Relationship Between Glottic View and Intubation Force During Macintosh and Airtraq Laryngoscopy and Intubation

Abstract

BACKGROUND: Because intubation-mediated cervical spine and spinal cord injury are likely determined by intubation force magnitude, understanding the determinants of intubation force magnitude is clinically relevant. With direct (Macintosh) laryngoscopy, when glottic view is less favorable, anesthesiologists apply greater force. We hypothesized that, when compared with direct (Macintosh) laryngoscopy, intubation force with an optical indirect laryngoscope (Airtraq) would be less dependent on glottic visualization. METHODS: Using data obtained in a prior clinical study, we tested whether the slope of the intubation force versus glottic view relationship differed between intubations performed in 14 patients who were intubated twice, once with a Macintosh and once with an Airtraq videolaryngoscope. Slopes were compared using least-squares linear regression and robust regression. RESULTS: The slope of the intubation force (N) versus glottic view (%) relationship with the Macintosh (−0.679 [standard error {SE}, 0.147]) was significantly more negative than that of the Airtraq (−0.076 [SE, 0.246]). The least-squares regression difference in slopes was −0.603 (SE, 0.287); P = .046. The robust regression difference in slopes was −0.747 (SE, 0.187); P = .0005. Thus, when compared with the Macintosh, intubation force magnitude with Airtraq laryngoscopy was less dependent on glottic visualization. CONCLUSIONS: Previously, we reported that intubation force with the Airtraq was less in magnitude compared with the Macintosh. Our current study adds that intubation force also is less dependent on glottic view with Airtraq compared with the Macintosh. (Anesth Analg 2022;135:815-9) KEY POINTS• Question: Does the relationship between glottic view and intubation force differ between direct (Macintosh) laryngoscopy and indirect (Airtraq) laryngoscopy? • Findings: Compared with the Macintosh, intubation force magnitude with Airtraq laryngoscopy was less dependent on glottic visualization. • Meaning: Force differences between direct and indirect laryngoscopes may depend, at least in part, on the mediating effect of glottic view. GLOSSARYASA = American Society of Anesthesiologists; CONSORT = Consolidated Standards of Reporting Trials; POGO = percentage of glottic opening; SD = standard deviation; SE = standard error

Association of variability in body size with neuroimaging metrics of brain health: a population-based cohort study

“…We used the slope method based on the least squares method to determine the trend (including direction and speed) of variability during the follow-up period. 21 Slope based on the least squares method is a classic trend detection method. 22 It fits the time series data by using least squares methods, and then judges the trend of the sequence according to the slope and corresponding p value.…”