Helium-oxygen mixtures during bronchoscopy.

Fiberoptic bronchoscopy in mechanically ventilated patients has been limited to endotracheal tubes of 8.0--8.5 mm diameter. When performed through smaller tubes, pressures exceeding ventilator limits may occur, alveolar ventilation may become impaired, or progressive hyperinflation from airway obstruction during expiration may result. In this study, the efficacy of a 70% helium-30% oxygen ventilating gas mixture was compared to 30% oxygen in air in a laboratory mechanical lung analog and during 15 bronchoscopies in 7 intubated patients. One patient with a 7.5 mm tube was studied. With the helium-oxygen mixture, ventilator pressures were not exceeded, alveolar ventilation was uncompromised, and hyperinflation did not occur. Bronchoscopy may be safely performed through endotracheal tubes smaller than 8.0 mm using a helium-oxygen mixture.