Evaluating the ventilatory effect of transnasal humidified rapid insufflation ventilatory exchange in apnoeic small children with two different oxygen flow rates: a randomised controlled trial.

Transnasal humidified rapid insufflation ventilatory exchange prolongs safe apnoeic oxygenation time in children. In adults, transnasal humidified rapid insufflation ventilatory exchange is reported to have a ventilatory effect with PaCO2 levels increasing less rapidly than without it. This ventilatory effect has yet to be reproduced in children. In this non-inferiority study, we tested the hypothesis that children weighing 10-15 kg exhibit no difference in carbon dioxide clearance when comparing two different high-flow nasal therapy flow rates during a 10-min apnoea period. Following standardised induction of anaesthesia including neuromuscular blockade, patients were randomly allocated to high-flow nasal therapy of 100% oxygen at 2 or 4 l.kg-1 .min-1 . Airway patency was ensured by continuous jaw thrust. The study intervention was terminated for safety reasons when SpO2 values dropped < 95%, or transcutaneous carbon dioxide levels rose > 9.3 kPa, or near-infrared spectroscopy values dropped > 20% from their baseline values, or after an apnoeic period of 10 min. Fifteen patients were included in each group. In the 2 l.kg-1 .min-1 group, mean (SD) transcutaneous carbon dioxide increase was 0.46 (0.11) kPa.min-1 , while in the 4 l.kg-1 .min-1 group it was 0.46 (0.12) kPa.min-1 . The upper limit of a one-sided 95%CI for the difference between groups was 0.07 kPa.min-1 , lower than the predefined non-inferiority margin of 0.147 kPa.min-1 (p = 0.001). The lower flow rate of 2 l.kg-1 .min-1 was non-inferior to 4 l.kg-1 .min-1 relative to the transcutaneous carbon dioxide increase. In conclusion, an additional ventilatory effect of either 2 or 4 l.kg-1 .min-1 high-flow nasal therapy in apnoeic children weighing 10-15 kg appears to be absent.

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 cmH2 O 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.

Pre-oxygenation using high-flow nasal oxygen vs. tight facemask during rapid sequence induction.

Pre-oxygenation using high-flow nasal oxygen can decrease the risk of desaturation during rapid sequence induction in patients undergoing emergency surgery. Previous studies were single-centre and often in limited settings. This randomised, international, multicentre trial compared high-flow nasal oxygen with standard facemask pre-oxygenation for rapid sequence induction in emergency surgery at all hours of the day and night. A total of 350 adult patients from six centres in Sweden and one in Switzerland undergoing emergency surgery where rapid sequence induction was required were included and randomly allocated to pre-oxygenation with 100% oxygen using high-flow nasal oxygen or a standard tight-fitting facemask. The primary outcome was the number of patients developing oxygen saturations <93% from the start of pre-oxygenation until 1 min after tracheal intubation. Data from 349 of 350 patients who entered the study were analysed (174 in the high-flow nasal oxygen group and 175 in the facemask group). No difference was detected in the number of patients desaturating <93%, five (2.9%) vs. six (3.4%) patients in the high-flow nasal oxygen and facemask group, respectively (p = 0.77). The risk of desaturation was not increased during on-call hours. No difference was seen in end-tidal carbon dioxide levels in the first breath after tracheal intubation or in the number of patients with signs of regurgitation between groups. These results confirm that high-flow nasal oxygen maintains adequate oxygen levels during pre-oxygenation for rapid sequence induction.

Evaluation of three unchannelled videolaryngoscopes and the Macintosh laryngoscope in patients with a simulated difficult airway: a randomised, controlled trial.

This prospective randomised, controlled trial compares the performance of three unchannelled videolaryngoscopes (KingVision™ , Airtraq™ , A.P. Advance™ MAC) and the standard Macintosh laryngoscope. With ethics committee approval and written informed consent, 480 patients were included. A difficult airway was created with a cervical collar, limiting mouth opening and neck movement. Primary outcome was first-attempt orotracheal intubation success. Overall success, laryngeal view, intubation difficulty scale, handling, intubation times and side-effects were secondary outcomes. First-attempt success rates were: KingVision 90% (95% CI 83-94%), Airtraq 82% (74-88%), A.P. Advance MAC 49% (40-58%), Macintosh 44% (35-53%; p < 0.001). The 95% confidence interval of first-attempt success rate was thus below 90% for all devices, but the KingVision and the Airtraq performed better than the A.P. Advance MAC and the Macintosh laryngoscope. Also, performance was better with the KingVision and the Airtraq in terms of overall success, laryngeal view, intubation difficulty scale and quality of view. Problems with tube advancement were a frequent cause of intubation failure. In summary, the KingVision and the Airtraq performed better than the A.P. Advance MAC and the Macintosh laryngoscope. Success rates of the unchannelled KingVision and Airtraq were similar to those of their channelled versions reported previously, indicating that performance largely depends on blade design rather than the presence of a channel for tube advancement.

Evaluation of six videolaryngoscopes in 720 patients with a simulated difficult airway: a multicentre randomized controlled trial.

BACKGROUND: Videolaryngoscopes are aggressively marketed, but independent evaluation in difficult airways is scarce. This multicentre, prospective randomized controlled trial evaluates six videolaryngoscopes in patients with a simulated difficult airway. METHODS: With ethics committee approval and written informed consent, 12 senior anaesthetists intubated the trachea of 720 patients. A cervical collar limited mouth opening and neck movement, making intubation difficult. We evaluated three unchannelled (C-MAC™ D-blade, GlideScope™, and McGrath™) and three channelled videolaryngoscopes (Airtraq™, A.P. Advance™ difficult airway blade, and KingVision™). The primary outcome was first-attempt intubation success rate. Secondary outcomes included overall success rate, laryngeal view, intubation times, and side-effects. The primary hypothesis for every videolaryngoscope was that the 95% confidence interval of first-attempt success rate is ≥90%. RESULTS: Mouth opening was decreased from 46 (sd 7) to 23 (3) mm with the cervical collar. First-attempt success rates were 98% (McGrath™), 95% (C-MAC™ D-blade), 87% (KingVision™), 85% (GlideScope™ and Airtraq™), and 37% (A.P. Advance™, P<0.01). The 95% confidence interval of first-attempt success rate was >90% only for the McGrath™. Overall success, laryngeal view, and intubation times differed significantly between videolaryngoscopes (all P<0.01). Side-effects were minor. CONCLUSIONS: This trial revealed differences in the performance of six videolaryngoscopes in 720 patients with restricted neck movement and limited mouth opening. In this setting, first-attempt success rates were 85-98%, except for the A.P. Advance™ difficult airway blade. Highest success and lowest tissue trauma rates were achieved by the McGrath™ and C-MAC™ D-blade, highlighting the importance of the videolaryngoscope blade design. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov: identifier NCT01692535.

Randomized clinical trial comparing double-lumen tube and EZ-Blocker for single-lung ventilation.

BACKGROUND: In several clinical situations, lung separation and single-lung ventilation (SLV) is essential. In these cases, the double-lumen tube (DLT) is the most widely used device. Bronchial blocker such as Univent or Arndt Blocker serves as an alternative. The EZ-Blocker(®) (EZ; AnaesthetIQ B.V., Rotterdam, The Netherlands) is a new device promising to exceed clinical performance of DLT. The aim of this study was to assess the clinical performance of EZ in comparison with conventional left-sided DLT. METHODS: Forty adult patients undergoing elective thoracic surgery requiring thoracotomy and SLV were included in this study. The patients were randomly assigned to one of two groups: EZ (combined with conventional 7.5 or 8.5 mm single-lumen tube) or DLT (37 or 39 Fr left-sided DLT). Time for intubation procedure and time to verification of the correct position of EZ or DLT using fibreoptic bronchoscopy (FOB) were recorded. After surgery, a thoracic surgeon rated the quality of collapse of the lung (1-3 on a three-level scale). RESULTS: Time for intubation using DLT 85.5 (54.8) s was significantly faster (P<0.001) than using EZ 192 (89.7) s, whereas time for bronchoscopy was not significantly different (P=0.556). Conditions of surgery were rated equally [DLT 1.3 (0.6) vs EZ 1.4 (0.6), P=0.681]. CONCLUSIONS: Although time for intubation was longer with the EZ, the device proved to be an efficient and easy-to-use device. The EZ is a valuable alternative device to conventional DLT. Verification of the correct position of the EZ by FOB seems to be obligatory. This study was registered at http://www.clinicaltrials.gov (identifier: NCT01171560).