A prospective, randomized trial of the Ambu AuraGain™ laryngeal mask versus the LMA® protector airway in paralyzed, anesthetized adult men.

BACKGROUND: We hypothesize that oropharyngeal leak pressures differ between the LMA® Protector™ and the AuraGain™, two novel supraglottic airway devices offering the possibility of intubation. METHODS: Ninety-eight male patients ASAI-II were randomly assigned to the AuraGainTM or ProtectorTM group. Oropharyngeal leak pressure was measured by incrementing cuff volume in 10 mL steps from 10 mL to 40 mL. The primary outcome was oropharyngeal leak pressure at 40 mL cuff volume. Secondary parameters such as transdevice intubation success, intubation time, the number of intubation attempts, and resistance during advancement of the endotracheal tube were determined. RESULTS: Mean (SD) oropharyngeal leak pressures at cuff volume of 40 mL was 30.1 (6) cmH2O for the AuraGainTM and 28.2 (7) cmH2O for the LMA ProtectorTM (P=0.142). The mean intracuff pressure for the AuraGainTM was 154 (41) cmH2O and 200 (43) cmH2O for the LMA Protector (P≤0.001). The number of attempts to insert the laryngeal mask was higher for the AuraGainTM group (P=0.002). Intubation time was lower in the AuraGainTM group (15.7 s vs. 18.5 s [ProtectorTM group]; P=0.004), and less resistance in advancing the tracheal tube through the AuraGainTM compared to LMA ProtectorTM device (P<0.001). There were no differences in fiberoptic placement of the endotracheal tube, the number of intubation attempts or postoperative morbidity between the groups. CONCLUSIONS: Because of the higher success rate in first time insertion of the laryngeal mask and the gastric tube, respectively, as well as the lower resistance to insertion of the endotracheal tube we conclude a possible easier handling of the AuraGainTM in anesthetized male patients.

Flexible bronchoscopic intubation through the AuraGain™ laryngeal mask versus a slit Guedel tube: a non-inferiority randomized-controlled trial.

PURPOSE: AuraGainTM, a novel third-generation laryngeal mask, can facilitate insertion of a gastric tube and provide the potential advantage of intubation. Data are lacking on intubation through the AuraGain laryngeal mask. METHODS: Eighty-eight hip or knee surgery patients were enrolled in this parallel randomized-controlled trial. We hypothesized that intubation time using the AuraGain laryngeal mask would be no longer than that for standard flexible bronchoscopic intubation over a slit Guedel tube, with a non-inferiority margin of five seconds. The following data were recorded during a maximum of three intubation attempts: intubation time, number of intubation attempts, degree of resistance to advance the endotracheal tube, and mask placement (i.e., Brimacombe score). Follow-up outcomes, including neck pain, hoarseness, and dysphagia, were also measured two and 24 hr postoperatively. Patients and outcome assessors remained blinded until the last examination. RESULTS: Mean intubation time was similar between the Guedel tube and AuraGain groups (23.6 sec vs 21.4 sec, respectively). The upper limit of the 95% confidence interval (CI) of the difference in mean intubation time between groups fell below our pre-specified non-inferiority margin; therefore, we found the AuraGain laryngeal mask to be non-inferior to the slit Guedel tube (adjusted group difference, -1.6 sec; 95% CI, -3.7 to 0.5). Successful intubation was achieved in the majority of patients (≥ 95%) in each group on the first attempt. No resistance to insertion of the endotracheal tube was encountered in the majority of patients in each group, and no complications were reported during the 24-hr postoperative period. There was no difference in the Brimacombe score or in the status of postoperative morbidity between the two groups. CONCLUSION: We conclude that flexible bronchoscopic intubation through an AuraGain laryngeal mask can be achieved at least as fast as standard bronchoscopic intubation without contributing to additional patient morbidity or postoperative discomfort. TRIAL REGISTRATION: www.clinicaltrials.gov , NCT 02570269. Registered 23 September 2015.

Do mask aperture bars of extraglottic airway devices prevent prolapse of epiglottis causing airway obstruction? A randomized crossover trial in anesthetized adult patients.

STUDY OBJECTIVE: The study objective is to determine whether extraglottic airway devices (EADs) with or without mask aperture bars (MABs) result in similar anatomical positions in patients undergoing surgery. DESIGN: Prospective, randomized, crossover comparison of four extraglottic airway devices. SETTING: Operating theatre at a large teaching hospital. PATIENTS: Eighty consenting patients scheduled to undergo surgery with general anesthesia. INTERVENTIONS: Patients were randomly allocated to receive anesthesia with one of four tested EADs. Two versions of each EAD were inserted in random order; one with and one without MABs. MEASUREMENTS AND MAIN RESULTS: Endoscopic evaluation did not demonstrate any difference between the EADs with or without MABs. Contact between MABs and arytenoids (n=15) and herniation of arytenoids (n=7) was restricted to the Cobra-group patients. In nine patients the epiglottis made contact with a MAB, although this contact was very limited and often unilateral. CONCLUSION: This study demonstrated that the anatomical position of the four tested single-use EADs is similar with or without mask aperture bars. We therefore question whether MABs have a protective role in prevention of airway occlusion and whether MABs are essential components. In the overall majority of EADs with MABs, the latter did not prevent contact with the epiglottis. Contact and herniation of the laryngeal structures are seen more frequently when more than two MABs are present.

Comparison of cuff-pressure changes in silicone and PVC laryngeal masks during nitrous oxide anaesthesia in spontaneously breathing children.

BACKGROUND: The purpose of this study was to evaluate the cuff pressures of four different laryngeal masks in paediatric patients undergoing routine surgery and to determine whether there is a substantial increase in cuff pressure when silicone masks are used compared to PVC laryngeal mask airways. METHODS: Hundred and forty patients aged < 16 yr were randomly allocated to receive one of four extra glottic airway devices: LMA-Classic; LMA-Unique; Soft Seal; or Cobra-PLA. Intracuff pressure was monitored continuously throughout the operative intervention. The primary outcome was measurement of an increase in cuff pressure. First attempt success rate, effective airway time, anatomical position of the airway and incidence of airway morbidity data were monitored. RESULTS: Mean cuff pressure increased within 5 min of N2O exposure, and was substantially higher in the silicone LMA-C,compared to the PVC-based extra glottic airway devices tested, reaching a plateau of the cuff pressure after 45 min.The overall first attempt success rate (97%) and the mean effective airway time (24 ± 9 sec) were very satisfactory and all patients underwent successful surgery. Anatomical position was adequate in most airways, although in 34%of the patients in the Cobra group herniation of either the epiglottis or arytenoids were detected. Airway morbidity due to the devices was insignificant. CONCLUSIONS: This study demonstrated a substantial increase in cuff pressure during anaesthesia for children in whom a silicone-based LMA-C was used, whereas PVC-based extra glottic airway devices showed a much lower increase.

Jaw thrust as a predictor of insertion conditions for the proseal laryngeal mask airway.

We test the hypothesis that the response to jaw thrust is an effective predictor of insertion conditions for the ProSeal laryngeal mask airway (ProSeal LMA). One hundred and sixty patients (ASA grade 1-3, aged >18 yr) were studied. Five anesthetists blinded to the response to jaw thrust participated in the study, each performed >30 insertions. Induction of anesthesia was with propofol titrated to loss of lash reflex and apnea. A standard amount of jaw thrust was applied and any motor response noted by three observers. The ProSeal LMA was inserted using the standard digital technique. Insertion conditions were considered optimal if there was no motor or upper airway reflex response to insertion. There was no response to jaw thrust in 86% (137/160) of patients and insertion was optimal in 76% (121/160) of patients. A response to jaw thrust predicted suboptimal insertion conditions in 74% (17/23) and a lack of response predicted optimal insertion conditions in 84% (115/137). The accuracy, sensitivity and specificity were 0.82, 0.95 and 0.44, respectively. We conclude thatjaw thrust is a reliable predictor of insertion conditions for the ProSeal LMA with the digital insertion technique after induction of anesthesia with propofol. We suggest that clinicians learn how to apply the correct amount of jaw thrust and perform this test routinely.

Gum elastic bougie-guided insertion of the ProSeal laryngeal mask airway is superior to the digital and introducer tool techniques in patients with simulated difficult laryngoscopy using a rigid neck collar.

BACKGROUND: We compared three techniques for insertion of the laryngeal mask airway ProSeal (PLMA) in patients with simulated difficult laryngoscopy using a rigid neck collar. METHODS: Ninety-nine anesthetized healthy female patients aged 19-68 yr were randomly allocated for PLMA insertion using the digital, introducer tool (IT) or guided techniques. Difficult laryngoscopy was simulated using a rigid neck collar. The laryngoscopic view was graded before PLMA insertion. The digital and IT techniques were performed according to the manufacturer's instructions. The guided technique involved priming the drain tube with an Eschmann tracheal tube introducer, placing the introducer in the esophagus under direct vision and railroading the PLMA into position. Failed insertion was defined by any of the following criteria: 1) failed pharyngeal placement, 2) malposition, and 3) ineffective ventilation. RESULTS: The median laryngoscopic view was 3 and the mean interincisor distance was 3.3 cm. Insertion was more frequently successful with the guided technique at the first attempt (guided 100%, digital 64%, IT 61%; P<0.0001), but success after three attempts was similar (guided 100%, digital 94%, IT 91%). The time taken for successful placement was similar among groups at the first attempt, but was shorter for the guided technique after three attempts (guided 31+/-8 s, digital 49+/-28 s, IT 54+/-37 s; P<0.02). CONCLUSION: The guided insertion technique is more frequently successful than the digital or IT techniques in patients with simulated difficult laryngoscopy using a rigid neck collar.

Anesthesia for pediatric gastroscopy: a study comparing the ProSeal laryngeal mask airway with nasal cannulae.

BACKGROUND: We tested the hypothesis that pediatric gastroscopy is more successful using the ProSeal laryngeal mask airway with the drain tube as a conduit to the stomach (ProSeal LMA group) than using nasal cannulae with conventional oral access to the stomach (NC group). METHODS: Sixty children were consecutively and randomly allocated into each group. Patients breathed spontaneously and were given sevoflurane/air/oxygen mixture with propofol 1 mg.kg-1 boluses, as required. Anesthesia was provided by experienced users of both techniques. The following data were collected by an unblinded observer: operation and anesthesia times; cardiorespiratory data; adverse events; and recovery scores. In addition, the surgeon scored the ease of performing the procedure. RESULTS: The mean (range) age and weight was 74 (24-144) months and 26 (10-61) kg. Operation (15 min vs 24 min, P<0.0001) and anesthesia (22 min vs 37 min, P<0.0001) times were shorter in the ProSeal LMA group, but propofol bolus requirements per unit time were similar. Oxygen saturation was higher in the ProSeal LMA group (100% vs 94%, P<0.0006), but other cardiorespiratory variables were similar. There were no differences in the ease of performing the procedure. Hypoxia occurred more frequently in the NC group (20% vs 0%). Recovery scores were similar. CONCLUSIONS: We conclude that pediatric gastroscopy is quicker and has fewer airway complications when performed through the ProSeal LMA than using nasal cannulae and a conventional approach by experienced users.

Guided insertion of the ProSeal laryngeal mask airway is superior to conventional tracheal intubation by first-month anesthesia residents after brief manikin-only training.

In the following pilot study, we compared conventional laryngoscope-guided tracheal intubation (tracheal intubation) and laryngoscope-guided, gum elastic bougie-guided ProSeal laryngeal mask airway insertion (guided ProSeal) for airway management by first-month anesthesia residents after brief manikin-only training. Five first-month residents with no practical experience of airway management were observed performing these techniques in 200 ASA I-II anesthetized, paralyzed adults. Each resident managed 40 patients, 20 in each group, in random order. The number of insertion attempts, effective airway time, ventilatory capability during pressure-controlled ventilation set at 15 cm H2O, airway trauma, and skill acquisition were studied. Data were collected by unblinded observers. Insertion was more frequently successful (100% versus 65%) and effective airway time was shorter (41 +/- 24 s versus 89 +/- 62 s) in the guided ProSeal group (both P < 0.0001). Expired tidal volume was larger (730 +/- 170 mL versus 560 +/- 140 mL) and end-tidal CO(2) lower (33 +/- 4 mm Hg versus 37 +/- 5 mm Hg) in the guided ProSeal group during pressure controlled ventilation (both P < 0.0001). Blood staining was more frequent on the laryngoscope (24% versus 2%; P < 0.0001) in the tracheal intubation group. There was evidence for skill acquisition in both groups. We conclude that laryngoscope-guided, gum elastic bougie-guided insertion of the ProSeal laryngeal mask airway is superior to conventional laryngoscope-guided tracheal intubation for airway management in terms of insertion success, expired tidal volume, and airway trauma by first-month anesthesia residents after brief manikin-only training. The guided ProSeal technique has potential for cardiopulmonary resuscitation by novices when conventional intubation fails.

Comparison of three disposable extraglottic airway devices in spontaneously breathing adults: the LMA-Unique, the Soft Seal laryngeal mask, and the Cobra perilaryngeal airway.

BACKGROUND: The authors compared three disposable extraglottic airway devices in spontaneously breathing anesthetized adults: the LMA-Unique (LMA-U; The Laryngeal Mask Company, San Diego, CA), the Soft Seal laryngeal mask (SS-LM; Portex Ltd., Hythe, United Kingdom), and the Cobra perilaryngeal airway (Cobra-PLA; Engineered Medical Systems, Inc. Indianapolis, IN). METHODS: Three hundred twenty consecutive adults (American Society of Anesthesiologists physical status I-III; aged 18-80 yr) were randomly allocated for airway management with one of the three devices. Anesthesia was with fentanyl-propofol for induction and a sevoflurane-nitrous oxide-oxygen-fentanyl mixture for maintenance. Intraoperative data were collected by an unblinded observer about ease of insertion, effective airway time, oropharyngeal leak pressure, anatomical position (determined with a rigid endoscope), intracuff pressure changes, and airway trauma. Data were collected by a blinded observer about sore throat, dysphagia, and dysphonia 2 h after surgery. RESULTS: Insertion was easier with the LMA-U and SS-LM than with the Cobra-PLA (P < 0.02), but the overall failure rates were similar. Effective airway times were similar among groups. Oropharyngeal leak pressure was lower with the LMA-U than with the SS-LM and Cobra-PLA (P < 0.001). Intracuff pressure increased during surgery with all extraglottic airway devices. Anatomical position was better with the Cobra-PLA than with the SS-LMA (P < 0.001) and better with the SS-LM than with LMA-U (P < 0.001). Blood staining was detected more frequently with the Cobra-PLA than with the LMA-U and SS-LM (P < 0.001), but there were no differences in airway morbidity. CONCLUSION: The LMA-U and SS-LM are easier to insert and cause less trauma than the Cobra-PLA, but the Cobra-PLA has a more effective seal than the LMA-U and better endoscopically determined anatomical position than the LMA-U and SS-LM.

Suction catheter guided insertion of the ProSeal laryngeal mask airway is superior to the digital technique.

PURPOSE: We tested the hypothesis that digital insertion of the ProSeal laryngeal mask airway (ProSeal LMA) is more successful when using a suction catheter (SC) as a guide. METHODS: Two hundred and forty-three patients (ASA physical status I-III; aged 18-84 yr) were randomly allocated for the digital or SC-guided technique. The digital technique was performed according to the manufacturer's instructions. The SC technique involved priming the drain tube with the SC so that it protruded by 15 cm, blindly inserting the SC into the pharynx to a depth of 15 cm, followed by the digital technique. Failed insertion was defined by any of the following criteria: 1) failed passage into the pharynx; 2) malposition; and 3) ineffective ventilation. Any airway trauma, and visible or occult blood was noted. Sore throat, dysphonia and dysphagia were assessed 16 to 24 hr postoperatively. RESULTS: Fewer insertion attempts were required with the SC-guided technique (P = 0.02), but first attempt and overall success were similar. The time taken to provide an effective airway was shorter for the SC-guided technique (36 +/- 24 sec vs 44 +/- 28 sec, P = 0.02). A lateral approach was required less frequently with the SC-guided technique (0% vs 4%, P = 0.0004). There were no adverse events. Mouth trauma was more frequent with the digital technique (P = 0.04), but overall trauma was similar. There were no differences in the frequency of visible or occult blood. There were no differences in postoperative airway morbidity. CONCLUSIONS: The SC-guided technique is more frequently successful than the digital technique and is associated with less mouth trauma during insertion of the ProSeal LMA. We suggest that the SC technique may be a useful alternative when the digital technique fails.

Middle ear pressure changes during anesthesia with or without nitrous oxide are similar among airway devices.

We tested the hypothesis that middle ear pressure (MEP) is influenced by the choice of airway device during anesthesia with or without nitrous oxide (N2O) in the gas mixture. Eighty consecutive anesthetized, paralyzed ventilated patients (ASA physical status I-II, 18-65 yr) were randomly allocated for airway management with the orally inserted tracheal tube, classic laryngeal mask airway, ProSeal laryngeal mask airway, or laryngeal tube suction with or without N2O 66% in the gas mixture. MEP was measured from both ears in random order by a blinded observer before induction of anesthesia and every 10 min for 70 min. In the N2O groups, N2O was changed to air after 40 min. There were no differences in MEP among the airway devices in the N2O or air groups. MEP was unchanged in the air groups but increased in the N2O groups with N2O (P < 0.0001) and decreased with air (P < 0.02). Baseline values for MEP were similar, but MEP was always higher for the N2O groups (P < 0.001). We conclude that the choice of airway device does not influence MEP among orally inserted tracheal tube, classic laryngeal mask airway, ProSeal laryngeal mask airway, and laryngeal tube suction during anesthesia with or without N2O in the gas mixture.

The feasibility of laryngoscope-guided tracheal intubation in microgravity during parabolic flight: a comparison of two techniques.

We determined the feasibility of laryngoscope-guided tracheal intubation (LG-TI) in microgravity obtained during parabolic flight and tested the hypothesis that LG-TI is similarly successful in the free-floating condition, with the patient's head gripped between the anesthesiologist's knees, as in the restrained condition, with the torso strapped to the surface. Three personnel with no experience in airway management or microgravity participated in the study. LG-TI of a sophisticated full-size manikin was attempted on seven occasions in each condition by each investigator after ground-based training. The parabolic flights, which took place in an Airbus 300 over the Atlantic Ocean, provided 23 s of microgravity. During this time, the investigator opened a box with airway equipment, performed LG-TI, and attached and held onto a self-inflating bag. The efficacy of ventilation was assessed during level flight by squeezing the bag and noting whether the manikin sensors indicated a tidal volume > or =300 mL. There were no differences in ventilation success (41% versus 33%) or time to successful insertion (both 18 s) between the free-floating and the restrained conditions. More than 90% of failures were caused by the inability to insert the tracheal tube within 23 s. There were no differences in performance among investigators. We conclude that LG-TI is feasible in microgravity obtained during parabolic flight, but the success rate is infrequent because of severe time restrictions. There were no differences in success rate between the free-floating condition, with the head gripped between the knees, and the restrained condition, with the torso strapped to the surface.