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UBC Theses and Dissertations

Peripheral chemoresponsiveness and exercise induced arterial hypoxemia in highly trained endurance athletes Cooper, Trevor Kenneth


To determine whether highly trained endurance athletes (HT) who develop exercise induced arterial hypoxemia (EIH) also demonstrate reduced peripheral chemoresponsiveness (PC) during exercise, twelve (N=12) HT male cyclists were selected for study. Basic pulmonary function data (FEV1 = 4.69 ± 0.66 L, PVC = 6.12 ± 0.82 L, FEV1 /FVC = 0.77 ± 0.08, FEFmax = 10.52 ± 1.57 L•sec⁻¹, and MVV = 194 ± 21 L.min⁻¹) were obtained on all subjects. Subjects exercised on a cycle ergometer to exhaustion to determine their maximal aerobic capacity (“O2max = 5.08 ± 0.32 L⁻¹min 66.6 ± 4.7mL min⁻¹ kg⁻¹), and ventilatory threshold (VO2TH = 3.29 ± 0.12 L1,min 44.3 ± 4.2 mL min⁻¹ kg⁻¹) Oxygen saturation of arterial hemoglobin (SaO2max) was monitored with an ear oximeter (Hewlett-Packard, 47201A), to determine whether subjects exhibited EIH (SaO2max 91%) during the maximal cycle ergometer test. Subjects with SaO2max 93% were placed in the normal saturation group (NOS, Sa°2max = 93.4 ± 0.4 %) while subjects whose SaO2max 91% were placed in the low saturation group (LOS,5a°2max = 89.9 ± 0.9 %). Ventilatory responses to hypercapnic (13% C,20 21% 02, 66% 2N)and hyperoxic (100% 02) gas mixtures were determined at rest, and during exercise on a cycle ergometer at approximately 25% VO2max, 50% VO2max,TV2h0. Hypercapnic peripheral chemoresponsiveness was lower in LOS subjects than NOS subjects and increased in both groups from rest to 50 %mV2aOx. Hyperoxic peripheral chemoresponsiveness was not different in LOS and NOS subjects and did not change with exercise. Pre-stimulus SaO2 fell significantly during exercise in all subjects with LOS having lower SaO2 than NOS atV2Oduring the hypercapnic chemoresponse tests only. No evidence for a relationship between pre-stimulus SaO2 and either hypercapnic or hyperoxic peripheral chemoresponsiveness was found. The results of this study provide information which may help explain variations in the ventilatory response to exercise in athletes. Additionally, data from this study suggest a role of altered ventilatory control in highly trained endurance athletes who do and do not demonstrate exercise induced arterial hypoxemia.

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