Airway Seal Research Articles

Comparison of the Effect on the Cuff Pressure of the Endotracheal Tubes Following Cuff Inflation with Air and With Nitrous Oxide – Oxygen during General Anaesthesia - A Prospective, Randomised Study

Background and aims: During general anaesthesia cuffed endotracheal tubes are used to provide airway seal and prevent aspiration. But it has been observed that use of nitrous oxide oxygen for ventilation during anaesthesia leads to rise in intracuff pressure which can be transmitted to the wall of trachea leading to complications. In this study we compared the effect on cuff pressure of Portex endotracheal tubes( high volume low pressure cuffs) and Armoured endotracheal tubes( low volume high pressure cuffs) when the cuffs were inflated with air and with nitrous oxide- oxygen mixture during general anaesthesia using nitrous oxide oxygen. Method:After institutional ethics committee approval 180 patients aged 18 -60 years of ASA status I & IIposted for elective surgeries were randomly allocated in four groups of 45 each. After taking consent and intravenous access general anaesthesia was given with endotracheal intubation. Group A1- Portexendotracheal tube cuff inflated with air. Group A2- Portex endotracheal tube cuff inflated with nitrous oxide- oxygen mixture. Group B1- Armoured endotracheal tube cuff inflated with air.Group B2- Armoured endotracheal tube cuff inflated with nitrous oxide- oxygen mixture. Controlled ventilation was done with nitrous oxide oxygen during the anaesthesia. Endotracheal tube cuff pressure was measured at inflation and at every 30 minutes interval till 90 minutes. Postoperatively patients were observed for any complications such as sore throat, difficulty in swallowing, hoarseness of voice, etc. Results: It was observed that the intracuff pressure in both the high volume low pressure and the low volume high pressure cuffed endotracheal tubes rises with time when the cuffs are inflated with air. The rise was not significant when nitrous oxide - oxygen was used for inflating the cuff in both the groups. Regardless of the type of inflating medium used for cuff inflation the incidence of complications was high in low volume high pressure cuffed endotracheal tubes as compared to high volume low pressure cuffed endotracheal tubes.

Comparison of efficacy of the Laryngeal tube with the Laryngeal mask airway in securing the upper airway

Introduction: The descriptive study is to compare this new device, the Laryngeal tube airway with the Laryngeal mask airway in securing the upper airway during short surgical procedures under general anesthesia. Methodology: After obtaining Institutional approval and written informed consent from all patients, 60 patients ASA I/II, aged 20-50 in this study. They were randomly classified into two groups, Group I (LT) and Group II (LMA). Results: The first attempt success rate in securing the airway with LT was 80.0% and the success rate with LMA was 86.6%. The time taken for securing the airway with LT was 37.76 + 5.27 and with LMA was 29.26 + 4.22 sec. Conclusion: Laryngeal tube is superior to LMA in providing a better airway seal. Keywords: Laryngeal mask airway, Laryngeal tube airway, Complications

Comparison of Proseal Laryngeal Mask Airway (Proseal LMA™) with I-Gel by Fireoptic View of Glottic Aperture in Anaesthetised Adult Patients

Background: The i-gel, a new supraglottic airway device, has been touted to have acceptable airway seal pressure and better ventilatory parameters than Proseal laryngeal mask airway (PLMA) in adults. We propose to test this hypothesis objectively, by comparing fibreoptic grading of positioning of the above airways in adult patients. Methods: Ninety two adult patients undergoing minor surgeries were randomly assigned to either the PLMA or the i-gel group for airway management. Fibreoptic bronchoscope was inserted through airway tube and glottis view was graded according to established scoring system. Other parameters noted include effective airway time, failed insertions, oropharyngeal leak pressure, ease of gastric tube insertion, airway morbidity. The incidence of sore throat, dysphonia, dysphagia was assessed after 24 hours. Results: There was no statistical difference between both groups with respect to effective airway time, success rates at first attempt of insertion, ease of gastric tube insertion, airway trauma during insertion and postoperative airway morbidity. Proseal laryngeal mask airway was placed better than i-gel as confirmed by fibreoptic scoring of glottic view. Oropharyngeal leak pressure was better with PLMA group than i-gel. Conclusion: We conclude that PLMA was placed better than i-gel as confirmed by better fibreoptic scores and had higher oropharyngeal leak pressure. Keywords: Proseal laryngeal mask airway, Fibreoptic view of glottis, igel, Oropharyngeal leak pressure

Supraglottic Airway Devices and Effect on Voice—Comparison of LMA Proseal and i-gel: Double-Blind Randomized Clinical Trial

Laryngeal mask airway (LMA) is an important alternative to endotracheal intubation for all professional voice users undergoing surgery. However, dysphonia is a known complication of LMA Proseal (PLMA) use. The i-gel airway (IGA) provides adequate airway seal without the need for an inflatable cuff. Hence, it helps to minimize the risk of tissue compression. This study compares effect of PLMA and IGA on voice at 24th hour after anesthesia. This is a double-blind randomized clinical trial. Ninety anesthesiologists class 1 adults scheduled for surgeries lasting up to 60-120minutes were included in the study. Participants were randomly allocated to group PLMA (n=43) and group IGA (n=43). Cuff pressure was monitored and maintained at just seal pressure in group PLMA. Voice was evaluated using perceptive and acoustic analysis (jitter, shimmer, and harmonics-to-noise ratio [HNR]) preoperatively and at 24th hour after anesthesia. Voice of patients with pharyngolaryngeal complaints was categorized into rough, breathy, asthenic, strain, or normal pattern. Acoustic parameters jitter, shimmer, and HNR deteriorated significantly in both group PLMA and IGA albeit the change being comparable. Incidence of pharyngolaryngeal complaints was similar in both the groups. A total of 10% patients in group PLMA and 12.5% in group IGA developed breathy voice significant deterioration in all acoustic variables at 24th postoperative hour, but differences were not significant between group PLMA and group IGA. PLMA and IGA both produce comparable and significant deterioration in acoustic variables at 24th hour after short duration general anesthesia.

Evaluation of glottic view through Air‐Q Intubating Laryngeal Airway in the supine and lateral position and assessing it as a conduit for blind endotracheal intubation in children in the supine position

We assessed the feasibility of blind orotracheal intubation in children using the Air-QILA as a conduit in supine position and the glottic view grading by fiberoptic bronchoscope (FOB) through it both in supine and lateral positions. After ethical approval and consent, 60 children were enrolled in the study. In the operating room, after attaching standard monitors to all children, anesthesia was induced with sevoflurane (2-8%) in oxygen (100%). Once the children became sedated, an i.v. access was established and injection glycopyrrolate (10 μg · kg(-1)), fentanyl (2 μg · kg(-1)), and atracurium (0.5 mg · kg(-1)) were administered. After 3 min, the Air-QILA was placed in supine position and glottic view was assessed by using FOB, in supine and right lateral decubitus position. In all children, gradings of glottic view in two different positions were noted. After that all children were turned supine, and orotracheal intubation was done blindly through the Air-QILA. The success rate, insertion time of the Air-QILA, and endotracheal intubation were noted. The Air-QILA placement was successful in 57 children in first attempt and three children required second attempt. However, blind endotracheal intubations through the Air-QILA were successful in 38 children in first attempt and 12 children required second attempt. In the remaining 10 children, where blind endotracheal intubation through the Air-QILA remained unsuccessful, conventional laryngoscopy was performed. In supine and lateral positions, Grade 1 glottic view was seen in 41 and 38 of total 60 patients, respectively. Turning of all children from supine to lateral decubitus position resulted in the deterioration of grading of glottic view in eight children and improvement in two children (P = 0.001). The Air-QILA is an easy to place supraglottic airway device with excellent airway seal and low airway morbidity. It may be useful as a conduit for blind orotracheal intubation in supine position and can be used as an effective alternative to FOB in low resource settings.

Clinical evaluation of the Baska Mask® laryngeal mask in adult patients in ambulatory surgery

ObjectiveTo evaluate the clinical performance of the Baska Mask®, a new second-generation supraglottic airway device with a self-inflating cuff and two side suction channels for continuous aspiration. Material and methodsEighty adult patients without difficult airways were prospectively included. Ease of insertion and number of attempts needed, quality of ventilation, airway seal pressure, fiberoptic view, ease of gastric access, and complications were assessed. Sizes 3, 4, 5 were analyzed and compared. ResultsFirst attempt insertion success rate was 88% and the overall rate was 100%, although additional maneuvers were necessary in 44% of the cases. The ventilation was adequate in 96%, with 39% of them requiring adjusting maneuvers. Size 3 needed significantly less adjustments, and achieved a higher seal pressure than sizes 4 and 5 combined. The airway seal pressure was 33±7cmH2O. Complete or partial vocal cords were visible in 90% of the 66 cases assessed. Partial obstruction, caused by distortion of the cuff-free border, was seen in 5%, and no glottic structures were identified in 5%. Gastric access was easy in all cases. Complications were mild and transient. ConclusionsThe Baska Mask achieves a high seal pressure, effective ventilation, and a quick access to drain gastric contents. However, additional adjustment maneuvers are frequently required to insert the mask and to optimize ventilation.

Evaluación clínica de la mascarilla laríngea Baska Mask® en pacientes adultos en cirugía mayor ambulatoria

ObjectiveTo evaluate the clinical performance of the Baska Mask®, a new second-generation supraglottic airway device with a self-inflating cuff and two side suction channels for continuous aspiration. Material and methodsEighty adult patients without difficult airways were prospectively included. Ease of insertion and number of attempts needed, quality of ventilation, airway seal pressure, fibreoptic view, ease of gastric access, and complications were assessed. Sizes 3, 4, 5 were analyzed and compared. ResultsFirst attempt insertion success rate was 88% and the overall rate was 100%, although additional maneuvers were necessary in 44% of the cases. The ventilation was adequate in 96%, with 39% of them requiring adjusting maneuvers. Size 3 needed significantly less adjustments, and achieved a higher seal pressure than sizes 4 and 5 combined. The airway seal pressure was 33±7cmH2O. Complete or partial vocal cords were visible in 90% of the 66 cases assessed. Partial obstruction, caused by distortion of the cuff-free border, was seen in 5%, and no glottic structures were identified in 5%. Gastric access was easy in all cases. Complications were mild and transient. ConclusionsThe Baska Mask achieves a high seal pressure, effective ventilation, and a quick access to drain gastric contents. However, additional adjustment maneuvers are frequently required to insert the mask and to optimize ventilation.

Safety and efficacy of laryngeal mask airways during tracheostomy

We read Price et al.'s report discouraging use of the laryngeal mask (LMA) during percutaneous dilatational tracheostomy with interest 1, as we have used a LMA Unique™ for this technique as standard practice for over a year. None of the 32 unselected critically ill patients that we have treated so far have experienced significant deterioration of cardiorespiratory function, and we have only experienced problems with the airway seal in one patient, who had a body mass index of over 30 kg.m−2 and required high ventilatory pressures, for whom tracheal intubation was required. We have used the correct size of LMA according to the manufacturer's instructions, but stabilise it by routinely inserting a cylinder of gauze on each side and securing it with tape. This reduces air leak, avoiding any clinically relevant derecruitment during tracheostomy. Subsequent fibreoptic bronchoscopy enables transillumination of soft tissue and tracheal structures at the tracheostomy site, as previously identified by clinical and ultrasonographic examination, and confirms correct placement of the PercuTwist tracheostomy tube, under direct vision. We suggest, therefore, that the problems Price et al. report may be due to either their choice of the LMA Supreme™ or their patient selection. Furthermore, we disagree with the authors that positioning the tracheal tube above the vocal cords during tracheostomy is safe, because this ‘traditional’ method does not guarantee airway protection, can facilitate complete tracheal tube dislodgment with potentially severe consequences, and could lead to cuff-related damage to the laryngeal structures. Price et al. are to be congratulated on adding valuable evidence to the published data in this area, but as our experience shows, it is too early to discount LMA-assisted percutaneous dilational tracheostomy as a safe alternative to ‘traditional’ tracheostomy.

Role of laryngeal mask airway in laparoscopic cholecystectomy.

Laparoscopic cholecystectomy is one of the most commonly performed surgical procedures and the laryngeal mask airway (LMA) is the most common supraglottic airway device used by the anesthesiologists to manage airway during general anesthesia. Use of LMA has some advantages when compared to endotracheal intubation, such as quick and ease of placement, a lesser requirement for neuromuscular blockade and a lower incidence of postoperative morbididy. However, the use of the LMA in laparoscopy is controversial, based on a concern about increased risk of regurgitation and pulmonary aspiration. The ability of these devices to provide optimal ventilation during laparoscopic procedures has been also questioned. The most important parameter to secure an adequate ventilation and oxygenation for the LMA under pneumoperitoneum condition is its seal pressure of airway. A good sealing pressure, not only state correct patient ventilation, but it reduces the potential risk of aspiration due to the better seal of airway. In addition, the LMAs incorporating a gastric access, permitting a safe anesthesia based on these commented points. We did a literature search to clarify if the use of LMA in preference to intubation provides inadequate ventilation or increase the risk of aspiration in patients undergoing laparoscopic cholecystectomy. We found evidence stating that LMA with drain channel achieves adequate ventilation for these procedures. Limited evidence was found to consider these devices completely safe against aspiration. However, we observed that the incidence of regurgitation and aspiration associated with the use of the LMA in laparoscopic surgery is very low.

Use of Microcuff(®) endotracheal tubes in paediatric laparoscopic surgeries.

Background and Aims:Traditionally, uncuffed endotracheal tubes have been used in children. Cuffed tubes may be useful in special situations like laparoscopy. Microcuff® endotracheal tube is a specifically designed cuffed endotracheal tube for the paediatric airway. We studied the appropriateness of Microcuff® tube size selection, efficacy of ventilation, and complications, in children undergoing laparoscopy.Methods:In a prospective, observational study, 100 children undergoing elective laparoscopy were intubated with Microcuff® tube as per recommended size. We studied appropriateness of size selection, sealing pressure, ability to ventilate with low flow, quality of capnography and post-extubation laryngospasm or stridor.Results:Mean age of the patients was 5.44 years (range 8 months 5 days–9 years 11 months). There was no resistance for tube passage during intubation in any patient. Leak on intermittent positive pressure ventilation at airway pressure ≤20 cm H2O was present in all patients. Mean sealing pressure was 11.72 (1.9 standard deviation [SD]) cm H2 O. With the creation of pnemoperitoneum, mean intracuff pressure increased to 12.48 (3.12 SD) cm H2 O. With head low positioning, mean cuff pressure recorded was 13.32 (2.92 SD). Ventilation at low flow (mean flow 1 L/min), plateau-type capnography was noted in all patients. Mean duration of intubation was 83.50 min. Coughing at extubation occurred in 6 patients. Partial laryngospasm occurred in 4 patients, which responded to continuous positive airway pressure via face mask. Severe laryngospasm or stridor was not seen in any patient.Conclusion:Microcuff® tubes can be safely used in children if size selection recommendations are followed and cuff pressure is strictly monitored. Advantages are better airway seal and effective ventilation, permitting use of low flows.

Comparative study between LMA-Proseal™ and Air-Q® Blocker for ventilation in adult eye trauma patients

BackgroundThe disposable Air-Q® Blocker Masked Laryngeal Airway (MLA) is a new supraglottic device used for intubation, rescue ventilation, and for esophageal suctioning. Laryngeal Mask Airway-Proseal™ is a well known supraglottic device in clinical practice. The aim of the study was to compare Air-Q® Blocker against LMA-Proseal™ as supraglottic devices for ventilation.MethodsSixty adult healthy patients scheduled for eye trauma surgeries under general anesthesia were randomly allocated into 2 groups; Group A (n = 30), where Air-Q® Blocker is used, Group P (n = 30), where LMA-Proseal™ is used. The success rate and time of their insertion were measured. Laryngeal view grading was assessed by fiberoptic bronchoscope. Ease of gastric tube placement and any post-operative complications (airway edema, sore throat or hoarseness) were also measured. Stress response of device insertion was measured using the vital sign measurements.ResultsSuccess of insertion at 1st attempt was (90%) in Group A and (83.3%) in Group P. Insertion time was 18.37 ± 3.77 s in Group (A), while 23.43 ± 3.54 s in Group P, (p < 0.001). Airway seal pressure was comparable in both groups. Full view of vocal cords amounted to (76.7%) in Group A, and (56.7%) in Group P respectively. 1st Attempt Gastric Tube Insertion was (93.3%) in Group A, and (83.3%) in Group P. comparison of previous data in both groups showed no statistical significant differences between them. The incidence of postoperative complications and post insertion hemodynamic stress response was statistically nonsignificant when compared between the 2 groups.ConclusionThe Air-Q® Blocker demonstrated to be remarkably good as a ventilatory device, with adequate airway seal pressure, and improved facilitation of gastric tube insertion compared to LMA-Proseal™. Minimal pressor response was achieved after insertion with no statistical significance.

Cross-Over Assessment of the AmbuAuraGain, LMA Supreme New Cuff and Intersurgical I-Gel in Fresh Cadavers

Background: The AmbuAuraGain is a new single-use supraglottic airway device with gastric channel designed to facilitate intubation. The aim of the study was to assess the anatomic position and the performance of the AuraGain in fresh cadavers compared to that of the Intersurgical i-gel and LMA Supreme New Cuff. Methods: The 3 devices were inserted in random order in 7 fresh cadavers without difficult airway criteria. The assessed items were: Insertion time, number of attempts and ease of insertion, airway seal pressure, ease of gastric tube insertion, endoscopic view of vocal cords, efficacy of guided tracheal intubation through the AuraGain and i-gel, and anatomic fit by lateral X-ray and neck dissections. Results: All devices were successfully inserted within 3 attempts, except for one case of the LMA Supreme. Adjusting manoeuvres were often required to accomplish correct insertion. A 16 G gastric tube was easily advanced through all AuraGain and LMA Supreme devices. Fiberoptic tracheal intubation was effectively achieved through all AuraGain and i-gel devices in less than 60 s. Lateral X-ray and neck dissections confirmed optimal alignment of all devices with the respiratory and digestive tracts. Conclusions: Insertion of the new AmbuAuraGain required adjusting manoeuvres in some cases, as observed with the other two devices, and achieved similar airway seal pressures. Passage of a large bore gastric tube was as fast as with the LMA Supreme and ease of guided intubation was similar to that of the i-gel.

A Randomised Comparison of the Performance of ProSeal® Laryngeal Mask Airway with the i-gel® for Spontaneous and Controlled Ventilation during Routine Anaesthesia in European Population

Study objective: The aim of the study was to determine if there is a clinically significant difference in the performance (Ease of insertion, manipulations, ventilator performance, leak pressures and complications) of two second generation supraglottic airways (LMA ProSeal® (Intavent Direct, UK) and the i-gel® (Intersurgical, Wokingham, UK) in non-paralysed European patient population group, during routine anaesthesia with spontaneous and controlled ventilation. Methods: Ninety-eight American Society Anaesthesiologists physical status class I-III patients, undergoing elective surgical procedures, judged suitable for general anaesthesia with a classic LMA were recruited for the trial. Patients were randomised to have either the LMA ProSeal® or the i-gel® group as the supraglottic airway for spontaneous and controlled ventilation during routine anaesthesia prior to induction. Measurements: The primary outcome was first attempt insertion success and time to insertion of either the LMA ProSeal® or i-gel®. Secondary outcomes were, ease of insertion, manipulations to establish patent airway, fibre optic view of larynx, complications during anaesthesia, emergence, recovery, and anaesthetist assessment of device performance. Results: First time insertion success rate was 86% in the LMA ProSeal® group and 78% in the i-gel® group (P=0.61). The number of insertion attempts did not differ between the two groups (P=0.31). The ease of insertion (P=0.64), time to establish a patent airway (P=0.06), number of manipulations (P=0.97) and anatomical positioning of the device (P=0.36) and ventilator performance were similar between the two groups. The number of patients reporting post-operative sequelae and the total number of complications were similar between devices in recovery (P=0.72) and at 24 hours (P=1.0). The leak pressure was significantly higher in the group LMA ProSeal® (28 cmH2O) compared to i-gel® (22 cmH2O) (P=0.002). Conclusion: The LMA ProSeal® and i-gel® have comparable performance characteristics during routine general anaesthesia in non-paralysed patients. The LMA ProSeal® has a higher airway seal that is statistically significantly different and may be clinically important.

Uso de máscara laríngea en un lactante con estenosis subglótica. Reporte de caso y revisión de la literatura

The laryngeal mask has become an alternative to manage the pediatric airway. This is a clinical case of an infant with VACTERL association requiring anesthesia for tracheoesophageal fistula closure and esophageal anastomosis; the infant was successfully managed with laryngeal mask upon failed intubation.The use of the laryngeal mask is an option for the management of the airway in neonates and infants with craniofacial malformations, either alone or as an adjuvant for tracheal intubation and also in neonates with normal airway for complex surgeries, including heart surgery. The evidence points to the use of second-generation devices that allow for an improved airway seal and suction of the GI tract (Proseal® or Supreme®). It is also an alternate device during neonatal resuscitation in patients over 2000 g that cannot be properly managed with a face mask or intubated.

The use of laryngeal mask in an infant with subglottic stenosis—Case report and literature review

The laryngeal mask has become an alternative to manage the pediatric airway. This is a clinical case of an infant with VACTERL association requiring anesthesia for tracheoesophageal fistula closure and esophageal anastomosis; the infant was successfully managed with laryngeal mask upon failed intubation.The use of the laryngeal mask is an option for the management of the airway in neonates and infants with craniofacial malformations, either alone or as an adjuvant for tracheal intubation and also in neonates with normal airway for complex surgeries, including heart surgery. The evidence points to the use of second-generation devices that allow for an improved airway seal and suction of the GI tract (Proseal® or Supreme®). It is also an alternate device during neonatal resuscitation in patients over 2000g that cannot be properly managed with a face mask or intubated.

A randomized crossover comparison between the Laryngeal Mask Airway‐Unique™ and the air‐Q Intubating Laryngeal Airway in children*

The purpose of this randomized crossover study was to evaluate the feasibility of the air-Q intubating laryngeal airway (ILA) in clinical practice when compared with the Laryngeal Mask Airway-Unique(™) (LMA-U), the current standard of care for primary airway maintenance. We hypothesized that the ILA would have better airway seal pressures and laryngeal alignment than the LMA-U in anesthetized nonparalyzed children. The ILA is a newer supraglottic airway for children with design features that allow it to be used for primary airway maintenance and as a conduit for tracheal intubations. Fifty healthy children, 6-36 months of age, 10-15 kg, who were scheduled for elective surgery in which the use of a size two LMA-U and size 1.5 ILA would be appropriate for airway maintenance, were enrolled into this randomized crossover study. Primary outcome measures were airway leak pressures and fiberoptic grades of view. Secondary outcome measures included ease and time for successful insertion, incidence of gastric insufflation, ventilation parameters, and complications. There were no statistically significant differences in regard to the ease of device insertion, time to ventilation, gastric insufflation, and ventilation parameters between the ILA and the LMA-U. All devices were successfully placed on the first attempt, and there were no instances of failure. There were statistically significant differences in the airway leak pressure between the ILA (19.0 ± 5.4 cmH(2)O) and the LMA-U (16.1 ± 4.9 cmH(2)O), P = 0.001. There were also statistically significant differences in the fiberoptic grades of view between the ILA and LMA-U, P = 0.004. The ILA had higher airway leak pressures and superior fiberoptic grades of view when compared with the LMA-U and can be a suitable alternative to the LMA-U in children weighing 10-15 kg.

The air-Q® intubating laryngeal airway vs the LMA-ProSealTM: a prospective, randomised trial of airway seal pressure*

We performed a prospective, open-label, randomised controlled trial comparing the air-Q(®) against the LMA-ProSeal™ in adults undergoing general anaesthesia. One hundred subjects (American Society of Anesthesiologists physical status 1-3) presenting for elective, outpatient surgery were randomly assigned to 52 air-Q(®) and 48 ProSeal devices. The primary study endpoint was airway seal pressure. Oropharyngolaryngeal morbidity was assessed secondarily. Mean (SD) airway seal pressures for the air-Q(®) and ProSeal were 30 (7) cmH (2) O and 30 (6) cmH(2) O, respectively (p = 0.47). Postoperative sore throat was more common with the air-Q(®) (46% vs 38%, p = 0.03) as was pain on swallowing (30% vs 5%, p = 0.01). In conclusion, the air-Q(®) performs well as a primary airway during the maintenance of general anaesthesia with an airway seal pressure similar to that of the ProSeal, but with a higher incidence of postoperative oropharyngolaryngeal complaints.

I-GEL(TM) VS. AURAONCE(TM) LARYNGEAL MASK FOR GENERAL ANAESTHESIA WITH CONTROLLED VENTILATION IN PARALYZED PATIENTS

The i-gel™ and the AuraOnce™ laryngeal mask are supraglottic airway devices used for airway management during general anaesthesia. Both devices are cheap, disposable and widely used. They may be used with both spontaneous and controlled ventilation. This study compared differences in the seal and peak pressures, and postoperative complications in these devices when used in paralyzed patients under controlled ventilation. A prospective randomized trial was designed to compare the i-gel™ and the AuraOnce™ in paralyzed adult patients under conditions of controlled ventilation. Two hundred and four patients (ASA class 1-3, age 18-89, weight 46-115 kg) were enrolled in the study. Standardized anaesthesia (fentanyl, propofol and sevoflurane in air-oxygen) was administered including neuromuscular blockade. The primary outcome measure was the difference in seal airway pressures between the two devices. Secondary outcome measures included peak airway pressures, insertion data and postoperative profiles--the incidence of sore throat, swallowing difficulties, numb tongue, hearing difficulties, neck pain, nausea and vomiting. First time insertions were 85.6% (i-gel) and 82% (AuraOnce) with overall success rates 96.3% (i-gel) and 94.2% (AuraOnce) (p=0.54). Average insertion times were 11.0 s (i-gel) and 11.6 s (AuraOnce) (p=0.19). Seal pressures were 30.4 cmH(2)O (i-gel) and 27.8 cmH(2)O (AuraOnce) (p=0.007). Peak pressures were 15.3 cmH(2)O (i-gel) and 15.6 cmH(2)O (AuraOnce) (p=0.57). Traumatic insertion occurred in 5.8% of i-gel™ and 2% of AuraOnce™ insertions. The overall incidence of postoperative complications was low, with the i-gel™ causing less sore throat and difficulty swallowing at 24h. Conclusion. Both devices provided effective seals for ventilation under positive pressure. I-gel™ may be a better alternative for the procedures with controlled ventilation because of higher seal pressures and lower incidence of sore throat postoperatively.

Laryngeal mask airway vs the endotracheal tube in paediatric airway management: A meta-analysis of prospective randomised controlled trials

A meta-analysis was performed on prospective randomised controlled trials to assess whether the laryngeal mask airway (LMA) offered any advantage over the conventional endotracheal tube in the paediatric age group. Using the Cochrane methodology, a literature search was carried out through peer-reviewed indexed journals in three medical databases to obtain all publications comparing the LMA with the endotracheal tube in the paediatric age group (age less than 12 years), available till December 2010. Data from 16 randomised controlled clinical trials were selected for analysis. A null hypothesis was formed against each of the seven issues tested using the Fisher's method of combining P values. The LMA was seen to have three advantages over the tracheal tube in the form of lower incidence of cough during emergence, lower incidence of postoperative sore throat and lower incidence of postoperative vomiting (P<0.05). It was seen to offer no advantage over the tracheal tube in incidence of bronchospasm or laryngospasm during emergence; also, it did not offer any advantage in increasing the efficacy of the airway seal. The only disadvantage the LMA had over the tracheal tube was its greater incidence of placement failure in the first attempt.

In reply to: Comparison of safety and efficacy of Supreme laryngeal mask airway and ProSeal laryngeal mask airway

Editor, We wish to thank Xue and colleagues for their interest and astute comments regarding our study. We would like to take the opportunity in this letter to clarify some aspects of our randomized controlled study comparing the safety and efficacy of the Supreme versus the ProSeal laryngeal mask airway. The primary outcome of interest was oropharyngeal leak pressure or airway sealing pressure. Xue et al.1 rightly alluded to the classic paper comparing four methods of airway sealing pressure assessment with the laryngeal mask airway. Keller et al.2 concluded that interobserver reliability of all four tests (audible noise, oral capnography, manometric stability and auscultation) were excellent with low intrinsic variability. For our purposes, we chose the first option – audible noise by listening over the mouth to assess the oropharyngeal leak pressure. Clinically, we found the audible noise test to closely correspond with the manometric stability test. A method similar to ours was performed in a previous published prospective study of 100 patients using the Supreme laryngeal mask airway conducted by Cook et al.3 We do concur that the patients' head and neck position may influence the assessment of oropharyngeal leak pressures for the ProSeal and the Supreme laryngeal mask airways. This was formerly illustrated in two studies for the ProSeal laryngeal mask airway by Xue et al.4 as well as Brimacombe et al.5 Our evaluation of oropharyngeal leak pressures was performed in the neutral position with the patient's occiput resting on a standard single-use foam pillow. This same head and neck posture would be the position in which our patients were placed for the duration of the operation. As yet, no investigator has evaluated the effects of the patients' head and neck position on ventilation and oropharyngeal leak pressures for the Supreme laryngeal mask airway. Certainly, this prompts us to think of it as a viable avenue for further research. Our group chose not to evaluate the anatomical positions of the two supraglottic devices using fibreoptic bronchoscopes, as logistical and ethical concerns proved to be impediments. Advancing this point, Xue et al.4 concluded previously that fibreoptic scoring of the ProSeal cuff position was not an accurate test to assess airway seal and ventilation function. Furthermore, Eschertzhuber et al.6 demonstrated in a cross-over study that there were no differences in fibreoptic position of the ProSeal and the Supreme laryngeal mask airways. The patient population we chose consisted of short duration day-surgery orthopaedic and urology cases at low risk of pulmonary aspiration. We excluded patients with gastrooesophageal reflux, obesity and hiatus hernia. In like fashion with our earlier laryngeal mask airway study,7 it is not our institutional practice to routinely place orogastric tubes with supraglottic airways in this low-aspiration-risk patient population. We had no reported cases of aspiration in both studies.7,8 We agree that intraoperative and postoperative analgesia may affect the assessment of pharyngolaryngeal adverse events such as sore throat, dysphonia and dysphagia. Likewise, so will distracting pain from the operative site. Fentanyl was titrated according to a standardized protocol intraoperatively by the anaesthesiologist and postoperatively by the postanaesthesia care unit nurses. Potential confounders were equally distributed with randomization as seen in Table 1 of our study.8 Assessment of pharyngolaryngeal adverse events was done at multiple time intervals of 1, 2 and 24 h postoperatively to take into account possible time, surgical site and analgesic regime bias. The first attempt success rate for the Supreme was statistically higher than that for the ProSeal laryngeal mask airway in a controlled operating room environment. We admit that extrapolation of our findings to the emergency airway management context with a different spectrum of practitioners in a more hostile location may be inequitable. However, we appeal to the readers of this reply to ponder whether the conduct of a prospective randomized controlled trial to address this specific emergency airway management situation is ethically, numerically and logistically possible.