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Effects of Defecation Strain at Various Bed Reclining Angles on Intrarectal Pressure and Cardiovascular Responses
Mika Imai1, Yuko Kuwahara, Makoto Hirai
1Mika Imai, RN, MS, is Assistant Professor, Department of Nursing, Ogaki Women's College, and Department of Nursing, Nagoya University School of Health Sciences, Japan. Yuko Kuwahara, DVM, PhD, is Research Associate, Department of Physiology, Aichi Medical University, Nagakute, Japan. Makoto Hirai, MD, PhD, is Professor, Department of Nursing, Nagoya University School of Health Sciences, Japan. Rumiko Nishimura, MS, is PhD Candidate; Naoki Nishimura, PhD, is Assistant Professor; and Yuuki Shimizu, PhD, is Assistant Professor, Department of Physiology, Aichi Medical University, Nagakute, Japan. Tetsuya Fujii, RN, PhD, is Professor, Department of Nursing, Seirei Christopher University, Hamamatsu, Japan. Satoshi Iwase, MD, PhD, is Professor, Department of Physiology, Aichi Medical University, Nagakute, Japan.
Background:
There is no clear information about the optimal bed reclining angle for promoting efficient and safe defecation in bedfast patients.
Objective:
The aim of this study was to examine the optimal bed reclining angle for facilitating increases in intrarectal pressure without causing marked cardiovascular changes in order to develop an efficient and safe defecation position for bedfast patients.
Methods:
Twelve healthy men participated in this study. The subjects were required to strain for 15 seconds at the end stage of inspiration while their bed was reclined at 0° (supine), 15°, 30°, or 60°. During straining, the subjects were asked to maintain (a) an intrarectal pressure of 20 mm Hg or (b) the maximal intrarectal pressure. Intrarectal pressure, blood pressure, heart rate, and abdominal muscle activity (electromyographic activity) were recorded continuously throughout the study period.
Results:
During straining, intrarectal pressure increased with the reclining angle, and a significant linear correlation was detected between the sine of the reclining angle of the bed and intrarectal pressure (η = .57, p < .01). When subjects were straining with the aim of maintaining maximal intrarectal pressure, the extent of the observed changes (delta) in blood pressure and heart rate did not differ significantly across the reclining angles. When subjects were straining with the aim of maintaining an intrarectal pressure of 20 mm Hg, the delta blood pressure decreased as the reclining angle increased 0°: M = 23.7, SD = 15.3 mm Hg, 95% CI [11.9, 35.4]; 15°: M = 25.9, SD = 10.8 mm Hg, 95% CI [17.6, 34.2]; 30°: M = 17.7, SD = 9.4 mm Hg, 95% CI [10.4, 24.9]; 60°: M = 15.5, SD = 9.5 mm Hg, 95% CI [8.1, 22.8]; 15° versus 30°: p < .05; 15° versus 60°: p < .05. The amount of muscle activity observed during straining decreased as the reclining angle increased.
Discussion:
In bedfast patients, it is suggested that higher reclining angles may enable safer and more efficient defecation, because it decreases the amount of muscle activity required to increase the intrarectal pressure and reduces the potentially deleterious effects of straining on the cardiovascular system to develop an efficient and safe defecation position for bedfast patients.
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