Erschienen in:
01.08.2011 | Original Article
Kinetics of skeletal muscle O2 delivery and utilization at the onset of heavy-intensity exercise in pulmonary arterial hypertension
verfasst von:
Priscila B. Barbosa, Eloara M. V. Ferreira, Jaquelina S. O. Arakaki, Luciana S. Takara, Juliana Moura, Rúbia B. Nascimento, Luiz E. Nery, J. Alberto Neder
Erschienen in:
European Journal of Applied Physiology
|
Ausgabe 8/2011
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Abstract
Impaired O2 delivery relative to O2 demands at the onset of exercise might influence the response profile of muscle fractional O2 extraction (≅Δ[deoxy-Hb/Mb] by near-infrared spectroscopy) either by accelerating its rate of increase or creating an “overshoot” (OS) in patients with pulmonary arterial hypertension (PAH). We therefore assessed the kinetics of O2 uptake \( \left( {\dot{V}{\text{O}}_{2} } \right), \) Δ[deoxy-Hb/Mb] in the vastus lateralis, and heart rate (HR) at the onset of heavy-intensity exercise in 14 females with PAH (connective tissue disease, IPAH, portal hypertension, and acquired immunodeficiency syndrome) and 11 age- and gender-matched controls. Patients had slower \( \dot{V}{\text{O}}_{2} \) and HR dynamics than controls (τ\( \dot{V}{\text{O}}_{2} \) = 62.7 ± 15.2 s vs. 41.0 ± 13.8 s and t
1/2-HR = 61.3 ± 16.6 s vs. 43.4 ± 8.8 s, respectively; p < 0.01). No study participant had a significant reduction in oxyhemoglobin saturation. In OS(−) subjects (6 patients and 7 controls), the kinetics of Δ[deoxy-Hb/Mb] relative to \( \dot{V}{\text{O}}_{2} \) were faster in patients (p = 0.05). Larger area under the OS and slower kinetics (MRT) of the “downward” component indicated greater O2 delivery-to-utilization mismatch in OS(+) patients versus OS(+) controls (477.4 ± 330.0 vs. 78.1 ± 65.6 a.u. and 74.6 ± 18.8 vs. 46.0 ± 17.0 s, respectively; p < 0.05). Resting pulmonary vascular resistance was higher in OS(+) than OS(−) patients (23.1 ± 12.0 vs. 10.7 ± 4.0 Woods, respectively; p < 0.05). We conclude that microvascular O2 delivery-to-utilization inequalities slowed the rate of adaptation of aerobic metabolism at the start of heavy-intensity exercise in women with PAH.