• Priscila B Barbosa, Eloara M V Ferreira, Jaquelina S O Arakaki, Luciana S Takara, Juliana Moura, Rúbia B Nascimento, Luiz E Nery, and J Alberto Neder.
• Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Respiratory Division, Department of Medicine, Federal University of São Paulo, Paulista School of Medicine (UNIFESP-EPM), Rua Professor Francisco de Castro 54, Vila Clementino, São Paulo, CEP 04020-050, Brazil.
• Eur. J. Appl. Physiol. 2011 Aug 1; 111 (8): 1851-61.

AbstractImpaired O(2) delivery relative to O(2) demands at the onset of exercise might influence the response profile of muscle fractional O(2) 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 O(2) uptake [Formula: see text] 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 [Formula: see text] and HR dynamics than controls (τ[Formula: see text] = 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 [Formula: see text] were faster in patients (p = 0.05). Larger area under the OS and slower kinetics (MRT) of the "downward" component indicated greater O(2) 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 O(2) delivery-to-utilization inequalities slowed the rate of adaptation of aerobic metabolism at the start of heavy-intensity exercise in women with PAH.

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