Kheterpal Sachin, Han Richard, Tremper Kevin K, Shanks Amy, Tait Alan R, O'Reilly Michael, Ludwig Thomas A
Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan 48103, USA.
Anesthesiology. 2006 Nov;105(5):885-91. doi: 10.1097/00000542-200611000-00007.
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.
面罩通气是气道管理的重要组成部分，但很少被作为主要结局进行研究。作者旨在确定困难和无法进行面罩通气的发生率及预测因素。
作者所在机构使用四点量表对面罩通气（MV）的困难程度进行分级。他们采用前瞻性观察性研究来确定3级MV（通气不足、不稳定或需要两名操作者）、4级MV（无法通气）及困难插管的病例。对各种患者病史和体格检查特征进行单因素和多因素分析，以确定3级和4级MV的危险因素。
在24个月期间，共记录了22660次MV尝试。观察到313例（1.4%）3级MV、37例（0.16%）4级MV以及84例（0.37%）3级或4级MV合并困难插管的病例。体重指数30kg/m²或更高、有胡须、Mallampati分级III或IV、年龄57岁或以上、下颌前突严重受限以及打鼾被确定为3级MV的独立预测因素。打鼾和甲状软骨-颏下距离小于6cm是4级MV的独立预测因素。下颌前突受限或严重受限、颈部解剖结构异常、睡眠呼吸暂停、打鼾以及体重指数30kg/m²或更高是3级或4级MV合并困难插管的独立预测因素。
作者观察到3级MV的发生率为1.4%，与对困难MV采用相同定义的研究结果相似。有胡须是困难MV唯一易于改变的独立危险因素。下颌前突试验可能是气道检查的重要组成部分。
