COMPARISON OF THE USE OF THE LARYNGEAL MASK AND FACE MASK BY INEXPERIENCED PERSONNEL

Ten junior doctors with no postgraduate anaesthetic experienceattempted to ventilate the lungs of 50 anaesthetized patients,using either a laryngeal mask or a Guedel airway and face mask.Success was defined as the production of two successive tidalvolumes exceeding 800 ml within 40 s. The failure rate was significantlygreater using the laryngeal mask compared with the face mask(P < 0.05) and the average time was significantly longerwith the laryngeal mask than with the face mask (P < 0.01). The results from this investigation suggest the laryngealmask airway cannot be recommended as a resuscitation devicefor use by inexperienced operators.     

The laryngeal tube compared with the laryngeal mask: insertion,gas leak pressure and gastric insufflation

Background. We have compared the laryngeal tube and laryngealmask in 22 patients for the success rate of insertion, gas leakpressure and the incidence of gastric insufflation. Method. In a randomized, crossover design, the laryngeal tubeand laryngeal mask were inserted in turn after induction ofanaesthesia and neuromuscular block. The cuffs were inflateduntil the intracuff pressure reached 60 cm H₂O. We measuredadequacy of ventilation and the minimum airway pressure at whichgas leaked around the cuff. The presence or absence of gastricinsufflation was studied at an inflation pressure of 20 cm H₂O. Results. It was possible to ventilate through the laryngealtube in 21 patients and through the laryngeal mask in 21 patients.The mean leak pressure for the laryngeal tube (26 (SD 5) cmH₂O) was significantly greater than that for the laryngeal mask(19 (4) cm H₂O) (P<0.01; 95% confidence intervals for meandifference: 5.3–10.2 cm H₂O). Gastric insufflation didnot occur when the laryngeal tube was used and was noted inthree patients when the laryngeal mask was used. Conclusion. The laryngeal tube provides a better seal in theoropharynx than the laryngeal mask. Br J Anaesth 2002; 89: 729–32     

ProSeal versus the Classic laryngeal mask airway for positive pressure ventilation during laparoscopic cholecystectomy

Background. We tested the hypothesis that the ProSeal laryngealmask airway (PLMA) is a more effective ventilatory device thanthe Classic laryngeal mask airway (LMA     

Complications associated with removal of the laryngeal mask airway: A comparison of removal in deeply anaesthetised versus awake patients

The purpose of the study was to compare the incidence of complications (coughing, biting, retching, vomiting, excessive salivation and airway obstruction) associated with removal of the laryngeal mask airway. The laryngeal mask airway was used in 100 adults undergoing urological procedures. The patients were randomly assigned to two groups. In 50 patients the laryngeal mask was removed by a nurse when the patient responded to commands in the recovery area. In the other 50 patients it was removed by the anaesthetist with the patient deeply anaesthetized in theatre. The majority of patients were elderly men who had relatively short procedures. The incidence of gastric regurgitation was assessed by measurement of pH of secretions at the tip of the laryngeal mask airway. Complications occurred more frequently in the awake patients (P < 0.01). Most were minor and occurred before removal of the laryngeal mask airway during emergence in the recovery room. Airway obstruction occurred in three patients in whom the laryngeal mask was removed in the recovery room. In two of these patients the oxygen saturation decreased below 80% and the other to 90%. No decrease in arterial oxygenation occurred in the anaesthetised patients in whom the laryngeal mask was removed by the anaesthetist. In 14 patients in the awake group the pH of secretions at the tip of the laryngeal mask was ≤3 compared with only four patients in the anaesthetised group (P < 0.05). It is concluded that it may be safer to remove the laryngeal mask airway whilst the patients are deeply anaesthetised in the operating room than when they are awake in the recovery room.     

Intubating laryngeal mask for airway management in lateral decubitus state: comparative study of right and left lateral positions

Background. The intubating laryngeal mask has been used forthe emergency management of the airway in patients placed inthe lateral decubitus position. We have conducted this prospectivestudy to compare the feasibility of placement of an intubatinglaryngeal mask and blind tracheal intubation guided by the intubatinglaryngeal mask in patients placed in the right and the leftlateral positions. Methods. A total of 82 adults of both sexes with normal airways,scheduled for cholecystectomy, were allocated randomly to beplaced in either the right (n=41) or left (n=41) lateral positionfor the insertion of an intubating laryngeal mask and blindtracheal intubation guided by the intubating laryngeal maskunder balanced general anaesthesia. A sequence of standard manoeuvreswas performed after each failed attempt at intubating laryngealmask placement and intubation. Results. The intubating laryngeal mask was placed in all patientsat the first attempt. Ventilation of the lungs through the intubatinglaryngeal mask was possible in 40 patients (97.5%) from eachgroup after the first attempt at insertion (P=1). Followingadjustments, adequate ventilation could be achieved in all patients.The first attempt success rates of blind tracheal intubationwere 85.3% (35/41) and 87.8% (36/41) in the right and left lateralgroups, respectively (P=1). The remaining patients from bothgroups (except for one patient in the left lateral group whohad a failed intubation) were intubated at the second attempt. Conclusion. Insertion of the intubating laryngeal mask and blindtracheal intubation through it in the lateral position is feasiblein patients with normal airways. These procedures have a highand comparable success rate when patients are placed in theright and left lateral positions.     

Cricoid pressure impedes placement of the laryngeal mask airway and subsequent tracheal intubation through the mask

We have studied 40 patients to see if cricoid pressure affectsthe success rate of ventilation through, and the position of,the laryngeal mask and subsequent fibrescope-aided trachealintubation. Adequate ventilation of the lungs was produced throughthe laryngeal mask in 19 of 20 patients in the control group,but in only 10 of 20 patients in the cricoid pressure group(P < 0.002). The laryngeal mask was positioned correctlyin 16 patients in the control group, but in only two patientsin the cricoid pressure group (P < 0.001). Tracheal intubationwas accomplished in 19 patients in the control group, but inonly three patients in the cricoid pressure group (P < 0.001).Release of cricoid pressure after placement of the laryngealmask improved the view of the glottis, but tracheal intubationwas still difficult because of laryngeal deviation. These resultsshow that cricoid pressure impedes placement of the laryngealmask and subsequent fibrescope-aided tracheal intubation. (Br.J. Anaesth. 1994; 72: 47–51)      

Cricoid pressure impedes placement of the laryngeal mask airway

We have studied 22 patients to examine whether or not cricoidpressure affects ventilation of the lungs via the laryngealmask and its correct positioning. In a randomized, crossoverdesign, the laryngeal mask was inserted with or without cricoidpressure applied with a standardized force of 30 N using a cricoidyoke. A standardized pillow (6 cm in height) was placed underthe patient occiput, but the neck was not supported. Ventilationof the lungs via the laryngeal mask was adequate in all patientswhen no cricoid pressurewas applied, but in only three of 22patients when cricoid pressure was applied (P <<0.001; 95% confidence interval (Cl) 0.72–1.0). The mask waspositioned correctly in 18 patients when no pressure was applied,and in none after application of cricoid pressure (P <<0.001; 95% Cl 0.66–0.98). We had planned to study, inan additional 20 patients, the effect of cricoid pressure withouta pillow under the occiput; placement of the mask, however,was difficult even when cricoid pressure was not applied andthere was a high incidence of bleeding from the oropharynx.We thus abandoned that part of the study after eight patients.In those eight patients, the success rate of ventilation viathe laryngeal mask was lower when cricoid pressure was applied.We conclude that when sufficient force was applied, cricoidpressure, regardless of the method of application, did impedeplacement of the laryngeal mask. (Br. J. Anaesth. 1995; 74:521–525)     

EFFECT OF THE LARYNGEAL MASK AIRWAY ON LOWER OESOPHAGEAL SPHINCTER PRESSURE IN PATIENTS DURING GENERAL ANAESTHESIA

We have studied the tone of the lower oesophageal sphincter(LOS) in 40 adults undergoing routine body surface surgery andallocated randomly to receive anaesthesia either by face maskand Guedel airway or by laryngeal mask airway. In the laryngealmask group there was a mean (SEM) decrease in barrier pressure(LOS minus gastric pressure) of 3.6 (1.4) cm H², compared witha mean increase of 2.2 (1.2) cm H2O in the face mask group (P< 0.005).     

Comparison of the reinforced laryngeal mask airway and tracheal intubation for nasal surgery

Airway maintenance and protection during anaesthesia and recovery provided by the reinforced laryngeal mask airway was compared with the sequential use of a tracheal tube followed by the Guedel airway in 66 patients having anaesthesia for nasal surgery. One patient was withdrawn from the laryngeal mask group because the airway was difficult to position. All patients had an oropharyngeal pack inserted and Moffett's solution instilled into the nasal cavities. At the end of surgery the nasal cavities were packed. During operation airway maintenance was good and airway protection was equally effective in both groups. Contamination of the lower airway occurred in only five patients. During recovery from anaesthesia the laryngeal mask and Guedel airway were well tolerated by most patients, but only the mask laryngeal provided an unobstructed airway in all patients. The laryngeal mask protects the larynx from contamination during and after operation until the return of the patient's own protective reflexes.     

ProSeal laryngeal mask protects against aspiration of fluid in the pharynx

Background. The ProSeal laryngeal mask airway (PLMA) is a newdevice designed to isolate the airway from the digestive tract. Methods. We studied the ability of the PLMA to isolate the airwayin 103 anaesthetized adults who were breathing spontaneouslyor given neuromuscular blocking agents, by filling the hypopharynxwith methylene blue-dyed saline introduced down the drainagetube once the mask was in place. At the beginning and end ofthe procedure, a fibre-optic bronchoscope was passed down theairway tube to observe any dyed saline in the bowl of the mask. Results. The PLMA was positioned correctly in all successfulattempts (102 out of 103 attempts) and was able to isolate theglottis from fluid in the hypopharynx in all patients initially.Leakage of saline into the bowl of the mask occurred in twopatients in whom displacement of the mask was caused by upperairway events during the procedure. In the remaining 100 patients,the glottis was isolated successfully for the duration of theprocedure. Conclusions. The PLMA can be positioned reliably. It can isolatethe airway from fluid in the hypopharynx. Br J Anaesth 2002; 88: 584–7     

Mucosal pressure and oropharyngeal leak pressure with the ProSeal versus laryngeal mask airway in anaesthetized paralysed patients

The ProSeal laryngeal mask airway (PLMA) is a new laryngealmask device with a larger, wedge-shaped cuff and a drainagetube. We tested the hypothesis that directly measured mucosalpressure and oropharyngeal leak pressure (OLP) are higher forthe PLMA compared with the laryngeal mask airway (LMA     

Cardiovascular changes with the laryngeal mask airway in cardiac anaesthesia

Background. The laryngeal mask airway (LMA) causes fewer haemodynamicchanges, particularly in mean arterial pressure (MAP) and heartrate (HR), than tracheal intubation using either laryngoscopyor the intubating LMA. There are no data for patients with coronaryartery disease. Method. We studied 27 patients having coronary artery bypassgrafting, prospectively randomized to be managed with eitherthe LMA or tracheal intubation using either laryngoscopy orthe ILMA. We used invasive monitoring to compare the haemodynamiceffects in each group during induction and emergence from anaesthesia. Results. Both methods of intubation caused an increase in MAPcompared with the LMA (P<0.05). Mixed venous oxygen saturationincreased in the intubated patients but not with the LMA (P<0.05).HR did not change at induction in the LMA group. Changes atextubation were similar in all groups but cardiac index waslower in the LMA group (P<0.05). Conclusion. The LMA allows airway management without hypertensionand tachycardia and should be considered when anaesthetizingpatients with coronary disease. Br J Anaesth 2004; 92: 885–7     

CRICOID PRESSURE MAY PREVENT INSERTION OF THE LARYNGEAL MASK AIRWAY

We have studied 42 female patients undergoing elective day-casesurgery allocated randomly to two groups. After induction ofanaesthesia an attempt was made to insert a laryngeal mask airwayafter application of cricoid pressure in one group or with nocricoid pressure in the other. The anaesthetist was unawareof the application, or not, of cricoid pressure. Successfulinsertion was achieved at the first or second attempt in 19of the 22 patients in the non-cricoidpressure group, but inonly three of the 20 patients in the cricoid pressure group(X² 18.62, P <0.001). The laryngeal mask airway was theninserted successfully in all 17 patients after removal of cricoidpressure. The implications of having to remove cricoid pressureif a laryngeal mask airway is to be inserted are discussed.(Br. J. Anaesth. 1992; 69: 465–467)     

The reinforced laryngeal mask in dental day surgery

Sixty adult patients undergoing removal of third molars under general anaesthetic in the Cambridge day surgery unit were randomly allocated to receive either a conventional anaesthetic employing nasotracheal intubation (NETT), pharyngeal gauze pack and inhalation agents or the reinforced laryngeal mask airway (RLMA) and total intravenous anaesthesia. Thirty patients were studied in each group. Immediate recovery times were significantly longer in the NETT group (P = 0.01). Surgical access was adequate in both groups. Postoperative muscle pains were significantly less in the reinforced laryngeal mask airway (RLMA) group (P= 0.0001). The RLMA provides a reliable method of airway management during removal of impacted third molars, with a reduction in postoperative morbidity when compared with conventional nasotracheal intubation involving the use of suxamethonium.     

The reinforced laryngeal mask in paediatric outpatient dental surgery

One hundred and twenty ASA I and II grade children aged 2-9 years scheduled for outpatient dental extractions under general anaesthesia were studied. They were allocated randomly to one of three groups for airway management: group R had anaesthesia with a reinforced laryngeal mask airway, group L with a standard laryngeal mask airway and group N with a nasal mask. Anaesthesia was induced in all children using halothane in 50% nitrous oxide with oxygen and maintained on halothane in 67% nitrous oxide with oxygen. An Ayre's T-piece with Jackson-Rees modification was used. The incidence of airway obstruction was significantly lower and surgical access significantly better with the reinforced laryngeal mask airway when compared with the standard laryngeal mask airway. However, the reinforced laryngeal mask airway was significantly more difficult to insert when compared with the standard laryngeal mask airway. On comparing the reinforced laryngeal mask airway with the nasal mask, there were significantly fewer episodes of airway obstruction, better oxygen saturation, less increase in heart rate and fewer arrhythmias in the reinforced laryngeal mask airway group. Total time for the procedures was the same for all three groups. Thus, the reinforced laryngeal mask airway was found to be a favourable alternative to the standard laryngeal mask airway and nasal mask for paediatric outpatient dental extractions.     

Efficacy and safety of the laryngeal mask airwayvs Guedel airway following tracheal extubation

PURPOSE: To compare the safety and efficacy of the laryngeal mask airway (LMA) with the Guedel airway during the recovery period. METHODS: In a prospective randomised trial in the Post Anesthesia Care Unit (PACU), 52 patients (ASA 1 and 2) were randomised to receive either a laryngeal mask airway (LMA: n = 26) or a Guedel airway (n = 26) during the recovery period after middle ear surgery. Ease of airway maintenance was graded and the presence of coughing was noted. Peripheral arterial oxygen saturation (SpO2) was measured continuously by pulse oximetry in the PACU. Readings were taken on arrival (time 0) and for five minutes afterwards. RESULTS: There was no difference in sex, age, weight or incidence of smoking between the two groups. In the LMA group 25 patients required no airway manipulation and only one patient required repositioning of the LMA. In the Guedel group severe difficulty maintaining the airway was experienced in two patients, moderate difficulty in five patients and mild difficulty in 12 patients. Seven patients required no airway manipulation. The LMA group showed higher ease of airway maintenance scores, (P = < 0.0001) and less coughing (P = 0.0496). At time 0 and at one minute the LMA group had higher median SpO2 (97% and 97%) than the Guedel group (95% and 96%), (P = 0.0002 and 0.0362). There was no further difference in SpO2. CONCLUSIONS: The LMA provides easier airway maintenance, less coughing and initially higher median SpO2 when compared with the Guedel airway in the recovery period.     

Fibreoptic views through the laryngeal mask and the intubating laryngeal mask.

BACKGROUND AND OBJECTIVE: The intubating laryngeal mask (intubating laryngeal mask airway) was designed to facilitate blind intubation. Its value as an adjunct to fibreoptic laryngoscopy has not been evaluated. This study compares the intubating laryngeal mask airway with the standard laryngeal mask airway as conduits for fibreoptic laryngoscopy. METHODS: The fibreoptic view of the laryngeal inlet was graded via both devices in 60 anaesthetized patients. The fibreoptic view through the intubating laryngeal mask airway was assessed after the central epiglottic elevator bar had been lifted out of the field of vision by an 8-mm Euromedical tracheal tube, which was inserted to a depth of 18 cm. The fibreoptic view from the aperture bars of the laryngeal mask was recorded. RESULTS: The vocal cords were viewed less frequently through the intubating laryngeal mask airway (52%) than through the laryngeal mask airway (92%) [difference = 40% (95% CI = 26% to 54%), P < 0.0001]. CONCLUSION: The view of the laryngeal inlet is better through the laryngeal mask airway than through a tracheal tube inserted to 18 cm in the intubating laryngeal mask.     

Removal of the laryngeal mask airway in children: anaesthetized compared with awake

We studied 60 children, aged 12 months to 8 yr, undergoing plastic surgery under general anaesthesia supplemented by regional anaesthesia. Patients were allocated randomly to have the laryngeal mask airway removed either on awakening or while anaesthetized. Subsequent observation of respiratory factors and oxygen saturation showed a significant difference between the groups for coughing (P < 0.001), with a greater incidence (17 of 33) in the awake group compared with those from whom the laryngeal mask airway was removed while anaesthetized (two of 27). There were no differences in the incidences of laryngospasm, desaturation (< 95%) and excess salivation between the groups. Removed of the laryngeal mask airway during deep anaesthesia reduced coughing in the immediate postoperative period.      

Use of the Cuffed Oropharyngeal Airway as an Alternative to the Laryngeal Mask Airway with Positive-pressure Ventilation

Background: The cuffed oropharyngeal airway is a modified Guedel-type oral airway with a cuff at its distal end. The objectives of this study were to compare the ability of the cuffed oropharyngeal airway and the laryngeal mask airway to provide positive-pressure ventilation during general anesthesia, and to assess their relative ease of use and ability to reduce total fresh gas flow rates.

Methods: In this prospective, randomized study, a cuffed oropharyngeal airway (n = 25) or a laryngeal mask airway (n = 25) device was inserted after induction of anesthesia intravenously using 2 mg/kg propofol. While anesthesia was maintained with sevoflurane and nitrous oxide, the leak pressure, leak fraction (the fractional difference between the inspired and expired tidal volume), minimum fresh gas flow rate, and need for airway manipulations were determined. The anesthesia provider who inserted the device completed an evaluation form at the end of the 15-min study period.

Results: Positive-pressure ventilation was established successfully on the first attempt in 92% of the patients when the cuffed oropharyngeal airway was used and in 88% of the patients when the laryngeal mask airway device was used. However, manipulations of the airway device were necessary more frequently (8 vs. 1 patients; P < 0.05) and the leak pressure was less (22 +/- 6 cm water vs. 26 +/- 5 cm water; P < 0.05) with the cuffed oropharyngeal airway than with the laryngeal mask airway. In addition, the leak fraction (0.19 +/- 0.18 vs. 0.31 +/- 0.22; P < 0.05) and the minimum fresh gas flow rate (1.3 +/- 1.5 vs. 2.4 +/- 2.5; P = 0.12) were less in the laryngeal mask airway group.     

Use of a ProSeal laryngeal mask airway for airway maintenance during emergency Caesarean section after failed tracheal intubation

We report the use of the ProSeal^TM laryngeal mask airway toestablish and maintain the airway during emergency Caesareansection when tracheal intubation had failed with conventionallaryngoscopy and mask ventilation was difficult. The ProSeal^TMlaryngeal mask allowed controlled ventilation without gas leakand facilitated drainage of the stomach. Br J Anaesth 2004; 92: 144–6