Prevention of Tracheal Injuries in Prolonged Ventilation

Prevention of Tracheal Iniuries in Prolonged

Ventilation· Laboratory and Clinical Observations on the -Use of Self-Inflating CuHs on Ventilating Tubes Jacob AbOUDv, M.D., F.G.G.P.,·· and Theodore N. Finley, M.D. t

We have previously described the design for a new selfInftatlag cd for use on endotracheal and tracheostomy tabes. The preI8IIft clulraderlstlcs of this new cutf have beeD reported. The present report presents oar experience with this self-bdlatiDg cuff In over 200 laboratory observatioDI demoDStrating its effectiveDess In preventing tracheal damage. Tracheostomy tubes mounted with self......... cutis were kept in the dogs for six weeks with-

out causing tracheal ulceration. Our cUnicaI experience In 52 patients Is also described. Endotracheal, nuotracheal, and tracheostomy tubes were used lntraopentively and for long periods of ventDatlon. No tracheal damage could be showD at postmortem examination ID two patients dying of their disease, 10 and 25 days after continuoUl ventilation.

Recent editorials attest to the seriousness of the complications which can occur after prolonged ventilation. 1.2 These complications include granulomas, tracheomalacia, tracheal stenosis, hemorrhage from erosion into major vessels in the neck, tracheoesophageal fistulae, and tracheal rupture.3-11 The most important cause for some of these complications is the damage to the tracheal mucosa produced by the pressure of the cuffs of the ventilating tubeS.5.8.12.13 This cuff-to-tracheal wall pressure, here referred to as lateral wall pressure, has been found to be excessive, much higher than capillary·pressure, in most of the commercially available tubes.14-18 In efforts to minimize these complications, various changes in methods of ventilation and additional· pressure-regulating equipment have been suggested, as well as different designs for the cuffs. 7-24 We have previously described a new self-inHating cuff, and we have published its pressure characteristicS. 15.25 We wish now to report the efficacy of the

cuH in preventing tracheal damage, as observed in the laboratory, and we will report our clinical experience with ventilating tubes mounted with selfinHating cuHs* in over 100 patients.

°From the Department of Surgery, Mount Zion Hospital and Medical Center; San Francisco; the Department of Medicine, University of California, Davis; and the Chest Service, Veterans Administration Hospital, Marinas, Calif. Associate Chief of Surgery in charge of Cardiac Surgery, Mount Zion Hospital and Medical Center. tProfessor of Medicine and Chief, Chest Service, Veterans Administration Hospital. Manuscript received February 23; revision accepted May 5. Reprint requem: Dr. Abouav, 2320 Sutter Street, Suite 204, San Francisco 94115

O.

CHEST, 71: 1, JANUARY, 1977

MATERIALS AND METHODS

Laboratory Obaeroations Lateral Wall Pressure. Adult mongrel dogs weighing 13.6 to 22.7 kg (30 to 50 lb) were anesthetized with sodium pentobarbital (Diabutal). Ventilation was maintained with commercially available ventilators (Bennett and Mark VII). An air-tight seal was created around a 5-mm strain gauge (Statham) inserted into the anterior wall of the trachea, from which a 3-mm segment of cartilage had been excised. Airway pressures were measured by a second strain gauge (Statham). Both gauges were calibrated individually and recorded simultaneously. Inftation pressures and flows were carried over a wide range, using both ventilating tubes mounted with selfinflating cuHs and commercially available tubes ( Portex, Rusch, soft--cuH, Shiley, Lantz, and flanged cuHs). The cuHs on the commercial tubes were inflated to sealing pressure, ie, the lowest bag pressure required to prevent discernible air . leak around the cuff at peak inspiratory pressures. The direct pressure of the cuff against the trachea was recorded by the gauge in the tracheal wall simultaneously with the intratracheal air pressures. Tracheal Mucosal Damage. Routine tracheostomies were performed by excising small segments of anterior tracheal walls in a paired series of dogs, comparing tubes mounted with self-inflating cuffs to commercially available cuffed tubes tClinical use of the tube was begun after extensive laboratory observation and after approval_ by the Committee on Human Experimentation at Mount Zion Hospital and Medical Center.

PREYENnON OF TRACHEAL INJURIES 13

as noted previously. The dogs were observed for 24 hours to six weeks. Tracheostomy tubes were removed daily, cleaned, and then replaced. The cuffs were initially inHated to their minimal occlusive pressures at peak inspiratory pressures of 20 em H20. Care was taken each day to reinHate the cuffs with volumes of air equal to those of the initial inHations. Aspiration Erperiment8. In the model lung, methylene blue solution was poured into the model trachea above the self-inHating cuff to determine the maximal height of the fluid column that could be supported by the cuff. Using dogs that had been intubated with endotracheal tubes mounted with seH-inflating culls and were ventilated with the Bennett respirator at a peak inspiratory pressure of 20 em H20, we instilled barium sulfate solution into the mouth and pharynx of the animals, filling them to the level of the lips. X-ray films were then made of the chest (anteroposterior and lateral views).

SINCUF

Clinical Obseroations Nasotr8.cheal, endotracheal, and tracheostomy tubes mounted with self-inHating cuffs were used in clinical settings. These included 106 patients undergoing various abdominal, thoracic, and cardiac surgical procedures and patients with acute and chronic respiratory distress syndromes. The number of clinical patients in each category was as follows: aortocoronary bypass, 52 patients; valve replacement, 25 patients; coarctation (adult), one patient; abial septal defect ( adult), five patients; ventricular aneurysm, three patients; abdominal aneurysm, one patient; pulmonary resections, five patients; esophageal resections, two patients; respiratory failure, ten patients; and cholecystectomy, two patients. The length of surgical procedures varied from 45 minutes (elective cholecystectomies) to six hours (cardiac operations). The ventilating tubes were kept in the cardiac surgical patients for at least 24 hours after the operations and were kept in patients with chronic respiratory insufticiency for 10 to 25 days. Actual duration of intubation varied from 45 minutes to three weelcs. . - --

REsuLTS Laboratory Observations

Measurements of Lateral Wall Pressure. The lateral wall pressure exerted by the self-inflating cull rises and falls, following closely the curve of the periods of inflation and deflation (Fig 1). This is in contrast to the lateral wall pressure of the inflatable culls, which is continuous once inflated. The lateral wall pressure of the inflatable culls varied inversely with the residual volume of the cuff; the higher the residual volume, the lower the lateral wall pressure. U5 It was observed that even in the soft-cuffed tubes, the lateral wall pressure was between 20 and 40 mm Hg (Fig 2), which is higher than the capillary pressure,18 and probably explains the occurrence of tracheal ulcers in patients ventilated with soft-cuffed tubes. 28 It was also observed that the seH-inflating cull was able to automatically adjust its sealing pressure to the intratracheal pressure at various peak inflation pressures. This is not the case with all of the com-

14 ABOUAV, FINLEY

20 em H20 FiGURE 1. Recordings of lateral wall pressure with seH-inHating cuff (SINCUF). Note that lateral wall pressure equals intratracheal pressures and that lateral wall pressure adjusts automatically to increasing peale inspiratory pressures and is exerted intermittently.

mercially available tubes. The inflatable culls often require additional aliquots of air to obtain a seal, and this results in increased lateral wall pressure (Fig 2). The latter observation is an added explanation for the severe damage noted in some patients treated with soft-euffed tubeS. IT Pressurelimited cuffsM have been observed not to function consistently with high peak inspiratory pressures. T~acheal Mucosal Changes. The changes noted in the tracheal mucosa in our series of patients undergoing tracheostomy were similar to those observed by other investigators. 28.29 The mucosal damage was time-related, starting with ulceration at 24 hours and culminating with perforation at four weeks. The trachea of a dog killed six weeks after tracheostomy in the series with self-inflating culls was noted to be free of any ulcer (Fig 3). Note the injection of the mucosa without ulceration. Modified self-inflating culls, as described by Jackson and Rokowskiso and by Martinez,81 failed to function after 24 to 48 hours. Fluid collected in the cuff, and CHEST, 71: 1, JANUARY, 1977

FORREGER SOFT CUFF TUBE

Intr~racheal

Calibration at

20 cm H20

Ventilator set at

20 cm H20

Effect of t cc increments of air on

L.W.P.

pressure

30 cm H20

t40 cm HlJ

2. Increased lateral wall pressure (LWP) with increased inHation of soft cuff. Resp, Respirator.

FIGURE

secretions plugged the tracheal openings, thus deforming the cuHs and making them inoperative. Aspiration Experiments. Figure 4 demonstrates that the column of fluid supported by the self-inflating cuH was as high as 7 cm H2O. Figure 5 is a roentgenogram showing all of the barium sulfate solution above the cuH and none below it. The redundancy of the cuH enables it to drape itself against the tracheal mucosa sufficiently to prevent massive aspiration. Clinical Observations

time. Occasionally a leak of 50 to 150 ml per cycle occurred at the onset of ventilation but disappeared as ventilation progressed, probably due to the wet· ting of the cuH by the secretions and subsequent sealing. Concentrations of arterial blood gases were maintained at good levels in all patients. Ventilation was possible at a peak inspiratory pressure as high as 60 em H20 in one case without any signi6cant leak. No episodes of aspiration were ob· served, and no tracheal ulcerations were seen in the patients ventilated for as long as three weeks. DISCUSSION

The redundancy of the folds of the self-inflating cuff obscures to some degree a clear view of the vocal cords, and our anesthesiologists voiced their objections; however, the objection was overcome by using a stylet and threading it one-quarter inch beyond the tip of the tube, thus permitting clear view of the cords during the passage of the stylet and threading the tube over it Sometimes slight pressure is required to pass the soft cuH through the cords. Furthermore, as experience was gained with the tubes, the stylet was discarded most of the

The complications of prolonged ventilation are serious and frequent. The tracheal complications result from excessive pressure exerted by the cuH against the tracheal mucosa at its point of maximal contact. It has, therefore, been our purpose to develop a cuH with different characteristics. The characteristics should include the following five features: 1. The cuH should exert the least lateral wall

FIGURE 3. Tracheal mucosa in dog with tube mounted with self-inflating cuff six weeks after tracheostomy. Note absence of ulceration and integrity of self·inftated cuff.

FIGURE

CHEST, 71: 1, JANUARY, 1977

4. Column of fluid supported by self-inHating cuH (7 em H20).

PREVENTION OF TRACHEAL INJURIES 15

FIGURE 5. Roentgenogram showing barium suHate solution above self-inflating cuff in anesthetized and ventilated dog.

pressure consistent with proper functioning of the ventilator. Adriani and Phillips32 indicated that the sealing pressure must equal intratracheal pressure to permit proper functioning of the ventilator. It is preferable that lateral wall pressure should never exceed the intratracheal pressure, a characteristic manifested by the self-inflating cuff (Fig 1). 2. Adriani and Phillips32 also observed that the

intratracheal pressure is inversely related to the pulmonary compliance. Therefore, the ideal cuff should be capable of automatically varying the sealing pressures required by the changing pulmonary compliances that occur during the course of prolonged ventilation. This capability is shown in Figure 1 and was observed in our clinical trials; tubes mounted with self-inflating cuffs functioned at peak pressures, which varied with the changing pulmonary compliances during the course of ventilation. 3. The sealing pressure should be exerted only when it is needed, that is, during the inspiratory period of the ventilatory cycle. In other words, the lateral wall pressure should be intermittent. 4. The cuff should be capable of prolonged use without requiring special attention by the nursing staff. 5. The cuff should prevent massive aspiration. None of the methods proposed to date23.24.30-32 has been uniformly successful. The various items of additional equipment111,20 on the ventilator to ensure intermittent inflation of the cuffs have been cumbersome and have required constant attention to prevent dangerous overinflation. Several attempts to design self-inflating intermittent-pressure cuffs by Jackson and Robowski,30 by Martinez,31 and Benviniste,33 have failed because of improper design. To date the soft cuffs have demonstrated the least number of complications, but serious damage has already been recorded even with those cuffs. 26.27 The pressure-limited cuffs24 are not consistently functional at high peak inspiratory pressures. The self-inflating intermittent cuff which we here describe has demonstrated the desirable characteristics enumerated previously, and it has functioned

Table l-Somple Dolo Patient, Age (yr)

Diagnosis

Duration of Ventilation

Inflation Pressure, cmHIO

Volumes, mI

Arter al Blood Gas Levels, mm Hg·

Comments

1,83

Cholecystitis

20hr

20

600-750

Nasalintubation, no difficulty

2,48··

Transthoracic hiatal hernia

30hr

~30

600-800

Endotracheal

3, 66

Mitral valve replacement

260 hr

20-45

500-1,500

PaOl, 83-240 PaCOs, 47-53

Endotracheal, no leak

4, 43

Respiratory insufficiency; terminal cancer

10 days

~70

900-1,800

PaOl, 83-240 PaCOI ,47....53

No leaks even at high pressures

5,67

Respiratory insufficiency; cancer of right upper lobe

6 days

800-1,000

PaOs,79t

No leak

·PaOs, arterial oxygen pressure; and PaCOs, arterial carbon dioxide tension. ··Patient 2 weighed 122 kg (270 Ib). tFractiona' concentration of oxygen in inspired gas, 30 percent.

16 ABOUAV, FINLEY

CHEST, 71: I, JANUARY, 1977

consistently in well over 200 laboratory experiments and in over 100 clinical trials. The cuff causes minimal mucosal irritation after prolonged use,. and we have demonstrated proper function for as long as six weeks without change of tube. ADDENDUM

We have recently learned that Abraham D. Merav, M.D., at Montefore Hospital in New York has been working with a cuff with characteristics similar to ours.

1 The price of therapeutic artificial ventilation (editorial). ~tI:II6I,I973

2 Ventilating cuJfs: A blessing or a curse? (editorial). Surgery 70:800, 1971 3 Salmon LFW: Tracheostomy. Proc R Soc Med 68:347356,1975 4 Pearson FG, Golberg M, da Silva AJ: Tracheal stenosis complicating tracheostomy with cuffed tubes. Arch Surg 97 :350-394, 1968 5 Miller DR, Gulsha S: Tracheal stenosis following prolonged intubation: Causes and prevention. Ann Surg 171: 283-293,1970 6 Cooper JD, Grillo HC: The evolution of tracheal injury due to ventilatory assistance through cuffed tubes: A pathological study. Ann Surg 169:334, 1969 7 Garley RS, Barcus V: Ulcerative tracheo-esophageal 6stula during treatment by tracheostomy and intermittent positive pressure ventilation. Thorax 27:338, 1972 8 Muck 0, Kurstensen HS, Larsen HCA: Tracheo-esophageal fistula. Lancet 1:66, 1961 9 Thomas AN: The diagnosis and treatment of tracheoesophageal fistula caused by cuffed tubes. J Thorac Cardiovasc Surg 65:612-619, 1973 10 Garland H: Hemorrhage from innominate artery ulceration. Proc R Soc Med 52:877, 1959 .11 Tamvall SS, Jackson KH, Oyanedel ET: Tracheal nlpture: Complication of cuffed endotracheal tubes. Chest 59:237-239, 1971 12 Ching NP, Ayres SM, Paegle RP, et aI: The conbibutioo of cuH volume and pressure in tracheostomy tube damage. J Thorac Cardiovasc Surg 62:402, 1971 13 Cooper JD, Grillo HC: Experimental production and prevention of injury due to cuffed tracheal tubes. Surg Gynecol Obstet 139: 1235, 1969 14 Nealon TF Jr, Ching N: Pressure of tracheostomy cuffs in ventilated patients. NY State J Med 71:1923, 1971

CHEST, 71: 1, JANUARY, 1977

15 Finley TN, Abouav J: Pressure characteristics of a parachute self-inflating cuff. Am Rev Respir Dis 107:1071, 1973 ' 16 . Knowlson GIG, Basset BFM: The pressure that is exerted on the trachea byendotrachea.l inflated cuHs. Br J Anaesth 42:834-837, 1970 17 Hardy KL, Fettel BE, Shiley DP: New tracheostomy tube. Ann Thorac Surg 10:58, 1970 18 Crosby WM: Automatic intermittent in8ation of tracheostomy tube coH. Lancet 2:509, 1964 19 Rainer WG, Sanchez M: Tracheal cuff inHation: Synchronous timed with inspiration. Ann Thorae Surg 9:384, 1970 20 Arens JF, Ochsner JL, Gee G: Volume limited intermittent cull inJlation for long-term respiratory assistance. J Thorac Cardiovasc Surg 58:837, 1969 21 Geffin B, Pontoppidan H: Reduction of tracheal damage by prestretching of inBatable cuffs. Anesthesiology 31: 462, 1969 22 Grillo HC, Cooper JD, Geffin B, et al: A low-pressure cuJf for tracheostomy tubes to minimize tracheal injury. J Thorac Cardiovasc Surg 62:898, 1971 23 Lomholt N: A new tracheostomy tube. Acta Anaesthiol Scand 11 :311, 1967 24 McGovern G, Shively JD, Fecht D, et a1: Clinical and Experimental Evaluation of a controlled-pressure intratracheal cuH. J Thorac Cardiovasc Surg 64:747, 1972 25 Abouav J, Finley TN: Self-inflating parachute coH: A new tracheostomy and endotracheal cull. Am J Surg 125:65, 1973 26 Ching NPH, Ayres SM, Spina RC, et al: Endotracheal damage during continuous ventilating support. Ann Surg 179:123-127, 1974 27 Nealon TF Jr, in discussion of McGovern G, Shively JD, Fecht D, et al: Clinical and experimental evaluation of a controlled-pressure intratracheal cuff. J Thorac Cardiovasc Surg64:747, 1972 28 Paegle RD, Ayres SM, Davis S: Rapid tracheal injury of cuffed airways and healing with loss of ciliated epithelium. Arch Surg 106:31-34, 1973 29 Lester RB, Trimble K: Reappraisal of tracheal injury from cuffed tracheostomy tubes: Experiment in dogs. JAMA 215:625,1971 30 Jackson RR, Rokowski WJ: A disposable endotracheal tube with self-inflating cuff. Arch Surg 94: 160, 1967 31 Martinez HE: An improved cuffed tracheostomy tube for use with intermittent positive pressure breathing. J Thorac Cardiovasc Surg 47 :404, 1964 32 Adriani J, Phillips M: Use of endotracheal cui: Some data pro and con. Anesthesiology 18:1-14, 1957 33 Benviniste D: Endotracheal and tracheostomy tubes with seH-inHating cuffs. Acta Anesthesiol Scand 11:85-89, 1967

PREVENTION OF TRACHEAL INJURIES 17