Continuous-flow apneic ventilation with small endobronchial catheters

This study compares gas exchange and hemodynamic parameters during bronchial insufflation with two different internal diameter (ID) catheters (2.5 and 1.4 mm) at a constant mean gas exit velocity. Anesthetized, paralyzed dogs were instrumented to monitor arterial, central venous, and airway pressures, blood gases, temperature, ECG, and ventilated using continuous flow apneic ventilation (CFAV) via 2.5-mm or 1.4-mm ID bronchial insufflation catheters positioned 1.25 bronchial diameter units (BDU) beyond the carina. Initially, flow was adjusted to provide adequate oxygenation and ventilation through the 2.5-mm ID catheters. After a 30-min stabilization, physiological parameters were recorded and the mean gas exit velocity was calculated. The 2.5-mm ID insufflation catheters were then replaced by 1.4-mm ID catheters and the bronchial insufflation flow adjusted so as to produce the same mean gas exit velocity as for the 2.5-mm ID catheters. After a 30-min stabilization period, physiological parameters were again recorded. No significant differences were noted in arterial, central venous, or airway pressures, temperature, heart rate, pH, PaCO2, and PaO2 between the 2.5-mm and 1.4-mm ID bronchial insufflation catheters. However, significantly less bronchial insufflation flow (69.7%) was required to maintain oxygenation and ventilation for the 1.4-mm ID bronchial insufflation catheters.