does elevation matter

[froggie48]

I recently moved from sea level to about 1.300 ft. Do I need to increase the flow of air,or change some other setting? I'm having trouble sleeping and choke,and gasp for air a lot thru the night. Thanks for any help.

[split_city]

Hi there,

Elevation is certainly known to affect OSA severity, particularly CSA. A quick Pubmed search reveals a number of studies looking at the impact of altitude on sleep disordered breathing:

Chest. 2006 Dec;130(6):1744-50. Links
The effect of altitude descent on obstructive sleep apnea.Patz D, Spoon M, Corbin R, Patz M, Dover L, Swihart B, White D.
St. Mary's Hospital, Box 1628, Grand Junction, CO 81502, USA. npatz@bresnan.net

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./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.

Respirology. 2006 Jan;11(1):62-9. Links
Erratum in:
Respirology. 2006 Mar;11(2):228.
Effect of simulated altitude during sleep on moderate-severity OSA.Burgess KR, Cooper J, Rice A, Wong K, Kinsman T, Hahn A.
Peninsula Private Sleep Laboratory, Manly, New South Wales, Australia. kburgess@nsccahs.health.nsw.gov.au

OBJECTIVE: These studies were conducted to test the hypothesis that isobaric hypoxia would switch OSA to central sleep apnoea (CSA). METHODS: Five adult men (mean age 54.2 +/- 5.5 years, mean BMI 29.9 +/- 6.7 kg/m(2)) with moderate OSA underwent overnight polysomnography at three altitudes. The highest altitude was simulated in a normobaric hypoxic chamber. RESULTS: The obstructive respiratory disturbance index fell from 25.5 +/- 14.4/h at 60 m to 17.3 +/- 9.2/h at 610 m and 0.5 +/- 0.7/h at 2750 m (P = 0.004 compared with 60 m). The central respiratory disturbance index rose from 0.4 +/- 0.5/h at 60 m to 8.1 +/- 5.8/h at 610 m and 78.8 +/- 29.7/h at 2750 m (P < 0.001 compared with 60 m). Mean sleep SaO(2) fell from 94 +/- 1% at 60 m to 93 +/- 1% at 610 m to 85 +/- 4% at 2750 m (P < 0.001 compared with 60 m). CONCLUSION: Moderate severity OSA at sea level (60 m) was completely replaced by severe CSA at a simulated altitude of 2750 m. The authors believe that the OSA resolved because of an increased respiratory drive [corrected] and an increase in upper airway tone, whereas CSA developed because of hypocapnia in non-rapid eye movement sleep.


Adv Exp Med Biol. 2006;588:57-63.Links
Mechanisms of sleep apnea at altitude.Whitelaw W.
Department of Medicine, University of Calgary, Calgary, Alberta, Canada. wwhitela@ucalgary.ca

At altitude normal people often develop periodic breathing in sleep--regularly recurring periods of hyperpnea and apnea. This phenomenon is probably explained by instability of the negative feedback system for controlling ventilation. Such systems can be modeled by sets of differential equations that describe behavior of key components of the system and how they interact. Mathematical models of the breathing control system have increased in complexity and the accuracy with which they simulate human physiology. Recent papers by Zbigniew Topor et al. (5,6) describe a model with two separate feedback loops, one simulating peripheral and the other central chemoreceptor reflexes, as well as accurate representations of blood components, circulatory loops and brain blood flow. This model shows unstable breathing when one chemoreceptor loop has high gain while the other has low gain, but not when both have high gain. It also behaves in counter-intuitive way by becoming more stable when brain blood flow is reduced and unresponsive to blood, gas changes. Insights from such models may bring us closer to understanding high altitude periodic breathing.


Respirology. 2004 Jun;9(2):222-9. Links
Central and obstructive sleep apnoea during ascent to high altitude.Burgess KR, Johnson PL, Edwards N.
Peninsula Private Sleep Laboratory, Manly, New South Wales, Australia. kburgess@doh.health.nsw.gov.au

OBJECTIVE: The aim of the study was to investigate the relationship between central sleep apnoea (CSA) at high altitude and arterial blood gas tensions, and by inference, ventilatory responsiveness. METHODOLOGY: Fourteen normal adult volunteers were studied by polysomnography during sleep, and analysis of awake blood gases during ascent over 12 days from sealevel to 5050 m in the Nepal Himalayas. RESULTS: Thirteen subjects developed CSA. Linear regression analysis showed tight negative correlations between mean CSA index and mean values for sleep SaO2, PaCO2 and PaO2 over the six altitudes (r2 > or = 0.74 for all, P < 0.03). Paradoxically there was poor correlation between the individual data for CSA index and those parameters at the highest altitude (5050-m) where CSA was worst (r2 < 0.12 for all, NS), possibly due to variation in degree of acclimatization between subjects. In addition, CSA replaced mild obstructive sleep apnoea during ascent. Obstructive sleep apnoea index fell from 5.5 +/- 6.9/h in rapid eye movement sleep at sealevel to 0.1 +/- 0.3/h at 5050 m (P < 0.001, analysis of variance), while CSA index rose from 0.1 +/- 0.3/h to 55.7 +/- 54.4/h (P < 0.001). CONCLUSION: There was a general relationship between decreasing PaCO2 and CSA, but there were significant effects from variations in acclimatization that would make hypoxic ventilatory response an unreliable predictor of CSA in individuals.

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CPAPopedia Keywords Contained In This Post (Click For Definition): AHI, CSA, Altitude

[Bearded_One]

Your machine will need to be adkusted to compensate for the altitude. The user's manual should tell you whether your machine automatically compensates for altitude or if it is a manual setting that can be done by the user.

It sounds like yours may need a manual setting. You didn't indicate which machine you have so we can't help with that information.

If you don't have a manual, post a question here about how how to set the altitude compensation for your particular machine. You can set up your profile so that your equipment information is automatically included in your posts.

[krousseau]

1300 feet should not make a significant difference-look for another cause for your symptoms. And make sure the CPAP machine didn't get jostled too much during the move.