Oxygen Supplementation Reduces OSA-Related Psychological Distress

Yael Waknine

June 24, 2005

June 24, 2005 — Oxygen supplementation alone may significantly improve symptoms of psychological distress associated with obstructive sleep apnea (OSA), according to the results of a small study presented at the Associated Professional Sleep Societies 19th Annual Meeting in Denver, Colorado.

"Continuous positive airway pressure [CPAP] is the most commonly used treatment for sleep apnea, and studies in the past have shown that it improves psychological symptoms in these patients," Wayne A. Bardwell, PhD, lead investigator, told Medscape. "However, it is unclear whether the effect is due to a reduction in sleep disturbance/apneic events or an improvement in oxyhemoglobin saturation [SaO2] levels."

Dr. Bardwell is a licensed clinical psychologist and assistant professor at the University of California San Diego, Department of Psychiatry and Behavioral Medicine.

In the study, investigators randomized 38 patients with untreated OSA (mean apnea/hypopnia index [AHI], 62.3 ± 31.4; % time SaO2 < 90% capacity, 6.7% ± 11.4%) to receive nocturnal oxygen supplementation (3 L/minute), CPAP, or placebo-CPAP therapy for two weeks. CPAP masks were used in all patients but only delivered sufficient pressure in the CPAP group.

"Oxygen supplementation had no clinically meaningful effect on sleep disruption but increased oxygen saturation levels by more than 50%," Dr. Bardwell said, adding that CPAP therapy normalized both severity measures, whereas no changes were observed in the placebo-CPAP group.

Psychological symptoms were self-reported by patients before and after treatment using the 53-item Brief Symptom Inventory (BSI), which includes nine psychological symptom subscales that can be summarized in a Global Severity Index (GSI).

Repeated measures analysis of covariance (controlling for OSA severity, AHI, and % time SaO2 < 90% capacity) revealed a significant interaction between treatment time and GSI score reduction (P = .038).

Post-hoc analysis showed that mean GSI scores significantly decreased from baseline in the CPAP (0.17 vs 0.29; P = .036) and oxygen supplementation (0.19 vs 0.38; P = .008) groups; no changes were observed in patients receiving placebo-CPAP (0.37 vs 0.35; P = .687).

"Both CPAP and oxygen supplementation had an impact on this global measure of psychological symptoms — patients in the CPAP group had about a 40% reduction in GSI score, and those receiving oxygen supplementation had an even greater reduction of approximately 50%," Dr. Bardwell stated. "Because the oxygen treatment does not affect the frequency of apneic events, we concluded that the change in oxygen saturation was responsible for the effect."

Further analysis of BSI scores showed that only oxygen supplementation significantly improved symptoms of depression. Although mean depression subscale scores showed a significant time-treatment interaction (P = .008) similar to that of the GSI, significant decreases from baseline occurred only in patients receiving oxygen treatment (0.18 vs 0.40; P = .025; CPAP, 0.19 vs 0.29; P = .171; placebo-CPAP, 0.56 vs 0.42; P = .210).

"The CPAP group showed a slight reduction in depression symptoms (by about a third) that was actually not statistically significant, and probably had more to do with our sample size than anything else," Dr. Bardwell noted. "However, oxygen supplementation reduced depressive symptoms by more than 50%."

"It is often assumed that the disturbance of respiration and interruption of sleep itself are responsible for the psychological distress reported by patients with sleep apnea, but our findings suggest that hypoxemia may play a stronger role than sleep disruption in causing these symptoms."

"Reduction of desaturation levels, regardless of changes in apneic events, may result in normalization of psychological symptoms in OSA patients," Dr. Bardwell concluded. "Although larger studies are needed to confirm these results, oxygen supplementation may be an effective alternative for reducing psychological distress in patients who find it difficult to adhere to CPAP therapy."

This study was funded by grants from the National Institutes of Health.

APSS 19th Annual Meeting: Abstract 0472. Presented June 22, 2005.

Reviewed by Gary D. Vogin, MD

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