Comparison of the LMA-classic with the new disposable soft seal laryngeal mask in spontaneously breathing adult patients

BACKGROUND: The laryngeal mask airway LMA-Classic has been used widely in clinical practice. A new disposable supraglottic airway device, the Soft Seal LM, has been introduced recently. In a randomized study, the authors compared the LMA-Classic and the disposable Soft Seal LM in terms of their clinical performance, cuff pressures during nitrous oxide anesthesia, position of the laryngeal mask in situ by fiberoptic evaluation, and morbidity in a wide range of routine general surgery procedures. METHODS: A total of 200 adult patients were randomly assigned to a size 4 laryngeal mask in two equal-sized groups for airway management during surgery: (1) LMA-Classic (Intavent Orthofix Ltd., Maidenhead, Berkshire, United Kingdom); or (2) Soft Seal LM (Portex Ltd., Hythe, Kent, United Kingdom). Anesthesia was administered with fentanyl, propofol, nitrous oxide, oxygen, and sevoflurane. The variables studied were ease of insertion, fiberoptic view, time in situ, incidence of blood on the laryngeal mask at the time of removal, and the incidence of postoperative sore throat at 2 and 24 h. The laryngeal mask cuff pressures were measured continuously. Intracuff pressure limitation was not attempted. RESULTS: The LMA-Classic and the Soft Seal LM showed similar clinical performances, as shown by their insertion time (successful insertion at first attempt was achieved within 20 s in 97% with LMA-Classic trade mark vs. 95% with Soft Seal LM), fiberoptic evaluation of the anatomic position of the laryngeal mask, and satisfactory anesthesia conditions. Laryngeal mask cuff pressures increased from 45 to 100.3 mmHg in the LMA-Classic and from 45 to 46.8 mmHg in the Soft Seal LM (P < 0.001). Macroscopic blood was seen on only four occasions in the LMA-Classic group. The incidence of sore throat was significantly increased at 2 h postoperatively when using the LMA-Classic, although there was no difference at 24 h after surgery. CONCLUSIONS: In spontaneously breathing adult patients requiring a size 4 laryngeal mask airway, the new disposable Soft Seal LM device is an acceptable alternative to the reusable LMA-Classic trade mark, resulting in a good laryngeal seal and offering similar clinical performance. Cuff pressures increase substantially when the LMA-Classic is used but not when using the Soft Seal LM. There was less trauma to patients using the Soft Seal LM, as assessed by the incidence of sore throat in the early postoperative period.     

Comparison of the LMA-Classic ™ with the New Disposable Soft Seal Laryngeal Mask in Spontaneously Breathing Adult Patients

Background: The laryngeal mask airway LMA-Classic (TM) has been used widely in clinical practice. A new disposable supraglottic airway device, the Soft Seal LM, has been introduced recently. In a randomized study, the authors compared the LMA-Classic (TM) and the disposable Soft Seal LM in terms of their clinical performance, cuff pressures during nitrous oxide anesthesia, position of the laryngeal mask in situ by fiberoptic evaluation, and morbidity in a wide range of routine general surgery procedures.

Methods: A total of 200 adult patients were randomly assigned to a size 4 laryngeal mask in two equal-sized groups for airway management during surgery: (1) LMA-Classic (TM) (Intavent Orthofix Ltd., Maidenhead, Berkshire, United Kingdom); or (2) Soft Seal LM (Portex Ltd., Hythe, Kent, United Kingdom). Anesthesia was administered with fentanyl, propofol, nitrous oxide, oxygen, and sevoflurane. The variables studied were ease of insertion, fiberoptic view, time in situ, incidence of blood on the laryngeal mask at the time of removal, and the incidence of postoperative sore throat at 2 and 24 h. The laryngeal mask cuff pressures were measured continuously. Intracuff pressure limitation was not attempted.

Results: The LMA-Classic (TM) and the Soft Seal LM showed similar clinical performances, as shown by their insertion time (successful insertion at first attempt was achieved within 20 s in 97% with LMA-Classic (TM)vs. 95% with Soft Seal LM), fiberoptic evaluation of the anatomic position of the laryngeal mask, and satisfactory anesthesia conditions. Laryngeal mask cuff pressures increased from 45 to 100.3 mmHg in the LMA-Classic (TM) and from 45 to 46.8 mmHg in the Soft Seal LM (P < 0.001). Macroscopic blood was seen on only four occasions in the LMA-Classic (TM) group. The incidence of sore throat was significantly increased at 2 h postoperatively when using the LMA-Classic (TM), although there was no difference at 24 h after surgery.     

Nitrous oxide diffusion into the cuffs of disposable laryngeal mask airways

The aim of this study was to investigate cuff pressure changes found in disposable size 3 laryngeal mask airways (LMAs) from different manufacturers during nitrous oxide exposure and to compare the results with the re-usable Classic LMA. In an in vitro experiment, laryngeal mask airway cuff pressures starting from a baseline pressure of 40 cm H(2)O were recorded using a pressure transducer for 60 min with the laryngeal mask airway cuff exposed to 66% N(2)O in oxygen. Cuff pressure increases within 5 min of nitrous oxide exposure were > 250% in the Classic LMA and were not significantly different from those found in the Marshall laryngeal mask airway. However, they were significantly greater than those in the Soft Seal, the Unique, the AMBU, and Intersurgical laryngeal mask airways, all of which demonstrated stable cuff pressure levels within the first 5 min. The cuff pressure increase following 60 min of nitrous oxide exposure was 13.0 +/- 1.1 and 14.6 +/- 0.7 cm H(2)O in the Intersurgical and Unique laryngeal mask airways, respectively, which was significantly lower than the cuff pressure increase in the Soft Seal and in the Ambu laryngeal mask airways (28.3 +/- 2.9 and 30.9 +/- 1.2 cm H(2)O, respectively). Unlike the re-usable Classic LMA and the disposable Marshall laryngeal mask airway, which have silicone cuffs, the disposable Ambu, Intersurgical, Portex Soft Seal and Unique laryngeal mask airways have cuffs constructed from PVC, which seems to be less susceptible to hyperinflation caused by nitrous oxide diffusion.     

Clinical comparison of the reusable LMA Classic laryngeal mask and the disposable Soft Seal mask in adult patients

OBJECTIVES: To compare the clinical behavior of the disposable Soft Seal laryngeal mask to the behavior of the reusable LMA Classic mask. METHODS: Patients were randomly assigned to 2 groups in which either the LMA Classic or the Soft Seal mask would be used. We assessed time required for positioning and number of attempts, seal pressure, fiberoptic bronchoscopic image, and complications. The masks were inserted by 2 anesthesiologists who were inexperienced in the use of laryngeal masks. We also compared compliance of the cuff in the laboratory. RESULTS: Sixty patients were enrolled. There were no differences in time required for insertion or number of attempts (first-try success, 83%). The mean (SD) seal pressure was greater in the Soft Seal group at 23 (4) cm H2O than in the LMA Classic group at 20 (4) cm H2O. There were no significant differences in the fiberoptic bronchoscopic images, ventilation, incidence of intraoperative complications, presence of blood on the cuff (LMA Classic, 6 out of 30 vs Soft Seal, 11 out of 29), or postoperative sore throat. In 3 patients in the Soft Seal group the laryngeal mask had to be replaced by an orotracheal tube. Cuff compliance in the laboratory was lower for the LMA Classic than for the disposable mask for all sizes assessed. CONCLUSIONS: Although the results suggest that the clinical behavior of the 2 masks is similar, the LMA Classic allowed for effective airway management in all of the cases assigned to it, whereas management was effective in 90% of the cases in which the Soft Seal mask was used. The inflatable cuff of the Soft Seal is more compliant in vitro and it provides a higher airway seal pressure than does the LMA Classic.     

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

BACKGROUND AND OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

Comparison of disposable and reusable laryngeal mask airways in spontaneously ventilating adult patients

Recent studies have indicated that despite stringent sterilization processes, the reusable silicone laryngeal mask airway (LMA) has the potential for disease transmission through residual biological debris. As a result, a polyvinyl chloride (PVC) disposable LMA has been introduced. This randomized trial involved 138 spontaneously ventilating adult patients who underwent elective surgery requiring airway management with an LMA to determine whether there is a clinical difference between the disposable Portex LMA (PLMA) and the standard reusable LMA in terms of ease of insertion, intra-operative cuff pressures and postoperative incidence of sore throat. There was no significant difference in first attempt insertion success rates (79% vs 84%) or difference in the incidence of postoperative sore throat observed between the two groups. Cuff pressure increases with nitrous oxide anaesthesia were significantly larger with the reusable LMA. The disposable PLMA provided a suitable airway in spontaneously ventilating patients without the risk of disease transmission inherent in a reusable device.     

Laryngeal mask airway cuff pressure and position during anaesthesia lasting one to two hours

The cuff of the laryngeal mask airway (LMA) is highly permeable to nitrous oxide (N₂O), and cuff pressure increases during N₂O/O₂ anaesthesia. The extent of these changes and their effect on LMA position have previously only been investigated for short procedures. The current study was designed to investigate the effects of nitrous oxide-oxygen (N₂O/O₂) anaesthesia lasting one to two hours on cuff pressure, LMA positioning and pharyngeal morbidity. Twenty-four male patients underwent spontaneous ventilation anaesthesia with 66% N₂O in oxygen and isoflurane. Following insertion and inflation of a #4 LMA with 30 ml air, mean (SD) cuff pressures immediately increased from 107 (9) to 145 (12) mmHg and then at a decreasing rate for 90 min to peak at 215 (12) mmHg. There was a correlation between N₂O concentration and final cuff volume (P < 0.001). There was no displacement of the LMA cuff in any patient. Three of 19 patients had a mild sore throat. This study demonstrates that the increase in LMA cuff pressure is self limiting over a one-to-two-hour period and does not cause displacement of the LMA. There is no evidence that cuff pressure monitoring and pressure limitation is necessary during LMA anaesthesia.     

Impact of laryngeal mask airway cuff pressures on the incidence of sore throat in children

Background:  Hyperinflation of laryngeal mask airway cuffs can cause harm to the upper airway mainly by exerting high pressures on pharyngeal and laryngeal structures thus impairing mucosal perfusion. Although cuff manometers can be used to guide the monitoring of cuff pressures, their use is not routine in many institutions. In a prospective audit, we assessed the incidence of sore throat following day-case-surgery in relation to the intracuff pressure within the laryngeal mask airway.
Methods:  Four hundred children (3–21 years) were consecutively included in this study. The laryngeal mask airway was inflated as deemed necessary by the attending anesthetist. Cuff pressures were measured using a calibrated cuff manometer (Portex Limited, Hythe, Kent, UK, 0–120 cmH₂O, pressures exceeding the measurement range were set at 140 cmH₂O for statistical purposes) at induction of anesthesia.
Results:  Forty-five children (11.25%) developed sore throat, 32 (8%) sore neck and 17 (4.25%) sore jaw. Of those that developed sore throat, 56.5% had cuff pressures exceeding >100 cmH₂O. In contrast, when cuff pressures were <40 cmH₂O, there were no episodes of sore throat, whilst there was only a 4.6% occurrence of sore throat if cuff pressures were between 40–60 cmH₂O.
Conclusion:  We have demonstrated that intra cuff pressure in laryngeal mask airways is closely related to the development of sore throat with higher pressures increasing its likelihood. Hence, cuff pressures should be measured routinely using a manometer to minimize the incidence of sore throat.     

Postoperative sore throat and hoarseness following tracheal intubation using air or saline to inflate the cuff--a randomized controlled trial

Sore throat and hoarseness following tracheal intubation is common. The aetiology may include high tracheal cuff pressures. We performed a double-blind, randomized controlled trial in 126 intubated patients to compare the incidence and severity of sore throat and hoarseness following inflation of the cuff using air or saline. Intra-cuff pressures were compared to assess any change due to inward diffusion of nitrous oxide. The incidence of significant sore throat and/or hoarseness overall was 15.0%. There was no statistically significant difference between the groups (air 15.9%, saline 14.5%). In the air group mean intra-cuff pressure increased significantly (start 14.0 mmHg, end 40.9 mmHg), while in the saline group there was no significant increase (start 12.7 mmHg, end 14.6 mmHg). The substitution of saline reliably results in sustained low intra-cuff pressures but high tracheal cuff pressure is not an important factor in the development of sore throat or hoarseness postoperatively within the pressure range and duration of operation studied.     

Evaluation of pressure changes in a new design tracheal tube cuff, the Portex Soft Seal, during nitrous oxide anaesthesia

We have measured pressure changes in a newly designed tracheal tube cuff, the Portex Soft Seal, during nitrous oxide anaesthesia compared with a Mallinckrodt Lo-Contour tube and a Portex Profile tube. The pressure increases in both control groups were significantly greater than those with the new design (P < 0.0001 in each case). The mean increase in pressure in the Mallinckrodt Lo-Contour tube cuff was 9.9 (SD 3.4) mm Hg compared with 10.3 (1.8) mm Hg in the Portex Profile tube cuff and 2.1 (1.5) mm Hg in the Portex Soft Seal tube cuff. We conclude that the Portex Soft Seal cuff prevented a significant increase in intracuff pressure during nitrous oxide anaesthesia.      

The effect of nitrous oxide on laryngeal mask cuff pressure

We have studied the effect of nitrous oxide on the cuff pressure of a laryngeal mask both in vitro and in vivo. In laboratory tests, we showed that nitrous oxide and carbon dioxide diffuse across the cuff wall much more rapidly than nitrogen and oxygen. Differing partial pressures of these gases across the cuff wall therefore give rise to changes in volume and pressure within the cuff. We then studied 18 patients undergoing general anaesthesia with nitrous oxide, and found a consistent and linear increase in cuff pressure in all patients. After 30 min, the mean pressure had increased by 30 mmHg, and there was approximately 10% nitrous oxide in the cuff. It is difficult to relate these findings to pressure on pharyngeal structures, but methods of limiting the rise in intracuff pressure are discussed.     

Laryngeal mask airway and tracheal tube cuff pressures in children: are clinical endpoints valuable for guiding inflation?

We prospectively assessed common clinical endpoints for their usefulness in avoiding hyperinflation of the cuffs of laryngeal mask airways (slight outward movement) and tracheal tubes (disappearance of an audible leak around the cuff during manual ventilation < 20 cmH₂O) in 640 children. Cuff pressures were measured at induction and immediately before emergence from anaesthesia. With the laryngeal mask airway (sizes 1–4), the median cuff pressures ranged from 90 to > 120 cmH₂O at induction and 105 to > 120 cmH₂O before emergence. With tracheal tubes (sizes 3–7 mm), median cuff pressures were 40–60 cmH₂O at induction and 45–70 cmH₂O at emergence. With the use of nitrous oxide a consistent rise in cuff pressure was observed between the first and second readings whereas cuff pressures remained constant when nitrous oxide was not used. The use of clinical endpoints alone was associated with significant hyperinflation of cuffs with both devices in almost all patients, with an exacerbation when nitrous oxide was used. In order to avoid unnecessary cuff hyperinflation in laryngeal mask airways and tracheal tubes, the routine use of cuff manometers is mandatory in children.     

Laryngo-pharyngeal complaints after use of the laryngeal mask airway

PURPOSE: To compare the incidence of dysphagia, dysphonia and sore throat following anesthesia, using the laryngeal mask airway (LMA), among patients receiving intermittent positive-pressure ventilation (IPPV) and those breathing spontaneously (SV) and with two different concentrations of nitrous oxide (N2O) in oxygen. METHODS: In a prospective trial, 120 patients (ASA I-III, 16-70 yr, > 60 kg) undergoing minor peripheral surgery were randomised into four groups with respect to type of ventilation and N2O concentration (50% or 66%) received. Cuff pressure measurements were monitored continuously. Twenty-four hours after surgery, patients were questioned for sore throat, dysphagia and dysphonia. RESULTS: At 30 min post-LMA insertion, increases in cuff pressure were 35.2+/-17.1 mmHg (22.8%) vs 50.1+/-16.3 mmHg (32.7%) in patients breathing 50 and 66% N2O, respectively (P < 0.01). There were no differences in cuff pressure increment between patients in the SV and IPPV groups. Cuff pressure values at the end of surgery depended on the duration of surgery and on the concentrations of N2O. The overall incidence of postoperative discomfort at 24 hr was dysphagia 11%, dysphonia 11% and sore throat 28.8%. Only two patients reported sore throat as more than mild. There was no relationship between cuff pressure and laryngo-pharyngeal complaints. The incidence of dysphonia in the groups receiving IPPV was higher than that in the groups with spontaneous ventilation (17.2 vs 5%, P < 0.05). CONCLUSION: Post-operative discomfort is related to the type of ventilation but not to variation in LMA cuff pressure.     

In cadavers, directly measured mucosal pressures are similar for the Unique™ and the Soft Seal™ laryngeal mask airway devices

PURPOSE: We compare the Soft Seal and Unique single-use, plastic laryngeal mask airway devices with respect to intracuff pressure, directly measured mucosal pressure and in vitro elastance. METHODS: Ten fresh male cadavers were studied. Microchip pressure sensors were attached to the following locations: A) the anterior middle part of the cuff side; B) the posterior tip of the cuff; C) the anterior base of the cuff; D) the posterior middle part of the cuff side; E) the backplate; and F) the posterior tube. The size 5 Unique and size 5 Soft Seal were inserted in random order using laryngoscope-guidance. Intracuff pressure and mucosal pressure were documented at 0 to 40 mL cuff volume in 10 mL increments. In vitro elastance was determined between 20 to 40 mL cuff volume. RESULTS: For both devices, mucosal pressure increased with cuff volume at most locations. Intracuff pressures and in vitro elastance (5.2 +/- 0.7 cm H(2)O/mL vs 3.8 +/- 0.4 cm H(2)O/mL, P < 0.0001) were higher for the Unique than the Soft Seal (P < 0.0001), but there were no differences in mucosal pressures at any location or cuff volume. CONCLUSION: Intracuff pressures and in vitro elastance are higher for the Unique than the Soft Seal, but mucosal pressures are similar suggesting that the airway morbidity will be similar.     

Randomized evaluation of the single-use SoftSeal and the re-useable LMA Classic laryngeal mask

A number of laryngeal masks are available, including both re-usable and single-use masks. Single-use laryngeal masks may decrease the risk of transmitting prion infections. We performed a single-blind randomized trial in 200 spontaneously breathing female patients under general anaesthesia with nitrous oxide, to compare a new single-use laryngeal mask, the SoftSeal (Portex Ltd, U.K.), with a re-usable laryngeal mask, the LMA Classic (Laryngeal Mask Company Ltd., Cyprus). The primary outcome was successful insertion at the first attempt. Size 4 single-use (n = 99) or re-usable (n = 100) laryngeal masks, inserted by experienced anaesthetists, were equivalent for successful placement at the first attempt (90% versus 91% respectively). The single-use mask was less easy to insert (47% difficult versus 9%, P < 0.001). Clinical and anatomical tests of position and function were similar. The cuff pressure of the re-usable mask increased significantly compared with the single-use mask (median +10 cm versus -2 cm H2O, P < 0.001). Forty per cent of patients allocated the single-use mask and 20% of those allocated the re-usable mask experienced sore throat at 24 hours postoperatively (P < 0.05). An estimation of cost per patient use was greater for the re-usable mask. We conclude that the SoftSeal single-use laryngeal mask and the LMA Classic re-usable laryngeal mask airway are of similar clinical utility in terms of successful insertion and airway maintenance. The re-usable laryngeal mask was easier to insert and associated with less postoperative sore throat, but costs were higher.     

Comparison of the re-usable LMA Classic and two single-use laryngeal masks (LMA Unique and SoftSeal) in airway management by novice personnel

In a single-blind randomized trial, three types of laryngeal masks: the reusable LMA Classic, the single-use LMA Unique and SoftSeal were inserted by novice medical officers in anaesthesia. Five successive attempts were undertaken with each mask type. The order of the mask type insertion was randomly selected. Mean (SD) insertion times for LMA Classic, LMA Unique and Soft Seal were 32.9 (12.3), 39.6 (23.4) and 49.4 (50.4) seconds respectively. Differences were only significant between LMA Classic and SoftSeal (P=0.012). There were no significant differences in first attempt success rates (LMA Classic 80%, LMA Unique 77% and SoftSeal 62%). The SoftSeal was most frequently associated with blood on the mask (32%) compared to the LMA Unique (9%) and LMA Classic (6%). Sore throat was experienced in 14% of patients in the LMA Unique group versus 41% and 42% in the LMA Classic and SoftSeal groups respectively. Mean +/- SD oropharyngeal leak pressure was significantly higher in the SoftSeal (21+/-6 cmH2O) compared to the LMA Classic (17+/-7 cmH2O) and LMA Unique (16+/-6 cmH2O). Novice medical doctors can be taught to insert disposable laryngeal masks. The SoftSeal took longer to insert, which resulted in a higher incidence of blood on the mask, but success rates did not differ The LMA Unique was associated with the lowest incidence of sore throat in the immediate postoperative period. A higher oropharyngeal leak pressure with the SoftSeal may indicate improved airway seal and protection against aspiration.     

Intracuff Pressures Do Not Predict Laryngopharyngeal Discomfort after Use of the Laryngeal Mask Airway

Background: The laryngeal mask airway (LMA) is a large foreign body that exerts pressure on the pharyngeal mucosa, which may lead to throat discomfort. To determine whether intracuff pressures are associated with such discomfort, a randomized, double-blind study was performed to determine the effect of high versus low intracuff pressures.

Methods: Seventy healthy women were randomly allocated to two groups with different LMA intracuff pressures: 30 mmHg (low pressure) or 180 mmHg (high pressure). Pressures were controlled with a microprocessor-controlled monitor. Insertion of the LMA was performed by one investigator and facilitated with propofol and verified fiberoptically. Anesthesia was maintained with enflurane and nitrous oxide. The LMAs were removed while the patients were still asleep. Patients assessed their laryngopharyngeal complaints (sore throat, dysphagia, hoarseness) at 8, 24, and 48 h after operation on a 101-point numerical rating scale.

Results: No significant difference was found in the overall incidence of complaints between both groups (low pressure: 50%; high pressure: 42%). On the day of surgery, dysphagia (38%) was more frequent than sore throat (16%) or hoarseness (6%) (P < 0.05) within the high-pressure group. In the low-pressure group, the incidence of these complaints was not significantly different (33%, 20%, and 23%, respectively). On the following day, dysphagia was still present in 20% of the women in both groups, and other symptoms comprised 10% or less of the reported complaints.     

A comparison of the Soft Seal disposable and the Classic re-usable laryngeal mask airway

Many new supraglottic airway devices have been recently introduced, their development motivated by the need for a single-use equivalent to the original re-usable laryngeal mask airway. We performed a randomised cross-over study in spontaneously breathing patients comparing the re-usable Laryngeal Mask Airway-Classic (LMA) and the disposable Soft Seal Laryngeal Mask in sizes 3, 4 and 5. Sixty patients had an LMA and a disposable laryngeal mask placed in random order. The primary outcome was first attempt insertion success rate. Ease of insertion was similar in both groups and there was no difference in first attempt success rates (96% with LMA and 92% with disposable laryngeal mask). The disposable laryngeal mask required significantly less air to inflate the cuff to produce a seal (10 [10-25] ml with disposable laryngeal mask and 15 [10-30] ml with laryngeal mask) and the cuff pressure produced was significantly lower (35 [20-80] cmH(2)O with disposable laryngeal mask and 75 [20-120] cmH(2)O with LMA). Data are median and range. We conclude that the disposable laryngeal mask is an acceptable alternative to the re-usable LMA.     

Emergence characteristics and postoperative laryngopharyngeal morbidity with the laryngeal mask airway: a comparison of high versus low initial cuff volume

In this study we tested the hypothesis that the initial cuff volume of the laryngeal mask airway influences emergence characteristics and postoperative laryngopharyngeal morbidity. One hundred and sixty adult patients undergoing minor surgery were randomly assigned for airway management with the laryngeal mask airway with either a fully inflated cuff (LMA-High) or a semi-inflated cuff (LMA-Low). Anaesthesia was with propofol, nitrous oxide, oxygen and isoflurane. Following insertion, the cuff was inflated with either 15 or 30 ml for the size 4 (females) and 20 or 40 ml for the size 5 (males). At the end of surgery, a blinded observer documented the presence or absence of adverse airway events (hypoxia, hypercapnea, coughing, retching, regurgitation/vomiting, airway obstruction, hypoventilation, hiccupping, biting, body movement or shivering) during every 1 min epoch and cardiorespiratory variables (heart rate, mean blood pressure, arterial oxygen saturation, end-tidal carbon dioxide and respiratory rate) every 5 min until the patient was awake and the laryngeal mask airway removed. Patients were interviewed about pharyngolaryngeal morbidity (sore throat, dysphonia and dysphagia) immediately before leaving the postanaesthesia care unit and 18-24 h following surgery. Analysis by epoch showed more partial airway obstruction in the LMA-High group, but analysis by patient numbers revealed no difference. Heart rate was slightly higher in the LMA-High group upon arrival in the postanaesthesia care unit, but otherwise there were no differences in cardiorespiratory responses. Sore throat and dysphagia were more common in the LMA-High group. We conclude that, in general, emergence characteristics with the laryngeal mask airway are not influenced by the volume of air used to inflate the cuff, but that postoperative sore throat and dysphagia are more likely at high initial cuff volumes.     

A comparison of the oropharyngeal leak pressure between the reusable Classic laryngeal mask airway and the single-use Soft Seal laryngeal mask airway

We tested the oropharyngeal leak pressure with the reusable laryngeal mask airway and the single-use Soft Seal laryngeal mask airway. These two types of laryngeal mask airway (LMA) have a similar design but the reusable LMA cuff is made from silicone whereas the Soft Seal LMA cuff is polyvinylchloride. Thirty-five healthy subjects were anaesthetized and paralyzed and the two types of Soft Seal LMA were compared in a blinded randomized cross-over trial. The oropharyngeal leak pressure was significantly higher with the Soft Seal than the reuable (21 +/- 7.6 and 16 +/- 6.7 cm H2O respectively, P = 0.002). However, in four subjects the oropharyngeal leak pressure was higher with the reusable by > 4 cm H2O. We concluded that the reusable LMA may provide a better seal in some individuals but that, on average, the Soft Seal provides a higher oropharyngeal leak pressure than the reusable LMA.