Prevalence and bedside predictors of difficult direct laryngoscopy in a Cambodian tertiary center: a retrospective cohort study of 3,080 adult elective surgeries
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Background Failure to anticipate difficult direct laryngoscopy (DDL) leads to catastrophic airway events. While Western algorithms exist, evidence from Southeast Asia—particularly in settings with high volumes of head-and-neck pathology—is limited. We investigated DDL prevalence and validated a simplified cumulative risk score in a Cambodian tertiary center. Methods We conducted a retrospective cohort study of 3,080 adults undergoing elective surgery with planned Macintosh laryngoscopy (January–June 2023) at Preah Ang Duong Hospital, Phnom Penh. DDL was defined as Cormack–Lehane grade III/IV or ≥ 3 attempts. Seven bedside predictors were analyzed using multivariable logistic regression. A composite risk score (range 0–3) was derived from the strongest independent predictors. Results DDL prevalence was 9.0% (278/3,080), rising to 13.5% in maxillofacial and 11.3% in ENT procedures 1 . Independent predictors included Mallampati class III–IV (Adjusted Odds Ratio [AOR] 4.14), limited neck mobility (AOR 2.18), Thyromental Distance (TMD) ≤ 6.5 cm (AOR 1.95), and obesity (BMI ≥ 27.5 kg/m²; AOR 1.86) 2 . The Upper Lip Bite Test was not predictive (p = 0.21) 3 . A simplified composite score (Mallampati + BMI + TMD) demonstrated superior discrimination (AUC 0.76) compared to single predictors. At a cutoff of ≥ 1, the score yielded a sensitivity of 71% and specificity of 87% Conclusions DDL affects nearly 1 in 11 elective surgical patients in this cohort, driven by a complex case-mix. A simple, three-point composite score offers a zero-cost tool to enhance preoperative risk stratification in resource-limited settings where advanced airway equipment may be scarce.
