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.

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　 During catheter placement, peripheral intravenous access is affected by the visibility of the vein, such that the risk of peripheral nerve injuries and arterial punctures, increases as the visibility decreases. This study examined the relation between vein visibility and (a) vein width, (b) vein depth, (c) position of the artery relative to the vein, and (d) skin color. This was an observational study with prospective data collection. A total of 20 healthy young women (58 veins and 18 arteries) were examined. As a result, vein visibility demonstrated significant differences in relation to vein depth, but not in relation to the other three factors. The mean depth (SD) was 2.7 (0.7) mm for visible veins and 4.6 (1.8) mm for invisible veins (p=0.0001). The cut off point was 3.0 mm (AUC=0.919　95％ CI-0.84 to 0.99), indicating that peripheral veins for catheter placement are more likely to be invisible when the depth is 3.0 mm or more. These findings highlight the need for two kinds of venipuncture skills : those for invisible veins with a depth of 3.0 mm or more, and those that will prevent arterial puncture regardless of vein visibility.

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Background : The aim of this study was to compare the influence of intrathoracic (IT) pressure at defecation on cardiovascular system in sitting and supine positions
　Methods : Twenty one healthy volunteers (age 32.7 ± 10.1 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%rh). All signals of BP and HR were digitally sampled.
　Results : In sitting and supine positions, the BP and HR showed the large change as the IT pressure increased. These reaction showed not only during IT pressure load but also after it release. At the IT pressure of 30 mmHg, the Δ SBP of phase Ⅰ to Ⅱ a was larger in sitting 41.43 ± 13.30 mmHg, than supine 26.86 ± 19.59 mmHg (p＜0.001). The IT pressure of 10 and 20 mmHg were the same. There was a large significant (p<0.01) increase in Δ HR of phase Ⅰ to Ⅱ a and Ⅲ to Ⅳ for sitting.
　Conclusions : The high IT pressure at the defecation might give the great influence to cardiovascular system. Under the same IT pressure, the sitting position may cause great influence to hemodynamics.

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[in Japanese]

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