The Association between Pulse Pressure and Stroke Volume during Lower Body Negative Pressure and Graded Hemorrhage

Due to the relationship between stroke volume (SV) and pulse pressure (PP) during lower body negative pressure (LBNP), we hypothesized that PP reflects SV during hemorrhage (HEM). After a 5‐minute baseline, 6 men were exposed to LBNP at ‐15, ‐30, and ‐45 mmHg for 5 minutes at each pressure. After 45 minutes of recovery, three progressive 333‐ml stages of HEM (1 L total) were performed. SV was assessed using a CC Nexfin and PP was calculated using an arterial catheter. SV (111 ± 2.1 vs. 77 ± 6.7 mL; p = 0.04) and PP (58±2.7 vs. 41 ± 4.3 mm Hg; p = 0.03) decreased from baseline to ‐45 mmHg LBNP. SV (118 ± 4.4 to 99 ± 6.8 mL; p = 0.06) and PP decreased (58 ± 2.9 to 48 ± 4.9 mmHg; p = 0.06) from baseline to ‐1 L of HEM. PP correlated with SV during HEM (amalgamated r 2 = 0.98) and LBNP (amalgamated r 2 = 0.99). There was limited inter‐subject variability in PP vs. SV during LBNP ( r 2 range 0.57 to 0.99, 5/6 had an r 2 >; 0.90), but substantial inter‐subject variability during HEM ( r 2 range 0.21 to 0.99, 2/6 had an r 2 >; 0.90). Reductions in PP induced by LBNP or HEM are strongly correlated with SV. However large inter‐individual differences in this correlation during HEM, which may indicate a significantly variable compensatory response in human arterial distensibility, may limit the use of PP as a surrogate for SV during clinical blood loss. Funded by U.S. Army MRMC Combat Casualty Care Research Program Grant # W81XWH‐11–1‐0823.