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CC BY-NC-ND 4.0 · Sleep Sci 2025; 18(02): e241-e244
DOI: 10.1055/s-0044-1795145
Case Report

Altitude-Associated Central Apnea in Continuous Positive Airway Pressure Therapy

Authors


Funding Source The author(s) received no financial support for the research.
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Abstract

Introduction At high altitudes, hypobaric hypoxia leads to central apneas in both healthy adults and patients with obstructive sleep apnea. This condition correlates with intermittent desaturation and disruption of sleep.

Materials and Methods The clinical case of a patient evaluated during a sleep medicine outpatient consultation at the Fundación Neumológica Colombiana (Bogotá, Colombia, 2,600 masl) is reported.

Case Study We present a 64-year-old male patient living in a high-altitude city, who was an aircrew member and was on continuous positive airway pressure (CPAP) therapy for severe obstructive sleep apnea (OSA). The patient had symptoms and central apneas only when he slept at high altitudes. Other causes of central apnea were ruled out, and these events were corrected with the administration of supplemental oxygen. Altitude-associated central apnea is a common disorder that can occur at altitudes higher than 1,600 m above sea level. Currently, the first-line treatments are acetazolamide and oxygen supplementation.

Conclusions Changes in altitude should be considered in patients with OSA in PAP therapy, as it can occur in many occupations and in recreational travels.


 

Keywords

PAP therapy - high-altitude periodic breathing - central apnea

Introduction

Altitude-associated central apnea is a respiratory disorder characterized by an oscillatory pattern of increased and decreased ventilation with periods of hyperventilation, alternating with central apneas or hypopneas. It is usually manifested in healthy individuals who are not adapted to high altitudes, being associated with desaturation, fragmented sleep, and nocturnal awakenings.[1] [2] Obstructive sleep apnea (OSA) is highly prevalent in the general population, and patients with this disease can either live or travel to high altitude for tourism or work. Sometimes, obstructive events can be replaced by central apneas with worsening desaturation.[3] This work presents the case study of an aircrew patient with OSA who was exposed to different altitudes. He was treated with continuous positive airway pressure therapy (CPAP) and had high residual respiratory events every time he slept at high altitude.


 

Materials and Methods

The clinical case of a patient evaluated during a sleep medicine outpatient consultation at Fundación Neumológica Colombiana (Bogotá, Colombia) is reported. Informed consent was given by the patient, and the institutional ethics committee approved the case report.


 

Clinic Case

A 64-year-old male patient who lives in Bogotá, Colombia, which is a city located at 2,600 m above sea level (masl), presented to the sleep medicine outpatient clinic at Fundación Neumológica Colombiana with complaints of tiredness, daytime sleepiness, loud snoring, and morning headaches. For more than 20 years he has worked as an aircrew member. In recent years, his travel itinerary has included cities located at sea level, 1,080 masl, 1,495 masl, and Bogotá. The patient had history of arterial hypertension with adequate treatment with olmesartan. Physical examination showed a body mass index (BMI) of 29 kg/m2, a neck circumference of 41 cm, and an abdominal circumference of 106 cm. The nocturnal in laboratory polysomnography (PSG) showed an apnea hypopnea index (AHI) of 103.5 events per hour, with an obstructive apnea hypopnea index (OAHI) of 53 events per hour, and a central apnea index (CAI) of 50.5 events per hour. Studies were performed to determine the possible causes of this condition, with normal results from echocardiogram, brain magnetic resonance imaging, arterial blood gases, and flow-volume curve.

Thereafter, he started CPAP at a pressure of 9 cm H2O according with the titration PSG report, with oronasal mask.

The CPAP adherence was optimal (daily mean use: 6 hours 53 minutes, percentage > 4 hours: 90%.) However, the AHI was high (31.9/h), with an IH of 1/h and CAI of 30.3/h. The AHI graph shows that the increase in respiratory events occurred only when the patient slept in Bogota, while when he was working in cities with an altitude below 1,500 masl, the respiratory events decreased ([Fig. 1]).

Zoom
Fig. 1 The CPAP compliance report with 10 cmH2O shows an increase in respiratory events at the expense of central apneas on the days that the patient sleeps at 2,600 masl.

Additionally, the patient noted that symptoms persisted only when he slept at Bogotá, described as tiredness, lack of energy, and headaches, and an Epworth sleepiness scale (ESS) of 16/24.

Another PSG was performed with manual CPAP titration (at 2,600 masl), presenting obstructive events that were corrected with a pressure of 10 cmH2O, with persistence of central events with an average oxygen saturation of 88%. Supplemental oxygen at 1 L/m, was added, achieving suppression of central events and an average saturation of 94%. We started CPAP plus 1 L/m oxygen when he was in Bogota and CPAP (without supplementary oxygen) in other cities. In the subsequent controls, the patient reported symptomatic improvement (ESS 3/24) and a median use time of 7 hours and 37 minutes, with adequate AHI values ([Fig. 2]).

Zoom
Fig. 2 The CPAP compliance report with 10 cmH2O and supplemental oxygen at 1 L/m at 2,600 masl.

 

Discussion

In 1868, the relationship between sleep-disordered breathing and high altitudes was established.[4] Central apnea is a frequent respiratory disorder that occurs in healthy individuals who are not adapted to altitudes higher than 2,000 masl but can also occur in some individuals from 1,600 masl and becomes universal at altitudes higher than 5,000 masl. It can acquire a periodic pattern (central apneas followed by an alternating short period of hyperventilation), called high-altitude periodic breathing.[2] [5]

Individuals at high altitudes are exposed to hypobaric hypoxemia and respiratory alkalosis. Some mechanisms of altitude-induced central apnea have been proposed. Considering the apnea as a consequence of “unsteady breathing,” this instability may be caused by control disturbances through a self-sustaining oscillatory system in situations where the magnitude of the correction is greater than the disturbance, known as “loop gain.” If the corrective response is disproportionate, it will cause an increase in the disturbance.[4] A high correlation between the severity of central apnea and loop gain has been described in mining drivers intermittently exposed to high altitudes.[6]

Unstable breathing is more likely to occur at high altitude if there is a disproportion between the hypoxic and hypercapnic ventilatory responses.

Altitude-associated central apneas respond to supplemental oxygen and acetazolamide. Also, several studies have shown a significant reduction in central apneas with supplemental oxygen administration, even using low doses, as was also observed in our patient.[7] However, caution is recommended on patients who have obstructive respiratory events, due to the risk of increasing the duration of these events.[8] Besides, acetazolamide may be considered, a medication that develops metabolic acidosis by inhibiting the effect of carbonic anhydrase. It is used to prevent acute mountain sickness and several studies indicate that it is effective in improving altitude-associated central apnea by reducing AHI, reducing the percentage of periodic breathing and increasing nocturnal oxygenation both in healthy subjects and in patients with sleep apnea.[9] [10] It has been suggested that doses greater than 500 mg daily do not provide increased benefit, instead increasing intolerance and adverse effects.[11]

Altitude-associated central apnea is a factor to be considered in patients who reside in altitude, and it has a high residual AHI. A research was performed using split-night PSG, where individuals were compared according to altitude in three groups (1,421, 1,808, and 2,165 masl); during that study was evidenced a direct relationship between the altitude and CAI's and percentage of individuals with > 5 events per hour, as well as poor quality of the PAP therapy titration, and the requirement of a new titration study.[12] We have reported that a significant percentage of individuals with OSA who lives in high altitudes had central apneas in the CPAP titration.[13]

It is not clear why this patient, who is a long resident in high altitude, has central apneas (without and with CPAP). It could be explained by the intermittent exposure to high altitude, which would not allow him to fully acclimatize. However, despite excluding the most frequent causes, we were not able to establish the exact cause of this patient's persistent apneas while at high altitude.

Aircrew members may have altitude variations in places where they must sleep, whether due to the assigned routes or they may live in a high-altitude city, which may be related to central apneas. This case highlights the importance of making a detailed evaluation of the CPAP report that can help make an accurate diagnosis to improve treatment.


 

Conclusions

In OSA patients living in or traveling to high altitudes due to work or tourism, the possible variations in AHI should be considered, especially regarding the CAI and its clinical impact to establish and adjust treatment.


 

 

Conflict of Interests

The authors have no conflict of interests to declare.

Author Agreement Statement

We undersigned declare that this manuscript is original, has not been published before, and is not currently being considered for publication elsewhere. We confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed.



Address for correspondence

María Angélica Bazurto-Zapata, MD

Publikationsverlauf

Eingereicht: 14. Februar 2024

Angenommen: 02. Oktober 2024

Artikel online veröffentlicht:
07. März 2025

© 2025. Brazilian Sleep Association. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

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Zoom
Fig. 1 The CPAP compliance report with 10 cmH2O shows an increase in respiratory events at the expense of central apneas on the days that the patient sleeps at 2,600 masl.
Zoom
Fig. 2 The CPAP compliance report with 10 cmH2O and supplemental oxygen at 1 L/m at 2,600 masl.