The Classic laryngeal mask airway (LMA), introduced in 1985, is well established for airway management when endotracheal intubation is not required [1,2]. The use is limited by the potential risk of aspiration especially due to gastric insufflation [3-5]. To avoid gastric insufflation and aspiration, the ProSeal™ Laryngeal Mask Airway (PLMA, Laryngeal Mask Company, Henley-on-Thames, UK), featuring an extra lumen for gastric drainage and a modified cuff for better airway seal than the standard LMA, was introduced in 2000 (Fig. 1) [6-8]. For positive pressure ventilation during laparoscopic cholecystectomy, it was found to be a more effective ventilatory device when compared with the Classic LMA . Simultaneously, a new supraglottic device with a pharyngeal and an oesophageal cuff, the laryngeal tube (LT), was developed . Recent studies comparing both devices (LMA or PLMA vs. LT) showed heterogeneous results concerning handling and performance of the devices [11-13]. Recently, a new LT with an extra lumen for gastric drainage, the Laryngeal Tube Suction (LTS, VBM Medizintechnik GmbH, Sulz am Neckar, Germany), was introduced [14,15]. With the head in neutral position, the tube is placed into the oropharynx until a resistance is noticed. Through a single port both cuffs (proximal and distal) are inflated (Fig. 1).
The two devices featuring an extra lumen for gastric drainage, PLMA and the new LTS, were compared for positive pressure ventilation in elective gynecological laparoscopic surgery. We hypothetized that there were no differences in handling (insertion attempts, time of insertion), quality of airway seal (leak pressure, incidence of gastric insufflation or regurgitation), ventilatory parameters (airway pressures, expiratory tidal volumes) and postoperative laryngeal discomfort between the two devices.
With institutional Ethics Committee approval and written, informed consent, 50 female patients (ASA I-II, aged 22-56 yr) undergoing elective gynaecological laparoscopic surgery, were randomly allocated (by opening a sealed envelope) for airway management and positive-pressure ventilation with PLMA or LTS. The patient characteristics are summarized in Table 1. Patients were excluded if their mouth opening was less than 2.5 cm, their body mass index (BMI) exceeded 35 kg m−2 or if they were at risk of aspiration (history of gastro-oesophageal reflux, non-fasted).
In the anaesthetic room patients were attached to routine monitoring with electrocardiogram, pulse oximeter and non-invasive blood pressure (BP), and the baseline data were recorded. A standard anaesthesia protocol was followed with the patient in a supine position, head on a standard pillow. After preoxygenation by breathing oxygen through a face mask for at least 3 min, anaesthesia was induced with fentanyl 3 μg kg−1 and propofol 3 mg kg−1. Maintenance was with 2-3% sevoflurane in 60% oxygen and air. Neuromuscular blockade was achieved after insertion of the airway device for the surgical procedure with rocuronium 0.4 mg kg−1.
According to the preoperative randomization, a PLMA or LTS (size 3, 4 or 5 according to the patients anatomy and manufacturer's instructions) was inserted by two anaesthetists experienced with both devices (>20 uses each). Before insertion, a water-soluble lubricant was applied on the cuffs and especially the lumen for the gastric tube. The cuffs were fully deflated and neck flexion/head extension performed to facilitate insertion of both devices. The introducer tool was not used with the PLMA to allow better comparison of the devices. After successful insertion, cuffs were inflated with a syringe with the maximum volumes recommended in the manufacturer's instructions and PLMA and LTS were connected to a circle breathing system. Correct position of the device was verified by auscultation over both, lungs and stomach, bilateral chest excursions and registration of a square-wave capnograph trace during manual ventilation. In addition, a drop of the clear, water-based gel used for lubrification was placed at the proximal end of the drain tube of both devices. Ejection of the gel during ventilation was considered as a sign of incomplete separation of airway and alimentary tract. In case of incorrect position, the device was removed and introduced in a second attempt. After two failed attempts, orotracheal intubation was to be performed. Time from discontinuing face mask ventilation until delivery of the first tidal volume in correct position was recorded.
The airway leak pressure was measured once an effective airway had been established and after adjustment of cuff pressures to 60 cmH2O using a cuff pressure gauge (cuff deflation in all patients). The head was placed in neutral position. The expiratory valve of the circle system was closed at a fixed gas flow of 3L min−1. The airway pressure at which the manometer reached equilibrium was recorded . The location of the gas leak was determined by listening for audible sound of gas escaping with the ear close to the mouth, auscultation over the epigastrium (audible sound of gas escaping into the oesophagus), and watching for bubbling or movement of the lubricant placed on the proximal end of the drainage tube of the devices. To avoid barotrauma, peak airway pressure was limited to 50 cmH2O.
In both groups, insertion of a 14-G gastric tube was attempted if there was no gas leak during ventilation. Correct position was controlled by injection of 10 mL of air during epigastic auscultation. Air and gastric fluid, if present, were aspirated thereafter. The gastric tube was left in place during the complete duration of the surgical procedure and removed at the end of anaesthesia. Failure to place a gastric tube was considered a reason for tracheal intubation.
Patients were ventilated with a tidal volume of 9 mL kg−1, a respiratory rate of 10 min−1, and an inspiratory/expiratory ratio of 1: 1.7. Resulting airway pressures were recorded before and after capnoperitoneum. Tidal volume was adjusted to reach an end-tidal carbon dioxide (CO2) level of 35 mmHg. The inspired oxygen concentration was adjusted when necessary to maintain SPO2 >95%. If oxygenation or ventilation failed during the procedure, the gas was to be released from the abdominal cavity and the trachea was to be intubated using a laryngoscope. The surgeon was to report any signs of gastric insufflation noted during laparoscopy. Intra-abdominal gas pressure was limited to 18 cmH2O, a Trendelenburg position with a maximum angle of 15° was used during laparoscopy.
After removing the airway devices, they were closely inspected for traces of gastric fluid or blood, respectively. Duration of anaesthesia and surgical procedure were recorded. Any adverse events (regurgitation, aspiration, bronchospasm, laryngospasm) were documented. Patients were monitored in the post-anaesthesia care unit for a minimum of 1 h. Six and 24 h after the end of anaesthesia patients were questioned for sore throat or dysphagia using a 10-point visual analogue scale (VAS).
Mann-Whitney U-test was used for the comparison of the groups. Fisher's exact test was used for the comparison of dichotomous variables between the groups. Paired t-test was used for comparison of repeated measurements (peak airway pressure, SaO2). Data are mean (standard deviation (SD); range) or number of patients unless stated otherwise. Significance was taken as P < 0.05.
The mean age, height and weight for the PLMA and LTS groups were similar. No difference in BMI was found (Table 1). Duration of surgery (PLMA 66 (±37; 15-180) min; LTS 45 (±34; 30-200) min) and anaesthesia (PLMA 92 (±42; 30-220) min; LTS 80 (±39; 45-250) min) differed between the two groups but lay within an acceptable range. Baseline heart rate (HR), systolic BP and oxygen saturation showed no difference between both groups (Table 1).
Both PLMA and LTS had an equal high success rate of insertion in the first attempt (92%, Table 2), a second attempt was necessary in 2 of 25 patients in each group (8%). There was no case of failed insertion after two insertion attempts. The time required for insertion was comparable for PLMA (23.2 (±6.1; 12-41) s) and LTS (23.5 (±6.6; 15-42) s).
The airway leak pressure was comparable for both devices (PLMA 45.4 (±4.9; 32-50) cmH2O vs. LTS 45.6 (±6.7; 30-50) cmH2O). Air leak into the mouth occurred in 14 of 25 patients in the PLMA group and in 10 of 25 patients in the LTS group. No air leak into the drain tube or into the oesophagus could be detected. In 11 of 25 patients in the PLMA group and in 15 of 25 patients in the LTS group, no air leak could be detected with the maximum airway pressure of 50 cmH2O allowed in this investigation.
A significant increase in peak airway pressure after induction of capnoperitoneum when compared to baseline values was found in both groups (P < 0.001, Table 3). Ventilation was not impaired and considered optimal in all patients of both groups before and after capnoperitoneum.
Gastric tube placement was successful in all patients of the PLMA and LTS group. Fluid was detected in 19 of 25 patients in the PLMA group (9 clear fluid, 10 bile-stained fluid) and in 21 of 25 patients in the LTS group (12 clear fluid, 9 bile-stained fluid). Fluid detection at the end of anaesthesia showed comparable results in both groups with fluid present in 21 of 25 PLMA patients and 20 of 25 LTS patients.
Ventilation was possible during the complete procedures with both devices without signs of gastric insufflation. No signs of regurgitation could be detected by inspection of the devices after removal, no other adverse events occurred in either group. Blood attachment on the airway device was visible in four patients of each group.
Laryngeal discomfort after removing the devices was infrequent and mild (Table 4). In the PLMA group, sore throat was found 6 h after the end of anaesthesia in one patient (VAS 2 of 10) and 24 h after the end of anaesthesia in zero patients. In the LTS group, two patients complained of sore throat 6 h after the end of anaesthesia (VAS 2.5 of 10) and one patient 24 h after the end of anaesthesia (VAS 1 of 10). Dysphagia was stated 6/24 h after the end of anaesthesia by 1/1 patient in the PLMA group and by 3/1 patients in the LTS group.
The use of supraglottic airway devices under conditions of elevated intra-abdominal pressure requires an excellent airway seal to divide respiratory and alimentary tract in a reliable manner due to the potential risk of regurgitation. Additionally, an easy access for gastric drainage is desirable. While Lu and colleagues  showed that the PLMA was superior to the LMA during laparoscopic surgery, the latter without access to the stomach, our study compares two devices allowing drainage of gastric contents, the PLMA and the newly developed LTS. First preliminary reports are available but the airway devices were not compared for ventilation during capnoperitoneum [17,18].
In contrast to former studies comparing PLMA and LT  or LMA and LT , we could not detect any marked differences concerning handling. Time for insertion was similar for both devices and only in two patients of each group a second attempt for placement was necessary (Table 2). This might be in part contributed to the fact that the investigators possessed sufficient experience with the use of the standard devices LT and the LMA-Classic™ as well as the LTS and PLMA in clinical routine before start of the trial. Quality of airway seal, represented by airway leak pressure in absence of signs of oral or gastric gas loss, was excellent for both devices (average > 45 cmH2O for PLMA and LTS). The average difference between airway leak pressure and peak airway pressure during capnoperitoneum (mean > 23 cmH2O) for both devices (Table 3) may be considered as a broad estimate of the safety margin offered by these new improved supraglottic airway devices.
In all patients, insertion of a gastric tube was successful, but there was a need for previous lubrification of both gastric tube and drain tube with the 14-G gastric tubes used. We moved the gastric tube through the lubrificated lumen of the device used a few times before insertion to facilitate the later placement of the gastric tube. The fact that gastric fluid was detected in a majority of patients supports the importance of gastric access in the patient collective studied.
Peak airway pressure, significantly increasing with capnoperitoneum in both groups, showed no difference between the devices. Since there were also no differences in tidal volume and respiratory rate, the airway resistance of both PLMA and LTS can be considered comparable.
The data concerning laryngeal discomfort showed no differences between the two devices, with only a trend to less complaints with the PLMA. The overall low rate of complaints of only a mild degree may be explained by the consequent limitation of cuff pressures to a maximum of 60 cmH2O as recommended by both manufacturers . In light of the few patients who stated postoperative complaints, a larger sample size may be necessary to detect or rule out differences between the devices as far as patient comfort is concerned.
Both devices are reusable: the PLMA 40 times, the LTS 50 times as stated by the manufacturers. While the thinner cuff of the LTS seems to be more vulnerable when compared to the PLMA, it remains unclear if this leads to a higher rate of damage in clinical routine use. In our trial, all devices were used repeatedly and sterilized and autoclaved between uses following manufacturer recommendations and institutional guidelines.
We conclude that both PLMA and LTS are easy to insert and provide a secure airway rapidly. Our results are supported by recent reports by other groups who compared the devices for surgical interventions without capnoperitoneum [17,18]. During anaesthesia with elevated intra-abdominal pressure due to capnoperitoneum in a supine Trendelenburg position, we found that ventilation with both PLMA and LTS was successful in all patients studied.
The supraglottic airway devices used in this study were provided by LMA-Vertriebs GmbH, Windhagen, Germany (PLMA) and VBM Medizintechnik GmbH, Sulz am Neckar, Germany (LTS). No further financial support was received for the study or the preparation of the manuscript.
1. Brain AI, McGhee TD, McAteer EJ, Thomas A, Abu-Saad MA, Bushman JA. The laryngeal mask airway
. Development and preliminary trials of a new type of airway. Anaesthesia
2. Verghese C, Brimacombe JR. Survey of laryngeal mask airway
usage in 11,910 patients: safety and efficacy for conventional and nonconventional useage. Anesth Analg
3. Weiler N, Latorre F, Eberle B, Goedecke R, Heinrichs W. Respiratory mechanics, gastric insufflation pressure, and air leakage of the laryngeal mask airway
. Anesth Analg
4. Barker P, Langton JA, Murphy PJ, Rowbotham DJ. Regurgitation of gastric contents during general anesthesia using the laryngeal mask airway
. Br J Anaesth
5. Brimacombe JR, Berry A. The incidence of aspiration associated with the laryngeal mask airway
: a meta-analysis of published literature. J Clin Anesth
6. Brain AI, Verghese C, Strube PJ. The LMA ‘ProSeal’ - a laryngeal mask with an oesophageal vent. Br J Anaesth
7. Brimacombe J, Keller C. The ProSeal laryngeal mask airway
: a randomized, crossover study with the standard laryngeal mask airway
in paralyzed, anesthetized patients. Anesthesiology
8. Brimacombe J, Keller C. Stability of the LMA-ProSeal and standard laryngeal mask airway
in different head and neck positions: a randomized crossover study. Eur J Anaesthesiol
9. Lu PP, Brimacombe J, Yang C, Shyr M. ProSeal versus the Classic laryngeal mask airway
for positive pressure ventilation during laparoscopic cholecystectomy. Br J Anaesth
10. Dörges V, Ocker H, Wenzel V, Schmucker P. The laryngeal tube
: a new simply airway device. Anesth Analg
11. Asai T, Kawashima A, Hidaka I, Kawachi S. The laryngeal tube
compared with the laryngeal mask: insertion, gas leak pressure and gastric insufflation. Br J Anaesth
12. Ocker H, Wenzel V, Schmucker P, Steinfath M, Dörges V. A comparison of the laryngeal tube
with the laryngeal mask airway
during routine surgical procedures. Anesth Analg
13. Figueredo E, Martinez M, Pintanel T. A comparison of the ProSeal laryngeal mask and the laryngeal tube
in spontaneously breathing anesthetized patients. Anesth Analg
14. Dörges V, Ocker H, Wenzel V, Steinfath M, Gerlach K. The Laryngeal Tube
S: a modified simple airway device. Anesth Analg
15. Genzwürker H, Finteis T, Hinkelbein J, Ellinger K. First clinical experiences with the new LTS. A laryngeal tube
with an oesophageal drain. Anaesthesist
16. Keller C, Brimacombe JR, Keller K, Morris R. Comparison of four methods for assessing airway sealing pressure with the laryngeal mask airway
in adult patients. Br J Anaesth
17. Gaitini LA, Vaida SJ, Somri M, Ben-David B, Hagberg CA. A randomized controlled trial comparing the Proseal Laryngeal Mask Airway
with the Sonda Laryngeal Tube
in mechanically ventilated patients. Anesthesiology
18. Carstensen S, Bein B, Claus L, Steinfath M, Dörges V. ProSeal Laryngeal Mask Airway
and Laryngeal Tube
S - modified airway devices for lung ventilation and gastric drainage. Anesthesiology
19. Matioc AA, Arndt G. The laryngeal tube
and pharyngeal mucosal pressure. Can J Anaesth
*Results were presented in part as a poster at the 2003 Annual Meeting of the American Society of Anesthesiologists in San Francisco, USA, 12-15 October 2003.