Cardiopulmonary effects of continuous negative pressure wound therapy in swine.

Background: Negative pressure wound therapy (NPWT) has been used for complex sternotomy wounds. Some reports describe foam placement below the posterior sternal table. We compared the hemodynamic and pulmonary effects of foam location during NPWT after median sternotomy.

Methods: Swine were randomized into four groups (n = 6 per group). A polyurethane open cell foam dressing was placed either within or below the sternal table. In one-half, a silicone mesh barrier was placed between the heart and the foam. The NPWT was applied at -125 mm Hg and then released to ambient pressure. This cycle was repeated two more times, and the foam was removed. Heart rate, mean arterial pressure, cardiac output, mixed venous oxygenation, central venous pressure, and pulmonary artery wedge pressure were measured. Peak inspiratory pressure, mean airway pressure, work of breathing, and intrathoracic pressure measurements were recorded.

Results: Intersternal placement of foam did not affect hemodynamic parameters. Substernal placement resulted in depression of hemodynamic variables which improved when negative pressure was applied. Pulmonary mechanics were not affected by foam location.

Conclusions: Initial placement of the foam dressing below the posterior sternal table caused reversible depression of cardiac function which appears to be consistent with direct cardiac compression. NPWT therapy had no clinically significant impact on pulmonary parameters. The use of a protective barrier does not alter hemodynamic or pulmonary parameters but continues to be recommended when NPWT is used for sternotomy wounds.