Oxygen therapy is sometimes used to treat sleep apnea, especially when concern for the disorder is first raised. However, in some settings, oxygen use may actually do more harm than good.
The Use of Oxygen in Sleep Apnea
Sleep specialists often encounter patients who are referred for a sleep study to diagnose and treat suspected sleep apnea. The referring physicians, out of an interest to protect their patients, often prescribe supplemental oxygen to be used overnight. This is delivered through plastic tubing called a nasal cannula, typically at a rate of several liters per minute. Is this appropriate?
The theory seems sound: The oxygen levels of the blood drop overnight (i.e., hypoxemia) due to repeated pauses in the breathing called apnea, so we will give supplemental oxygen to get things back into the normal range. Unfortunately, though the oxygen numbers may normalize, other changes caused by the apnea may not.
Why Oxygen Does Not Work
Using supplemental oxygen in people with sleep apnea and normal respiratory function has mixed results. The measured oxygen level will indeed improve. However, the effect on the apnea-hypopnea index (AHI) and the length of apneic events is negligible. Excessive daytime sleepiness, a significant complaint in sleep apnea, does not improve. Moreover, the levels of carbon dioxide during the daytime may increase when oxygen is used overnight. Finally, it does not improve the levels of excessive carbon dioxide that may accumulate during sleep.
The Danger of Oxygen Use with Sleep Apnea and COPD
There are situations where the use of oxygen to treat sleep apnea may actually be dangerous. When chronic obstructive pulmonary disease (COPD), such as emphysema, occurs alone, oxygen has been shown to be beneficial. However, when it occurs with obstructive sleep apnea, a different picture emerges.
In this so-called "overlap syndrome," the use of nocturnal oxygen without relief of the airway obstruction can cause worsened breathing overnight. This may result in complaints such as morning headache or confusion. Therefore, it is important that continuous positive airway pressure (CPAP) be used to treat the obstruction, with supplemental oxygen infused into the system as needed to confer the other benefits.
Therefore, it is important that individuals with COPD undergo a sleep study if there is suspicion of sleep apnea contributing to their complaints. And clearly, oxygen alone is not an adequate treatment for those suspected of having sleep apnea.
Gold, A et al. "The effect of chronic nocturnal oxygen administration upon sleep apnea." Am Rev Respir Dis 1986;134:925.
Masa, JF et al. "Noninvasive positive pressure ventilation and not oxygen may prevent overt ventilatory failure in patients with chest wall diseases." Chest 1997;112:207.