Abstract
The purpose of this study was to investigate the relationship of intrathoracic (IT) and intra-rectal (IR) pressures in sitting and supine positions and to clarify the effects of the positions on easiness of the defecation. Nineteen healthy volunteers (age 32.4 ± 11.5. years, 12 men) consented to participate in this study. They followed the protocols to perform IT pressures at 10, 20, and 30 mmHg in supine and sitting positions for each 15 sec in the environmentally controlled room chamber (27 ℃, 50%). All signals of IT and IR pressures sampled at 1kHz were stored on the hard disk. The eas iness of defecation was investigated by the self-registering questionnaire.
In sitting and supine positions, the IR pressure rose as the IT pressure increased. The IR pressure was significantly higher at the IT pressure of 30 mmHg than 10 mmHg (supine : 17.3 ± 2.6 vs 6.8 ± 1.0 mmHg，p=0.002，sitting : 20.4 ± 3.0 vs 9.7 ± 1.8 mmHg，p=0.01). Under the same IT pressure, IR pressure of sitting position was significantly higher compared to supine position (20.4 ± 3.0 vs 17.3 ± 2.6 mmHg，p=0.018, at 30 mmHg of IT pressure). Questionnaires revealed that the sitting position could intentionally increase in IR pressure more easily except one who was using Japanese-style toilet in daily life. In the sitting position the IT pressure might transmit into the rectum more effectively than the supine. The data proved that we could empty the rectum easily in the sitting position from the physiological viewpoint.
