High frequency ventilation in dogs with open chests

This study evaluated and compared the physiological responses to high frequency percutaneous transtracheal ventilation in dogs before and after median sternotomy thoracotomy. Standard intermittent positive pressure ventilation (IPPV) was established before and after high frequency rates (100 and 300 breath/min) with the chest closed and then after thoracotomy. Gas exchange as judged by arterial and mixed venous blood gases, and cardiac performance as judged by pulmonary capillary wedge pressure, pulmonary and systemic arterial pressures, vascular resistances, and cardiac index all remained clinically acceptable. Physiologically, ventilation in the open chest condition was adequate but was associated with a slight decrease in PaCO2 and a decrease in PaO2. Peak and mean airway pressures were similar for IPPV and high frequency modes of ventilation.