WISE‐2005: Drug‐induced changes in compliance affect model flow calculation of stroke volume

Abstract

Model flow (MF) estimates of cardiac stroke volume (SV) from the finger pressure wave form (Finometer) have been compared to SV estimates from pulsed Doppler ultrasound (DU) of the ascending aorta. Data were collected at rest and during the administration of 0.005 and 0.01 ug/kg/min isoproterenol (Iso), 10 and 50 ng/kg/min norepinephrine (NE) by intravenous infusion, and 0.3 mg nitroglycerin (NG) by sublingual spray. Data are from 12 women participating in the WISE bed rest study in the pre-bed rest condition. There was no significant difference between SV recorded with DU (68.3±10.2 ml, mean±SD) and MF (70.7±11.5 ml) at baseline (p=0.22). However, estimates of SV differed (p<0.01) between DU and MF during 0.01 ug/kg/min Iso (DU +57±20%, MF +21±21%), 50 ng/kg/min NE (DU −14±12%, MF +7±7%), and NG (DU +7±12 %, MF −8±11%). The model flow method uses assumed values for aortic compliance and peripheral vascular resistance. In this investigation total peripheral resistance (TPR) was significantly increased from baseline (1.3 PRU) during 50 ng/kg/min NE (1.7 PRU, p<0.01) and reduced during 0.01 ug/kg/min Iso (0.6 PRU, p<0.01) and 0.3 mg NG (1.1 PRU, p=0.04). Hence, with reduced TPR MF underestimated SV while an increase in TPR resulted in an overestimation. We have shown that SV values determined by MF should be interpreted with caution when measured during drug administration. Supported by Canadian Space Agency, NASA, ESA, CNES