regarding alternative approaches and risks with any potentially hazardous part of an anaesthetic technique. Most of the time informed consent can be obtained and documented in the medical record without causing undue anxiety for the patient, his family, or the surgeon. One can only justify doing things to patients without their knowledge and consent under emergency circumstances or when the information would impair the patient's chances of having a good outcome. In the USA, it has been difficult to establish the latter grounds for failing to obtain informed consent in the legal forum. Pecuniary concerns are often raised by anaesthetists who contemplate the practice offibreoptic endoscopy. Unlike some medical specialists, the thoracic anaesthetist does not derive a major portion of his income from endoscopic procedures. Consequently, he is less interested in investing substantial funds and time. The most obvious problem is the purchase and maintenance cost of endoscopic equipment. Indeed, if use of flexible fibreoptic instruments is not carefully controlled, the cost of repairs can exceed the purchase value of the instrument within 2 3 years. The cost of light sources and preventative maintenance is not ordinarily substantial since most centres large enough for thoracic surgery cases have dealt with this issue already. Unless the thoracic anaesthetist has so busy a practice that the light source must be dedicated only to that use, the light source can be 'pooled' for use with other endoscopes commonly used in hospitals. An effective preventative maintenance programme requires a special locked area for storage and cleaning of the instruments. If such an area exists, the anaesthetist would do well to employ it and to utilize dedicated personnel. If not, it is best to become proficient in cleaning and maintenance. As in most areas of practice, personnel costs are more significant than cleaning space and supplies. If the instrument is cleaned immediately after each use the suction channel and optics are less likely to be damaged. Also, new submersible instruments can be leak-tested by pressurizing the interior via a pressure relief vent. Natural fatigue of the external (and internal) coating of the FFB associated with repeated use and the passage of intraluminal cleaning brushes is accelerated by cleaning the instrument in glutaraldehyde solutions or by an ethylene oxide autoclave. Small perforations of the protective coating will allow cleaning solutions, drugs and secretions to gain entry into the fibre and steering bundle channels. When this occurs, fluid is drawn along the bundles by capillary action. This either distorts the optical image by leaving residue on the ends of fibres and disrupting fibre coherence and alignment by separating them, or by increasing the resistance to steering bundle motion, thereby 'freezing' the flexible tip. Repair of either of these problems costs approximately half the purchase value of a new endoscope when it is possible. Early recognition of the leak allows prompt repair. Simply sealing the leak area or recoating the endoscope before internal damage has occurred is much less costly and time consuming. Some of the newer endoscopes are totally submersible and provide a vent which allows equalization of external and internal pressures during gas sterilization. Venting decreases the risk of damage to the endoscope's protective coating. Recently, one manufacturer

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has provided a pressure gauge which fits on to the pressure vent system and allows early recognition of tears in the outer coating of the endoscope. Clearly the submersible instrument and optimal leak testing system is cost-effective. Periodic preventative maintenance can ensure complete sterility and identify the need for repair before significant damage occurs. In countries where the anaesthetist directly bills his patients or their assurance companies for services rendered, the additional cost of fibreoptic endoscopy can be 'passed through' to his patient, occasionally with profit. The introduction of new technology is more difficult to justify when an additional group like a national medical service or hospital system must be petitioned for access to it. Since endoscopic equipment also offers a less expensive (in terms of procedural cost, patient morbidity and time) approach to the difficult airway than tracheostomy and/or cricothyrotomy and can be used in other settings outside the thoracic operating room, it has not been difficult to justify an initial investment on these grounds to public hospitals in the USA. Unfortunately, although there is data which suggests that use of the FFB enhances patient safety in the thoracic surgical setting, no cost justification study has as yet been published. Indeed since most thoracic anaesthetists have successfully trained and practised without using fibreoptic endoscopes in the past, justification of the investment remains problematic if it is to be used for thoracic anaesthesia alone. As with many technical innovations, experience is required before the advantages become manifest to the practitioner.

SUMMARY

The bronchoscope was initially employed for the removal of foreign bodies from the airway and, later, as part of the evaluation of patients with anatomical airway problems, infection, airway bleeding and carcinoma of the lung. Recently, advances in fibreoptic technology and a renaissance of interest in safer means of achieving lung isolation for one-lung anaesthesia during thoracic surgery and selective lung ventilation have led to widespread interest in newer, small diameter flexible fibreoptic instruments. The fibreoptic technique for placing both right and left double-lumen endobronchial tubes and blockers is a straightforward modification of the earlier, more difficult techniques which employed the rigid intubating bronchoscope. Now 'paediatric' instruments are available from several manufacturers. A bronchoscope with an external diameter of less than 4 mm allows passage via the 4.5 mm ID and larger lumina of double- and single-lumen tubes without loss of the multipurpose 'suction channel'. Newer endobronchial tubes made of transparent PVC, with a colour-coded bronchial lumen, cuff and pilot balloon, offer a considerable advantage to the endoscopist. The primary advantage offered by newer fibreoptic instruments, ease of use, places fibreoptic techniques within the reach of the thoracic anaesthetist who is not trained in rigid endoscopy. As the anaesthesiologist's experience with the instrument grows, the smaller instrument also allows a wider range of use than was practical with earlier instruments. The flexible intubating bronchoscope can be used as an adjunct for placement of tracheal tubes when upper or

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lower airway p a t h o l o g y might complicate tracheal intubation. The clinician can sidestep expensive, indirect means o f evaluating pre-existent airway p a t h o l o g y and obtain a d y n a m i c airway assessment prior to anaesthesia. A w a k e fibreoptic intubation is often less stressful, less traumatic and better tolerated than other 'awake' techniques. It is the only practical means o f stenting the compressed trachea with a tracheal tube prior to exploratory t h o r a c o t o m y or median sternotomy for evaluation or excision o f mass lesions. Fibreoptic e n d o s c o p y under anaesthesia also allows the thoracic anaesthesiologist to diagnose unexpected airway problems, clear secretions, evaluate bronchial suture lines and prevent postoperative atelectasis due to secretion retention or pooling in dependent airways. Therapeutic fibreoptic bronchoscopy m a y also be necessary in the immediate postoperative period for similar reasons. Extensive experience with fibreoptic endoscopes in both the medical and surgical setting has clearly defined procedural risks and established an excellent safety record provided basic precautions are taken. The thoracic anaesthesiologist is often called u p o n to provide anaesthesia for, or otherwise assist with, b r o n c h o s c o p y in the operating theatre. Given the utility o f the tool and the anaesthesiologist's extensive experience with the monitoring and m a n a g e m e n t o f patients who undergo endoscopy under anaesthesia, it is surprising that the fibreoptic b r o n c h o s c o p e has not found more universal use in the thoracic anaesthesia setting. It is logical that experts trained in airway m a n a g e m e n t and the perioperative care Of respiratory patients should add flexible fibreoptic b r o n c h o s c o p y to their a r m a m e n t a r i u m o f technical adjuncts for thoracic anaesthesia practice.

Acknowledgements The author wishes to thank Mrs Maria Soukhanova Watson for her patient assistance with chapter preparation and to acknowledge the support and assistance of Drs Bataglini and Keagy from the Cardiothoracie Division of the Department of Surgery and of Drs Norfleet, Mueller, Kates, Saltzman and Clapham from the Department of Anesthesiology at the University of North Carolina in Chapel Hill, who shared their patients and assisted in the conduct of a series of investigations performed at that institution from 1981 to 1985.

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