Title
Continuous stroke volume monitoring by modelling flow from non-invasive measurement of arterial pressure in humans under orthostatic stress
Author
Harms, M.P.M.
Wesseling, K.H.
Pott, F.
Jenstrup, M.
van Goudoever, J.
Secher, N.H.
van Lieshout, J.J.
TNO Biomedical Instrumentation
Publication year
1999
Abstract
The relationship between aortic flow and pressure is described by a three-element model of the arterial input impedance, including continuous correction for variations in the diameter and the compliance of the aorta (Modelflow). We computed the aortic flow from arterial pressure by this model, and evaluated whether, under orthostatic stress, flow may be derived from both an invasive and a non-invasive determination of arterial pressure. In 10 young adults, Modelflow stroke volume (MFSV) was computed from both intra-brachial arterial pressure (IAP) and non-invasive finger pressure (FINAP) measurements. For comparison, a computer-controlled series of four thermodilution estimates (thermodilution-determined stroke volume; TDSV) were averaged for the following positions: supine, standing, head-down tilt at 20°(HDT20) and head-up tilt at 30°and 70°(HUT30 and HUT70 respectively). Data from one subject were discarded due to malfunctioning thermodilution injections. A total of 155 recordings from 160 series were available for comparison. The supine TDSV of 113 ± 13 ml (mean ± S.D.) dropped by 40% to 68 ± 14 ml during standing, by 24% to 86 ± 12 ml during HUT30, and by 51% to 55 ± 15 ml during HUT70. During HDT20, TDSV was 114 ± 13 ml. MFSV for IAP underestimated TDSV during HDT20 (-6 ± 6 ml; P < 0.05), but that for FINAP did not (-4 ± 7 ml; not significant). For HUT70 and standing, MFSV for IAP overestimated TDSV by 11 ± 10 ml (HUT70; P < 0.01) and 12 ± 9 ml (standing; P < 0.01). However, the offset of MFSV for FINAP was not significant for either HUT70 (3 ± 8 ml) or standing (3 ± 9 ml). In conclusion, due to orthostasis, changes in the aortic transmural pressure may lead to an offset in MFSV from IAP. However, Modelflow correctly calculated aortic flow from non-invasively determined finger pressure during orthostasis.
Subject
Health
Cardiovascular
Fingers
Posture
Thermodilution
Tilt-table test
Adult
Blood Pressure Determination
Female
Fingers
Hemodynamic Processes
Humans
Male
Models, Cardiovascular
Monitoring, Physiologic
Posture
Regional Blood Flow
Stress
Stroke Volume
Thermodilution
Tilt-Table Test
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http://resolver.tudelft.nl/uuid:71b1d8d1-5507-4ecf-8883-01e7117bc803
DOI
https://doi.org/10.1042/cs19990061
TNO identifier
235161
ISSN
0143-5221
Source
Clinical Science, 97 (3), 291-301
Document type
article