Four adult cats received alternating high‐frequency oscillatory ventilation (HFOV) and high‐frequency jet ventilation (HFJV) at equivalent proximal airway pressures. Physiologic measurements were made before and after each ventilator change. Proximal airway pressures were then adjusted as necessary to reestablish normal pH and Pa CO 2 values. Aortic, pulmonary artery, and central venous pressures were monitored. Cardiac outputs were measured. Pulmonary and systemic vascular resistance, intrapulmonary shunt, and alveolar‐arterial oxygen gradient were determined. Following the change from HFOV to HFJV at similar proximal airway pressures, HFJV always produced higher pH values (P < 0.0001), higher Pa CO 2 values (P < 0.05), lower Pa CO 2 values (P < 0.0001), as well as higher cardiac outputs (P < 0.01), lower pulmonary artery pressures (P < 0.001), and lower pulmonary vascular resistances (P < 0.001). Following the reciprocal crossover, from HFJV to HFOV, HFJV pH values were again higher (P < 0.001), and Pa CO 2 values were again lower (P < 0.001). A comparison of HFOV and HFJV at similar pH and Pa CO 2 values showed that HFOV consistently required higher peak inspiratory pressures (P < 0.001), higher mean airway pressure (P < 0.001), and higher pressure wave amplitudes (P < 0.001). Under the circumstances of this study, HFJV produced better gas exchange at lower proximal airway pressures. Pediatr Pilmonol. 1989; 7:35–41.
- Proximal airway pressure
- P o 2, P co 2, pH, alv.‐art. O gradient
- aortic pressure
- central venous pressure
- mean airway pressure
- peak inspiratory pressure
- pulmonary vascular resistance