Mallampati class, obesity, and a novel airway trajectory measurement to predict difficult laryngoscopy.

OBJECTIVES/HYPOTHESIS: To determine whether Mallampati class correlates with Cormack-Lehane grade in obese adults, and investigate a novel airway trajectory measurement (ATM) to anticipate difficult laryngoscopy.

STUDY DESIGN: Retrospective cohort plus a pilot study.

METHODS: One hundred eighty-four nonobese and 160 obese adults underwent laryngoscopy. Spearman correlations, gamma coefficients (G), and Kendall's τ investigated body mass index (BMI):Mallampati, BMI: Cormack-Lehane, and Mallampati:Cormack-Lehane. A z test compared the two groups. Twenty-six volunteers had neck x-rays taken in the sniffing position to examine trajectories to the larynges (ATM).

RESULTS: Positive predictive value of high Mallampati for difficult laryngoscopy was 8.57%. BMI did not correlate with Mallampati (r = 0.055 [nonobese], r = -0.056 [obese]) or Cormack-Lehane [r = -0.014 [nonobese], r = -0.022 [obese]). Among nonobese adults, gamma coefficients for BMI:Mallampati was 0.039 (P = .63), for BMI:Cormack-Lehane was 0.02 (P = .85), and for Mallampati:Cormack-Lehane was 0.43 (P = .004). Among obese adults, gamma coefficients for BMI:Mallampati was -0.127 (P = .16), for BMI:Cormack-Lehane was 0.014 (P = .88), and for Mallampati:Cormack-Lehane was 0.365 (P = .01). Kendall's τ were comparable to gamma coefficients in all analyses. When comparing gamma coefficients for Mallampati:Cormack-Lehane among the nonobese and obese, z = 0.04 (P = .98). In the ATM study, only Mallampati and upper lip bite test had a significant relationship (G = 1.00, P < .001).

CONCLUSIONS: Mallampati correlates poorly with Cormack-Lehane, regardless of BMI. Pilot data suggest that ATM is feasible.