Hypoxic ventilatory response predicts the extent of maximal breath-holds in man

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To understand the factors influencing breath-holding performance, we tested whether the hypoxic (HVR) and hypercapnic ventilatory responses (HCVR) were predictors of the extent of maximal breath-holds as measured by breath-hold duration, the lowest oxyhemoglobin saturation (Sp O 2min ), lowest calculated Pa O 2 (Pa O 2min ) and highest end-tidal P CO 2 (P et CO 2max ) reached. Steady state isocapnic HVR and hyperoxic HCVR were measured in 17 human volunteers. Breath-holds were made at total lung capacity (TLC), at TLC following hyperventilation, at functional residual capacity, and at TLC with F i O 2 = 0.15. Sp O 2 was measured continuously by pulse oximetry, and alveolar gas was measured at the end of breath-holds by mass spectrometry. Pa O 2min was calculated from Sp O 2min and P et CO 2max . HVR was a significant predictor of both Sp O 2min and Pa O 2min . HVR and forced vital capacity were predictors of breath-hold duration by multiple linear regression. HCVR had no significant predictive value. We conclude that HVR, but not HCVR, is a significant predictor of breath-holding performance.