Acute effects of intermittent hypoxia–hyperoxia exposure on cardiovascular autonomic function and blood pressure in sedentary older adults: A pilot randomized controlled trial

BACKGROUND: The aim of this study was to evaluate the acute effects of a single session of intermittent hypoxia-hyperoxia exposure on cardiovascular autonomic regulation, blood pressure, and arterial oxygen saturation in sedentary older adults. METHODS: A double-blind randomized controlled trial with pre- and post-intervention assessment was conducted in a residential care physiotherapy setting. Sixteen sedentary older adults were randomly assigned to an experimental group (n = 8) or a control group (n = 8). The experimental group received one session of intermittent hypoxia-hyperoxia exposure consisting of six cycles of hypoxia (FiO₂ 10-14% for 5 minutes) followed by hyperoxia (FiO₂ 30-40% for 3 minutes), administered via a hypoxic generator. The control group received a sham intervention consisting of normoxic breathing (FiO₂ 21%). Heart rate variability (SDNN, RMSSD, LF/HF), systolic and diastolic blood pressure, heart rate, and arterial oxygen saturation were measured at baseline and immediately after the intervention. RESULTS: Compared with the control group, the experimental group showed significant increases in SDNN and RMSSD and a significant reduction in the LF/HF ratio (p < 0.01), indicating improved autonomic regulation. Systolic and diastolic blood pressure and heart rate decreased significantly in the experimental group compared with controls (p < 0.01). Arterial oxygen saturation showed a small but significant increase in the experimental group (p < 0.01). No adverse events or withdrawals were reported. CONCLUSIONS: In this pilot randomized controlled trial, a single session of intermittent hypoxia-hyperoxia exposure was associated with acute changes in heart rate variability indices and blood pressure in sedentary older adults. These preliminary findings should be interpreted cautiously and require confirmation in larger, adequately powered trials.