Effects of positive and negative pressure breathing on muscle sympathetic nerve activity in humans.

To clarify the dynamic effects of short-term continuous positive-pressure breathing (CPPB) and continuous negative-pressure breathing (CNPB) on sympathetic nerve activity, we measured muscle sympathetic nerve activity (MSNA) in the tibial nerve together with blood pressure, heart rate, and central venous pressure (CVP) during spontaneous breathing: 5, 10, and 15 mm Hg (CPPB), and -5, -10, and -15 mm Hg (CNPB) for 5 min, respectively, in six healthy male volunteers. Increasing levels of CPPB at 5, 10, and 15 mm Hg produced increasing levels of MSNA, however, during CNPB, MSNA was virtually constant. Mean blood pressure decreased and heart rate increased during CNPB, while neither factor changed significantly during CPPB. CVP increased during CPPB and decreased during CNPB. These results suggest that CPPB and CNPB do not have the inverse effects on MSNA.