Comparison of high and low pillow heights for tracheal tube intubation with the Pentax-AWS Airwayscope®: a prospective randomized clinical trial

Abstract

Editor—The appropriate pillow height for tracheal intubation with the Pentax-AWS Airwayscope® (AWS) has not been assessed.1Asai T Liu EH Matsumoto S et al.Use of the Pentax-AWS in 293 patients with difficult airways.Anesthesiology. 2009; 110: 898-904Crossref PubMed Scopus (187) Google Scholar This randomized clinical trial aimed to compare pillow height for tracheal intubation with the AWS in patients undergoing elective surgery. The primary outcome was time to intubation. The Research Ethics Committee of Osaka Medical College approved the study protocol. This study is listed in the UMIN Clinical Trials Registry under registration number UMIN000018208. Tracheal intubation with the AWS was performed with a high pillow (HP group, 12 cm pillow height, 40 patients) or low pillow (LP group, 4 cm pillow height, 40 patients). Anaesthesia was induced with propofol and remifentanil.2Komasawa N Kido H Miyazaki Y Tatsumi S Minami T Cricoid pressure impedes tracheal intubation with the Pentax-AWS Airwayscope®: a prospective randomized trial.Br J Anaesth. 2016; 116: 413-416Abstract Full Text Full Text PDF PubMed Scopus (41) Google Scholar Intubation time, the primary outcome measure, was assessed using the Mann–Whitney U-test to compare between groups. For interest, we also applied the following hypothesis tests to compare the secondary outcome measures: the Mann–Whitney U-test for the number of attempts required for insertion of the Intlock blade, the percentage of glottis opening (POGO) score, the number of attempts required for tracheal intubation, and visual analog scale (VAS); χ2 test for Cormack–Lehane classification; and Fisher's exact test for the incidence of hoarseness and pharyngeal pain. Data are presented as mean (sd). A value of P<0.05 was considered statistically significant. We performed a preliminary study, in which 16 patients underwent tracheal intubation using the AWS with either an HP or an LP (n=8 in each group). Intubation time was 29.2 (9.2) s with an LP and 41.2 (10.7) s with an HP. To detect this difference with 80% power at a 5% significance level, 34 patients were required for each group. Therefore, we planned to recruit 40 patients for each group to adjust for missing data. Patient characteristics including age, sex, body weight, height, BMI, duration of surgery, duration of anaesthesia, Mallampati score, and tracheal tube size were similar. No patient was abandoned or lost to follow-up during this trial. The results are shown in Table 1. Intubation time was significantly shorter in the LP group than in the HP group [LP group 27.9 (12.3) s vs HP group 46.2 (15.0) s; P<0.001]. The number of insertions of the Intlock blade, Cormack classifications, and POGO scores did not differ between groups (P=0.14, P=0.69, and P=0.38, respectively). The number of attempts at tracheal intubation was significantly smaller in the LP group than in the HP group (P=0.003). The VAS scores for laryngoscopy and passage of a tube through the glottis were significantly smaller in the LP group than in the HP group (P=0.001 and P<0.001, respectively). Hoarseness was observed in four patients in the LP group and eight patients in the HP group (P=0.21). The incidence of pharyngeal pain did not differ between groups (P=0.32).Table 1Comparison of several factors related to airway management between groups. Data were analysed using the Mann–Whitney U-test, χ2 test, or Fisher's exact test. Data are presented as mean (sd) or number of patients. HP group, tracheal intubation with the Pentax-AWS Airwayscope® with high pillow; LP group, tracheal intubation with the Pentax-AWS Airwayscope® with low pillow; VAS visual analog scale. *P<0.05 was considered statistically significantParameterLP group n=40HP group n=40P-valueIntubation time (s)27.9 (12.3)46.2 (15.0)<0.001*Number of attempts to Intlock insertion (1/2/3/failure)38/2/0/034/6/0/00.14Number of attempts to tracheal tube progression (1/2/3/failure)36/4/0/024/8/8/00.003*Cormack grade (1/2/3/4)36/4/0/037/3/0/00.69POGO score (%)99.3 (3.5)98.3 (5.5)0.38Lateral opening of the glottis (close/insufficient/sufficient)37/3/039/1/00.30VAS score for laryngoscopy (mm)16.1 (17.6)32.4 (25.3)0.001*VAS score for passage of a tube through the glottis (mm)13.1 (14.9)44.4 (27.4)<0.001*Number of patients with pharyngeal pain480.21Number of patients with hoarseness10140.32 Open table in a new tab In conclusion, AWS intubation with an LP was associated with a better tracheal intubation profile than with an HP, possibly as a result of smoother passage of the tube through the glottis. None declared.