Abstract:
:The purpose of this study was to compare the kinetics of estimated capillary blood flow (Qcap) to those of femoral artery blood flow (QFA) and estimated muscle oxygen uptake (VO2m). Nine healthy subjects performed a series of transitions from rest to moderate (below estimated lactate threshold, 6 min bouts) knee extension exercise. Pulmonary oxygen uptake (VO2) was measured breath by breath, (QFA) was measured continuously using Doppler ultrasound, and deoxyhaemoglobin ([HHb]) was estimated by near-infrared spectroscopy over the rectus femoris throughout the tests. The time course of (Qcap) was estimated by rearranging the Fick equation (i.e. Qcap = VO2m/(a-v)O2), (arterio - venous O2 difference) using the primary component of VO2 to represent VO2m and [HHb] as a surrogate for (a - v)O2. The overall kinetics of QFA (mean response time, MRT, 13.7 +/- 7.0 s), VO2m (tau, 27.8 +/- 9.0 s) and Qcap (MRT, 41.4 +/- 19.0 s) were significantly (P < 0.05) different from each other. We conclude that for moderate intensity knee extension exercise, conduit artery blood flow (QFA) kinetics may not be a reasonable approximation of blood flow kinetics in the microcirculation (Qcap), the site of gas exchange. This temporal dissociation suggests that blood flow may be controlled differently at the conduit artery level than in the microcirculation.
journal_name
Exp Physioljournal_title
Experimental physiologyauthors
Harper AJ,Ferreira LF,Lutjemeier BJ,Townsend DK,Barstow TJdoi
10.1113/expphysiol.2005.032904subject
Has Abstractpub_date
2006-07-01 00:00:00pages
661-71issue
4eissn
0958-0670issn
1469-445Xpii
expphysiol.2005.032904journal_volume
91pub_type
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