HEMODYNAMIC DIFFERENCES BETWEEN CONTINUAL POSITIVE AND 2 TYPES OF NEGATIVE-PRESSURE VENTILATION

In seven anesthetized dogs, ventilated with matching lung volumes, tidal volumes, and respiratory rates, we compared the effects on cardiac output (CO), arterial venous oxygen saturation difference (Sa(O2) - Sv(O2)BAR), and femoral and inferior vena cava pressure gradient (P(FEM-IVC)) of: (1) intermittent positive pressure ventilation with positive end-expiratory pressure (CPPV); (2) iron-lung ventilation with negative end-expiratory pressure (ILV-NEEP); (3) grid and wrap ventilation with NEEP applied to the thorax and upper abdomen (G&W-NEEP). The values of CO and Sa(O2) - Sv(O2)BAR with ILV-NEEP were similar to those with CPPV. However, with G&W-NEEP as compared with ILV-NEEP, mean CO was greater (2.9 versus 2.6 L/min, p = 0.02) and mean (Sa(O2) - Sv(O2)) was lower (26.6% versus 28.3%, p = NS). Mean P(FEM-IVC) was higher with G&W-NEEP than with the other types of ventilation. We conclude that (1) ILV-NEEP is hemodynamically equivalent to CPPV and (2) G&W-NEEP has less adverse hemodynamic consequences.