High‐frequency oscillatory ventilation versus conventional ventilation: hemodynamic effects on lung and heart

High‐frequency oscillatory ventilation (HFOV) may improve gas exchange in patients who are inadequately ventilated by conventional mechanical ventilation (CV); however, the hemodynamic consequences of switching to HFOV remain unclear. We compared the effects of CV and HFOV on pulmonary vascular conductance and left ventricular (LV) preload and performance at different airway and filling pressures. In anesthetized dogs, we measured LV dimensions, aortic and pulmonary artery (PA) flow, and mean airway ([Image: see text] (AW)) and pericardial pressures. Catheter‐tip pressure manometers measured aortic, LV, left atrial, and PA pressures. The pericardium and chest were closed. At LV end‐diastolic pressure (P(LVED)) = 5 mmHg and 12 mmHg, PEEP was varied (6 cm H(2)O, 12 cm H(2)O, and 18 cm H(2)O) during CV. Then, at airway pressures equal to those during CV, HFOV was applied at 4 Hz, 10 Hz, and 15 Hz. Increased [Image: see text] (AW) decreased pulmonary vascular conductance. As cardiac output increased, conductance increased. At P(LVED )= 12 mmHg, conductance was greatest during HFOV at 4 Hz. LV preload (i.e., A(LV), our index of end‐diastolic volume) was similar during HFOV and CV for all conditions. At P(LVED )= 12 mmHg, SW(LV) was similar during CV and HFOV, but, at P(LVED )= 5 mmHg and [Image: see text] (AW) 10 cm H(2)O, SW(LV) was lower during HFOV than CV. Compared to pulmonary vascular conductance at higher frequencies, at P(LVED )= 12 mmHg, conductance was greater at HFOV of 4 Hz. Effects of CV and HFOV on LV preload and performance were similar except for decreased SW(LV) at P(LVED )= 5 mmHg. These observations suggest the need for further studies to assess their potential clinical relevance.