title: Kinetics of skeletal muscle O2 delivery and utilization at the onset of heavy-intensity exercise in pulmonary arterial hypertension.
abstract: Impaired 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.
authors.affiliation: 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.
authors.forename: Priscila B
authors.initials: PB
authors.lastname: Barbosa
authors.forename: Eloara M V
authors.initials: EM
authors.lastname: Ferreira
authors.forename: Jaquelina S O
authors.initials: JS
authors.lastname: Arakaki
authors.forename: Luciana S
authors.initials: LS
authors.lastname: Takara
authors.forename: Juliana
authors.initials: J
authors.lastname: Moura
authors.forename: Rúbia B
authors.initials: RB
authors.lastname: Nascimento
authors.forename: Luiz E
authors.initials: LE
authors.lastname: Nery
authors.forename: J Alberto
authors.initials: JA
authors.lastname: Neder
mesh_terms: D000293:Adolescent; D000328:Adult; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D065627:Familial Primary Pulmonary Hypertension; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000378:metabolism* / Q000503:physiopathology*; D007700:Kinetics; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism / Q000493:pharmacokinetics*; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology; D055815:Young Adult
chemical_list: D010100:Oxygen