Safety and effectiveness of acute intermittent hypoxia during a single treatment at different hypoxic severities.

Examine the cardiovascular, muscular function, cognitive, and neural plastic responses to determine the safety and effectiveness of acute Intermittent hypoxia (AIH) at a low, high, and control fractional inspired oxygen (FiO2) dosage METHODS: Thirteen human participants performed 30-min of AIH in 60-s intervals at FiO2's of 0.21 (AIH21), 0.15 (AIH15), and 0.09 (AIH9). Heart rate variability (root mean squared of successive differences; RMSSD), heart rate, oxygen saturation (SpO2), blood pressure, muscular strength, neuromuscular activation, cerebral hemodynamic responses, cognition, symptomology, and brain-derived neurotrophic factor (BDNF) responses were measured before (Pre-AIH), after (post-AIH), and at 20-min of recovery (Recovery-AIH) RESULTS: There were no differences between AIH protocols for heart rate, RMSSD, blood pressure, or SpO2. Muscular strength improved Post-AIH for AIH15 (10 %) and AIH9 (14 %) and remained elevated (6 %) at Recovery-AIH. Neuromuscular activation increased Pre-AIH to Post-AIH for AIH15 (10 %) and AIH9 (11 %). Cerebral hemodynamic responses were not impacted between conditions. Both AIH15 and AIH9 increased BDNF Post-AIH (62 %) and Recovery-AIH (63 %) CONCLUSION: Acute intermittent hypoxia is generally safe and effective at producing neural plastic responses, but further examination of co-occurring cardiovascular diseases is needed. This study provides safety focused findings which will widen the adoption and refinement of AIH protocols.