October 28, 2011Journal of Applied PhysiologyOpen Access

The intramuscular contribution to the slow oxygen uptake kinetics during exercise in chronic heart failure is related to the severity of the condition

Q: What is the clinical evidence from this study?

Population: Chronic heart failure (n=15). Intervention: Prior moderate-intensity exercise (warm-up) vs. Rest (first exercise bout without prior warm-up). Primary outcome: V˙O2 time constant (τV˙O2) (p=0.003).

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Key result

Prior moderate-intensity exercise improved muscle oxygenation and speeded the pulmonary oxygen uptake time constant from 49 to 41 seconds in men with chronic heart failure.

Why the study?

Does prior moderate-intensity exercise improve muscle oxygenation and speed Vo2 kinetics in men with chronic heart failure?

Structured PICO

Does prior moderate-intensity exercise improve muscle oxygenation and speed Vo2 kinetics in men with chronic heart failure?

Population

15 men with stable chronic heart failure (NYHA class I-III) due to left ventricular systolic dysfunction who performed repeated moderate-intensity exercise transitions.

Intervention

Prior (warm-up) exercise consisting of a 6-min moderate-intensity exercise transition from rest to 90% of lactate threshold on a cycle ergometer

Comparator

Initial exercise bout without prior warm-up (bout 1 vs bout 2 separated by 6 min of rest)

Outcome

Muscle tissue oxygenation index (TOI) and pulmonary O2 uptake (Vo2) kinetics (time constant)surrogate

Main Result

Absolute Event Rate: 41% vs 49%

p-value: p=0.003

Prior moderate-intensity warm-up exercise improves muscle oxygenation and speeds oxygen uptake kinetics in patients with chronic heart failure, highlighting a potential therapeutic target for exercise intolerance.

Limitations

Small sample size of only 15 male patients.
NIRS measurement of microvascular oxygenation was limited to a small region of the quadriceps muscle.
Abrupt changes in total hemoglobin at exercise onset clouded the interpretation of [HHb] and [HbO2] measured by the Beer-Lambert method.
Potential influence of changes in skin blood flow on tissue oxygenation index (TOI) dynamics.
The degree to which fundamental pulmonary V˙O2 kinetics reflect muscle O2 consumption has not been confirmed in CHF.
Patients used beta-blockers, which are known to slow the V˙O2 response.
NIRS-derived signals may include absorption from Hb and myoglobin chromophores

Discussion

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Implication

May aid exercise tolerance in heart failure; hypothesis-generating and requires confirmation in larger trials.

Cite This Study

Bowen et al. (2011) studied Chronic heart failure (n=15). Prior moderate-intensity exercise (warm-up) vs. Rest (first exercise bout without prior warm-up) was evaluated on V˙O2 time constant (τV˙O2) (p=0.003). Prior moderate-intensity exercise improved muscle oxygenation and speeded the pulmonary oxygen uptake time constant from 49 to 41 seconds in men with chronic heart failure.

synapsesocial.com/papers/6a71e6dd439bab0cabc3b34e https://doi.org/10.1152/japplphysiol.00779.2011

Topics

Heart failure HFrEF treatment

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The intramuscular contribution to the slow oxygen uptake kinetics during exercise in chronic heart failure is related to the severity of the condition

Structured PICO

Main Result

Limitations

Discussion

Implication

Cite This Study

Topics

The intramuscular contribution to the slow oxygen uptake kinetics during exercise in chronic heart failure is related to the severity of the condition

Structured PICO

Main Result

Limitations

Discussion

Implication

Cite This Study

Also Consider

Topics

Also Consider