Muscle capillary blood flow kinetics estimated from pulmonary O<sub>2</sub> uptake and near-infrared spectroscopy

Ferreira, Leonardo F.; Townsend, Dana K.; Lutjemeier, Barbara J.; Barstow, Thomas J.

doi:10.1152/japplphysiol.00907.2004

Cited by 146 publications

(213 citation statements)

References 55 publications

(142 reference statements)

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“…2, A-C), the dynamic adjustment of blood flow during the first moderate-intensity exercise transition could not be systematically characterized in all subjects since the Q cap time course was actually nonexponential in one-third of the them. While conformity of the Q cap response to an exponential profile is not necessary in order for it to be considered "physiologically reasonable" ("priming" exercise may make this less likely), this response profile has been reported previously (4,7). Indeed, in the subjects in whom an exponential characterization of the response was feasible, a faster adjustment of microvascular blood flow (i.e., a lower MRT of the Q cap response) was associated with a smaller…”

Section: Resultsmentioning

confidence: 55%

“…The profile of muscle capillary blood flow (Q cap) was estimated using the methods described by Ferreira et al (7). Briefly, the Qcap response was derived on a second-by-second basis from the kinetic profiles of V O2p (l/min) and [HHb] (M) with the assumption that the kinetics of the primary component of V O2p during constant work-rate exercise approximates that of the muscle V O2 (V O2m) (9) and that the NIRS-derived [HHb] is a function of the balance between V O2m and muscle blood flow (5,8), thus representing a proxy measure for O2 extraction (and a-vO2diff).…”

Section: Methodsmentioning

confidence: 99%

“…When this method is used, the amplitude of Qcap is quantitatively uncertain because the actual contribution of arterial and venous blood to the [HHb] signal is unknown. However, the temporal characteristics of [HHb], and thus Q cap, should be preserved (7). The Qcap response to exercise, in 5-s averages, from the onset to the end of the exercise (360 s), was fitted by means of a single exponential model with a TD (as in Eq.…”

Section: Methodsmentioning

confidence: 99%

“…However, this method does not reflect microvascular blood flow as derived from the Fick equation. In this regard, an estimation of capillary blood flow (Q cap ) has been proposed (7,10). When this method is used, [HHb] is substituted directly into the Fick equation in place of the arterio-venous O 2 difference (avO 2diff ), and kinetic profiles of muscle V O 2 (V O 2m ) are derived using the parameters of pulmonary V O 2 (V O 2p ).…”

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confidence: 99%

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Noninvasive estimation of microvascular O₂ provision during exercise on-transients in healthy young males

Murias

Spencer

Pogliaghi

et al. 2012

American Journal of Physiology-Regulatory, Integrative and Comp

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(V O 2p ). An obvious limitation to this methodology is that, even though [HHb] reflects the balance between O 2 delivery and O 2 utilization, and thus, it is used as a proxy for O 2 extraction, neither the actual O 2 content in the arterial nor venous circulations is precisely known, and then, its use for replacing a-vO 2diff in the Fick equation is questionable. As such, the Q cap can only potentially reflect the time course of the adjustment in microvascular blood flow but provides no information on the actual changes in its magnitude.In recent years, our group has provided evidence that improved microvascular delivery of O 2 , as reflected by a smaller normalized [HHb]/V O 2 ratio throughout the exercise on-transient, plays an important role in the control of the rate of adjustment of oxidative phosphorylation (14 -16, 18, 22). These studies collectively showed that, although intracellular mechanisms are likely the principal putative factors controlling the adjustment of V O 2 kinetics during the initial response to a step increment in power output, for pulmonary V O 2p time constant (V O 2p ) values greater than ϳ20 s, the rate of adjustment of phase II V O 2p is also constrained by the matching of local O 2 delivery to muscle V O 2 . More specifically, we have shown recently that a significant reduction in the phase II V O 2p when moderate-intensity exercise is preceded by a bout of heavy-intensity (i.e., supra-lactate threshold) "priming" exercise was related to improvements in the matching of O 2 delivery to O 2 utilization, as reflected by reductions in the [HHb]/V O 2 ratio (16,22). Using a somewhat similar approach, Buchheit et al. (4) indicated that a smaller V O 2p during the second bout of moderate-intensity running in those participants in whom the first bout showed a rather slow rate of adjustment for phase II V O 2p was related to improvements in O 2 provision, as reflected by a faster adjustment of Q cap [i.e., Q cap mean response time (MRT)]. Although the proposed mechanisms explaining the smaller V O 2 in these two studies using a similar intervention were the same, the association between changes in the rate of adjustment of V O 2 and changes in the [HHb]/V O 2 ratio or, alternatively, the Q cap remain to be elucidated.Thus, the goal of this study was to compare two different and established methods for estimation of the changes in microvascular O 2 delivery during the on-transient of exercise and to evaluate the two approaches in determining the role of the adjustment of the estimated microvascular O 2 delivery in the speeding of V O 2 kinetics during moderate-intensity exercise preceded by a bout of heavy-intensity "priming" exercise. We hypothesized that 1) with priming exercise, faster moder-

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Section: Resultsmentioning

confidence: 55%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Noninvasive estimation of microvascular O₂ provision during exercise on-transients in healthy young males

Murias

Spencer

Pogliaghi

et al. 2012

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Consequently, the estimation of Q m by taking into account the dynamics of oxygen stores and muscle blood flow (Kemp 2005) is more accurate than that based on a Fick relationship (Barstow et al 1990;Ferreira et al 2005aFerreira et al , 2005b, which is strictly valid only at steady state (Stringer et al 2005). In our model, blood flow dynamics are approximated by a single exponential with time constant τ Q m similar to that of heart rate (τ HR ) determined from measurements of heart rate dynamics (DeLorey et al 2004;Miyamoto et al 1982).…”

Section: Blood Flow and Oxygen Uptakementioning

confidence: 99%

Relating pulmonary oxygen uptake to muscle oxygen consumption at exercise onset: in vivo and in silico studies

et al. 2006

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Assessment of the rate of muscle oxygen consumption, UO 2m , in vivo during exercise involving a large muscle mass is critical for investigating mechanisms regulating energy metabolism at exercise onset. While UO 2m is technically difficult to obtain under these circumstances, pulmonary oxygen uptake, VO 2p , can be readily measured and used as a proxy to UO 2m . However, the quantitative relationship between VO 2p and UO 2m during the nonsteady phase of exercise in humans, needs to be established. A computational model of oxygen transport and utilizationbased on dynamic mass balances in blood and tissue cells-was applied to quantify the dynamic relationship between model-simulated UO 2m and measured VO 2p during moderate (M), heavy (H), and very heavy (V) intensity exercise. In seven human subjects, VO 2p and muscle oxygen © Springer-Verlag 2006 Correspondence to: M. E. Cabrera, mec6@cwru.edu. NIH Public Access

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Exercise: Kinetic Considerations for Gas Exchange

Rossiter

2010

Comprehensive Physiology

171

255

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The activities of daily living typically occur at metabolic rates below the maximum rate of aerobic energy production. Such activity is characteristic of the nonsteady state, where energy demands, and consequential physiological responses, are in constant flux. The dynamics of the integrated physiological processes during these activities determine the degree to which exercise can be supported through rates of O₂ utilization and CO₂ clearance appropriate for their demands and, as such, provide a physiological framework for the notion of exercise intensity. The rate at which O₂ exchange responds to meet the changing energy demands of exercise--its kinetics--is dependent on the ability of the pulmonary, circulatory, and muscle bioenergetic systems to respond appropriately. Slow response kinetics in pulmonary O₂ uptake predispose toward a greater necessity for substrate-level energy supply, processes that are limited in their capacity, challenge system homeostasis and hence contribute to exercise intolerance. This review provides a physiological systems perspective of pulmonary gas exchange kinetics: from an integrative view on the control of muscle oxygen consumption kinetics to the dissociation of cellular respiration from its pulmonary expression by the circulatory dynamics and the gas capacitance of the lungs, blood, and tissues. The intensity dependence of gas exchange kinetics is discussed in relation to constant, intermittent, and ramped work rate changes. The influence of heterogeneity in the kinetic matching of O₂ delivery to utilization is presented in reference to exercise tolerance in endurance-trained athletes, the elderly, and patients with chronic heart or lung disease.

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Muscle capillary blood flow kinetics estimated from pulmonary O₂ uptake and near-infrared spectroscopy

Cited by 146 publications

References 55 publications

Noninvasive estimation of microvascular O₂ provision during exercise on-transients in healthy young males

Noninvasive estimation of microvascular O₂ provision during exercise on-transients in healthy young males

Relating pulmonary oxygen uptake to muscle oxygen consumption at exercise onset: in vivo and in silico studies

Exercise: Kinetic Considerations for Gas Exchange

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Muscle capillary blood flow kinetics estimated from pulmonary O2 uptake and near-infrared spectroscopy

Cited by 146 publications

References 55 publications

Noninvasive estimation of microvascular O2 provision during exercise on-transients in healthy young males

Noninvasive estimation of microvascular O2 provision during exercise on-transients in healthy young males

Relating pulmonary oxygen uptake to muscle oxygen consumption at exercise onset: in vivo and in silico studies

Exercise: Kinetic Considerations for Gas Exchange

Contact Info

Product

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About

Muscle capillary blood flow kinetics estimated from pulmonary O₂ uptake and near-infrared spectroscopy

Noninvasive estimation of microvascular O₂ provision during exercise on-transients in healthy young males

Noninvasive estimation of microvascular O₂ provision during exercise on-transients in healthy young males