Hypoalgesic effects, safety, and feasibility of a 6-minute high-lung-volume static apnea intervention

Repeated apneas may induce hypoalgesia, but the impact of high-lung-volume static apneas remains unexplored.

Eighty-one healthy participants were randomized into an apnea group (AG) or control group (CG). The AG performed a 6-minute static intermittent apnea at high lung volume, while the CG breathed normally in supine. Pressure pain thresholds (PPTs) at the thumb, tibialis anterior and the 7^th cervical vertebra (C7), along with heart rate (HR), oxygen saturation (SpO₂), and systolic and diastolic blood pressure (SBP, DBP), were recorded. Qualitative analysis assessed sensations, emotions, and adverse effects.

ANCOVA showed no significant differences in PPT between groups in the thumb (mean difference [MD] = 0.306 kg/cm²; bias-corrected and accelerated [BCa] 95% confidence intervals [CI] = [-0.192, 0.775]; P = 0.215), tibialis (MD = 0.213 kg/cm²; BCa 95% CI = [-0.181, 0.629]; P = 0.303) and C7 (MD = 0.213 kg/cm²; BCa 95% CI = [-0.101, 0.543]; P = 0.190). No differences were found in SpO₂ (MD = 0.385%; P = 0.065). However, %HR_max (MD = 2.879%; P < 0.001), SBP (MD = 9.221 mmHg; P < 0.001) and DBP (MD = 6.604 mmHg; P < 0.001) were slightly higher in the AG. The AG presented greater distress-related sensations and emotions, while the CG reported more comfort-related experiences. AG presented with more, although mild, adverse effects.

High-lung-volume static apneas showed no clear hypoalgesic effect and participants reported slightly greater discomfort. Further studies should explore the dose-effect relationships in healthy and clinical populations.