Risk factors for intraoperative hypoxemia during monopulmonary ventilation: an observational study

BACKGROUND: Left double-lumen endotracheal tubes have been widely used in thoracic, esophageal, vascular, and mediastinal procedures to provide lung separation. Lacking clear objective guidelines, anesthesiologists usually select appropriately sized double-lumen endotracheal tubes based on their experience with 35 and 37 Fr double-lumen endotracheal tubes, which are the most commonly used. We hypothesized the patients with a left main bronchus of shorter length (<40 mm) had a greater chance of experiencing desaturation during one lung ventilation, due to obstruction in the orifice of the left upper lobe with the bronchial tube. METHODS: We included 360 patients with a left double-lumen intubated between September 2014 and August 2015. The patient's age, sex, height, weight, and underlying disease were recorded along with type of surgical procedure and the desaturation episodes. In addition, the width of the trachea and the width and length of the left bronchus were measured using computed tomography. RESULT: Patients with a left main bronchus length of less than 40 mm who underwent intubation with a left double-lumen endotracheal tubes had significantly higher incidence of desaturation (Odds Ratio (OR: 8.087)) during one-lung ventilation. Other related factors of patients identified to be at risk of developing hypoxia were diabetes mellitus (OR: 5.368), right side collapse surgery (OR: 4.933), and BMI (OR: 1.105). CONCLUSIONS: We identified that patients with a left main bronchus length of less than 40 mm have a great chance of desaturation, especially if other desaturation risk factors are present.