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Randomized crossover comparison of ProSeal® Laryngeal Mask Airway with Laryngeal Tube Sonda® during anaesthesia with controlled ventilation†
British Journal of Anaesthesia 95 (2): 261–6 (2005)
doi:10.1093/bja/aei167
Advance Access publication May 27, 2005
RESPIRATION AND THE AIRWAY Randomized crossover comparison of ProSeal Laryngeal Mask Airway with Laryngeal Tube Sonda during anaesthesia with controlled ventilation{ T. M. Cook* and J. Cranshaw Royal United Hospital, Combe Park, Bath BA1 3NG, UK *Corresponding author. E-mail: [email protected]
Methods. The devices were studied in 32 ventilated patients by randomized crossover trial. Primary outcome was airway seal pressure. Secondary outcomes included insertion success and time, manipulations required, ventilation quality, peak and plateau airway pressures, ability to pass a gastric tube and fibreoptic laryngeal view. Results. The PLMA produced a higher seal pressure (median values, PLMA 26 cm H2O and LTS 24 cm H2O, P<0.01). First-attempt insertion succeeded with PLMA 28 times and LTS 22 times (P>0.05). The PLMA required fewer manipulations (P<0.05) in fewer patients (P<0.05) and took less time to insert (P<0.01). All PLMA patients and 22 LTS patients achieved optimal ventilation (P<0.01). Peak airway pressure was lower with the PLMA than with the LTS (P<0.01). The vocal cords were visible through the PLMA in 32 patients and through the LTS in nine patients (P<0.001). The laryngeal view was superior through the PLMA (P<0.001). Conclusion. The difference in seal pressure between devices was clinically unimportant. However, the LTS had an unexpectedly high failure rate. PLMA performance exceeded LTS performance in many clinically useful measures. The PLMA has greater clinical utility than the LTS during controlled ventilation. Br J Anaesth 2005; 95: 261–6 Keywords: equipment, masks, laryngeal; equipment, tubes, laryngeal Accepted for publication: May 6, 2005
The ProSeal Laryngeal Mask Airway (PLMA) (Intavent Orthofix, Maidenhead, UK) and the Laryngeal Tube Sonda (LTS) (VBM, Medizintechnik, Sulz, Germany) are two recently introduced devices for maintaining the airway during controlled ventilation under general anaesthesia. The PLMA was developed from the classic LMA (cLMA) and includes an oesophageal drainage tube, a deeper bowl and a posterior cuff (Fig. 1). The PLMA produces a higher pressure seal with pharynx than a cLMA.1 The LTS is a development of the Laryngeal Tube (LT) which also includes an oesophageal drainage tube (Fig. 2). The oesophageal drainage tubes in these devices may reduce the risk of airway contamination by preventing gastric insufflation and diverting emerging gastro-oesophageal contents away from the larynx.2 3 They may also guide gastric tube insertion for deliberate decompression and emptying of the stomach.1
For these reasons, these devices may have a role in both airway management during anaesthesia and airway rescue; the LTS has been advocated for prehospital emergency airway management,4 and the PLMA has been reported as a rescue device after failed intubation during rapidsequence induction.5 We have previously compared the clinical performance of the PLMA and the LT in patients undergoing controlled ventilation under general anaesthesia.6 The present investigation compared the performance of the PLMA and LTS in a randomized controlled crossover manner. Primary outcome was airway seal pressure. Secondary outcomes {
Declaration of interest. T.M. Cook has received honoraria for lecturing from Intavent Orthofix and the Laryngeal Mask Company, the distributors of the ProSeal Laryngeal Mask Airway.
# The Board of Management and Trustees of the British Journal of Anaesthesia 2005. All rights reserved. For Permissions, please e-mail: [email protected]
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Background. The Laryngeal Tube Sonda (LTS) is a supraglottic airway which, like the ProSeal Laryngeal Mask Airway (PLMA), incorporates a drain tube. We compared the performances of LTS and PLMA during controlled ventilation anaesthesia.
Cook and Cranshaw
Pilot tube and balloon
15 mm connector Drain tube
Airway tube
Drain tube tip
Bite block
Cuff
Laryngeal tube
Distal cuff
Proximal cuff
15 mm connector
Drain tube
Pilot tube
Laryngeal tube sonda
Fig 2 The Laryngeal Tube Sonda .
included insertion success and time, manipulations required, ventilation quality, peak and plateau airway pressures, ability to pass a gastric tube, and fibreoptic laryngeal view.
Patients and methods The local research ethics committee approved the study and all patients gave written informed consent before taking part. Thirty-two patients (ASA I–III) undergoing elective surgery in the supine or lithotomy position, in whom neuromuscular blockade and the use of an LMA were appropriate, were recruited. Patients were excluded if they had any pathology of the neck, upper respiratory tract or upper alimentary tract, if they were at increased risk of pulmonary aspiration of gastric contents, if they weighed <50 kg or had a height <155 cm. Preoperatively the view of the oropharynx on mouth-opening was scored as described by Mallampati7 and modified by Samsoon and Young.8 Standard monitoring devices were attached before induction of anaesthesia. The patient’s head was supported on a firm pillow. After preoxygenation, anaesthesia was induced
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Fig 1 The Proseal Laryngeal Mask Airway.
with fentanyl 1 mg kg 1 and a target controlled infusion of propofol 4–7 mg ml 1, which was also used to maintain anaesthesia. Neuromuscular blockade was produced by rocuronium 0.6 mg kg 1 and was confirmed using a peripheral nerve stimulator (train-of-four count=0) before airway manipulation. The patients were then randomly allocated to one of the two groups using sequentially numbered sealed opaque envelopes naming the airway device to be evaluated first. The LTS was inserted following the manufacturer’s instructions. Before insertion, the cuff was deflated and a water-soluble lubricant (KY Jelly ) was applied. The patient’s head was extended on the neck (‘sniffing position’). Jaw thrust was used to assist airway placement in all cases. The tip of the LTS was placed against the hard palate behind the upper incisors and the device was advanced in the centre of the mouth until resistance was felt. If no resistance was felt the LTS was positioned with the second bold line on the tube between the upper and lower incisors. The cuffs were inflated using a cuff inflator (VBM, Germany) to an intracuff pressure of 80–90 cm H2O which was then reduced to 60–70 cm H2O.9 A size 4 LTS was used for patients of height 155–180 cm and a size 5 for those of height >180 cm.9 The PLMA was inserted according to the manufacturer’s instruction manual,10 but jaw thrust and a PLMA introducer were used to assist placement in all cases. The back of the cuff was lubricated with KY Jelly . A size 4 PLMA was used for females and a size 5 for males.11 The cuff was inflated using the same cuff inflator as the LTS until the intracuff pressure reached 60–70 cm H2O.10 If it was not possible to insert a device at the first attempt, one more attempt was made. If insertion was impossible after this attempt, study of that device was abandoned. The number of attempts required to insert a device was recorded and where insertion was abandoned this was also recorded. The time taken to insert a device from picking it up to attaching it to the breathing system was only recorded for devices that were successfully inserted and enabled initial ventilation. An initial assessment of ventilation was made after the device had been connected to the breathing system by gently squeezing the reservoir bag and observing end-tidal carbon dioxide waveforms and chest movements. If ventilation was difficult, attempts were made to improve the airway using a chin lift, jaw thrust, head extension or neck flexion manoeuvre. The LTS could also be gently pushed or pulled according to the manufacturer’s instructions.9 After each manoeuvre, adequacy of ventilation was reassessed. The device was tied in place if clinically adequate ventilation was achieved. However, if ventilation was inadequate after these manoeuvres, the device was withdrawn completely and reinserted. If it was still not possible to ventilate after reinsertion and further application of the allowed airway manoeuvres, study of the device was abandoned. Similarly, if airway obstruction occurred during maintenance
PLMA or LTS during controlled ventilation anaesthesia
At the end of the operation, neuromuscular paralysis was reversed, the target-controlled infusion of propofol was stopped, spontaneous ventilation was established and the device was left in place. The device was routinely removed after the patient regained consciousness and opened his or her mouth to command, but if necessary was removed before this point if necessitated by airway obstruction, coughing or retching. Before removal, the cuffs of the LTS were deflated, but the cuff of the PLMA was left inflated in accordance with the manufacturer’s recommendations.9 10 Complications, previously defined, were recorded for each phase of anaesthesia (establishing an airway, maintenance, removal and recovery).
Statistical analysis The primary aim of this study was to compare the seal pressures generated in the larynx by the PLMA and the LTS. The PLMA was considered as the ‘control’ group. Based on the results of our previous studies, the PLMA has a seal pressure of 29 cm H2O with a standard deviation of 5 cm H2O.1 6 Power analysis determined that a study of 32 patients had 80% power to detect a difference in airway seal pressure of 5 cm H2O. Secondary outcomes included success of insertion, number of manipulations and time required to achieve an airway, peak and plateau airway pressures during ‘optimal’ ventilation, manipulations and complications throughout anaesthesia, ability to pass a gastric tube successfully into the stomach through the drain port and the fibreoptic laryngeal view through the device. A Wilcoxon signed rank test was used to compare insertion times and airway seal, peak and plateau pressures, and the number of manipulations required in patients with the two devices. A x2-test or a Fischer exact test was used to compare the proportions of patients in whom first-time device insertion was successful, the proportion requiring further airway manipulation and the proportion in which it was possible to pass a gastric tube. A sign test was used to compare the number of manipulations required in patients with the LTS and PLMA and the difference in laryngoscopic grade through the two devices. A Mann– Whitney test was used to compare the number of complications occurring with each device. Paired tests were not used because, despite the crossover design of the study, even after insertion of the devices a number of failures in one group meant that to use paired tests would mean discarding a considerable amount of data from the group without failures; to do so would introduce bias. Statistical analysis was performed using the statistical package Analyse it! and Microsoft Excel v6.0.
Results The characteristics of the patients are presented in Table 1 and the results of the study are summarized in Table 2. By the nature of the study design, the insertion and initial
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of anaesthesia, the allowed airway manoeuvres and one reinsertion were permitted. If it was still not possible to ventilate after reinsertion and the allowed additional airway manoeuvres, study of the device was terminated. The number of manipulations and abandonment of each device after insertion and during maintenance of anaesthesia was recorded. The efficacy of the airway seal created by each device was determined after insertion and necessary manipulation by measuring the minimum airway pressure at which gas audibly leaked around it using a fresh gas flow of 5 litre min 1 with the adjustable pressure-limiting (APL) valve completely closed. Airway pressure was not permitted to exceed 40 cm H2O. Controlled mandatory ventilation with oxygen–air mixture was employed with a programmed inspiratory tidal volume of 7 ml kg 1. The ventilatory frequency was adjusted to maintain end-tidal carbon dioxide concentration in the normal range and was delivered with a fixed inspiratory: expiratory ratio of 1:2. If the expired tidal volume was measured as <7 ml kg 1, the programmed inspiratory tidal volume was increased to a maximum of 10 ml kg 1 until the measured expired tidal volume reached 7 ml kg 1. Ventilatory variables were kept the same when comparing the two devices in the same patient. The device was recorded as facilitating ‘optimal’ ventilation if adequate chest movement, an expired tidal volume of 7 ml kg 1, stable oxygenation and ‘square-wave’ capnography were all observed simultaneously and consistently. ‘Suboptimal ventilation’ was recorded if one of these standards was not maintained. Peak airway and plateau pressures were recorded in all patients in whom device insertion and lung ventilation were possible. Patients receiving clinically adequate ventilation and oxygenation were preoxygenated before the breathing system was briefly disconnected and a 4 mm fibrescope was inserted through the airway port of the device in use. The best view of the laryngopharynx was sought from the bowl of the PLMA or from either of the two orifices of the LTS before removing the fibrescope and replacing the breathing system. Views were graded from 1 to 4: 1=vocal cords entirely visible; 2=vocal cords or arytenoid cartilages partially visible; 3=epiglottis only visible; 4=no laryngeal structures visible.12 The second device was studied in an identical manner after the patient had been preoxygenated, neuromuscular paralysis confirmed (train-of-four count=0) and the first device had been removed. The second device, if successfully inserted and clinically adequate, was used for the duration of anaesthesia. If time allowed, a 16 French gauge gastric tube, lubricated with KY Jelly , was gently advanced through the oesophageal port of the device being used to maintain the airway intraoperatively. The gastric tube was inserted to 50 cm and aspirated or flushed with 5 ml of air to confirm gastric placement. One attempt was allowed and success or failure was recorded.
Cook and Cranshaw
Table 1 Patient characteristics. The results are given as absolute number of patients, median (range), or median (SD) Males:females Age (yr) Weight (kg) BMI Operation by surgical specialty General Urological Orthopaedic Gynaecological ASA I/II Mallampati class 1/2/3/4
17:15 41.5 (21–78) 70 (18.1) 25.5 (19.4–31.1) 11 11 4 14 3 13/9 20/15/4/0
Table 2 Results of the study. The results are presented as absolute number of patients or as median (range) *Unable to insert two LTS. {One LTS abandoned after insertion because of inability to establish a patent airway
Device insertion No. of patients Attempts (one/two/abandoned) No. of patients Insertion time (s) Patients requiring manipulations Total no. of manipulations Patients with complications Total no. of complications Initial ventilation No. of patients Airway seal pressure (cm H2O) Optimal/suboptimal/adequate Peak airway pressure (cm H2O) Plateau pressure (cm H2O) Fibreoptic laryngeal view (1/2/3/4) Ventilation during maintenance No. of patients Patients with complications Total no. of complications Patients requiring manipulations Total no. of manipulations Optimal/suboptimal/adequate/abandoned Gastric tube insertion attempts (1/2) During recovery No. of patients Patients with complications Total no. of complications
LTS
32 32 28/4/0 22/8/2 32 30* 12 (10–50) 18 (8–180) 4 10 4 18 2 13 2 22
P-value
>0.05 <0.01 <0.05 <0.05 <0.01 <0.01
32 26 (18–40) 32/0/0 14 (9–33) 11 (6–25) 25/7/0/0
29{ 24 (10–40) 22/4/3 16 (9–40) 12 (3–36) 6/3/7/13
<0.01 <0.01 <0.01 >0.05 <0.001
16 2 2 1 1 14/2/0/0 13/0
13 9 18 7 15 7/3/2/1 9/1
<0.01 <0.01 <0.05 <0.01 <0.01 >0.05
16 0 0
12 5 9
<0.05 <0.001
efficacy of each type of device was compared in all 32 patients and each device could have been used in 16 patients for the rest of the anaesthesia. Although the PLMA was studied from induction to emergence from anaesthesia in all 16 allocated patients, the LTS could only be studied during maintenance in 13 patients because of insertion failure in two patients and inability to establish a patent airway in one patient. The LTS had to be removed intraoperatively from one patient because of hypoxaemia. Therefore the LTS could only be studied in the recovery phase in 12 patients. On four occasions the LTS had to be removed and replaced because of cuff rupture recognized after insertion. The data from these insertion attempts were not included in the analysis. During insertion and establishment of the airway, the first insertion attempt was successful in 28 patients with the
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PLMA
PLMA and in 22 patients with the LTS (P>0.05). In two patients the LTS could not be inserted at all and in one case it was inserted but a clear airway could not be established. Insertion of the PLMA was ultimately successful in all 32 patients. After insertion of the LTS, a total of 22 complications, predominantly hypoxaemia and difficulty in establishing a patent airway, occurred in 13 patients. In comparison, after insertion of the PLMA, there were two complications in total (both difficulty establishing a patent airway, P<0.01) in only two patients (P<0.01). To obtain a clinically adequate airway after insertion, the PLMA required manipulation in four patients and the LTS in 10 patients (P<0.05). In total, 18 manoeuvres were performed in the patients with LTS and four manoeuvres in the patients with PLMA (P<0.05). The number of manipulations required in individual patients with the LTS was also greater (PLMA, median 1 [range 0–1]; LTS 1 [0–3]; P<0.01) as was the time required to obtain a clinically adequate airway (PLMA, 12 [10–50] s; LTS 18 [8–180] s; P<0.01). During initial ventilation, ‘optimal ventilation’ was achieved in all patients with the PLMA and 22 with the LTS (P<0.01). ‘Suboptimal ventilation’ was achieved with the LTS in four patients. The PLMA produced a higher seal pressure than the LTS (PLMA, 26 [18–40] cm H2O; LTS, 24 [10–40] cm H2O; P<0.01). The peak airway pressure with the PLMA was lower than with the LTS (PLMA, 14 [9–33] cm H2O; LTS, 16 [9–40] cm H2O; P<0.01). Plateau pressure was not significantly different (PLMA, 11 [6–23] cm H2O; LTS 12 [6–36] cm H2O; P>0.05). The vocal cords were visible in all cases through the PLMA and in nine cases through the LTS (P<0.01). Grade of laryngeal view was superior through the PLMA (PLMA: grade 1, 25; grade 2, 7; grade 3, 0; grade 4, 0; LTS: grade 1, 6; grade 2, 3; grade 3, 7; grade 4, 13; P<0.001). A gastric tube passed successfully on all 13 first attempts through the drain tube of the PLMA and on nine of 10 first attempts through the drain tube of the LTS (P>0.05). During maintenance of ventilation, partial or total obstruction meant that a total of 18 complications occurred in nine patients with the LTS and a total of two complications occurred in two patients with the PLMA (P<0.01). To manage the obstruction, 15 manoeuvres were required in seven patients with the LTS and one manoeuvre was required in a patient with PLMA (P<0.01). By the end of maintenance, seven patients had been ventilated ‘optimally’, three patients ‘suboptimally’ and three patients, at times, less than suboptimally with the LTS (one had to have the LTS replaced with a PLMA). With the PLMA, 14 patients had been ventilated ‘optimally’ and two patients at times ‘suboptimally’ (P<0.01). During recovery, nine complications, predominantly airway obstruction and hypoxaemia, occurred in five patients with the LTS. An adequate airway was lost in three patients and the device had to be removed prematurely. No recovery problems were encountered with the PLMA (Table 2).
PLMA or LTS during controlled ventilation anaesthesia
Discussion
the LT and LTS also differs; these factors may or may not account for apparent performance differences. During the recovery phase of anaesthesia, problems with partial obstruction and hypoxaemia occurred only in patients with the LTS (five of 12 patients [42%]). This observation is important, as both the LTS and the PLMA are specifically modified for positive-pressure ventilation. However, to be useful they must still accommodate spontaneous ventilation and the return of pharyngeal tone during emergence from anaesthesia. Complications at this time may occur in an environment where personnel highly skilled in airway management are not immediately available. The reasons for the marked differences between our findings and those of other investigators are not immediately obvious. Other anaesthetic protocols used bolus propofol for induction (2–3.2 mg kg 1), more opioid (fentanyl 3–4 mg kg 1, remifentanil 5 mg kg 1 min 1) and inhalational agents for maintenance. However, this should not account for differences between our findings and those of Gaitini and colleagues16 who also used monitored neuromuscular blockade. The characteristics of the patients, where stated by other investigators, appear to be similar to those in the present study but the surgery performed may have differed. None of the other studies were of a crossover design. We have considerable experience with both devices and it is unlikely that familiarity with one device is the sole explanation. Indeed, our insertion times and overall insertion success rates for each device were similar to those of other investigators. The LTS has two small airway orifices compared with a single large orifice in the PLMA. We were able to view the larynx from the PLMA in 100% of cases but from the LTS in only 31%. Thus resistance to gas flow through the LTS and through the pharynx might explain the higher peak airway pressures observed with the LTS. Although the numbers were small, there was a high success rate in passing a gastric tube via the oesophageal ports of both devices. These results are in keeping with those of other investigators.14–16 The ability to pass a gastric tube via the PLMA has been associated with partial or total visualization of the vocal cords.18 Complete success in passing a gastric tube in this study and the high rate of positioning of the PLMA orifice over the larynx support this association. In addition to proposed roles during anaesthesia, the LTS and the PLMA have suggested roles in airway rescue and emergency airway maintenance. In these circumstances desirable features of a supraglottic airway device are an ability to ventilate the lungs, drain the oesophagus and act as a conduit through which to intubate the trachea. Although both devices appear to be able to drain the oesophagus equally, our results would favour the use of a PLMA in an emergency. First, insertion and ventilation were more quickly and successfully achieved with the PLMA. Secondly, fibreoptic-guided intubation is only likely to be successful if the tube passes easily through the device and the larynx is visible. In our study, the larynx could be seen
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The primary outcome measure in this study was the airway seal pressure created by the two airway devices. The median airway seal pressure obtained with PLMA was 26 cm H2O and that with LTS was 24 cm H2O. This difference, although statistically significant, is unlikely to be clinically important and is less than the 5 cm H2O that the study was powered to detect. The range of seal pressures produced by the PLMA and LTS was comparable to those found by other investigators,13 14 although one investigator comparing the two devices (and allowing airway pressures to rise to 60 cm H2O) found seal pressures >45 cm H2O for both devices.15 However, we have found marked differences in clinical performance between the two devices. First-time insertion success (88% vs 69%), overall insertion success (100% vs 94%), initial provision of optimal ventilation (100% vs 73%) and overall abandonment rate (0% vs 19%) all favoured the PLMA. These differences were all statistically significant and are clinically relevant. In addition, the PLMA provided an effective airway in all patients in whom an LTS either could not be inserted or did not facilitate adequate ventilation. Three other groups of investigators have compared the LTS and the PLMA. One study is published,16 and the others are reported as abstracts.14 15 In these studies first-time insertion success was sometimes lower for the PLMA (76%) and higher for the LTS (80%)17 than in our study, but overall insertion success using two or three attempts was similar: 94–100% for the LTS13 14 16 and 93–100% for the PLMA.13 14 16 However, in contrast with our results, previous studies found broadly equivalent performance of the LTS and the PLMA with regard to ease of insertion and clinical performance. In our hands, the LTS was inserted less successfully, with more complications and a greater need for manipulation. The LTS also provided poorer quality ventilation. After insertion, only 69% of patients could be ventilated optimally with the LTS compared with 100% with the PLMA. During maintenance, ventilation with the LTS failed more often and led to more complications and manipulations. By the end of maintenance less than half the patients ventilated with the LTS had consistently received optimal ventilation and the decreasing performance of one device had necessitated removal. Only two patients had been ventilated suboptimally with the PLMA. Thus initial success with either device does not guarantee optimal ventilation under surgical conditions, but the reliability of the PLMA may be greater than that of the LTS. Some investigators have reported successful ventilation in all patients with each device,14 15 while others have recorded difficulties in 2–7% of patients with both devices.16 We have previously evaluated laryngeal tube (LT) performance and found it rather more successful than the LTS.6 17 The tip of the LTS differs quite considerably in design from that of the LT, and the configuration of the airway holes in
Cook and Cranshaw
Acknowledgement The LTS devices used in this study were provided by VBM, Medizintechnik, Germany free of charge.
References 1 Cook TM, Nolan JP, Verghese C et al. A randomized crossover comparison of the Pro-Seal with the classic laryngeal mask airway in unparalysed anaesthetized patients. Br J Anaesth 2002; 88: 527–33 2 Evans NR, Gardner SV, James MF. ProSeal Laryngeal Mask protects against aspiration of fluid in the pharynx. Br J Anaesth 2002; 88: 584–7 3 Brain AIJ, Verghese C, Strube PJ. The LMA ‘ProSeal’—a laryngeal mask with an oesophageal vent. Br J Anaesth 2000; 84: 650–4 4 Genzwuerker HV, Finteis T, Hinkelbein J, Kreiter H. The LTS (Laryngeal Tube Sonda) a new device for emergency airway management. Scand J Trauma Emerg Med 2003; 11: 125–31 5 Awan R, Nolan J, Cook TM. Use of the ProSeal LMA for airway maintenance during emergency Caesarean section after failed intubation. Br J Anaesth 2004; 92: 144–6
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6 Cook TM, McKinstry C, Hardy R, Twigg S. Randomized crossover comparison of the ProSeal laryngeal mask airway with the Laryngeal Tube during anaesthesia with controlled ventilation. Br J Anaesth 2003; 91: 678–83 7 Mallampati SR, Gatt SP, Gugino LD et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J 1985; 32: 429–34 8 Samsoon GLT, Young JRB. Difficult tracheal intubation: a retrospective study. Anaesthesia 1987; 42: 487–90 9 Laryngeal Tube Sonda Instructions. Sulz, Germany: VBM GmBH, 2000 10 Laryngeal Mask Airway ProSeal Instruction Manual. Maidenhead, UK: Intavent Ltd, 2002 11 Kihara S, Brimacombe J, Yaguchi Y, Taguchi N, Watanabe S. A comparison of gender and weight-based ProSealTM laryngeal mask size selection criteria: a randomised study of healthy anesthetized, paralysed adult patients. Anesthesiology 2004; 94: 1023–7 12 Verghese C, Berlet J, Kapila A, Pollard R. Clinical assessment of the single use laryngeal mask airway—the LMA-Unique. Br J Anaesth 1998; 80: 677–9 13 Cartensen S, Bein B, Claus L, Steinfath M, Do¨rges V. ProSeal Laryngeal Mask Airway and Laryngeal Tube S—modified airway devices for lung ventilation and gastric drainage. Anesthesiology 2003; 99: A-1257 (abstract) 14 Do¨rges V, Carstensen S, Bein B, Claus L, Steinfath M. The newly developed Laryngeal Tube S—a comparison with the Combitube during routine surgical procedures Anesthesiology 2003; 99: A-1243 (abstract) 15 Genzwurker HV, Roth H, Rothhaas A, Finteis T, Schmeck J. Comparison of LMA-Proseal and LTS for ventilation during laparoscopic gynaecological surgery. Anesthesiology 2003; 99: A-1194 (abstract) 16 Gaitini LA, Vaida SJ, Somri M, Yanovski B, Ben-David B, Hagberg CA. A randomized controlled trial comparing the ProSeal Laryngeal Mask Airway with the Laryngeal Tube Suction in mechanically ventilated patients. Anesthesiology 2004; 101: 316– 20 17 Cook TM, McCormick B, Asai T. Randomized comparison of laryngeal tube with classic laryngeal mask airway for anaesthesia with controlled ventilation. Br J Anaesth 2003; 91: 373–8 18 Agro F, Antonelli S, Cataldo R, Mentecchia F, Barzoi G, Pettiti T. The Proseal Laryngeal mask airway: fibreoptic vizualisation of the glottic opening is associated with ease of insertion of the gastric tube. Can J Anaesth 2002: 49: 867–70
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through the PLMA in all cases, but through an adequately functioning LTS in only 31% of cases. Gaitini and colleagues16 saw the vocal cords in 96% of cases through the PLMA but in only 89% through the LTS.16 The largest tracheal tube that can be passed through an LTS is 4.5 mm compared with 6.0 mm with a PLMA. We suggest, on the basis of our results, that the PLMA may be a more reliable airway than the LTS when subsequent access to the trachea might be desirable. In summary, the LTS and PLMA performed equally well in measures of laryngeal seal pressure and ability to drain the stomach (design features central to both devices). However, the quality of airway maintenance and the ability to ventilate the patient’s lungs via the LTS was inferior to that via the PLMA. The PLMA also afforded a more reliable and better view of the larynx. We conclude that the PLMA is likely to be a more useful device than the LTS for routine anaesthesia requiring controlled ventilation.
doi:10.1093/bja/aei167
Advance Access publication May 27, 2005
RESPIRATION AND THE AIRWAY Randomized crossover comparison of ProSeal Laryngeal Mask Airway with Laryngeal Tube Sonda during anaesthesia with controlled ventilation{ T. M. Cook* and J. Cranshaw Royal United Hospital, Combe Park, Bath BA1 3NG, UK *Corresponding author. E-mail: [email protected]
Methods. The devices were studied in 32 ventilated patients by randomized crossover trial. Primary outcome was airway seal pressure. Secondary outcomes included insertion success and time, manipulations required, ventilation quality, peak and plateau airway pressures, ability to pass a gastric tube and fibreoptic laryngeal view. Results. The PLMA produced a higher seal pressure (median values, PLMA 26 cm H2O and LTS 24 cm H2O, P<0.01). First-attempt insertion succeeded with PLMA 28 times and LTS 22 times (P>0.05). The PLMA required fewer manipulations (P<0.05) in fewer patients (P<0.05) and took less time to insert (P<0.01). All PLMA patients and 22 LTS patients achieved optimal ventilation (P<0.01). Peak airway pressure was lower with the PLMA than with the LTS (P<0.01). The vocal cords were visible through the PLMA in 32 patients and through the LTS in nine patients (P<0.001). The laryngeal view was superior through the PLMA (P<0.001). Conclusion. The difference in seal pressure between devices was clinically unimportant. However, the LTS had an unexpectedly high failure rate. PLMA performance exceeded LTS performance in many clinically useful measures. The PLMA has greater clinical utility than the LTS during controlled ventilation. Br J Anaesth 2005; 95: 261–6 Keywords: equipment, masks, laryngeal; equipment, tubes, laryngeal Accepted for publication: May 6, 2005
The ProSeal Laryngeal Mask Airway (PLMA) (Intavent Orthofix, Maidenhead, UK) and the Laryngeal Tube Sonda (LTS) (VBM, Medizintechnik, Sulz, Germany) are two recently introduced devices for maintaining the airway during controlled ventilation under general anaesthesia. The PLMA was developed from the classic LMA (cLMA) and includes an oesophageal drainage tube, a deeper bowl and a posterior cuff (Fig. 1). The PLMA produces a higher pressure seal with pharynx than a cLMA.1 The LTS is a development of the Laryngeal Tube (LT) which also includes an oesophageal drainage tube (Fig. 2). The oesophageal drainage tubes in these devices may reduce the risk of airway contamination by preventing gastric insufflation and diverting emerging gastro-oesophageal contents away from the larynx.2 3 They may also guide gastric tube insertion for deliberate decompression and emptying of the stomach.1
For these reasons, these devices may have a role in both airway management during anaesthesia and airway rescue; the LTS has been advocated for prehospital emergency airway management,4 and the PLMA has been reported as a rescue device after failed intubation during rapidsequence induction.5 We have previously compared the clinical performance of the PLMA and the LT in patients undergoing controlled ventilation under general anaesthesia.6 The present investigation compared the performance of the PLMA and LTS in a randomized controlled crossover manner. Primary outcome was airway seal pressure. Secondary outcomes {
Declaration of interest. T.M. Cook has received honoraria for lecturing from Intavent Orthofix and the Laryngeal Mask Company, the distributors of the ProSeal Laryngeal Mask Airway.
# The Board of Management and Trustees of the British Journal of Anaesthesia 2005. All rights reserved. For Permissions, please e-mail: [email protected]
Downloaded from http://bja.oxfordjournals.org/ at New York University on June 10, 2015
Background. The Laryngeal Tube Sonda (LTS) is a supraglottic airway which, like the ProSeal Laryngeal Mask Airway (PLMA), incorporates a drain tube. We compared the performances of LTS and PLMA during controlled ventilation anaesthesia.
Cook and Cranshaw
Pilot tube and balloon
15 mm connector Drain tube
Airway tube
Drain tube tip
Bite block
Cuff
Laryngeal tube
Distal cuff
Proximal cuff
15 mm connector
Drain tube
Pilot tube
Laryngeal tube sonda
Fig 2 The Laryngeal Tube Sonda .
included insertion success and time, manipulations required, ventilation quality, peak and plateau airway pressures, ability to pass a gastric tube, and fibreoptic laryngeal view.
Patients and methods The local research ethics committee approved the study and all patients gave written informed consent before taking part. Thirty-two patients (ASA I–III) undergoing elective surgery in the supine or lithotomy position, in whom neuromuscular blockade and the use of an LMA were appropriate, were recruited. Patients were excluded if they had any pathology of the neck, upper respiratory tract or upper alimentary tract, if they were at increased risk of pulmonary aspiration of gastric contents, if they weighed <50 kg or had a height <155 cm. Preoperatively the view of the oropharynx on mouth-opening was scored as described by Mallampati7 and modified by Samsoon and Young.8 Standard monitoring devices were attached before induction of anaesthesia. The patient’s head was supported on a firm pillow. After preoxygenation, anaesthesia was induced
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Fig 1 The Proseal Laryngeal Mask Airway.
with fentanyl 1 mg kg 1 and a target controlled infusion of propofol 4–7 mg ml 1, which was also used to maintain anaesthesia. Neuromuscular blockade was produced by rocuronium 0.6 mg kg 1 and was confirmed using a peripheral nerve stimulator (train-of-four count=0) before airway manipulation. The patients were then randomly allocated to one of the two groups using sequentially numbered sealed opaque envelopes naming the airway device to be evaluated first. The LTS was inserted following the manufacturer’s instructions. Before insertion, the cuff was deflated and a water-soluble lubricant (KY Jelly ) was applied. The patient’s head was extended on the neck (‘sniffing position’). Jaw thrust was used to assist airway placement in all cases. The tip of the LTS was placed against the hard palate behind the upper incisors and the device was advanced in the centre of the mouth until resistance was felt. If no resistance was felt the LTS was positioned with the second bold line on the tube between the upper and lower incisors. The cuffs were inflated using a cuff inflator (VBM, Germany) to an intracuff pressure of 80–90 cm H2O which was then reduced to 60–70 cm H2O.9 A size 4 LTS was used for patients of height 155–180 cm and a size 5 for those of height >180 cm.9 The PLMA was inserted according to the manufacturer’s instruction manual,10 but jaw thrust and a PLMA introducer were used to assist placement in all cases. The back of the cuff was lubricated with KY Jelly . A size 4 PLMA was used for females and a size 5 for males.11 The cuff was inflated using the same cuff inflator as the LTS until the intracuff pressure reached 60–70 cm H2O.10 If it was not possible to insert a device at the first attempt, one more attempt was made. If insertion was impossible after this attempt, study of that device was abandoned. The number of attempts required to insert a device was recorded and where insertion was abandoned this was also recorded. The time taken to insert a device from picking it up to attaching it to the breathing system was only recorded for devices that were successfully inserted and enabled initial ventilation. An initial assessment of ventilation was made after the device had been connected to the breathing system by gently squeezing the reservoir bag and observing end-tidal carbon dioxide waveforms and chest movements. If ventilation was difficult, attempts were made to improve the airway using a chin lift, jaw thrust, head extension or neck flexion manoeuvre. The LTS could also be gently pushed or pulled according to the manufacturer’s instructions.9 After each manoeuvre, adequacy of ventilation was reassessed. The device was tied in place if clinically adequate ventilation was achieved. However, if ventilation was inadequate after these manoeuvres, the device was withdrawn completely and reinserted. If it was still not possible to ventilate after reinsertion and further application of the allowed airway manoeuvres, study of the device was abandoned. Similarly, if airway obstruction occurred during maintenance
PLMA or LTS during controlled ventilation anaesthesia
At the end of the operation, neuromuscular paralysis was reversed, the target-controlled infusion of propofol was stopped, spontaneous ventilation was established and the device was left in place. The device was routinely removed after the patient regained consciousness and opened his or her mouth to command, but if necessary was removed before this point if necessitated by airway obstruction, coughing or retching. Before removal, the cuffs of the LTS were deflated, but the cuff of the PLMA was left inflated in accordance with the manufacturer’s recommendations.9 10 Complications, previously defined, were recorded for each phase of anaesthesia (establishing an airway, maintenance, removal and recovery).
Statistical analysis The primary aim of this study was to compare the seal pressures generated in the larynx by the PLMA and the LTS. The PLMA was considered as the ‘control’ group. Based on the results of our previous studies, the PLMA has a seal pressure of 29 cm H2O with a standard deviation of 5 cm H2O.1 6 Power analysis determined that a study of 32 patients had 80% power to detect a difference in airway seal pressure of 5 cm H2O. Secondary outcomes included success of insertion, number of manipulations and time required to achieve an airway, peak and plateau airway pressures during ‘optimal’ ventilation, manipulations and complications throughout anaesthesia, ability to pass a gastric tube successfully into the stomach through the drain port and the fibreoptic laryngeal view through the device. A Wilcoxon signed rank test was used to compare insertion times and airway seal, peak and plateau pressures, and the number of manipulations required in patients with the two devices. A x2-test or a Fischer exact test was used to compare the proportions of patients in whom first-time device insertion was successful, the proportion requiring further airway manipulation and the proportion in which it was possible to pass a gastric tube. A sign test was used to compare the number of manipulations required in patients with the LTS and PLMA and the difference in laryngoscopic grade through the two devices. A Mann– Whitney test was used to compare the number of complications occurring with each device. Paired tests were not used because, despite the crossover design of the study, even after insertion of the devices a number of failures in one group meant that to use paired tests would mean discarding a considerable amount of data from the group without failures; to do so would introduce bias. Statistical analysis was performed using the statistical package Analyse it! and Microsoft Excel v6.0.
Results The characteristics of the patients are presented in Table 1 and the results of the study are summarized in Table 2. By the nature of the study design, the insertion and initial
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of anaesthesia, the allowed airway manoeuvres and one reinsertion were permitted. If it was still not possible to ventilate after reinsertion and the allowed additional airway manoeuvres, study of the device was terminated. The number of manipulations and abandonment of each device after insertion and during maintenance of anaesthesia was recorded. The efficacy of the airway seal created by each device was determined after insertion and necessary manipulation by measuring the minimum airway pressure at which gas audibly leaked around it using a fresh gas flow of 5 litre min 1 with the adjustable pressure-limiting (APL) valve completely closed. Airway pressure was not permitted to exceed 40 cm H2O. Controlled mandatory ventilation with oxygen–air mixture was employed with a programmed inspiratory tidal volume of 7 ml kg 1. The ventilatory frequency was adjusted to maintain end-tidal carbon dioxide concentration in the normal range and was delivered with a fixed inspiratory: expiratory ratio of 1:2. If the expired tidal volume was measured as <7 ml kg 1, the programmed inspiratory tidal volume was increased to a maximum of 10 ml kg 1 until the measured expired tidal volume reached 7 ml kg 1. Ventilatory variables were kept the same when comparing the two devices in the same patient. The device was recorded as facilitating ‘optimal’ ventilation if adequate chest movement, an expired tidal volume of 7 ml kg 1, stable oxygenation and ‘square-wave’ capnography were all observed simultaneously and consistently. ‘Suboptimal ventilation’ was recorded if one of these standards was not maintained. Peak airway and plateau pressures were recorded in all patients in whom device insertion and lung ventilation were possible. Patients receiving clinically adequate ventilation and oxygenation were preoxygenated before the breathing system was briefly disconnected and a 4 mm fibrescope was inserted through the airway port of the device in use. The best view of the laryngopharynx was sought from the bowl of the PLMA or from either of the two orifices of the LTS before removing the fibrescope and replacing the breathing system. Views were graded from 1 to 4: 1=vocal cords entirely visible; 2=vocal cords or arytenoid cartilages partially visible; 3=epiglottis only visible; 4=no laryngeal structures visible.12 The second device was studied in an identical manner after the patient had been preoxygenated, neuromuscular paralysis confirmed (train-of-four count=0) and the first device had been removed. The second device, if successfully inserted and clinically adequate, was used for the duration of anaesthesia. If time allowed, a 16 French gauge gastric tube, lubricated with KY Jelly , was gently advanced through the oesophageal port of the device being used to maintain the airway intraoperatively. The gastric tube was inserted to 50 cm and aspirated or flushed with 5 ml of air to confirm gastric placement. One attempt was allowed and success or failure was recorded.
Cook and Cranshaw
Table 1 Patient characteristics. The results are given as absolute number of patients, median (range), or median (SD) Males:females Age (yr) Weight (kg) BMI Operation by surgical specialty General Urological Orthopaedic Gynaecological ASA I/II Mallampati class 1/2/3/4
17:15 41.5 (21–78) 70 (18.1) 25.5 (19.4–31.1) 11 11 4 14 3 13/9 20/15/4/0
Table 2 Results of the study. The results are presented as absolute number of patients or as median (range) *Unable to insert two LTS. {One LTS abandoned after insertion because of inability to establish a patent airway
Device insertion No. of patients Attempts (one/two/abandoned) No. of patients Insertion time (s) Patients requiring manipulations Total no. of manipulations Patients with complications Total no. of complications Initial ventilation No. of patients Airway seal pressure (cm H2O) Optimal/suboptimal/adequate Peak airway pressure (cm H2O) Plateau pressure (cm H2O) Fibreoptic laryngeal view (1/2/3/4) Ventilation during maintenance No. of patients Patients with complications Total no. of complications Patients requiring manipulations Total no. of manipulations Optimal/suboptimal/adequate/abandoned Gastric tube insertion attempts (1/2) During recovery No. of patients Patients with complications Total no. of complications
LTS
32 32 28/4/0 22/8/2 32 30* 12 (10–50) 18 (8–180) 4 10 4 18 2 13 2 22
P-value
>0.05 <0.01 <0.05 <0.05 <0.01 <0.01
32 26 (18–40) 32/0/0 14 (9–33) 11 (6–25) 25/7/0/0
29{ 24 (10–40) 22/4/3 16 (9–40) 12 (3–36) 6/3/7/13
<0.01 <0.01 <0.01 >0.05 <0.001
16 2 2 1 1 14/2/0/0 13/0
13 9 18 7 15 7/3/2/1 9/1
<0.01 <0.01 <0.05 <0.01 <0.01 >0.05
16 0 0
12 5 9
<0.05 <0.001
efficacy of each type of device was compared in all 32 patients and each device could have been used in 16 patients for the rest of the anaesthesia. Although the PLMA was studied from induction to emergence from anaesthesia in all 16 allocated patients, the LTS could only be studied during maintenance in 13 patients because of insertion failure in two patients and inability to establish a patent airway in one patient. The LTS had to be removed intraoperatively from one patient because of hypoxaemia. Therefore the LTS could only be studied in the recovery phase in 12 patients. On four occasions the LTS had to be removed and replaced because of cuff rupture recognized after insertion. The data from these insertion attempts were not included in the analysis. During insertion and establishment of the airway, the first insertion attempt was successful in 28 patients with the
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PLMA
PLMA and in 22 patients with the LTS (P>0.05). In two patients the LTS could not be inserted at all and in one case it was inserted but a clear airway could not be established. Insertion of the PLMA was ultimately successful in all 32 patients. After insertion of the LTS, a total of 22 complications, predominantly hypoxaemia and difficulty in establishing a patent airway, occurred in 13 patients. In comparison, after insertion of the PLMA, there were two complications in total (both difficulty establishing a patent airway, P<0.01) in only two patients (P<0.01). To obtain a clinically adequate airway after insertion, the PLMA required manipulation in four patients and the LTS in 10 patients (P<0.05). In total, 18 manoeuvres were performed in the patients with LTS and four manoeuvres in the patients with PLMA (P<0.05). The number of manipulations required in individual patients with the LTS was also greater (PLMA, median 1 [range 0–1]; LTS 1 [0–3]; P<0.01) as was the time required to obtain a clinically adequate airway (PLMA, 12 [10–50] s; LTS 18 [8–180] s; P<0.01). During initial ventilation, ‘optimal ventilation’ was achieved in all patients with the PLMA and 22 with the LTS (P<0.01). ‘Suboptimal ventilation’ was achieved with the LTS in four patients. The PLMA produced a higher seal pressure than the LTS (PLMA, 26 [18–40] cm H2O; LTS, 24 [10–40] cm H2O; P<0.01). The peak airway pressure with the PLMA was lower than with the LTS (PLMA, 14 [9–33] cm H2O; LTS, 16 [9–40] cm H2O; P<0.01). Plateau pressure was not significantly different (PLMA, 11 [6–23] cm H2O; LTS 12 [6–36] cm H2O; P>0.05). The vocal cords were visible in all cases through the PLMA and in nine cases through the LTS (P<0.01). Grade of laryngeal view was superior through the PLMA (PLMA: grade 1, 25; grade 2, 7; grade 3, 0; grade 4, 0; LTS: grade 1, 6; grade 2, 3; grade 3, 7; grade 4, 13; P<0.001). A gastric tube passed successfully on all 13 first attempts through the drain tube of the PLMA and on nine of 10 first attempts through the drain tube of the LTS (P>0.05). During maintenance of ventilation, partial or total obstruction meant that a total of 18 complications occurred in nine patients with the LTS and a total of two complications occurred in two patients with the PLMA (P<0.01). To manage the obstruction, 15 manoeuvres were required in seven patients with the LTS and one manoeuvre was required in a patient with PLMA (P<0.01). By the end of maintenance, seven patients had been ventilated ‘optimally’, three patients ‘suboptimally’ and three patients, at times, less than suboptimally with the LTS (one had to have the LTS replaced with a PLMA). With the PLMA, 14 patients had been ventilated ‘optimally’ and two patients at times ‘suboptimally’ (P<0.01). During recovery, nine complications, predominantly airway obstruction and hypoxaemia, occurred in five patients with the LTS. An adequate airway was lost in three patients and the device had to be removed prematurely. No recovery problems were encountered with the PLMA (Table 2).
PLMA or LTS during controlled ventilation anaesthesia
Discussion
the LT and LTS also differs; these factors may or may not account for apparent performance differences. During the recovery phase of anaesthesia, problems with partial obstruction and hypoxaemia occurred only in patients with the LTS (five of 12 patients [42%]). This observation is important, as both the LTS and the PLMA are specifically modified for positive-pressure ventilation. However, to be useful they must still accommodate spontaneous ventilation and the return of pharyngeal tone during emergence from anaesthesia. Complications at this time may occur in an environment where personnel highly skilled in airway management are not immediately available. The reasons for the marked differences between our findings and those of other investigators are not immediately obvious. Other anaesthetic protocols used bolus propofol for induction (2–3.2 mg kg 1), more opioid (fentanyl 3–4 mg kg 1, remifentanil 5 mg kg 1 min 1) and inhalational agents for maintenance. However, this should not account for differences between our findings and those of Gaitini and colleagues16 who also used monitored neuromuscular blockade. The characteristics of the patients, where stated by other investigators, appear to be similar to those in the present study but the surgery performed may have differed. None of the other studies were of a crossover design. We have considerable experience with both devices and it is unlikely that familiarity with one device is the sole explanation. Indeed, our insertion times and overall insertion success rates for each device were similar to those of other investigators. The LTS has two small airway orifices compared with a single large orifice in the PLMA. We were able to view the larynx from the PLMA in 100% of cases but from the LTS in only 31%. Thus resistance to gas flow through the LTS and through the pharynx might explain the higher peak airway pressures observed with the LTS. Although the numbers were small, there was a high success rate in passing a gastric tube via the oesophageal ports of both devices. These results are in keeping with those of other investigators.14–16 The ability to pass a gastric tube via the PLMA has been associated with partial or total visualization of the vocal cords.18 Complete success in passing a gastric tube in this study and the high rate of positioning of the PLMA orifice over the larynx support this association. In addition to proposed roles during anaesthesia, the LTS and the PLMA have suggested roles in airway rescue and emergency airway maintenance. In these circumstances desirable features of a supraglottic airway device are an ability to ventilate the lungs, drain the oesophagus and act as a conduit through which to intubate the trachea. Although both devices appear to be able to drain the oesophagus equally, our results would favour the use of a PLMA in an emergency. First, insertion and ventilation were more quickly and successfully achieved with the PLMA. Secondly, fibreoptic-guided intubation is only likely to be successful if the tube passes easily through the device and the larynx is visible. In our study, the larynx could be seen
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The primary outcome measure in this study was the airway seal pressure created by the two airway devices. The median airway seal pressure obtained with PLMA was 26 cm H2O and that with LTS was 24 cm H2O. This difference, although statistically significant, is unlikely to be clinically important and is less than the 5 cm H2O that the study was powered to detect. The range of seal pressures produced by the PLMA and LTS was comparable to those found by other investigators,13 14 although one investigator comparing the two devices (and allowing airway pressures to rise to 60 cm H2O) found seal pressures >45 cm H2O for both devices.15 However, we have found marked differences in clinical performance between the two devices. First-time insertion success (88% vs 69%), overall insertion success (100% vs 94%), initial provision of optimal ventilation (100% vs 73%) and overall abandonment rate (0% vs 19%) all favoured the PLMA. These differences were all statistically significant and are clinically relevant. In addition, the PLMA provided an effective airway in all patients in whom an LTS either could not be inserted or did not facilitate adequate ventilation. Three other groups of investigators have compared the LTS and the PLMA. One study is published,16 and the others are reported as abstracts.14 15 In these studies first-time insertion success was sometimes lower for the PLMA (76%) and higher for the LTS (80%)17 than in our study, but overall insertion success using two or three attempts was similar: 94–100% for the LTS13 14 16 and 93–100% for the PLMA.13 14 16 However, in contrast with our results, previous studies found broadly equivalent performance of the LTS and the PLMA with regard to ease of insertion and clinical performance. In our hands, the LTS was inserted less successfully, with more complications and a greater need for manipulation. The LTS also provided poorer quality ventilation. After insertion, only 69% of patients could be ventilated optimally with the LTS compared with 100% with the PLMA. During maintenance, ventilation with the LTS failed more often and led to more complications and manipulations. By the end of maintenance less than half the patients ventilated with the LTS had consistently received optimal ventilation and the decreasing performance of one device had necessitated removal. Only two patients had been ventilated suboptimally with the PLMA. Thus initial success with either device does not guarantee optimal ventilation under surgical conditions, but the reliability of the PLMA may be greater than that of the LTS. Some investigators have reported successful ventilation in all patients with each device,14 15 while others have recorded difficulties in 2–7% of patients with both devices.16 We have previously evaluated laryngeal tube (LT) performance and found it rather more successful than the LTS.6 17 The tip of the LTS differs quite considerably in design from that of the LT, and the configuration of the airway holes in
Cook and Cranshaw
Acknowledgement The LTS devices used in this study were provided by VBM, Medizintechnik, Germany free of charge.
References 1 Cook TM, Nolan JP, Verghese C et al. A randomized crossover comparison of the Pro-Seal with the classic laryngeal mask airway in unparalysed anaesthetized patients. Br J Anaesth 2002; 88: 527–33 2 Evans NR, Gardner SV, James MF. ProSeal Laryngeal Mask protects against aspiration of fluid in the pharynx. Br J Anaesth 2002; 88: 584–7 3 Brain AIJ, Verghese C, Strube PJ. The LMA ‘ProSeal’—a laryngeal mask with an oesophageal vent. Br J Anaesth 2000; 84: 650–4 4 Genzwuerker HV, Finteis T, Hinkelbein J, Kreiter H. The LTS (Laryngeal Tube Sonda) a new device for emergency airway management. Scand J Trauma Emerg Med 2003; 11: 125–31 5 Awan R, Nolan J, Cook TM. Use of the ProSeal LMA for airway maintenance during emergency Caesarean section after failed intubation. Br J Anaesth 2004; 92: 144–6
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6 Cook TM, McKinstry C, Hardy R, Twigg S. Randomized crossover comparison of the ProSeal laryngeal mask airway with the Laryngeal Tube during anaesthesia with controlled ventilation. Br J Anaesth 2003; 91: 678–83 7 Mallampati SR, Gatt SP, Gugino LD et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J 1985; 32: 429–34 8 Samsoon GLT, Young JRB. Difficult tracheal intubation: a retrospective study. Anaesthesia 1987; 42: 487–90 9 Laryngeal Tube Sonda Instructions. Sulz, Germany: VBM GmBH, 2000 10 Laryngeal Mask Airway ProSeal Instruction Manual. Maidenhead, UK: Intavent Ltd, 2002 11 Kihara S, Brimacombe J, Yaguchi Y, Taguchi N, Watanabe S. A comparison of gender and weight-based ProSealTM laryngeal mask size selection criteria: a randomised study of healthy anesthetized, paralysed adult patients. Anesthesiology 2004; 94: 1023–7 12 Verghese C, Berlet J, Kapila A, Pollard R. Clinical assessment of the single use laryngeal mask airway—the LMA-Unique. Br J Anaesth 1998; 80: 677–9 13 Cartensen S, Bein B, Claus L, Steinfath M, Do¨rges V. ProSeal Laryngeal Mask Airway and Laryngeal Tube S—modified airway devices for lung ventilation and gastric drainage. Anesthesiology 2003; 99: A-1257 (abstract) 14 Do¨rges V, Carstensen S, Bein B, Claus L, Steinfath M. The newly developed Laryngeal Tube S—a comparison with the Combitube during routine surgical procedures Anesthesiology 2003; 99: A-1243 (abstract) 15 Genzwurker HV, Roth H, Rothhaas A, Finteis T, Schmeck J. Comparison of LMA-Proseal and LTS for ventilation during laparoscopic gynaecological surgery. Anesthesiology 2003; 99: A-1194 (abstract) 16 Gaitini LA, Vaida SJ, Somri M, Yanovski B, Ben-David B, Hagberg CA. A randomized controlled trial comparing the ProSeal Laryngeal Mask Airway with the Laryngeal Tube Suction in mechanically ventilated patients. Anesthesiology 2004; 101: 316– 20 17 Cook TM, McCormick B, Asai T. Randomized comparison of laryngeal tube with classic laryngeal mask airway for anaesthesia with controlled ventilation. Br J Anaesth 2003; 91: 373–8 18 Agro F, Antonelli S, Cataldo R, Mentecchia F, Barzoi G, Pettiti T. The Proseal Laryngeal mask airway: fibreoptic vizualisation of the glottic opening is associated with ease of insertion of the gastric tube. Can J Anaesth 2002: 49: 867–70
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through the PLMA in all cases, but through an adequately functioning LTS in only 31% of cases. Gaitini and colleagues16 saw the vocal cords in 96% of cases through the PLMA but in only 89% through the LTS.16 The largest tracheal tube that can be passed through an LTS is 4.5 mm compared with 6.0 mm with a PLMA. We suggest, on the basis of our results, that the PLMA may be a more reliable airway than the LTS when subsequent access to the trachea might be desirable. In summary, the LTS and PLMA performed equally well in measures of laryngeal seal pressure and ability to drain the stomach (design features central to both devices). However, the quality of airway maintenance and the ability to ventilate the patient’s lungs via the LTS was inferior to that via the PLMA. The PLMA also afforded a more reliable and better view of the larynx. We conclude that the PLMA is likely to be a more useful device than the LTS for routine anaesthesia requiring controlled ventilation.