Residence at moderate altitude improves ventilatory response to high altitude

Stephen R. Muza, Paul B. Rock, Michael F. Zupan, James C. Miller, William R. Thomas, Allen Cymerman

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Background: This study compared the distribution of arterial oxygen saturation (SaO2) and susceptibility to Acute Mountain Sickness (AMS) in moderate altitude residents (MAR) and low altitude residents (LAR) following rapid ascent to 4056 m. Methods: Resting PETCO2 and SaO2 were measured in 38 subjects residing for > 3 mo near Colorado Springs, CO (MAR group), at 1940 m (USAF Academy), and after ∼1 h at 4056 m on the summit of Pikes Peak, CO, following ascent by car. SaO2 was also measured at 610-m elevation intervals during the ascent. Of the LAR (50 m) group, 39 subjects were exposed to a similar ascent profile in a hypobaric chamber. Results: At 1940 m the MAR SaO2 and PETCO2 were 94 ± 1% (X̄ ± SD) and 33.6 ± 2.8 mmHg, respectively. At 3048 m and higher, MAR SaO2 decreased, reaching 86 ± 2% (p < 0.001) at 4056 m, and PETCO2 (32.1 ± 4.5 mmHg) decreased (p < 0.05). At 50 m the LAR SaO2 and PETCO2 were 98 ± 1% and 38.7 ± 2.7 mmHg, respectively. At 1940 m and higher, LAR SaO2 decreased (p < 0.001), reaching 82 ± 5% at 4056 m, and PETCO2 (36.4 ± 3.5 mmHg) decreased (p < 0.05). Above 2438 m, the MAR SaO2 was higher (p < 0.001) than the LAR. Only one MAR subject, but nine LAR subjects reported AMS symptoms. Conclusions: Ventilatory acclimatization developed during moderate altitude residence substantially enhances arterial oxygenation during rapid ascents to higher altitudes. Compared with prior studies, the level of ventilatory acclimatization achieved at moderate altitude is similar to residing at 4056 m for approximately 5-9 d.

Original languageEnglish
Pages (from-to)1042-1048
Number of pages7
JournalAviation Space and Environmental Medicine
Volume75
Issue number12
StatePublished - 1 Dec 2004

Keywords

  • Acute mountain sickness
  • Arterial oxygen saturation
  • Hypoxia

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