Airway Leak Pressure Research Articles

Exposure to anaesthetic trace gases during general anaesthesia: CobraPLA vs. LMA classic

To prospectively investigate the performance, sealing capacity and operating room (OR) staff exposure to waste anaesthetic gases during the use of the Cobra perilaryngeal airway (CobraPLA) compared with the laryngeal mask airway classic (LMA). Sixty patients were randomly assigned to the CobraPLA or the LMA group. Insertion time, number of insertion attempts and airway leak pressures were assessed after induction of anaesthesia. Occupational exposure to nitrous oxide (N(2)O) and Sevoflurane (SEV) was measured at the anaesthetists' breathing zone and the patients' mouth using a photoacoustic infrared spectrometer. N(2)O waste gas concentrations differed significantly in the anaesthetist's breathing zone (11.7+/-7.2 p.p.m. in CobraPLA vs. 4.1+/-4.3 p.p.m. in LMA, P=0.03), whereas no difference could be shown in SEV concentrations. Correct CobraPLA positioning was possible in 28 out of 30 patients (more than one attempt necessary in five patients). Correct positioning of the LMA classic was possible in all 30 patients (more than one attempt in three patients). Peak airway pressure was higher in the CobraPLA group (16+/-3 vs. 14+/-2 cmH(2)O, P=0.01). The average leak pressure of the CobraPLA was 24+/-4 cmH(2)O, compared with 20+/-4 cmH(2)O of the LMA classic (P<0.001; all values means+/-SD). Despite higher airway seal pressures, the CobraPLA caused higher intraoperative N(2)O trace concentrations in the anaesthetists' breathing zone.

Disposable Versus Reusable Laryngeal Tube Suction for Ventilation in Patients Undergoing Laparoscopic Cholecystectomy

The laryngeal tube suction II (LTS-II) is a recent version of reusable supraglottic airway devices allowing gastric drainage. In this prospective, randomized study we compared insertion and ventilation of disposable LTS-II (LTS-D) with reusable type (LTS-II) for airway management under conditions with elevated intra abdominal pressure induced by capnoperitoneum. 60 ASA I and II patients undergoing elective laparoscopic cholecystectomy were randomized to receive either a LTS-D (n=30) or LTS-II (n=30) for airway management. After induction of general anaesthesia the devices were inserted, their correct placement was verified and airway leak pressure was measured. Ease of insertion, quality of airway seal, fiberoptic view, risk of gastric insufflation, insertion of nasogastric tube and postoperative pharyngeal morbidity were examined. First time and second time success rates were comparable for both groups (86% vs. 93% and 96% vs. 96% in LTS-D and LTS-II groups, respectively). One patient in each group could not be intubated after three attempts. After gas insufflation, ventilation of one patient in LTS-D and 2 patients in LTS-II groups was faulty and the patients were intubated with endotracheal tube. Time until delivery of first tidal volume for LTS-D and LTS-II was 20.8 +/- 11.6 s, and 18.2 +/- 4.8 seconds respectively (p = 0.27), fixation and manipulation time was 73.3 +/- 18.5 and 65.5 +/- 16.2 seconds, respectively (p = 0.096). Nasogastric tube insertion was successful in all patients. There were no significant differences in postoperative complaints. Both devices provide a secure airway under conditions of elevated intra abdominal pressure.

Randomized crossover comparison between the i-gel and the LMA-Unique in anaesthetized, paralysed adults

The i-gel differs from other supraglottic airway devices, in that it has a softer, non-inflatable cuff. This study was designed to compare the performance of the i-gel and the LMA-Unique (LMA-U) when used during anaesthesia in paralysed patients. Both devices were studied in 39 anaesthetized, paralysed patients in a randomized crossover trial. The primary outcome was airway leak pressure. Secondary outcomes included time to insertion, the number of insertion and reposition attempts, leak volumes, and leak fractions. There was no significant difference between the airway leak pressures of the two devices [median (IQR) leak pressures 25 (22-30) vs 22 (20-28) cm H(2)O for the i-gel and LMA-U, respectively; P=0.083, 95% CI of the mean difference -0.32 to 4.88 cm H(2)O]. The median (IQR) insertion time for the i-gel was significantly less than for the LMA-U [12.2 (9.7-14.3) vs 15.2 (13.2-17.3) s; P=0.007]. All the LMA-U devices and 38 of 39 i-gel airways were inserted at the first attempt. The number of manipulations required after insertion to achieve a clear airway was the same in both the groups (four in each). There were no statistically significant differences in leak volumes or leak fractions during controlled ventilation. We found no difference in leak pressures and success rate of first-time insertion between the i-gel and the LMA-U. Time to successful insertion was significantly shorter for the i-gel. We conclude that the i-gel provides a reasonable alternative to the LMA-U for controlled ventilation during anaesthesia.

Supreme! Or is it?

We would like to congratulate Dr Cook et al. on an excellent study [1]. Having a degree of experience in using LMA Supreme™ (SLMA, Intavent Orthofix, Maidenhead, UK), we would like to add some comments. We use the SMLA for selective patient groups and specific surgery, for example, dacrocystorhinostomy where we use total intravenous anaesthesia and ventilate the lungs via the single-use SMLA. Due to the nature of the surgery there is nasopharyngeal bleeding and blood trickles into the oropharynx. In these cases the perceived advantages of the SLMA are better airway protection from nasopharyngeal bleeding, the achievement of higher airway leak pressure during positive pressure ventilation and the option to pass a gastric tube via the drain tube to aspirate blood from the stomach. After reading Cook et al’s paper, however, we feel that we may need to re-assess our practice. Reasons for this include, firstly, their finding that airway leak pressure was no higher that that achieved with i-gel™ (Intersurgical, Wokingham, UK) in a similar study [2] and does not achieve levels seen with Pro-seal™ LMA (PLMA; Intavent Orthofix, Maidenhead, UK) [3]. Importantly, in the i-gel study only size 4 was used in all patients (weight range 42–113 kg), although no data were presented on how many of these were outside the manufacturer’s recommended weight range of 40–90 kg for this size. In this study the SLMA was sized appropriately and despite this, faired no better than the i-gel. As the study mentioned, the other two clinical studies of the SLMA reported a higher airway leak pressure of 28 cmH2O [4] and 37 cmH2O [5], but both were much smaller studies. Consequently, it seems that the SLMA does not confer any advantages over its direct competitors in this respect. Secondly, it is well recognised that an ideal supraglottic airway device provides access to the glottis so that an tracheal tube, Aintree catheter or a bronchoscope with a loaded tracheal tube could be passed into the trachea. Due to its design the SLMA is unable to achieve this and therefore, in our opinion, this gives its direct competitors an advantage. Moreover, it is fairly rigid and anatomically preformed, which possibly facilitates introduction in normal airways, but in fixed flexed neck deformities where one might use a supraglottic airway device, it may be very difficult or impossible to introduce into the mouth. Again, in our opinion, its direct competitors would fair better in this respect. Finally, the ability to pass a gastric tube into the stomach is a useful feature. The SLMA has this ability, with similar success rates to other devices; however even here it fairs no better than the PLMA as the drain tube only allows the passage of a smaller gastric tube (14 Fr vs 16 Fr), but it is larger than the i-gel allows (drain tube size 12 Fr for size 4). Although it seems reasonable to suggest that the drain tube size could play a major role in preventing aspiration in cases of regurgitation, there are no data to confirm it to date. To conclude, after reading this paper we now think that the SLMA falls in between the PLMA and the i-gel as a choice of supraglottic airway device. Which device should we choose? Perhaps now we would choose to use one or the other over the SLMA in most clinical situations, as there are no proven benefits of it over the other two and at least some theoretical drawbacks. Of course, we are happy to be proved wrong by further research.

A comparison of the i‐gel™ with the LMA‐Unique™ in non‐paralysed anaesthetised adult patients

This study assessed two disposable devices; the newly developed supraglottic airway device i-gel and the LMA-Unique in routine clinical practice. Eighty patients (ASA 1-3) undergoing minor routine gynaecologic surgery were randomly allocated to have an i-gel (n = 40) or LMA-Unique (n = 40) inserted. Oxygen saturation, end-tidal carbon dioxide, tidal volume and peak airway pressure were recorded, as well as time of insertion, airway leak pressure, postoperative sore-throat, dysphonia and dysphagia for each device. Time of insertion was comparable with the i-gel and LMA-Unique. There was no failure in the i-gel group and one failure in the LMA-Unique group. Ventilation and oxygenation were similar between devices. Mean airway pressure was comparable with both devices, whereas airway leak pressure was significantly higher (p < 0.0001) in the i-gel group (mean 29 cmH(2)O, range 24-40) compared with the LMA-Unique group (mean 18 cmH(2)O, range 6-30). Fibreoptic score of the position of the devices was significantly better in the i-gel group. Post-operative sore-throat and dysphagia were comparable with both devices. Both devices appeared to be simple alternatives to secure the airway. Significantly higher airway leak pressure suggests that the i-gel may be advantageous in this respect.

Laryngeal tube S II, ProSeal laryngeal mask, and EasyTube during elective surgery: a randomized controlled comparison with the endotracheal tube in nontrained professionals

EasyTube (EZT), ProSeal laryngeal mask airway (PLMA), and Laryngeal tube S II (LTS II) have recently been introduced as supraglottic airway devices and have been proposed as emergency airway alternatives. The purpose of this study was to compare the performance of the three devices, if used by anaesthesiologists without extensive hands-on training, with the endotracheal tube during routine surgical procedures. After informed consent, 88 ASA I-II patients scheduled for routine minor surgery were randomly allocated to EZT (n=22), PLMA (n=22), and LTS II (n=22) groups and the endotracheal tube (n=22) group, respectively. Overall success rates, insertion times, cuff pressures, and resulting airway leak pressures as well as subjective assessment of handling were determined. Overall insertion success rate of the EZT, PLMA, LTS II, and endotracheal tube was 14 out of 22 (64%), 20 out of 22 (91%), 21 out of 22 (96%), and 21 out of 22 (96%), respectively. Time to first successful ventilation with the EZT was significantly (P<0.05) longer than that with PLMA, LTS II, and endotracheal tube [median (minimum-maximum): 56 (27-150), 25 (12-70), 24 (11-150), and 20 (8-74) s, respectively]. The lowest airway leak pressure could be observed with the EZT [median (minimum-maximum), 19 (9-40) cmH2O] and the highest airway leak pressure with the LTS II [median (minimum-maximum), 40 (22-40) cmH2O]. Subjective assessment of handling was significantly (P<0.05) poorer in the EZT group compared with PLMA, LTS II, and endotracheal tube groups, respectively. In contrast to the EZT, both PLMA and LTS II proved to be suitable for routine airway management by anaesthesiologists without extensive hands-on device training.

Crossover Comparison of the Laryngeal Mask Supreme™ and the i-gel™ in Simulated Difficult Airway Scenario in Anesthetized Patients

The single-use supraglottic airway devices LMA-Supreme (LMA-S; Laryngeal Mask Company, Henley-on-Thames, United Kingdom) and i-gel (Intersurgical Ltd, Wokingham, Berkshire, United Kingdom) have a second tube for gastric tube insertion. Only the LMA-S has an inflatable cuff. They have the same clinical indications and might be useful for difficult airway management. This prospective, crossover, randomized controlled trial was performed in a simulated difficult airway scenario using an extrication collar limiting mouth opening and neck movement. Sixty patients were included. Both devices were placed in random order in each patient. Primary outcome was overall success rate. Other measurements were time to successful ventilation, airway leak pressure, fiberoptic glottic view, and adverse events. Success rate for the LMA-S was 95% versus 93% for the i-gel (P = 1.000). LMA-S needed shorter insertion time (34 +/- 12 s vs. 42 +/- 23 s, P = 0.024). Tidal volumes and airway leak pressure were similar (LMA-S 26 +/- 8 cm H20; i-gel 27 +/- 9 cm H20; P = 0.441). Fiberoptic view through the i-gel showed less epiglottic downfolding. Overall agreement in insertion outcome was 54 (successes) and 1 (failure) or 55 (92%) of 60 patients. The difference in success rate was 1.7% (95% CI -11.3% to 7.6%). Both airway devices had similar insertion success and clinical performance in the simulated difficult airway situation. The authors found less epiglottic downfolding and better fiberoptic view but longer insertion time with the i-gel. Our study shows that both devices are feasible for emergency airway management in patients with reduced neck movement and limited mouth opening.

Evaluation of the LMA Supreme™ in 100 non‐paralysed patients*

We studied the LMA Supreme in 100 elective, anaesthetised, healthy patients assessing: ease of use, airway quality, anatomical and functional positioning, airway leak and complications. Insertion was successful on first, second or third attempt in 90, nine and one patient respectively. Thirty manipulations were required in 22 patients to achieve a clear airway. Median [interquartile (range)] insertion time was 18 [10-25 (5-120)] s. During ventilation, an expired tidal volume of 7 ml x kg(-1) was achieved in all patients. Median [interquartile (range)] airway leak pressure was 24 [20-28 (13-40)] cmH(2)O. On fibreoptic examination via the device, vocal cords were visible in 83 patients (85%). During maintenance, five patients (5%) required 13 airway manipulations. There was one episode of minor regurgitation, without aspiration. Other complications and patient side-effects were mild and few. The LMA Supreme is easily and rapidly inserted, providing a reliable airway and good airway seal. Further studies are indicated to assess safety and performance compared to other supraglottic airway devices.

Use of ProSeal™ Laryngeal Mask Airway in 2114 Adult Patients: A Prospective Study

There have been numerous studies published on the ProSeal laryngeal mask airway (PLMA). However, few have investigated its utility in a large practice setting. We sought to gather comprehensive data about the characteristics, efficacy, and safety of its use by a representative group of anesthesiologists working at a teaching center. Information was collected on a standardized data collection form. Clinical information obtained included user characteristics, patient characteristics, type and duration of operation, details of airway management and anesthetic technique, details of adverse events, and postoperative status of the patient. Use of the PLMA was documented in 2114 patients by 81 anesthesiologists (57% trainee, 43% staff grade). The insertion success rate was 99% within a maximum of 3 attempts. Mean airway leak pressure was 28 (11-40) cm H(2)O. In 3.2% of cases, the PLMA was abandoned in favor of the endotracheal tube. Ventilation was controlled in 98%. Clinically "relevant" adverse events were recorded in 3.3% of all cases, of which 0.6% were classified as "serious." No long-term adverse sequelae resulted. No signs of aspiration were found in 12 patients with apparent regurgitation of gastric fluid through the drain tube of the PLMA. Five cases of difficult ventilation and 16 cases of difficult endotracheal intubation were successfully managed by the use of the PLMA. This study demonstrates that airway management using the PLMA is safe and effective in a general practice setting. The results support the assumption that a correctly positioned PLMA can protect from pulmonary aspiration of regurgitate gastric fluid. The data also support use of the PLMA for the management of the difficult airway.

Evaluation of the size 4 i‐gel™ airway in one hundred non‐paralysed patients*

We studied the i-gel in 100 elective, anaesthetised patients (55:45 male:female, median age 53 years) assessing: ease of use, airway quality, positioning, seal and complications. First insertion attempt was successful in 86 patients, second attempt in 11 patients, and third attempt in three patients. Fifty three manipulations were required in 26 patients (median 1) to achieve a clear airway. Median insertion time was 15 s. During ventilation, expired tidal volume of 7 ml x kg(-1) was achieved in 96 (96%) patients. Median airway leak pressure was 24 cmH(2)O. On fibreoptic examination via the device, vocal cords were visible in 87 patients (91%). During maintenance, six patients (6%) required 12 airway manipulations. There was one episode of regurgitation, without aspiration. Other complications and patient side-effects were mild and few. The i-gel is easily and rapidly inserted, providing a reliable airway in over 90% of cases. Further studies are indicated to assess safety and performance compared to other supraglottic airway devices.

Randomized Prospective Study Comparing the Laryngeal Tube Suction II with the ProSeal ™ Laryngeal Mask Airway in Anesthetized and Paralyzed Patients

The Laryngeal Tube Suction II (LTSII; VBM, Medizintechnik, Sulz, Germany) is a recent revision of the Laryngeal Tube Suction. This study compared insertion and ventilation profiles of the LTSII and the ProSeal Laryngeal Mask Airway (PLMA; Laryngeal Mask Company, Henley-on-Thames, United Kingdom) in anesthetized and paralyzed patients. One hundred adult male patients were randomly allocated to an LTSII or PLMArade mark group. The rate of successful insertion, insertion time, airway leak pressure at a cuff pressure of 60 cm H2O, tidal volume during pressure-controlled ventilation, incidence of gas leakage with cuff pressure reduced and with the shaft inclined, position of LTSII under fluoroscopic observation, and postoperative airway morbidity were determined. Insertion was successful in 37 and 48 of 50 patients with LTSII and PLMA, respectively (P = 0.002), with similar insertion times. Tidal volume was lower with LTSII than with PLMA. Median airway leak pressures of LTSII and PLMA were 16 and 21 cm H2O, respectively (P = 0.006). Gas leakage around the cuff was observed more frequently with LTSII than with PLMA when the cuff pressure was reduced or the shaft of the device inclined. The position of LTSII varied significantly and did not statistically correlate with patient height. Postoperative airway-related morbidity was not significantly different. Finally, tracheal misplacement of LTSII occurred in 5 of 50 patients (10%), but ventilation was possible in 4 of them, and misplacement was identified only after fluoroscopic examination was performed. Airway management with LTSII is inferior to that with PLMA.

This Month in Anesthesiology

The change from earth's anoxic to oxic atmosphere in relation to the development of life is discussed. See the accompanying Editorial View on page 1 Total intravenous anesthesia was not associated with improved neurologic outcome in traumatic brain injury.Orally administered cannabis extract did not show analgesic efficacy.The need for large randomized trials to determine whether treatment strategies aimed at glucose control will improve patient outcomes is reviewed. See the accompanying Editorial View on page 1 1 Obesity is a major cause of type 2 diabetes, clinically evidenced as hyperglycemia. The altered glucose homeostasis is caused by faulty signal transduction via the insulin signaling proteins which results in decreased glucose uptake by the muscle, altered lipogenesis, and increased glucose output by the liver. The etiology of this derangement in insulin signaling is related to a chronic inflammatory state, which modifies the insulin signaling proteins' functions. There are substantial differences in the molecular mechanisms of insulin resistance among different organs. Multipronged therapies aimed at rectifying obesity-induced anomalies in the central nervous system and peripheral tissues may be beneficial in obesity-induced insulin resistance.The Laryngeal Tube Suction II (LTSII) is a recent revision of the Laryngeal Tube Suction. This study compared insertion and ventilation profiles of LTSII and ProSeal ™ Laryngeal Mask Airway (PLMA™) in anesthetized patients. The rate of successful insertion, insertion time, airway leak pressure, tidal volume, and postoperative airway morbidity were among many parameters measured. Insertion was successful in 37 and 48 of 50 patients with LTSII and PLMA™, respectively. The PLMA™ was superior to the LTSII in most measures of ventilation performance. Airway management with LTSII is inferior to that with PLMA™.In this editorial, Hogan reviews and comments on the implications of a pharmacogenomics study of nitrous oxide by Nagele et al. In Nagele et al. 's study, patients with a certain genetic mutation develop higher plasma homocysteine levels after nitrous oxide anesthesia than normal patients. The study suggests that deleterious events after nitrous oxide exposure may be enriched in a subset of patients with certain genetic predisposition. Hogan states that trials of nitrous oxide exposure in the clinical setting will be substantially strengthened by inclusion of single-carbon genotyping. Furthermore, knowing in advance who can breathe nitrous oxide without fear of clinically relevant hyperhomocysteinemia may help to sustain its safe use in the future.Recent investigations have focused on increased operating room (OR) throughput without increasing total OR time. The authors examined if a system of parallel processing for lower extremity joint arthroplasties sustainably reduces nonoperative time and increases throughput. The high-throughput parallel processing strategy included neuraxial anesthesia, an induction room, patient selection, an additional circulating nurse, and specific end-of-case transfer to recovery. Throughput increased from 2.6 to 3.4 arthroplasties per day per room. Both nonoperative time and operative time decreased. Because joint arthroplasties generated a positive margin greater than the incremental cost, the high-throughput system improved financial performance. See the accompanying Editorial View on page 3

A randomised, crossover comparison between the CobraPLA® and the LMA Classic™ in paralysed patients*

We performed a randomised, crossover study in 38 anaesthetised and paralysed patients to compare the performance of the CobraPLA and the LMA Classic during controlled ventilation. The median (IQR [range]) airway leak pressure was 23.0 (20-24 [12-30]) cmH(2)O for the CobraPLA and 15.0 (12-19 [8-30]) cmH(2)O for the LMA Classic (p < 0.001). The median (IQR [range]) insertion time was 15.0 (11-26 [9-31]) s for the CobraPLA and 22.5 (20-25 [15-50]) s for the LMA Classic (p < 0.001). There was no significant difference between the two devices for the number of insertion and reposition attempts, the anatomical position scored by fibreoptic bronchoscopy or the peak and plateau airway pressures. There were no adverse events during anaesthesia. The CobraPLA provides a better airway leak pressure and takes less time to insert than the LMA Classic in paralysed patients. Our data show that the CobraPLA can be used to secure a patent airway during controlled ventilation in selected patients.

Prospective randomized comparison of the new Laryngeal Tube Suction LTS II and the LMA‐ProSeal for elective surgical interventions

The Laryngeal Tube Suction (LTS) has recently undergone considerable changes in design. The new LTS II was compared with the LMA-ProSeal to determine device performance during general anaesthesia and controlled ventilation. After Institutional Review Board approval, 100 elective surgical patients were randomized to be ventilated with LTS II or LMA-ProSeal. The number of attempts (maximum of two, and then other device tested) and time until first tidal volume were recorded. Ventilation was standardized (tidal volume, 7 ml/kg; respiratory rate, 12 breaths/min) and the resulting end-tidal CO(2) was recorded. The airway leak pressure (maximum of 40 cmH(2)O) was measured at cuff pressures of 60 cmH(2)O. The ease of gastric tube insertion was evaluated. The devices were inspected for traces of blood after removal. Patients were questioned regarding post-operative complaints. The Mann-Whitney U-test was used to compare the groups. The demographic data, American Society of Anesthesiologists' group, Mallampati score, and haemodynamic and respiratory variables were comparable for both groups of 50 patients. Insertion was successful in the first/second attempts in 44/4 patients for LTS II and in 43/6 patients for LMA-ProSeal. After two failed attempts, the other device was successfully used in one patient for LMA-ProSeal and in two patients for LTS II. The times until first tidal volume for LTS II and LMA-ProSeal were 25.0 +/- 10.1 and 25.5 +/- 11.5 s, respectively. The airway leak pressures were comparable: 33.1 (15-40) and 32.0 cmH(2)O (18-40 cmH(2)O) for LTS II and LMA-ProSeal, respectively. Gastric tube insertion failed in two patients in each group. Traces of blood were found in two patients with LTS II and in three patients with LMA-ProSeal. In both groups, post-operative complaints were mild and infrequent. In this prospective randomized trial, LMA-ProSeal and LTS II were comparable in all respects.

A comparison of the laryngeal tube-S™ and Proseal™ laryngeal mask during outpatient surgical procedures

The Laryngeal Tube Sonda (LTS) and the ProSeal Laryngeal Mask Airway (PLMA) are two new devices introduced for maintaining the airway during controlled ventilation under general anaesthesia. The present investigation compared their performance in a randomized controlled study. One hundred ASA I-II patients, aged 18-60 yr undergoing elective minor surgery, were randomized to receive either an LTS (n = 50) or PLMA (n = 50) for airway management. After induction of general anaesthesia, the devices were inserted, its correct placement was verified and airway leak pressure was measured. Ease of insertion, quality of airway seal, fibre-optic view and postoperative pharyngeal morbidity were examined. There were no differences in patient characteristics for both groups. First-time and second-time success rates were comparable for both groups (86 vs. 88% and 96 vs. 98% in LTS and PLMA groups, respectively). The airway of one patient in each group could not be managed with these devices after three attempts. Time until delivery of first tidal volume for LTS and PLMA was 24.5 +/- 6.9 and 28.8 +/- 10.3 s. Fixation and manipulation time was 54.9 +/- 15.2 and 73.2 +/- 25 s, respectively (P < 0.05). Airway seal pressure (cm H(2)O) for LTS and PLMA was 20 +/- 8.6 and 24.1 +/- 10.8, respectively (P = 0.04). Patients were questioned on a variety of postoperative pharyngeal morbidities. Only hoarseness was more frequent in the LTS group. Both devices provide a secure airway, are similar in clinical utility and are easy to insert. Better airway seal was detected in the PLMA group.

Comparison of LMA Unique, Ambu laryngeal mask and Soft Seal laryngeal mask during routine surgical procedures

This study was performed to compare three disposable airway devices, the LMA Unique (LMA-U), the Ambu laryngeal mask (Ambu LM) and the Soft Seal laryngeal mask (Soft Seal LM) for elective general anaesthesia during controlled ventilation in non-paralysed patients. One hundred and twenty ASA I-III patients scheduled for routine minor obstetric surgery were randomly allocated to the LMA-U (n = 40), Ambu LM (n = 40) or Soft Seal LM (n = 40) groups, respectively. Patients were comparable with respect to weight and airway characteristics. A size 4 LMA was used in all patients and inserted by a single experienced anaesthesiologist. Oxygenation, overall success rate, insertion time, cuff pressure and resulting airway leak pressure were determined as well as a subjective assessment of handling and the incidence of sore throat, dysphagia and hoarseness. Time of insertion was shortest with the Ambu LM, while failure rates were comparable with the LMA-U, the Ambu LM and the Soft Seal LM (median 19 s; range 8-57 s; success rate 100% vs. 14; 8-35; 97% vs. 20; 12-46; 95%). Insertion was judged 'excellent' in 75% of patients in the LMA-U group, in 70% of patients in Ambu LM group and in 65% of patients in the Soft Seal LM group. There was no difference between devices with respect to postoperative airway morbidity at 6 h or 24 h following surgery. All three disposable devices were clinically suitable with respect to insertion times, success rates, oxygenation, airway and leak pressures, as well as to subjective handling and postoperative airway morbidity.

Prospective, randomized comparison of laryngeal tube and laryngeal mask airway in pediatric patients

While reports of the use of laryngeal mask airway (LMA)-Classic in great patient numbers are available, data on the use of the laryngeal tube (LT) in this age group is limited. The two devices are compared in a prospective randomized trial to evaluate success rates and quality of airway seal. Sixty children, aged 2-8 years, scheduled for elective surgical interventions were randomized to be ventilated with LMA or LT. Standardized anesthesia was induced with fentanyl and propofol. Number of insertion attempts, time until first tidal volume and intraoperative tidal volumes, and peak pressures were recorded. Airway leak pressure was measured with cuff pressure adjusted to 60 cmH(2)O. Demographic data were comparable, average age in the LMA/LT group was 5.2 +/- 1.9/5.3 +/- 1.9 years. Insertion was successful in 29 of 30 patients in the LMA group (second attempt 8) and in all patients in the LT group (second attempt 3). Time until first tidal volume for LMA/LT was 23.1 +/- 7.3/19.2 +/- 8.6 s (P < 0.05). Peak airway pressures for LMA and LT were 15.3 +/- 3.4 and 17.1 +/- 4.0 cmH(2)O (P < 0.05) with tidal volumes of 10.2 +/- 2.2 and 10.2 +/- 1.9 ml.kg(-1), airway leak pressure was 19.2 +/- 8.6 cmH(2)O for LMA and 26.3 +/- 7.3 cmH(2)O for LT (P < 0.001). Insertion success rate is high with both LMA and LT in the age group studied. The airway leak pressure, serving as an estimate to judge quality of airway seal, is higher with the LT.

Use of the LMA-ProSeal® in an Experimental Pig Model - A Potential Animal Model for Laryngeal Mask Airway Research: Results of a Pilot Study

In light of the increased use of the LMA-ProSeal (P-LMA) it seems desirable to consider the P-LMA for prolonged surgical cases or post-operative ventilation. Long-term use could carry the risk of serious complications. An experimental pig model could be used to gain basic knowledge about long-term use before conducting clinical trails. In this randomized controlled study we tested the hypothesis if prolonged positive pressure ventilation (PPV) with the P-LMA in the pig is possible. The P-LMA was used for airway maintenance under general anaesthesia and PPV in 15 German country pigs. Randomised into 3 groups, the animals were ventilated for 90, 150 and 390 minutes, respectively. Arterial blood gas measurements were used to determine adequacy of ventilation. Airway leak pressure (P (leak)) and maximum tidal volume (TV) were measured in the supine, lateral and prone positions. A bronchoscopic examination was performed to detect signs of aspiration. Adequate ventilation was demonstrated both after 120 min (4.7 +/- 0.4 kPa) and 360 min (4.7 +/- 0.5 kPa). The corresponding PaO(2) at FiO(2) = 1.0 was 59 +/- 5 kPa and 64 +/- 10 kPa, respectively. The mean P (leak) was 34 +/- 7 cm H(2)O. Change of position did not result in any significant change in P(leak) or maximum TV kg (-1). There was no bronchoscopic evidence of aspiration in any pig. It was possible to ensure sufficient PPV with the P-LMA in the pig over different periods of time and in different body positions without any complications of airway management. The P-LMA can be used for PPV in the pig for durations of up to 390 minutes. We conclude that investigations into the long-term use of the LMA can be carried out in a pig model.

Auswirkung einer neuromuskulären Blockade auf den Leckagedruck der ProSeal®-Kehlkopfmaske

The ProSeal laryngeal mask airway (PLMA) is increasingly used for surgical procedures that might require the intraoperative use of neuromuscular blocking agents. The airway seal of the PLMA depends on the interplay of the surrounding soft tissue of the neck and the cuff of the mask. An intraoperative neuromuscular blockade could lead to a decrease of the airway leak pressure (P (leak)) secondary to the relaxation of the muscles of the neck. With this study we tested the hypothesis that a neuromuscular blockade can result in a decreased P (leak) of the PLMA. The P (leak) of the PLMA was studied in 73 female patients under total intravenous anaesthesia with propofol (0.1 - 0.15 mg kg (-1) min (-1)) and remifentanil (0.1 - 0.3 microg kg (-1) min (-1)) before and after a complete neuromuscular blockade produced by intravenous injection of 0.6 mg kg (-1) Rocuronium. The P (leak) decreased by more than 10 % of the baseline P (leak) in 8 out of 73 patients (11 %); however, in the entire study population there was no significant difference between the mean baseline P (leak) (28.5 +/- 7.3 cm H(2)O) and the mean P (leak) after complete neuromuscular blockade (29.1 +/- 7.0 cm H(2)O); (p = 0.128). No general correlation between application of a neuromuscular blocking agent and a decrease of the mean P (leak) was found. However, the decrease of the P (leak) by more than 10 % in 11 % of the patients shows that in certain patients the application of neuromuscular blocking agents can result in a decreased P (leak) of the PLMA and indicates the necessity to control the P (leak) of the PLMA under complete muscle paralysis preoperatively when neuromuscular blocking agents are used.

Vergleich von zwei Larynxmaskenmodellen zur Atemwegssicherung bei Patienten mit Immobilisation der Halswirbelsäule

Reduced cervical spine mobility can impair laryngoscopy and tracheal intubation. Supraglottic airway devices can be important alternatives for oxygenation under these circumstances. The Ambu laryngeal mask (ALM) and the LMA-Classic (LMA) are compared in patients with immobilization of the cervical spine. In 60 patients scheduled for elective ambulatory interventions, ALM or LMA were inserted after cervical immobilization with an extrication collar and assessment of laryngoscopic view. Insertion time (removal of facemask until first tidal volume), number of insertion attempts, airway leak pressure (cuff pressure 60 cm H(2)O), intraoperative complications and postoperative complaints were assessed. Demographical data, insertion attempts, insertion time (ALM 15.6+/-4.4 s, LMA 15.5+/-4.9 s) and airway leak pressure (ALM 25.6+/-5.2 cm H(2)O, LMA 26.5+/-6.5 cm H(2)O) were comparable. Traces of blood were found in 6 LMAs and 3 ALMs after removal, mild trouble with swallowing (visual analogue scale, VAS 2-4) in the recovery room and after 24 h were complaints by 1 ALM and 2 LMA patients. LMA-Classic and Ambu laryngeal masks are suitable for rapid and reliable airway management in patients with cervical immobilization.