You Need More Oxygen When You Get High

Sleep apnea patients taking acetazolamide with CPAP at high altitude fared better

(RxWiki News) A vacation in the mountains can be incredibly refreshing – unless you're so high the air is too thin to breathe. This can particularly be a problem for those with sleep apnea.

During sleep apnea, individuals are already not getting the oxygen they need while sleeping. Thinner mountain air can make this worse.

A recent study looked at whether adding a medication to the use of standard treatment for sleep apnea might help individuals with the condition while at high altitudes. The researchers found that taking the medication acetazolamide at the same time as standard continuous positive airway pressure (CPAP) therapy at high altitudes led to more oxygen in the patients' blood while sleeping.

The patients also had fewer incidents of paused or shallow breathing while taking the acetazolamide and using CPAP.

"Plan ahead for high altitude trips."

The small study, led by Tsogyal D. Latshang, MD, from the Sleep Disorders Center at the University of Zurich in Switzerland, aimed to determine whether taking a medication used for reducing altitude sickness symptoms might help patients with sleep apnea when sleeping at higher altitudes.

Acetazolamide has been prescribed to reduce the risk of mountain sickness, but it has also been prescribed for central sleep apnea because it is a respiratory stimulant, according to William Kohler, MD, a dailyRx expert and the director of the Florida Sleep Institute in Spring Hill, Florida.

Central apnea is a little different than obstructive sleep apnea, though both involve pauses in breathing during sleep. During obstructive sleep apnea, a person attempts to inhale but cannot because the upper airways are collapsed.

During central sleep apnea, the signals in the brain that tell the body to breathe don't work and the person does not automatically inhale as their body normally would. Dr. Kohler said that central apneas will often start to develop at higher altitudes.

Therefore in this study, the researchers included 51 patients with obstructive sleep apnea in the study. All the participants lived below 800 meters (2600 feet) and were using CPAP therapy for their sleep apnea. The patients all underwent sleep studies at at 490 meters (about 1600 feet) in a hospital and then took two 3-day trips in high-altitude mountain villages, where the researchers studied their symptoms and outcomes.

Two days occurred at a village at 1,630 meters (about 5300 feet) and one day in a village at 2,590 meters (about 8500 feet) During one of the 3-day trips, the patients took either a placebo (fake pill) or 750 mg of acetazolamide each day. Acetazolamide is a medication used to offset or prevent the effects of altitude sickness.

During the second 3-day trip, the patients took whatever they had not taken on the first trip. If they were given acetazolamide on the first trip, they took a placebo on the second trip and vice versa. The patients all continued to use their CPAP therapy during all the nights. The researchers measured the oxygen saturation the patients had in their blood and their apnea/hypopnea index.

An apnea/hypopnea index refers to how frequently patients either breathe very shallowly or else stop breathing for at least ten seconds at a time. This measurement is used to determine the severity of their sleep apnea.

The study results showed that the patients had a higher saturation of oxygen in their blood while taking the acetazolamide along with using CPAP compared to taking the placebo along with CPAP.

At 1,630 meters, the patients had an average blood oxygen saturation of 94% while taking acetazolamide compared to 93% while taking the placebo. At 2,590 meters, the patients taking acetazolamide had an average oxygen saturation of 91% compared to 89% while taking a placebo.

On average, taking the acetazolamide appeared to increase the patients' oxygen saturation 1% at the lower elevation and 2% at the higher elevation.

At the highest elevation, the patients' spent about four times as much of their sleeping time with an oxygen saturation level below 90% if they were not taking the acetazolamide. (The mid-range for those taking acetazolamide was spending about 13 percent of the night with oxygen saturation below 90% compared to a mid-range of about 57 percent of the time while taking placebo.)

In addition, the patients experienced fewer apnea/hypopnea events during each hour of sleep while taking the acetazolamide. At 1,630 meters, those taking the medication had a typical 5.8 events per hour compared to 10.7 per hour when taking the placebo. At 2,590 meters, the patients taking acetazolamide had about 6.8 events of paused or shallow breathing per hour compared to 19.3 events per hour while taking placebo.

The researchers concluded that taking the acetazolamide along with CPAP improved obstructive sleep apnea symptoms in patients while they slept at higher altitudes than they were used to.

"Acetazolamide has been used as a standard therapy at high altitudes to try to prevent central apneas where the signals to breathe aren't there," Dr. Kohler told dailyRx. "So combining the acetazolamide, which is effective for central apneas, and the CPAP, which is effective for obstructive apnea, the combination therapy helps prevent the apneas that will occur at high altitude."

No serious adverse effects were reported, but up to 30 percent of the participants did experience mild side effects from taking the acetazolamide.

Common side effects of acetazolamide include nausea, loss of appetite, thirst and feelings of tingling or numbness in the fingers and toes. Other side effects that have been reported with acetazolamide include feeling exceptionally thirsty and needing to urinate frequently, drowsiness, headache, confusion, fever, rash, blood in the urine, painful urination, yellowing in the skin or eyes, seizures, sore throat and unusual bleeding or bruising.

If any of these occur, the patient should notify a healthcare provider.

Due to the small size of the study, more research is likely needed to confirm that these results would be applicable to the general population.

The study was published December 11 in JAMA. The research was funded by the Swiss National Science Foundation, Lung Leagues of Zurich and Schaffhausen, Center for Clinical Research, University of Zurich, University Hospital Zurich and a grant from Philips Respironics, which manufactures CPAP machines. One author has previously received grant money from Philips Respironics and ResMed and has consulted for imtmedial. No other conflicts of interest were reported.

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Review Date: 
December 11, 2012