A pilot study in men to show the effects of postural fluid shifts on the severity of obstructive sleep apnea.
Level 3 - non-randomized controlled study
Non-randomized crossover physiological study with consecutive night testing
PubMed 32166715 · doi:10.1007/s11325-020-02044-x
What was done
Twenty-two men underwent overnight polysomnography on two consecutive nights. The bed was set horizontally on the control night, while the foot section was angled down by 30° on the experimental night to decrease rostral fluid shift toward the neck. Sleep parameters, anthropometric measures, and leg fluid volume changes were measured.
What was found
Compared to the control night, the experimental night showed a decrease in mean supine apnea-hypopnea index from 66.6 events/hour (95% CI, 57.6–75.6) to 61.2 (95% CI, 52.0–70.4; p < 0.001) and a decrease in oxygen desaturation index from 69.5 events/hour (95% CI, 56.4–82.6) to 61.6 (95% CI, 50.5–72.6; p = 0.004). Overnight reduction in leg fluid volume dropped from 17.7% (95% CI, 15.7–19.8) to 4.7% (95% CI, 1.9–7.5; p < 0.001).
Why it matters
This study provides experimental evidence that overnight rostral fluid shift from the legs contributes to the severity of obstructive sleep apnea. Interventions that limit fluid redistribution to the neck may offer a non-invasive adjunct approach to reducing airway obstruction.
Limits
The sample size was very small (22 participants) and included only men. The nights were conducted consecutively without reported randomization or counterbalancing, leaving results vulnerable to order or habituation effects. Direct neck fluid volume was not reported.
Cited by
- supports When lying down horizontally, fluid shifts rostrally into the neck, contributing to upper airway obstruction in sleep apnea.