The Effect of Altitude Descent on Obstructive Sleep Apnea

doi:10.1378/chest.130.6.1744

Chest

Volume 130, Issue 6, December 2006, Pages 1744-1750

https://doi.org/10.1378/chest.130.6.1744 Get rights and content

Background

The present requirement for “at facility” polysomnograms requires many residents in mountain communities to descend in elevation for sleep testing, which may cause misleading results regarding the severity of obstructive sleep apnea (OSA).

Design

Eleven patients with previously undiagnosed sleep apnea living at an altitude > 2,400 m (7,900 feet) in Colorado underwent diagnostic sleep studies at their home elevation and at 1,370 m (4,500 feet), and 5 of the 11 patients were also studied at sea level.

Results

The mean (SE) apnea-hypopnea index (AHI) fell from 49.1 (10.5)/h to 37.0 (11.2)/h on descent to 1,370 m (p = 0.022). In the five patients who traveled to sea level, the AHI dropped from 53.8 (13.2)/h at home elevation to 47.1 (14.8)/h at 1,370 m, and to 33.1 (12.6)/h at sea level (p = 0.018). The reduction in AHI was predominantly a reduction in hypopneas and central apneas, with little change in the frequency of obstructive apneas. Duration of the obstructive apneas lengthened with descent. Of eight patients with an AHI < 50/h at their home elevation, two patients had their AHI fall to < 5/h at 1,370 m, and a third patient dropped to < 5/h at sea level, ie, below many physicians’ threshold for providing therapy. Patients with the most severe OSA had the least improvement with descent.

Conclusions

Because AHI decreases significantly with descent in altitude, polysomnography is most accurately done at the home elevation of the patient. Descent to a sleep laboratory at a lower elevation may yield false-negative results in patients with mild or moderate sleep apnea.

Section snippets

Study Design and Enrollment

Eleven individuals with suspected sleep apnea living at an altitude > 2,400 m in western Colorado underwent attended full-night diagnostic polysomnography at two elevations, one in the home and one in a clinical sleep laboratory in Grand Junction at 1,370 m. Five of the 11 patients also underwent a third polysomnogram in a clinical sleep laboratory at sea level. Each patient was referred from a primary practitioner who was aware of the study protocol and was concerned about the possibility of

Results

Table 1 summarizes the individual patient data, and Table 2summarizes how the respiratory indexes (mean [SE]) changed with altitude descent. The patients were 46 to 70 years old (mean 55 ± 7.3 years). Three of the 11 patients were women. Body mass index was 20 to 58 kg/m² (mean, 33.9 ± 11.3 kg/m²). The home elevations ranged from 2,417 to 3,139 m (7,930 to 10,300 feet) [mean, 2,701 ± 214 m]. Home elevation severity of sleep apnea in these patients ranged from mild to severe, with AHIs from 13.5

Discussion

The AHI decreased with descent to lower elevations, with the reduction being primarily secondary to fewer hypopneas and central apneas. This finding suggests that the increased oxygen content in the air at lower elevation is the more important of the three atmospheric factors affecting respiratory events with elevation change, within the altitude range studied.

Our findings parallel the findings of other investigators who noted AHI decreased with supplemental oxygen therapy. Smith et al² found

Conclusion

For patients residing between 2,400 m and 3,139 m, the AHI and RDI decrease with descent. All of the changes we observed regarding the effect of altitude descent paralleled previous observations on the effect of oxygen on OSA patients at sea level. Central apneas and hypopneas decreased in number, and obstructive apneas lengthened. It is important to appreciate that some patients with mild or moderate sleep apnea traveling from their home elevation in the mountains to lower urban sleep centers

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Reported changes in sleep architecture include a shift to lighter sleep [11]. Finally, some authors recommend that polysomnograms be recorded the altitude at which the patient resides [12]. There are concerns that a stay at high altitude will expose susceptible OSA patients, in particular those of advanced age and with co-morbidities, to an excessive risk of cardiovascular and other adverse events [13].
Sleep disorders are common but underdiagnosed conditions, which are associated with obesity. In Colombia, the distribution of sleep disorders remains unclear. We aimed to describe the distribution of sleep disorders, according to demographic, geographic and anthropometric characteristics, in adult Colombian populations.
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Nearly two-thirds of the population reported at least one sleep disorder according to their results on the five scales (59.6% [95%CI 57.4; 61.81)]. This proportion was similar by sex. Prevalence of overweight was 34.8% and of obesity was 14.4%. Sleep disorders were more frequent among those aged 65 years or more (91.11 [95%CI 86.1; 94.43]), those who were obese (83.71% [95%CI 78.94; 87.56]) and those who resided in the cities at the lowest altitude (72.4% [95%CI 70.2; 74.5]). Waist circumference showed a stronger association with sleep disorders among women than among men.
Sleep disorders are common in Colombia, irrespective of sex and geographical location. They are associated with obesity. Abdominal obesity could explain the high frequency of sleep disorders among women.
We believe that this part of the study will substantially contribute to the understanding of sleep disorders. Further research is needed to identify key factors behind the high prevalence rates of sleep disorders and obesity in Colombia.
Greater risk of hospitalization in children with down syndrome and OSA at higher elevation
2015, Chest
Children with Down syndrome (DS) are at high risk for OSA. Increasing elevation is known to exacerbate underlying respiratory disorders and worsen sleep quality in people without DS, but whether altitude modulates the severity of OSA in DS is uncertain. In this study, we evaluate the impact of elevation (≤ 1,500 m vs > 1,500 m) on the proportion of hospitalizations involving OSA in children with and without DS.
Merging the 2009 Kids' Inpatient Database with zip-code linked elevation data, we analyzed differences in the proportion of pediatric hospitalizations (ages 2-20 years) involving OSA, pneumonia, and congenital heart disease (CHD), with and without DS. We used multivariable logistic regression to evaluate the association of elevation with hospitalizations involving OSA and DS, adjusting for key comorbidities.
Proportionately more DS encounters involved OSA, CHD, and pneumonia within each elevation category than non-DS encounters. However, the risk difference for hospitalizations involving OSA and DS increased disproportionately at higher elevations (DS: 16.2% [95% CI, 9.2%-23.2%]; non-DS: 0.1% [95% CI, −0.4% to 0.7%]). Multivariable estimates of relative risk indicate increased risk for hospitalization involving OSA at higher elevations for people with DS and in children aged 2 to 4 years or with two or more chronic conditions.
At elevations > 1,500 m, children with DS and OSA have a disproportionately higher risk for hospitalization than children with OSA without DS. This finding has not been described previously. With further validation, this finding suggests the need for greater awareness and earlier screening for OSA and its complications in patients with DS living at higher elevations.
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Put another way, 2 patients with the same upper airway tendency to collapse, but one healthy and the other with chronic lung disease, might have very different apnea-hypopnea indices. A similar observation that makes the same point is that the AHI improves with descent from altitude, largely because of a decrease in the number of hypopneas.52 Nevertheless, there are no current alternative scoring criteria or guidelines for OSA diagnosis in the setting of chronic lung disease.
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The apnea–hypopnea index (AHI) was defined as the total number of apneas and hypopneas per hour of sleep. The severity of OSA was determined according to AHI: Mild: 5–15/h; moderate: 16 to 30/h; and severe: more than 30/h [14]. Oxygen desaturation was defined by a SpO2 lower than 90%.
To describe the SpO₂ in wakefulness, sleep and during the apnea–hypopnea in adults living in Bogotá, located at 2640 m above sea level.
Descriptive observational study in adults referred for polysomnogram (PSG). A normal Apnea hypopnea index (AHI) was defined as ≤5 and obstructive sleep apnea (OSA) was classified as mild (AHI 5–15), moderate (AHI 15–30), and severe (AHI >30). T-test or ANOVA test for SpO₂ differences between groups was used.
1799 patients, 33% women. 222 (12.8%) did not have OSA (normal IAH), 268 (14.9%) mild OSA, 315 (17.5%) moderate ,and 993 (55.2%) severe. In all cases a low SpO₂ (SpO₂<90%) was found.
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It was initially recommended in popular high-altitude medicine publications that those with OSA should avoid ascending to high altitude because the OSA is likely to get worse (Pollard and Murdoch, 1997). Based on pathophysiological considerations and uncontrolled observations in a small number of patients, it has been reported that a stay at altitude aggravates sleep-related breathing disturbances in patients with OSA as reflected by elevations in central apneas and reductions in obstructive apnea (Burgess et al., 2006; Patz et al., 2006). In a recent randomized controlled trial, it was shown that altitude exposure (up to 2590 m) in untreated patients with OSA aggravates hypoxemia, increases sleep-related breathing disturbances due to frequent central apneas/hypopneas, impairs driving simulator performance and induces cardiovascular stress (Nussbaumer-Ochsner et al., 2010).
We provide an updated review on the current understanding of breathing and sleep at high altitude in humans. We conclude that: (1) progressive changes in pH initiated by the respiratory alkalosis do not underlie early (<48 h) ventilatory acclimatization to hypoxia (VAH) because this still proceeds in the absence of such alkalosis; (2) for VAH of longer duration (>48 h), complex cellular and neurochemical re-organization occurs both in the peripheral chemoreceptors as well as within the central nervous system. The latter is likely influenced by central acid-base changes secondary to the extent of the initial respiratory responses to initial exposure to high altitude; (3) sleep at high altitude is disturbed by various factors, but principally by periodic breathing; (4) the extent of periodic breathing during sleep at altitude intensifies with duration and severity of exposure; (5) complex interactions between hypoxic-induced enhancement in peripheral and central chemoreflexes and cerebral blood flow – leading to higher loop gain and breathing instability – underpin this development of periodic breathing during sleep; (6) because periodic breathing may elevate rather than reduce mean SaO₂ during sleep, this may represent an adaptive rather than maladaptive response; (7) although oral acetazolamide is an effective means to reduce periodic breathing by 50–80%, recent studies using positive airway pressure devices to increase dead space, hyponotics and theophylline are emerging but appear less practical and effective compared to acetazolamide. Finally, we suggest avenues for future research, and discuss implications for understanding sleep pathology.

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Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).

Dr. D. Patz directs and owns a private sleep laboratory in Grand Junction, Western Colorado Sleep Institute, which financed the research study. Dr. White receives income from Respironics (Murrysville, PA) for being Chief Medical Officer, but this had nothing to do with the choice of sleep recording systems in this study. Mobile Sleep Diagnostics owned Alice IV (Respironics) recording equipment for years prior to the conception of this research study. The study was also completed before Dr. White began his employment with Respironics. Dr. White is also a consultant for AspireMedical, WideMed, PAVAD, and Itamar Medical. The authors have no conflicts of interest to report.

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Chest

Original Research: Sleep MedicineThe Effect of Altitude Descent on Obstructive Sleep Apnea

Background

Design

Results

Conclusions

Section snippets

Study Design and Enrollment

Results

Discussion

Conclusion

Electroencephalogr Clin Neurophysiol

A manual of standardized terminology, techniques, and scoring system for sleep stages of human subjects

The effects of oxygen on patients with sleep apnea

Am Rev Respir Dis

A shift from central and mixed sleep apnea to obstructive sleep apnea resulting from low-flow oxygen

Am Rev Respir Dis

Central sleep apnea

Tailoring oxygen therapy to obstructive sleep apnea patients with a high loop gain [abstract]

Sleep

Diaphragmatic and genioglossal electromyogram responses to isocapnic hypoxia in humans

Am Rev Respir Dis

Original Research: Sleep Medicine
The Effect of Altitude Descent on Obstructive Sleep Apnea