Ventilatory and hemodynamic effects of continuous positive airway pressure in dogs with acute cardiogenic pulmonary edema

Objective: To investigate the ventilatory and hemodynamic effects of continuous positive airway pressure (CPAP) in acute cardiogenic pulmonary edema (ACPE) in dogs.

Methods: Cardiac output (CO), heart rate (HR), blood pressure (BP), pulmonary artery wedge pressure (PAWP), central venous pressure (CVP) and intrathoracic negative pressure (Pt) were measured. These parameters were recorded at spontaneous breath, 5 cm H2O, 10 cm H2O, and 15 cm H2O CPAP in ten dogs before (healthy state) and after the induction of ACPE.

Results: When ACPE occurred, the dogs showed rapid breath, higher Pt [-(10.90 +/- 0.75) versus -(4.90 +/- 0.09) cm H2O], decreased CVP and CO [(10.1 +/- 0.4) versus (8.0 +/- 0.7) mm Hg and (1.52 +/- 0.13) versus (0.85 +/- 0.09) L/min, respectively], increased PAWP [(9.64 +/- 0.54) versus (17.77 +/- 0.79) mm Hg, all P < 0.05]. The correlation coefficient of the change of CVP and the change of Pt was 0.78 (P < 0.01). The addition of 5 or 10 cm H2O CPAP decreased Pt [-(6.53 +/- 0.11), -(5.14 +/- 0.25) cm H2O], which resulted in increased cardiac function. CO was also increased [(1.45 +/- 0.11), (1.24 +/- 0.11) L/min], with decreased PAWP [(15.80 +/- 0.55), (17.40 +/- 0.70) mm Hg; P < 0.05]. After the application of 15 cm H2O CPAP, Pt reached nearly zero [-(0.82 +/- 0.37) cm H2O], CO decreased to (0.82 +/- 0.07) L/min and PAWP increased to (19.23 +/- 0.73) mm Hg (P < 0.05).

Conclusions: ACPE induced rapid breath, elevated Pt and decreased CVP and CO. Proper CPAP can improve CO by regulating Pt, hence the improvement of other hemodynamic parameters.