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Modeling reflex changes in pulsatile mechanics emphasizes a role for vascular capacitance in forearm vasomotor control
Author(s) -
Goswami Ruma,
Salzer Deborah,
Zamir Mair,
Shoemaker J. Kevin
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a563
Subject(s) - vasomotor , medicine , cardiology , reflex , forearm , vasoconstriction , pulsatile flow , blood pressure , brachial artery , vascular resistance , cold pressor test , heart rate , blood flow , anesthesia , anatomy
Although sympathetic activation generally elicits vasoconstriction in skeletal muscle, it has variable effects on forearm vasomotor control across individuals, at least based on measures of resistance (R) that reflect changes in vascular caliber. However, R neglects changes in vascular capacitance (C) which is a critical determinant of the oscillatory component of pulsatile flow. The purpose of this study was to determine whether capacitance (C) can provide an additional measure of reflex vascular control. A modified Windkessel model that compares the pressure and flow waveforms was used to quantify the effects of R and C. Concurrent measures of brachial artery pressure (Finometer) and mean blood velocity waveforms (Doppler ultrasound) were acquired during baseline, −40 mmHg lower‐body negative pressure (LBNP) and a cold pressor test (CPT) (n=5). LBNP increased heart rate (p<0.05) with no change in mean arterial pressure. CPT caused an increase in mean arterial pressure (p<0.05) with no change in heart rate. R increased in 4 out of 5 subjects during LBNP (p<0.05) and in 3 of 5 subjects during CPT (n.s.). Regardless of the change in R, C was decreased in all subjects during both LBNP (−32%) and CPT (−30%) (p<0.05, both tests). These early results suggest that C may be an extended measure of reflex changes in vasomotor control. Supported by Natural Sciences and Engineering Research Council of Canada and Canadian Institutes of Health Research.