Prior oxygenation, but not chemoreflex responsiveness, determines breath‐hold duration during voluntary apnea

Central and peripheral respiratory chemoreceptors are stimulated during voluntary breath holding due to chemostimuli (i.e., hypoxia and hypercapnia) accumulating at the metabolic rate. We hypothesized that voluntary breath‐hold duration (BHD) would be (a) positively related to the initial pressure of inspired oxygen prior to breath holding, and (b) negatively correlated with respiratory chemoreflex responsiveness. In 16 healthy participants, voluntary breath holds were performed under three conditions: hyperoxia (following five normal tidal breaths of 100% O2), normoxia (breathing room air), and hypoxia (following ~30‐min of 13.5%–14% inspired O2). In addition, the hypoxic ventilatory response (HVR) was tested and steady‐state chemoreflex drive (SS‐CD) was calculated in room air and during steady‐state hypoxia. We found that (a) voluntary BHD was positively related to initial oxygen status in a dose‐dependent fashion, (b) the HVR was not correlated with BHD in any oxygen condition, and (c) SS‐CD magnitude was not correlated with BHD in normoxia or hypoxia. Although chemoreceptors are likely stimulated during breath holding, they appear to contribute less to BHD compared to other factors such as volitional drive or lung volume. Breath holding stimulates respiratory chemoreceptors, likely affecting volitional breath‐hold duration (BHD). We tested the effects of varying prior oxygenation (PO2; hypoxia [~14% inspired], normoxia [room air], and hyperoxia [100% inspired]) and chemoreflex responsiveness on voluntary BHD. BHD was longer in the hyperoxic condition and shorter in the hypoxic condition compared to normoxia, but chemoreflex responsive did not determine BHD. A multitude of factors likely determine when breathing resumes following a voluntary breath hold.