Mitigating Ventilation Impairments During Bronchoscopy: New Prospective Study

A prospective bench and simulation study shows that bronchoscopy in mechanically ventilated patients sharply increases airway resistance and can precipitate hypoxemia by narrowing the endotracheal lumen.

The team combined bench measurements across multiple tube-bronchoscope configurations with ventilator simulations and an active lung model, using intrinsic PEEP accumulation and reductions in delivered tidal volume as primary endpoints.

The longstanding “≥2 mm difference” rule proves insufficient when ventilator settings and patient mechanics are considered. The investigators report that small reductions in effective diameter produce large resistance increases and a greater risk of intraprocedural ventilation impairment. That scaling makes tube choice a function of ventilator mode and patient respiratory mechanics, not a fixed numeric gap.

Three factors combine to raise airway resistance and reduce delivered tidal volume: small endotracheal tube internal diameters, larger bronchoscope outer diameters, and ventilator settings that fail to compensate for the added resistance. In pressure-control simulations, effective diameters below about 7 mm produced progressive declines in tidal volume. In volume-control scenarios, effective diameters below roughly 5 mm produced marked intrinsic PEEP.

Automatic tube compensation (ATC) during pressure-controlled ventilation was the principal mitigation identified. It preserved tidal volumes and prevented intrinsic PEEP accumulation in the simulated cases. ATC offsets added tube resistance by adjusting airway pressure to maintain target tracheal pressure throughout inspiration and expiration, avoiding flow limitation and dynamic hyperinflation. Bench measurements showed tidal volumes remained approximately constant and intrinsic PEEP was avoided across most tube-scope combinations, unless ventilator pressure limits were reached.

Based on these data, the authors propose a quantitative tube-selection model that integrates effective tube diameter, ventilator settings (mode and pressures), and patient respiratory mechanics rather than relying on a simple numeric gap.