Predicting difficult intubation with indirect laryngoscopy
Related Experiment Video
Updated: Nov 2, 2026

Point-of-Care Ultrasound: A Review of Ultrasound Parameters for Predicting Difficult Airways
Published on: April 7, 2023
K Yamamoto1, T Tsubokawa, K Shibata
1Department of Anesthesiology and Intensive Care Medicine, School of Medicine, Kanazawa University, Japan. kenyam@med.kanazawa-u.ac.jp
Background:
It is not always possible to predict when tracheal intubation will be difficult or impossible. The authors wanted to determine whether indirect laryngoscopy could identify patients in whom intubation was difficult.
Methods:
Indirect laryngoscopy was done in 2,504 patients. The Wilson risk sum score and the modified Mallampati score were also studied in a different series of 3,680 patients for comparison. These predictive methods were compared according to three parameters: positive predictive value, sensitivity, and specificity.
Results:
Of 6,184 patients studied, the trachea proved difficult to intubate in 82 (1.3%). Positive predictive value (31%) and specificity (98.4%) with indirect laryngoscopy were greater than the other two predictive methods (P < 0.01), whereas sensitivity with indirect laryngoscopy (69.2%) was greater than that of the Wilson risk sum score (55.4%) (P < 0.01).
Conclusions:
Although in 15% of patients indirect laryngoscopy could not be performed because of excessive gag reflex, indirect laryngoscopy can serve as an effective method to predict difficult intubation.
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