Abstract

Background

A recent study demonstrates that central apnea becomes significantly more common at increasing altitudes in both diagnostic and treatment portions of split-night polysomnography in patients with significant OSA.

Case Presentation

A physically fit, middle-aged man with a normal BMI is an avid cyclist with a resting heart rate and blood pressure. Despite his peak physical health, he was diagnosed with mild positional obstructive sleep apnea. He is currently using positional therapy to successfully treat his OSA.

 

During a consultation with the Wesper Sleep Expert, the patient was asked about any lifestyle or behavioral changes that occurred during the 6-week period when their sleep apnea severity increased. It was revealed that the patient, who normally resides in a low-altitude area of the United States, had traveled to an area of the US that was 5,280 feet (approximately 1 mile) above sea level.

Conclusion

For those with sleep apnea, higher altitude can make respiration more difficult. Clinical studies have shown that higher altitudes not only increase OSA severity but they can also cause acute central sleep apnea. Higher altitudes can also make therapies for both OSA and CSA less effective.

Background

A recent study demonstrates that central apnea becomes significantly more common at increasing altitudes in both diagnostic and treatment portions of split-night polysomnography in patients with significant OSA.

 

An exponential increase in the percentage of OSA patients with a CAI > 5.0 occurs with increasing altitude. Altitude-associated central apnea significantly negatively affects the quality of OSA treatment obtained during PAP titration for patients living at the altitudes addressed in this study.

 

The causes of CSA at sea level have been extensively explored in the context of patients with congestive heart failure. However, independent of heart failure, CSA also occurs almost universally at high altitudes, but the mechanisms are less completely understood.

 

The development of hypoxic-induced periodic breathing during sleep has been attributed to the marked increase in ventilatory responses to hypoxia and hypercapnia (controller gain), with consequent narrowing of the difference between eupneic Pco2 and apneic threshold.

 

The common trigger to both CSA in heart failure and high-altitude exposure is transient arterial hypocapnia during light (stages 1 and 2 non-rapid eye movement) sleep.

Case presentation

A physically fit, middle-aged man with a normal BMI is an avid cyclist with a resting heart rate and blood pressure. Despite his peak physical health, he was diagnosed with mild positional obstructive sleep apnea. He is currently using positional therapy to successfully treat his OSA.

 

The patient had successfully completed 70 Wesper tests, which include 62 non-diagnostic tests and 8 Wesper Lab diagnostic tests, which do include the pulse oximeter. During routine testing with Wesper Lite, the user’s breathing events increased significantly by nearly 2 times in the span of 6 weeks.

 

Before the 6-week significant increase in breathing events, the user’s average number of breathing events per hour without the use of positional therapy was 11.31. This was consistent with his medical tests, which indicated mild sleep apnea. His medical test findings across 5 tests:

 

• Average AHI: 10.87
• Average ODI: 10.10
• Average Mean SPO2: 95%
• Average Min SPO2: 84.8%

 

The patient only used Wesper Lab during the 6 weeks when the noticeable increase in breathing events occurred. During this time, the user’s average number of breathing events per hour increased by 2 times from 11.31 to 22.13, which is 2 times higher.

 

The user didn’t report any major changes to their diet, drug use, alcohol consumption, sleep routine, or health during this time period on their survey questionnaires.

 

While the breathing event score is not the same as AHI, the severity level of a breathing score directly correlates with AHI’s severity. If someone has a breathing event score of 15-30, we expect the patient’s AHI to fall into this range. Therefore, we predict that the patient’s OSA severity would have increased from mild to moderate during this time period.

 

During a consultation with the Wesper Sleep Expert, the patient was asked about any lifestyle or behavioral changes that occurred during the 6-week period when their sleep apnea severity increased. It was revealed that the patient, who normally resides in a low-altitude area of the United States, had traveled to an area of the US that was 5,280 feet (approximately 1 mile) above sea level.

 

While the user reported being more physically active during this time, most aspects of his life, including diet, medication, alcohol consumption, and sleep routine, didn’t change.

Conclusions

For those with sleep apnea, higher altitude can make respiration more difficult. Clinical studies have shown that higher altitudes not only increase OSA severity, but they can also cause acute central sleep apnea. Higher altitudes can also make therapies for both OSA and CSA less effective.

 

The patient was informed that his travel to a higher altitude increased his OSA severity. The sleep expert discussed ways to improve his breathing while in high altitudes.

 

Because his OSA was very recently successfully treated with positional therapy (AHI decreased from 10.87 to 2.06; ODI decreased from 10.10 to 6.36), he was advised to continue using his Positional Therapy during his next trip to a high altitude. It was also recommended that the patient closely monitor his sleep with Wesper Lab to monitor his sleep apnea.

 

It is important that all sleep apnea sufferers are made aware of the impact of high altitudes on their respiration. These patients should closely monitor their sleep apnea during these periods to ensure their sleep apnea therapies remain effective.

 

Explanation of metrics

 

1. Apnea/Hypopnea Index (AHI) – the combined average number of apneas and hypopneas that occur per hour of sleep
2. Respiratory Event Index (REI) – the total number o3. Oxygen Desaturation Index (ODI) – the number of times per hour of sleep that the blood oxygen level drops by ≥ 4% from baseline
3. Mean SPO2: The average blood oxygen saturation score
4. Minimum SPO2: The lowest blood oxygen saturation score
5. Breathing events—Moments of increased respiratory effort include reduced airflow and prolonged breathing stoppages.

References

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3227706/
2. https://journals.physiology.org/doi/full/10.1152/japplphysiol.01462.2012
3. https://www.mayoclinic.org/diseases-conditions/central-sleep-apnea/symptoms-causes/syc-20352109