Does the route of local anesthesia and insertion influence oxygenation in patients undergoing flexible bronchoscopy?

Hypoxemia is a common complication of flexible bronchoscopy (FFB). This study compares the degree of hypoxemia produced with two approaches to FFB: nebulized lidocaine (NBL) followed by endotracheal tube (ETT) placement, and transcricoid injection of lidocaine (TCL) followed by transnasal insertion of the bronchoscope. A total of 50 patients (49 males; mean age, 48 ± 7.6 years) examined by two practitioners for diagnostic purposes was included in the study. Patients were premedicated with diazepam and atropine sulfate and examined in the supine position. According to the techniques used for local anesthesia and instrument approach, patients were randomly allocated into two groups: NBL/oral group - 27 subjects had NBL followed by peroral passage of the scope through a 9-mm-inner diameter (ID) ETT; and TCL/nasal group - 23 subjects had a TCL and perinasal passage of the scope. Arterialized capillary blood from the ear lobe was sampled: (1) 15-30 min prior to FFB, (2) immediately after local anesthesia, (3) during FFB, and (4) 20-30 min after FFB. TCL initially produced more depression of P_cO₂ than NBL, but this trend reversed after introduction of the bronchoscope and continuation of the procedure. Additional lidocaine during the procedure was given to 21 patients in the NBL/oral group, compared to 3 patients in the TCL/nasal group (p < 0.005). P_cO₂ decreased (from 9.5 ± 1.6 to 8.2 ± 1.6kPa; p < 0.05) during FFB in the NBL/oral group but not in the TCL/nasal group (P_cO₂ = 8.8 ± 1.2 before and 8.6 ± 1.8 kPa during FFB; NS). No significant CO₂ retention during the procedure was observed in either of the groups. FFB through an orally inserted ETT using nebulized local anesthetic is associated with greater desaturation than nasal FFB with TCL. The technique used for local anesthesia and the amount of fluid applied to the airways may contribute to a greater extent to the development of hypoxemia than the introduction of a 9-mm-ID ETT in the airway.