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

BACKGROUND: The purpose of this study was to examine individual stroke volume-pulse pressure (PP) relationships in healthy young men and women. METHODS: Sixteen healthy men and women were assessed at baseline and during four 12-minute stages of progressive lower body negative pressure (LBNP) at -15, -30, -45, and -60 mm Hg. RESULTS: Throughout staged LBNP, systolic blood pressure (105 ± 7.8 vs. 103 ± 8.3 mm Hg) and mean arterial pressure were not statistically different (81 ± 5.6 vs. 83 ± 5.9 mm Hg). There was also a significant increase in diastolic blood pressure (69 ± 5.3 vs. 72 ± 5.9 mm Hg) and heart rate (63 ± 8.3 vs. 86 ± 14.2 bpm) as well as a decrease in PP (37 ± 5.7 vs. 31 ± 7.0 mm Hg) and stroke volume (80 ± 17.0 vs. 26.6 ± 10.0 mL). There was a strong positive relationship for LBNP versus stroke volume (r2 = 0.99), PP (r2 = 0.96), and heart rate (r2 = -0.92), as well as for stroke volume versus PP (r2 = 0.98) and stroke volume versus heart rate (r = -0.94). Substantial intersubject variability in the stroke volume and PP correlations were presented. Strong, significant correlations were only displayed for 38% of the participants, while heart rate and stroke volume was strongly associated in 63% of these individuals. CONCLUSIONS: This work highlights the limitations of using PP when assessing trauma patients because of large interindividual differences.