Predictors of difficult intubation defined by the intubation difficulty scale (IDS): predictive value of 7 airway assessment factors

Abstract

BackgroundThe intubation difficulty scale (IDS) has been used as a validated difficulty score to define difficult intubation (DI). The purpose of this study is to identify airway assessment factors and total airway score (TAS) for predicting DI defined by the IDS.MethodsThere were 305 ASA physical status 1-2 patients, aged 19-70 years, who underwent elective surgery with endotracheal intubation. During the pre-anesthetic visit, we evaluated patients by 7 preoperative airway assessment factors, including the following: Mallampati classification, thyromental distance, head & neck movement, body mass index (BMI), buck teeth, inter-incisor gap, and upper lip bite test (ULBT). After endotracheal intubation, patients were divided into 2 groups based on their IDS score estimated with 7 variables: normal (IDS < 5) and DI (IDS ≥ 5) groups. The incidence of TAS (> 6) and high score of each airway assessment factor was compared in two groups: odds ratio, confidence interval (CI) of 95%, with a significant P value ≤ 0.05.ResultsThe odds ratio of TAS (> 6), ULBT (class III), head & neck movement (< 90°), inter-incisor gap (< 4 cm), BMI (≥ 25 kg/m2) and Mallampati classification (≥ class III) were respectively 13.57 (95% CI = 2.99-61.54, P < 0.05), 12.48 (95% CI = 2.50-62.21, P < 0.05), 3.11 (95% CI = 0.87-11.13), 2.32 (95% CI = 0.75-7.19), 2.22 (95% CI = 0.81-6.06), and 1.22 (95% CI = 0.38-3.89).ConclusionsWe suggest that TAS (> 6) and ULBT (class III) are the most useful factors predicting DI.

Incidental Lingual Thyroid Informs Surgery

“…A difficult intubation can result in serious morbidity and mortality in clinical practice (1,6). The Mallampati classification may be used to assess risk before intubation, with the highest risk being associated with an overly large base of tongue overshadowing the larynx (1,6).…”

“…The Mallampati classification may be used to assess risk before intubation, with the highest risk being associated with an overly large base of tongue overshadowing the larynx (1,6). This makes the larynx difficult to visualize during direct laryngoscopy (6).…”

“…A difficult intubation during surgery can have fatal consequences (1). The uncommon embryologic condition of an ectopic lingual thyroid can pose difficulties with intubation because of hemorrhaging and airway compression (2), especially when the presence of a lingual thyroid is unknown before intubation.…”

Identifying Predictors of a Difficult Thyroidectomy

“…There is, however, research examining factors predictive of complications after surgical procedures in other disciplines (16,17), such as intubation, laparoscopy, cataract surgery, and aneurysm repair (19)(20)(21)(22)(23).…”

Difficult Endotracheal Intubation—Scales and Causes

“…Before intubation, the seven preoperative factors are assessed: Mallampati classification, thyromental distance, head and neck movements, BMI (body mass index), buck teeth, inter-incisor gap, and ULBT (upper lip bite test) ( Table 1). Based on this assessment, TAS > 6 and ULBT class III are the predictors of difficult intubation [8]. Some authors consider that Mallampati classification (class III and IV), thyromental distance < 6.5 cm, limited neck movement, inter-incisor gap < 2.5 cm, and body mass index > 26 are independent predictors of difficult intubation.…”