Hemodynamic consequences of increasing mean airway pressure during high-frequency jet ventilation

Six critically ill patients with acute respiratory failure were ventilated using high-frequency jet ventilation (HFJV)-frequency 100.min-1, driving pressure 35 psi, 1.8 mm inside diameter injector cannula. Hemodynamic measurements using radial artery and Swan-Ganz catheters, esophageal pressure (EP), and mean airway pressure (Paw) were measured at four different I:E ratios: 0.25, 0.43, 0.67 and 1.0. Static respiratory compliance, using the super syringe method, was measured during intermittent positive pressure ventilation (IPPV) and during HFJV. The results suggested that decreased venous return, increased right ventricular afterload, and decreased PaCO2 accounted for the decrease in cardiac index observed during HFJV using elevated I:E ratios. These variations, related to marked increases in intrathoracic pressures, are very similar to those observed during conventional ventilation with PEEP.