Abstract des Autors

To assess the impact of continuous negative-pressure breathing (CNPB) on the regulation of skin blood flow, we measured forearm blood flow (FBF) by venous-occlusion plethysmography and laser-Doppler flow (LDF) at the anterior chest during exercise in a hot environment (ambient temperature = 30øC, relative humidity = ca. 30%). Seven male subjects exercised in the upright position at an intensity of 60% peak oxygen consumption rate for 40 min with and without CNPB after 20 min of exercise. The esophageal temperature (Tes) in both conditions increased to 38.1øC by the end of exercise, without any significant differences between the two trials. Mean arterial pressure (MAP) increased by ca. 15 mmHg by 8 min of exercise, without any significant difference between the two trials before CNPB. However, CNPB reduced MAP by ca. 10 mmHg after 24 min of exercise (P<0.05). The increase in FBF and LDF in the control condition leveled off after 18 min of exercise above a Tes of 37.7øC, whereas in the CNPB trial the increase continued, with a rise in Tes despite the decrease in MAP. These results suggest that CNPB enhances vasodilation of skin above a Tes of ca. 38øC by stretching intrathoracic baroreceptors such as cardiopulmonary baroreceptors. Verf.-Referat