Incidence and Predictors of Difficult and Impossible Mask Ventilation

TLDR

Mask ventilation is a critical airway management technique that has seldom been studied as a primary outcome. The study aimed to determine how often difficult or impossible mask ventilation occurs and what predicts it. A prospective observational study graded mask‑ventilation difficulty on a four‑point scale and analyzed patient history and physical exam features to identify risk factors for grades 3 and 4 ventilation. Among 22,660 mask‑ventilation attempts, 1.4 % were grade 3, 0.16 % grade 4, and 0.37 % were grade 3/4 with difficult intubation; independent predictors included BMI ≥ 30 kg/m², beard, Mallampati III/IV, age ≥ 57 yr, limited jaw protrusion, snoring, thyromental distance < 6 cm, abnormal neck anatomy, and sleep apnea, with beard being the only easily modifiable factor.

Abstract

Mask ventilation is an essential element of airway management that has rarely been studied as the primary outcome. The authors sought to determine the incidence and predictors of difficult and impossible mask ventilation.A four-point scale to grade difficulty in performing mask ventilation (MV) is used at the authors' institution. They used a prospective, observational study to identify cases of grade 3 MV (inadequate, unstable, or requiring two providers), grade 4 MV (impossible to ventilate), and difficult intubation. Univariate and multivariate analyses of a variety of patient history and physical examination characteristics were used to establish risk factors for grade 3 and 4 MV.During a 24-month period, 22,660 attempts at MV were recorded. 313 cases (1.4%) of grade 3 MV, 37 cases (0.16%) of grade 4 MV, and 84 cases (0.37%) of grade 3 or 4 MV and difficult intubation were observed. Body mass index of 30 kg/m or greater, a beard, Mallampati classification III or IV, age of 57 yr or older, severely limited jaw protrusion, and snoring were identified as independent predictors for grade 3 MV. Snoring and thyromental distance of less than 6 cm were independent predictors for grade 4 MV. Limited or severely limited mandibular protrusion, abnormal neck anatomy, sleep apnea, snoring, and body mass index of 30 kg/m or greater were independent predictors of grade 3 or 4 MV and difficult intubation.The authors observed the incidence of grade 3 MV to be 1.4%, similar to studies with the same definition of difficult MV. Presence of a beard is the only easily modifiable independent risk factor for difficult MV. The mandibular protrusion test may be an essential element of the airway examination.