Effects of voluntary abdominal breathing on sleepiness and heart rate variability after modest sleep restriction

Abstract

examined to establish how strain pressure affects heart rate, heart rate variability, blood pressure, blood pressure variability, and intrarectal pressure, in the supine and sitting positions, during a Valsalva's maneuver (VM) performed with a mouthpiece connected to a manometer. Bioelectrical impedance variables indicating intrathoracic blood volume, strain pressure, intrarectal pressure, heart rate, and blood pressure were measured simultaneously. The variables were recorded before, during, and after a 15-s Valsalva's maneuver at 10, 20 and 30 mm Hg of strain pressure. The increase in intrarectal pressure during the Valsalva's maneuver was greater in the sitting than in the supine position, and the effects of the Valsalva's maneuver were more marked in the subjects in sitting position. We conclude that it was easier to raise intrarectal pressure in the sitting position than in the supine position, because in the sitting position gravity made the effects of Valsalva's maneuver on hemodynamics more marked. However, no significant difference in hemodynamics was seen during strain pressure at 30 mm Hg, because other factors, e.g., muscle activity, exceeded the influence of gravity observed with a lesser strain pressure. Defecation may be safer when an increase in abdominal pressure is obtained with less strain pressure. The heart and peripheral vessels thus apparently play different roles in regulating cardiac output in higher position-related strain pressure. (The Autonomic Nervous System, 48: 48–55, 2011)