Submitted on May 8, 2006
Accepted on February 19, 2007
Effects of posture on peripheral vascular responses to lower body positive pressure
Takeshi Nishiyasu1*, Shigeko Hayashida1, Asami Kitano2, Kei Nagashima3, and Masashi Ichinose1
1 Institute of Health and Sports Science, University of Tsukuba, Tsukuba, Ibarakki, Japan
2 Yasuda Women's University, Japan
3 School of Human Sciences, Waseda University, Tokorozawa, Saitama, Japan
* To whom correspondence should be addressed. E-mail: nisiyasu{at}taiiku.tsukuba.ac.jp.
We tested the hypothesis that peripheral vascular responses (in the lower and upper limbs) to application of lower body positive pressure (LBPP) are dependent on the posture of the subjects. We measured heart rate (HR), stroke volume (SV), mean arterial pressure (MAP), leg (LBF) and forearm (FBF) blood flow (using the Doppler ultrasound technique), and leg (LVC) and forearm (FVC) vascular conductance in 11 subjects (9 male, 2 female) with and without LBPP (25 and 50 mmHg) in supine and upright postures. MAP increased in proportion to increases in LBPP and was greater in supine than upright subjects. HR was unchanged when LBPP was applied to supine subjects but was reduced in upright ones. LBF and LVC were both reduced by LBPP in supine subjects (LVC: 4.8 ± 4.0, 3.6 ± 3.5, 1.4 ± 1.8, ml min-1 mmHg-1, before LBPP and during 25 and 50 mmHg LBPP, respectively, p<0.05), but were increased in upright ones (LVC: 2.0 ± 1.2, 3.4 ± 3.4, 3.0 ± 2.0 ml min-1 mmHg-1, respectively, p<0.05). FBF and FVC both declined when LBPP was applied to supine subjects (FVC: 1.3 ± 0.6, 1.0 ± 0.4, 0.9 ± 0.6 ml min-1 mmHg-1, respectively, p<0.05), but remained unchanged in upright ones (FVC: 0.7 ± 0.4, 0.7 ± 0.4, 0.6 ±0.5 ml min-1 mmHg-1, respectively). Taken together, these findings indicate that the leg vascular response to application of LBPP is posture-dependent and that the response differs in the lower and upper limbs when subjects assume an upright posture.
