Use of a Helium-Oxygen Mixture to Facilitate Ventilation During Bronchoscopy Through a Laryngeal Mask Airway

Abstract

Purpose: Flexible fiberoptic bronchoscopy may be performed in infants and children for various diagnostic and therapeutic purposes. In infants and children, general anesthesia may be used to facilitate the procedure. When general anesthesia is used, a laryngeal mask may be used to control the airway. However, as the passage of the bronchoscope decreases the cross-sectional airway inside the laryngeal mask airway (LMA) for gas exchange, increases in respiratory resistance may occur. We present our experience with the use of a helium—oxygen mixture to facilitate bronchoscopy through an LMA during general anesthesia in infants and children. Methods: We retrospectively reviewed changes in tidal volume, respiratory rate, and transcutaneous carbon dioxide (TC-CO2) during 3 phases of general anesthetic care. Phase 1 was pressure support breathing of an air—oxygen mixture through an LMA during sevoflurane anesthesia prior to the start of bronchoscopy, phase 2 was with the bronchoscope inserted through the LMA during pressure support ventilation of sevoflurane in an air—oxygen mixture, and phase 3 was with the bronchoscope inserted through the LMA during pressure support breathing of sevoflurane in a helium—oxygen mixture. Results: The study cohort included 6 patients, ranging in age from 14 to 49 months. There was a statistically significant increase in respiratory rate, increase in TC-CO2, and decrease in tidal volume with the insertion of the bronchoscope through the LMA when compared to baseline values (phase 2 vs phase 1). These values returned to values that were comparable to the baseline values when a helium—oxygen mixture was administered (phase 1 vs phase 3). Conclusions: A helium—oxygen mixture decreases resistance to gas flow during bronchoscopy through an LMA in infants and children receiving general anesthesia with sevoflurane and pressure support ventilation.