Effect of ventilation on oxygen transfer during early exercise.

Auchincloss, J. Howland; Gilbert, Robert; Baule, Gerhard

doi:10.1152/jappl.1966.21.3.810

Cited by 71 publications

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“…Breath-by-breath V O 2 was computed by the Grønlund algorithm (8). Indeed, classical algorithms for single-breath determination of alveolar gas exchange, all based on the concepts originally introduced by Auchincloss et al (1), require the assumption of a fixed value for the end-expiratory alveolar volume. This assumption was demonstrated to increase the variability of breath-by-breath V O 2 assessment (18).…”

Section: Discussionmentioning

confidence: 99%

Simultaneous determination of the kinetics of cardiac output, systemic O₂ delivery, and lung O₂ uptake at exercise onset in men

Lador¹,

Kenfack²,

Moia³

et al. 2006

American Journal of Physiology-Regulatory, Integrative and Comp

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Simultaneous determination of the kinetics of cardiac output, systemic O 2 delivery, and lung O2 uptake at exercise onset in men. Am J Physiol Regul Integr Comp Physiol 290: R1071-R1079, 2006. First published October 20, 2005 doi:10.1152/ajpregu.00366.2005.-We tested whether the kinetics of systemic O 2 delivery (Q aO2) at exercise start was faster than that of lung O 2 uptake (V O2), being dictated by that of cardiac output (Q ), and whether changes in Q would explain the postulated rapid phase of the V O2 increase. Simultaneous determinations of beat-by-beat (BBB) Q and Q aO 2, and breath-by-breath V O2 at the onset of constant load exercises at 50 and 100 W were obtained on six men (age 24.2 Ϯ 3.2 years, maximal aerobic power 333 Ϯ 61 W). V O2 was determined using Grønlund's algorithm. Q was computed from BBB stroke volume (Q st, from arterial pulse pressure profiles) and heart rate (f H, electrocardiograpy) and calibrated against a steadystate method. This, along with the time course of hemoglobin concentration and arterial O 2 saturation (infrared oximetry) allowed computation of BBB Q aO 2. The Q , Q aO2 and V O2 kinetics were analyzed with single and double exponential models. f H, Qst, Q , and V O2 increased upon exercise onset to reach a new steady state. The kinetics of Q aO 2 had the same time constants as that of Q . The latter was twofold faster than that of V O2. The V O2 kinetics were faster than previously reported for muscle phosphocreatine decrease. Within a two-phase model, because of the Fick equation, the amplitude of phase I Q changes fully explained the phase I of V O2 increase. We suggest that in unsteady states, lung V O2 is dissociated from muscle O 2 consumption. The two components of Q and Q aO2 kinetics may reflect vagal withdrawal and sympathetic activation. cardiovascular response AT THE ONSET OF SQUARE-WAVE light aerobic exercise, O 2 consumption increases to attain a steady level, proportional to the exerted mechanical power. Its increase rises at a finite rate in response to the step increase in power, so that an O 2 deficit is incurred in the first minutes of exercise. The O 2 deficit reflects the decrease in high-energy phosphate concentration that is necessary to accelerate aerobic metabolic pathways (5,19,35,37). Analogous to the charge of a single capacitance, the increase in O 2 consumption was described by monoexponential equations (5,15,19). The monoexponential decrease in phosphocreatine concentration upon square-wave exercise onset (6, 46) is perhaps the strongest evidence provided so far in favor of this single capacitance model for O 2 consumption. Assuming close correspondence between O 2 consumption by the working muscles and O 2 uptake at the lungs (V O 2 ), the V O 2 was investigated to gain information on O 2 consumption (15, 16).This correspondence, however, was questioned. In fact, the kinetics of O 2 consumption requires that it be sustained by adequate O 2 transfer from ambient air to mitochondria. Thus, concomitant with the increase in O 2 consumption, th...

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Section: Discussionmentioning

confidence: 99%

Simultaneous determination of the kinetics of cardiac output, systemic O₂ delivery, and lung O₂ uptake at exercise onset in men

Lador¹,

Kenfack²,

Moia³

et al. 2006

American Journal of Physiology-Regulatory, Integrative and Comp

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show abstract

“…Blood pressure was taken with an automated cuff (Tango, SunTech Inc.) every 3 min during the maximal exercise test. Calculations of VO 2p and VCO 2p were based on the expired gas under the assumption that the fractional concentration of inspired and expired nitrogen are equal (Auchincloss et al 1966) then no changes of gas lung stores were considered.…”

Section: Experimental Studiesmentioning

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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“…The first need was to improve the time resolution up to the single breath, the duration of which is a physiological barrier. This was initially achieved in 1966, when Auchincloss et al (1966) published their algorithm for single-breath determination of _ V O 2 . Attempts at improving the time resolution beyond the single-breath duration could rely only on computational manipulations, such as superposition of several trials and interpolation procedures.…”

Section: The Problem Of Gas Flow Analysis On a Breath-by-breath Basismentioning

confidence: 99%

“…The second need was to improve the signal-tonoise ratio during the exercise transient, in order to reduce the error of fitting procedures, a key step in the calculation of parameters of exponential equations. The algorithm by Auchincloss et al (1966) requires a correct determination of the changes in the amount of gas stored in the lungs over each breath. This quantity cannot be measured, so they estimated it by imposing fixed pre-defined values of endexpiratory lung volumes.…”

Section: The Problem Of Gas Flow Analysis On a Breath-by-breath Basismentioning

confidence: 99%

Exercise Transients

Ferretti¹

2015

Energetics of Muscular Exercise

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The steady state of light constant-power submaximal exercise is attained after at least 3 min since the exercise start. Although the application of mechanical power is practically immediate, the rate of oxygen uptake _ V O 2 À Á increases at a remarkably slower rate: a metabolic transient phase occurs, during which _ V O 2 , despite increasing, is insufficient to provide all the metabolic power that is necessary to sustain ATP resynthesis, so that an oxygen deficit is incurred. The oxygen deficit consists of (i) an obligatory component, covered by phosphocreatine breakdown, reflecting the kinetics of glycolysis activation in the contracting muscles, and characterized by an invariant time constant independent of the exercise intensity and (ii) a facultative component, covered by anaerobic lactic metabolism (early lactate accumulation), due to the dissociation between cardiopulmonary response and muscular response at elevated powers, and characterized by a time constant depending on the exercise intensity. The kinetics of _ V O 2 upon exercise onset is described with exponential equations. The implications of single-and doubleexponential models are discussed. The former model carries along the assumption that the kinetics of _ V O 2 determined at the mouth reflects the kinetics of _ V O 2 in the contracting muscles. This correspondence, however, does not hold anymore when early lactate appears. The latter model, in particular, implies a rapid phase (phase I), which has been related to the fast cardiovascular responses at exercise start. A singleexponential model assumes also that the exercising muscles behave as dynamic linear first-order systems that, as such, admit only one transfer function. On this basis, ramp exercise and sinusoidal exercise, typically two unsteady-state conditions, are discussed. More recently, at powers higher than the critical power (see Chap. 5), the so-called slow component, or third phase of the _ V O 2 kinetics, has been also characterized. The energetic meaning of the slow component is also discussed. Finally, some methodological aspects of single-breath analysis of pulmonary gas exchange are discussed.

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Effect of ventilation on oxygen transfer during early exercise.

Cited by 71 publications

References 0 publications

Simultaneous determination of the kinetics of cardiac output, systemic O₂ delivery, and lung O₂ uptake at exercise onset in men

Simultaneous determination of the kinetics of cardiac output, systemic O₂ delivery, and lung O₂ uptake at exercise onset in men

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

Exercise Transients

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Effect of ventilation on oxygen transfer during early exercise.

Cited by 71 publications

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Simultaneous determination of the kinetics of cardiac output, systemic O2 delivery, and lung O2 uptake at exercise onset in men

Simultaneous determination of the kinetics of cardiac output, systemic O2 delivery, and lung O2 uptake at exercise onset in men

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

Exercise Transients

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Simultaneous determination of the kinetics of cardiac output, systemic O₂ delivery, and lung O₂ uptake at exercise onset in men

Simultaneous determination of the kinetics of cardiac output, systemic O₂ delivery, and lung O₂ uptake at exercise onset in men