ProSeal?-Kehlkopfmaske in normalgewichtigen und adip?sen Patienten

Background

Most of the data on combining pressure-controlled ventilation (PCV) with positive end-expiratory pressure (PEEP) come from studies with an endotracheal tube (ETT) whereas data on utilization of PEEP with a laryngeal mask airway (LMA) are limited. The LMA-ProSeal? (PLMA) forms a more effective seal of the airway than the LMA-Classic? (CLMA). The application of PEEP when PCV is used with the PLMA could have an impact on oxygenation in adult patients.

Methods

For this study 148 patients with an mean age of 44 years (range18?C65 years) and mean weight of 86?kg (range 49?C120?kg) were recruited in 2 groups: group?N _(Normal): body-mass index (BMI) <30?kg/m² and group?O _(Obesity) BMI ??30 and <36?kg/m². Cardiovascular and pulmonary disease and a history of smoking were exclusion criteria in addition to the usual LMA contraindications. The bispectral index-guided (BIS) anesthesia technique was used with propofol, fentanyl, and remifentanil without muscle relaxants. Measurement of PLMA seal pressure served as recruitment maneuver and PCV was randomly combined with 0?cmH₂O, 5?cmH₂O or 8?cmH₂O PEEP. An arterial blood gas sample was taken 50?min after induction of anesthesia under an inspiratory oxygen fraction (F_IO₂₎ of 0.3. In the first part partial oxygen pressure (p_aO₂) under 0?cmH₂O was compared with p_aO₂ under 5?cmH₂O and in the second part p_aO₂ under 5?cmH₂O was compared with p_aO₂ under 8?cmH₂O. A significant difference was set as p<0.025.

Results

The PLMA could be placed after 3 attempts in 147 patients. The mean seal pressure was in the range of 24?C30?cm?H₂O. Application of randomized PEEP was possible in all patients and ventilation was comparable between corresponding groups. In group?N no differences were found in part?1 (139±28 vs. 141±28?mmHg, p=0.88) or part?2 (127±24 vs. 134±26?mmHg, p=0.35). In group?O there was a significant difference in p_aO₂ in part?1 (75±12 vs. 94±18?mmHg, p=0.02) but not in part?2 (92±21 vs. 103±18?mmHg, p=0.04).

Conclusions

The application of PEEP when PCV is used with the PLMA results in improved oxygenation in obese patients with a BMI ??30 and <36?kg/m² but not in normal weight patients. Alveolar recruitment produced by seal pressure measurements below 30?cm?H₂O was sufficient to produce a clinically significant improvement in oxygenation in most obese patients and there was a significant improvement of oxygenation with PEEP=5?cmH₂O. Both findings are in contrast to findings of studies using an ETT which suggests that higher pressures (40?cmH₂O) are needed for recruitment of collapsed alveoli and higher PEEP (10?cmH₂O) is needed to produce a clinically significant improvement in oxygenation in obese patients. The results of this study support data showing that the consequences of bronchopulmonary airway reactions known to occur with an ETT are less pronounced or absent when an LMA is used.     

A randomized crossover comparison between the Laryngeal Mask Airway-Unique™ and the air-Q intubating laryngeal airway in children

Objectives: 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. Aim: We hypothesized that the ILA would have better airway seal pressures and laryngeal alignment than the LMA‐U in anesthetized nonparalyzed children. Background: 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. Methods: 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. Results: 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 cmH₂O) and the LMA‐U (16.1 ± 4.9 cmH₂O), P = 0.001. There were also statistically significant differences in the fiberoptic grades of view between the ILA and LMA‐U, P = 0.004. Conclusions: 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.     

Oesophageal seal of the novel supralaryngeal airway device I-GelTM in comparison with the laryngeal mask airways ClassicTM and ProSealTM using a cadaver model

Background: Supraglottic airway devices are increasingly used in anaesthesiaand emergency medicine. This study was designed to investigatethe oesophageal seal of the novel supralaryngeal airway device,I-Gel^TM (I-Gel), in comparison with two of the laryngeal maskairways, Classic^TM (cLMA) and ProSeal^TM (pLMA), in a model ofelevated oesophageal pressure. Methods: The three supralaryngeal airway devices were inserted into eightunfixed cadaver models with exposed oesophagi that had beenconnected to a water column producing both a slow and a fastoesophageal pressure increase. The pressure applied until theloss of oesophageal seal during a slow and fast pressure increasewas measured. Results: During the slow increase of pressure, the pLMA withstood anoesophageal pressure up to a median of 58 cm H₂O, while thecLMA was able to block the oesophagus up to a median of 37 cmH₂O, and I-Gel already lost its seal at 13 cm H₂O. One minuteafter maximum pressure had been applied, the pLMA withstoodan oesophageal pressure of 59 cm H₂O, the cLMA of 46 cm H₂O,and I-Gel airway of 21 cm H₂O. A fast release of oesophagealfluid was accomplished through the oesophageal lumen of boththe pLMA and I-Gel. Conclusions: Both the pLMA and cLMA provided a better seal of the oesophagusthan the novel I-Gel airway. The pLMA and I-Gel drain off gastrointestinalfluid fast through the oesophageal lumen. Thus, tracheal aspirationmay be prevented with their use. Further study is necessary.     

Evaluation der neuen Kehlkopfmasken Ambu AuraOnce™ und Intersurgical i-gel™

Background

Supraglottic airway devices (SGAD) have become more important in airway management over the past years and an objective comparison of the available devices is in order.

Methods

In a prospective study the four SGADs LMA-Classic?(cLMA), LMA-ProSeal? (PLMA), Ambu AuraOnce? and Intersurgical i-gel? were compared in groups of 40 patients in ambulatory surgery, with respect to the feasibility of positioning, leak tightness, patient comfort and airway morbidity. The seal test of the airway devices was carried out with a specially constructed pneumotachograph.

Results

Adequate placement on the first attempt was achieved in 92.5% with the cLMA, 85% with the PLMA, 92.5% with the AuraOnce? and 82.5% with the i-gel? (p>0.05). There were no clinically relevant differences in mean insertion times: cLMA 13.8 s (±3.4 s), PLMA 13 s (±3.2 s), AuraOnce? 11.2 s (±2.7 s; p<0.05) and 13.9 s (±3.6 s) with the i-gel?. A tight seal at a constant oropharyngeal pressure of 15 cmH₂O was achieved in 85% of the cases (34 cases) with the cLMA, 90% (36 cases) with the PLMA, 97.5% (39 cases) with the AuraOnce and 72.5% (29 cases) with the i-gel? (p<0.05). A tight seal at a constant oropharyngeal pressure of 20 cmH₂O was seen in 62.5% with the cLMA, 60% with the PLMA, 67.5% with the AuraOnce? and in 50% with the i-gel? of the cases (p>0.05). Airway morbidity was not observed in any group. Significantly more patients complained of a sore throat after using the cLMA (p<0.05).

Conclusion

The tested SGADs were comparable with regard to ease of insertion, insertion times and airway morbidity. Considering leak tightness and patient comfort the PLMA and the AuraOnce fared better with regard to tightness of seal and patient comfort.     

The air-Q(®) intubating laryngeal airway vs the LMA-ProSeal(TM) : 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) cmH₂O and 30 (6) cmH₂O, 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. You can respond to this article at http://www.anaesthesiacorrespondence.com     

Comparison of the Intersurgical SolusTM laryngeal mask airway and the i‐gel supralaryngeal device

We compared the performance of the Intersurgical Solus^TM laryngeal mask airway (LMA) with that of the i‐gel in 120 patients of ASA physical status during general anaesthesia with respect to oropharyngeal leak pressure, peak airway pressure, airway manipulation, insertion time, fibreoptic view, ventilatory parameters, and peri‐operative complications . After receiving a standardised induction of anaesthesia, either a Solus LMA (60 patients) or an i‐gel (60 patients) was inserted. One hundred and fifteen patients completed the study. The leak pressure was significantly higher in the LMA group than the i‐gel group (mean (SD) 22.7 (7.7) cmH₂O vs 19.3 (7.1) cmH₂O; p = 0.02). A better fibreoptic view of the larynx was obtained in patients in the LMA group (p = 0.02) compared to those in the i‐gel group and less airway manipulation was required in the LMA group (p < 0.01). Both devices have good performance with very low peri‐operative complications . However, the Solus LMA provides a better oropharyngeal seal, provides a better fibreoptic view, and requires less manipulation to secure the airway than the i‐gel.     

Efficacy of a new dual channel laryngeal mask airway,the LMA®Gastro™ Airway,for upper gastrointestinal endoscopy: a prospective observational study

Background

Significant cardiorespiratory events are frequent in patients undergoing gastrointestinal endoscopy. Central to the occurrence of respiratory events is an unsecured airway. This study sought to determine the efficacy of a new laryngeal mask airway, the LMA^®Gastro^TM Airway (Teleflex Medical, Athlone, Ireland), in patients undergoing upper gastrointestinal endoscopy. New design features include a dedicated channel for oesophageal intubation and separate channel with terminal cuff for lung ventilation.

The effect of a cervical collar on the seal pressure of the LMA Supreme™: a prospective,crossover trial

For personnel inexperienced in airway management, supraglottic airway devices may be the first choice in an emergency. Changing head position is known to reduce the seal pressure of a laryngeal mask airway. The aim of this study was to investigate whether the use of a cervical collar improves the stability of airways secured with the LMA Supreme? (The Laryngeal Mask Company Limited, Mahé, Seychelles). In this crossover trial, the primary endpoint was the difference in the seal pressure of the LMA Supreme in anaesthetised patients in maximum passive extension of the neck, with and without a cervical collar. The median (IQR [range]) seal pressure was 18 (13.8–22.1 [0–30]) cmH₂O in maximum passive extension without a cervical collar. With a cervical collar in place, the seal pressure increased to 28 (22.8–30 [17–30]) cmH₂O (p < 0.001). In the neutral head position, the seal pressure was 22 (17.6–24.5 [12–30]) cmH₂O without and 27 (22–30 [12–30]) cmH₂O with a cervical collar in place (p < 0.001). We found that a cervical collar stabilises the airway with an LMA Supreme in place and we recommend this combination for (pre‐hospital) emergency cases.     

The LMA® ProtectorTM in anaesthetised,non-paralysed patients: a multicentre prospective observational study

We evaluated the LMA ^® Protector^TM in 280 ASA physical status 1–3 patients aged 18–75 years by assessing the ease of insertion, insertion time, oropharyngeal leak pressure, ease of gastric tube passage and complications. First-attempt and overall insertion success was 234/280 (84; 95%CI 79–88%) and 274/280 (98; 95–99%). Median (IQR [range]) insertion time was 17 (12–25 [5–44]) s, and manoeuvres to facilitate insertion were required in 56 (50–63)% of patients. Median oropharyngeal leak pressure was 31 (26–36 [14–40]) cmH₂O. Multivariate analysis identified two risk factors for oropharyngeal leak pressure < 25 cmH₂O: male sex (OR 2.44; 1.01–5.91, p = 0.048) and the insertion of a LMA size different to that recommended by weight (OR 1.98; 0.97–4.03, p = 0.06). Gastric tube insertion was possible in 256 out of 274 patients (93%). On fibreoptic view, vocal cords were visible in 86% of patients. During maintenance, 14 patients (5%) required airway manipulation. There were no episodes of regurgitation or aspiration. Blood staining on LMA removal was present in 70 out of 280 patients (25%). Use of the LMA Protector appears safe and is associated with a high success rate, provision of a highly effective seal and low rates of clinical complications. These attributes would suggest considerable potential for use during anaesthesia.     

A clinical evaluation of the i‐gelTM supraglottic airway device in children

Background: The i‐gel^TM is one of the latest commercially available, second‐generation supraglottic airway devices (SADs). Specific features include a distal cuff made of a thermoplastic elastomer gel that does not require inflation and a gastric side channel to allow passage of a gastric tube, venting of gas from the stomach, and an early indication of regurgitation. Previous studies in older children and adults have shown that it is a reliable, efficient, and safe device for airway management. Methods: We evaluated the i‐gel^TM in sizes ranging from 1 to 2.5 in children considered suitable for a supraglottic device. We assessed successful rates of insertion, airway leak pressure, position confirmed by fiberoptic laryngoscopy, gastric tube placement, manipulations required, and complications. Results: The i‐gel^TM was used in 154 children over a period of 12 months. The median age [interquartile range (IQR)] was 4 years 11 months (2–7 years), median weight (IQR) 19 kg (13–26), and median (IQR) duration of procedure 29 (30–45) min. First insertion attempt was successful in 93.5% of patients, and second attempt in 5.8%. The median (IQR) time to insertion was 14 (13–16) s. The median (IQR) leak pressure was 20 (15–25) cmH₂0. Gastric tube placement was successful in 90% of cases. On fiberoptic examination, the vocal cords were visible in 97% of patients. Complications arose in 20% of patients, but the majority were minor. Anesthetists commented that the device had a tendency to displace upward out of the mouth and that extension toward the forehead and flexion toward the feet of the proximal tube altered the quality of the airway. Overall, in seven (4.5%) patients, the device was abandoned and an alternative airway was used. Conclusions: Pediatric i‐gel^TM sizes 1.5–2.5 provided a satisfactory airway during anesthesia for spontaneously breathing infants and children. However, to ensure a clear airway, considerable vigilance is required when fixing the device in the mouth and to avoid the negative effects of flexion of the proximal tubing. The i‐gel^TM is more expensive than first‐generation devices. Whether this additional cost for the potential benefit of greater airway protection is considered acceptable will depend on longer‐time evaluation and surveillance to establish overall safety.     

Lower cuff pressures improve the seal of pediatric laryngeal mask airways

Background: Hyperinflation of laryngeal mask airway (LMA) cuffs may be harmful because of the exertion of high pressures on pharyngeal and laryngeal structures. Although cuff manometers may be used to monitor cuff pressure, their use is not routine in many institutions and clinical endpoints are used instead. Furthermore, it is common clinical practice to add air to the cuff in the presence of an air leak to obtain a better seal. Methods: In a prospective audit, the authors assessed air leakage around pediatric sized LMAs (n = 200) following inflation guided by common clinical endpoints (slight outward movement of the LMA) and then following adjustment of the cuff pressure to the recommended pressure range (<60 cmH₂O) according to institutional guidelines with the use of a calibrated cuff manometer, directly after induction of anesthesia. Following induction, all children were gently ventilated with pressure control ventilation with 10 cmH₂O and a positive end‐expiratory pressure of 5 cmH₂O. Results: Following inflation of the cuff guided by clinical endpoints, the median initial cuff pressure (LMA size 1–3) was 92 (size 3) to >120 cmH₂O (size 1) and the median leakage around the cuff ranged from 0.66 to 1.07 ml·kg^?1. Following cuff pressure adjustment according to the recommended pressure range (<60 cmH₂O), the leakage decreased significantly to 0.51–0.79 ml·kg^?1 (P = 0.002 for size 1, P < 0.001 for size 1.5–3). Conclusion: The use of clinical endpoints to inflate LMA cuffs is not only associated with significant hyperinflation in the majority of patients but also with an increased leakage around the LMA cuff when compared with adjusted LMA cuff pressures. Therefore, cuff manometers should routinely be used not only to avoid unnecessary hyperinflation but also to improve cuff sealing of LMA in children.     

Evaluation of air-Q™ intubating laryngeal airway as a conduit for tracheal intubation in infants--a pilot study

Background: Air‐Q^TM intubating laryngeal airway (ILA) has been used successfully as a conduit for tracheal intubation in pediatric difficult airway. However, its use as an airway device and conduit for intubation in infants is not yet evaluated. Aims: The primary objective was to evaluate ILA as a conduit for tracheal intubation in infants, and secondary objectives were to evaluate ILA in terms of ease of insertion and ventilation, oropharyngeal leak pressure (OLP), glottic view, and complications. Methods: Twenty infants with normal airway were included. After induction of general anesthesia and neuromuscular blockade, ILA (size 1.0/1.5) was inserted. Fiberoptic bronchoscope (FOB)–guided intubation and removal of ILA with the stabilizing stylet was attempted. Results: The mean age and weight of the infants were 7.5 ± 2.3 months and 7.3 ± 1.8 kg. The ILA sizes 1.0 and 1.5 were inserted in 10 infants each according to the weight of the infants. The mean OLP was 18.5 ± 1.8 cm H₂O, and mean time for insertion of ILA was 13.3 ± 3.9 s. Glottic view was grade I in 6, grade II in 1, grade III in 4, and grade IV in nine infants. Tracheal intubation was successful in 19/20 infants. The mean endotracheal tube (ETT) insertion time and mean total time (ILA insertion to the confirmation of ETT placement) were 95.6 ± 32.3 s and 306.42 ± 120.2 s respectively. Conclusion: The ILA is a safe and easy‐to‐use supraglottic airway device for intubation with FOB in infants with normal airway. Insertion and removal of ILA are easy with satisfactory oropharyngeal seal and ventilation.     

Reduced air leakage by adjusting the cuff pressure in pediatric laryngeal mask airways during spontaneous ventilation

Background: Optimal inflation of the laryngeal mask airway (LMA) cuff should allow ventilation with low leakage volumes and minimal airway morbidity. Manufacturer’s recommendations vary, and clinical end‐points have been shown to be associated with cuff hyperinflation and increased leak around the LMA. However, measurement of the intra‐cuff pressure of the LMA is not routine in most pediatric institutions, and the optimal intra‐cuff pressure in the LMA has not been determined in clinical studies. Methods: This was a prospective audit in100 pediatric patients undergoing elective general anesthesia breathing spontaneously via LMA (size 1.5–3). Cuff pressure within the LMA was adjusted using a calibrated pressure gauge to three different values (60, 40, and 20 cmH₂O) within the manufacturers’ recommended LMA cuff pressure range (≤60 cmH₂O). Three corresponding inspiratory and expiratory tidal volumes were recorded, and the differences were calculated as the ‘leak volume’. Results: Compared with 20 and 60 cmH₂O intra‐cuff pressure, measured leakage volumes were the lowest at cuff inflation pressures of 40 cmH₂O [median (range) 0.42 (0.09–1.00) ml·kg^?1] in most patients (83%), while 17% of children demonstrated minimally smaller leakages at 20 cmH₂O [0.51 (0.11–1.79) ml·kg^?1]. Maximum leakage values occurred with cuff pressures of 60 cmH₂O in all groups [0.65 (0.18–1.27) ml·kg^?1] and were not associated with the smallest value of air leakage in any patient. Conclusion: Using cuff manometry, an intra‐cuff pressure of 40 cmH₂O was associated with reduced leak around the LMA while higher (60 cmH₂O) and lower (20 cmH₂O) cuff pressures resulted in higher leak volumes during spontaneous ventilation. In spontaneously breathing children, reducing the intra‐cuff pressure of pediatric‐sized LMAs even below the manufacturers’ recommendations allows ventilation with minimized leakage around the LMA cuff.     

Directly measured mucosal pressures produced by the i-gel™ and Laryngeal Mask Airway Supreme™ in paralysed anaesthetised patients

The i‐gel^TM and LMA Supreme^TM are extraglottic airway devices with non‐inflatable and inflatable cuffs, respectively. We hypothesised that directly measured mucosal pressures would differ between these devices in anesthetised paralysed patients. Thirty patients were randomly allocated to receive one of these two devices. Four pressure sensors were attached to all airway devices used to measure mucosal pressure at the base of the tongue, the distal oropharynx, the hypopharynx and the pyriform fossa. At these four places, median (IQR [range]) i‐gel mucosal pressures were 8.0 (2.7–10.7 [0–26.7]), 5.0 (2.7–7 [1.0–37.3]), 9.3 (2.7–13.3 [0–22.7] and 8.0 (2.7–10.7 [0–25.3]) cmH₂O, respectively, and for the LMA Supreme, these were 5.0 (0.5–8.0 [0–33]), 4.0 (1.3–9.3 [0–24]), 10.7 (4–17.3 [0–26.7]) and 8.0 (0–10.7 [0–36]) cmH₂O, respectively. Mucosal pressures were low and similar for both devices. The LMA Supreme mucosal pressures were higher in the hypopharynx than in the distal oropharynx (p = 0.04) and base of the tongue (p = 0.011). There were no pressure differences between the locations for the i‐gel.     

Measurement of airway pressure during high-flow nasal therapy in apnoeic oxygenation: a randomised controlled crossover trial*

It is recognised that high-flow nasal therapy can prevent desaturation during airway management. Studies in spontaneously breathing patients show an almost linear relationship between flow rate and positive airway pressure in the nasopharynx. Positive airway pressure has been suggested as one of the possible mechanisms explaining how high-flow nasal therapy works. However, data on pressures generated by high-flow nasal therapy in apnoeic adults under general anaesthesia are absent. This randomised controlled crossover trial investigated airway pressures generated by different flow rates during high-flow nasal therapy in anaesthetised and paralysed apnoeic patients, comparing pressures with closed and open mouths. Following induction of anaesthesia and neuromuscular blockade, a continuous jaw thrust was used to enable airway patency. Airway pressure was measured in the right main bronchus, the middle of the trachea and the pharynx, using a fibreoptically-placed catheter connected to a pressure transducer. Each measurement was randomised with respect to closed or open mouth and different flow rates. Twenty patients undergoing elective surgery were included (mean (SD) age 38 (18) years, BMI 25.0 (3.3) kg.m^-2, nine women, ASA physical status 1 (35%), 2 (55%), 3 (10%). While closed mouths and increasing flow rates demonstrated non-linear increases in pressure, the pressure increase was negligible with an open mouth. Airway pressures remained below 10 cmH₂O even with closed mouths and flow rates up to 80 l.min⁻¹; they were not influenced by catheter position. This study shows an increase in airway pressures with closed mouths that depends on flow rate. The generated pressure is negligible with an open mouth. These data question positive airway pressure as an important mechanism for maintenance of oxygenation during apnoea.     

Randomized evaluation of the size 2 laryngeal tube and classical laryngeal mask airway in different head and neck positions in children under positive pressure ventilation

Purpose

The aim of this study was to evaluate the applicability of the laryngeal tube (LT) size 2 and the classical laryngeal mask airway (LMA) size 2 in different head–neck positions under positive pressure ventilation in children by measuring leak pressures, peak pressures and the achievable tidal volumes under positive pressure ventilation.

Methods

Forty children were randomized to receive airway management by either the LT or LMA as the primary device. Leak pressures, peak pressures and tidal volumes under positive pressure ventilation were measured in the neutral, anteflection, retroversion, left-rotation and right-rotation head–neck positions.

Results

In all head–neck positions, the leak pressures were significantly higher for the LT than for the LMA (neutral 25.9 ± 7.0 vs. 19.1 ± 5.7 cmH₂O; anteflection 29.7 ± 7.1 vs. 24.2 ± 8.9 cmH₂O; retroversion 24.1 ± 7.6 vs. 17.2 ± 6.9 cmH₂O). In both devices, the peak ventilation pressures were higher in the anteflection position (LT 27.1 ± 6.3 cmH₂O; LMA 17.8 ± 6.7 cmH₂O) than in the retroversion position (LT 13.7 ± 3.9 cmH₂O; LMA 12.7 ± 3.6 cmH₂O). Compared to the respirator settings, lower tidal volumes were achieved in the anteflection position (LT 65 ± 48 vs. 129 ± 38 ml, LMA 100 ± 21 vs. 125 ± 29 ml) as compared to the other positions.

Conclusion

Based on our results, we suggest that in anaesthetized children, the size 2 LT, compared to the size 2 LMA, may be more suitable for positive pressure ventilation due to favorable leak and peak pressures. Both devices can be safely used in head–neck positions other than neutral. Most disadvantageous with regards to the measured parameters was the anteflection position, especially for the LT.     

The laryngeal mask airway for fibreoptic bronchoscopy in children

A size 2 laryngeal mask airway (ID 7 mm) was used for general anaesthesia during fibreoptic bronchoscopy in a six-year-old child. The mask permitted the use of an adult bronchoscope with an external diameter of 5 mm. Throughout bronchoscopy, adequate controlled ventilation could be achieved easily without excessive air leak or airway resistance; the Spo₂ was always > 97%, and the endtidal Pco₂ ranged between 3·9–4·5 kPa (30–35 mmHg).     

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

Background: To prospectively investigate the performance, sealing capacity and operating room (OR) staff exposure to waste anaesthetic gases during the use of the Cobra perilaryngeal airway (CobraPLA) compared with the laryngeal mask airway classic (LMA). Methods: Sixty patients were randomly assigned to the CobraPLA or the LMA group. Insertion time, number of insertion attempts and airway leak pressures were assessed after induction of anaesthesia. Occupational exposure to nitrous oxide (N₂O) and Sevoflurane (SEV) was measured at the anaesthetists' breathing zone and the patients' mouth using a photoacoustic infrared spectrometer. Results: N₂O waste gas concentrations differed significantly in the anaesthetist's breathing zone (11.7±7.2 p.p.m. in CobraPLA vs. 4.1±4.3 p.p.m. in LMA, P=0.03), whereas no difference could be shown in SEV concentrations. Correct CobraPLA positioning was possible in 28 out of 30 patients (more than one attempt necessary in five patients). Correct positioning of the LMA classic was possible in all 30 patients (more than one attempt in three patients). Peak airway pressure was higher in the CobraPLA group (16±3 vs. 14±2 cmH₂O, P=0.01). The average leak pressure of the CobraPLA was 24±4 cmH₂O, compared with 20±4 cmH₂O of the LMA classic (P<0.001; all values means±SD). Conclusion: Despite higher airway seal pressures, the CobraPLA caused higher intraoperative N₂O trace concentrations in the anaesthetists' breathing zone.     

Pressure versus volume-controlled ventilation with a laryngeal mask airway™ in paediatric patients

BACKGROUND: The utility of positive pressure ventilation with the laryngeal mask airway (LMA) in children was described previously, but the possibility of gastric insufflation, related to high peak airway pressure, continues to be a disadvantage. In this prospective study, inspiratory pressures, air leak and signs of gastric insufflation were compared between volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) using an LMA. METHODS: Thirty-two ASA I patients, aged 4.5 +/- 4 years, who were scheduled for elective procedures under combined general anaesthesia and caudal analgesia, were enrolled. After inhalation induction and LMA insertion, each patient was randomly assigned to receive successively PCV and VCV. Peak pressures (PCV) and tidal volumes (VCV) were changed in order to achieve adequate ventilation [endtidal CO2 5-5.4 kPa (38-42 mmHg)]. RESULTS: Peak airway pressures were significantly lower with PCV than VCV (14.1 +/- 1.6 cmH2O versus 16.7 +/- 2.3 cmH2O, P < 0.001). No patient ventilated with PCV required peak pressure higher than 20 cmH2O compared with six patients ventilated with VCV (P < 0.05). Haemodynamic parameters, expiratory tidal volume and percent of leak were similar in both ventilatory modes and no signs of gastric insufflation were detected. CONCLUSIONS: During general anaesthesia in children using an LMA, PCV offers lower peak inspiratory airway pressures while maintaining equal ventilation compared with VCV. Although no signs of gastric insufflation were detected in both groups, the lower pressures might be significant in patients with reduced chest wall or lung compliance.     

Pressure vs. volume control ventilation: effects on gastric insufflation with size-1 LMA

Background: In this randomized prospective study, peak airway pressure (PAP) and gastric insufflation were compared between volume control ventilation (VCV) and pressure control ventilation (PCV) using size‐1 laryngeal mask airway (LMA) in babies weighing 2.5–5 kg. Methods: Forty ASA I and II children, weighing 2.5–5 kg, undergoing elective infraumbilical surgeries (duration < 60 min) were randomized to two groups of 20 each to receive either PCV or VCV. Patients at risk of aspiration, difficult airway and upper respiratory tract infection, and poor lung compliance were excluded. Anesthesia technique included sevoflurane/O₂/N₂O without neuromuscular blockade. PAP in PCV and tidal volume in VCV modes were changed to achieve adequate ventilation (P_ECO₂ of 5–5.4 kPa). PAP was maintained below 20 cm H₂O. Chi‐squared test, Mann–Whitney U‐test and Wilcoxon W‐test were applied; P < 0.05 was considered significant. Results: Mean PAP (cm H₂O) was 12.2 ± 1.09 in PCV and 13.60 ± 0.94 in VCV groups (P = 0.000). The confidence interval of mean difference of PAP varied from 0.79 to 2.10. Significant increases in abdominal circumference were observed in both groups: PCV: 0.94 ± 1.04 cm and VCV: 2.2 ± 1.3 cm; (P = 0.000). The SpO₂ and hemodynamic variables did not differ between the groups. One patient in VCV group (with PAP = 14 cm H₂O) could not be ventilated to the target P_ECO₂, and the LMA had to be replaced with tracheal tube. Conclusion: In conclusion, PCV should be the preferred mode to provide positive pressure ventilatio (PPV), when using the size‐1 cLMA in babies weighing 2.5–5 kg, in view of less gastric insufflation associated with it for surgeries of brief duration. More studies are required to validate the clinical significance of these two modes of ventilation in longer procedures, in this subpopulation.