A questionable association of stroke volume and arterial pulse pressure under gravitational stress

Abstract

Arterial pulse pressure (PP) has been shown to be correlated strongly with stroke volume (SV) when humans are subjected to a gravitational stress. The purpose of this investigation was to assess the PP and SV response to progressive lower body negative pressure (LBNP) using individual responses rather than the mean response per stage of LBNP as reported previously. Sixteen healthy men and women (Age(SD) = 24.4(3.0)) were assessed during a 12 min baseline collection, during four 12‐minute stages of progressive LBNP at −15, −30, −45 and −60 mm Hg, and during 12 min of recovery. Hemodynamic measures were compared from baseline throughout −60 mm Hg. Systolic blood pressure (105 ± 7.8 to 103± 8.3 mm Hg) and mean arterial pressure were not statistically different (81 ± 5.6 to 83 ± 5.9 mm Hg); however, there was a significant difference for diastolic blood pressure (69 ± 5.3 to 72 ± 5.8 mm Hg), PP (37 ± 5.7 to 31 ± 7.0), SV (80 ± 17.0 to 26.6 ± 10.0) and heart rate (63 ± 8.3 to 86 ± 14.2). Typical group analysis revealed a strong positive relationship between LBNP and SV (r2= 0.99), LBNP and PP (r2= 0.96), and SV and PP (r2= 0.97). When comparing the individual slopes there was a more modest relationship (r2 = 0.53). Our results show high individual variability in response to LBNP and the need to consider individual PP and SV responsiveness. Natural Sciences and Research Council of Canada, Canadian Institutes of Health Research, Michael Smith Foundation