The influence of thoracic gas compression and airflow density dependence on the assessment of pulmonary function at high altitude

Troy J. Cross, Courtney Wheatley, Glenn M. Stewart, Kirsten Coffman, Alex Carlson, Jan Stepanek, Norman R. Morris, Bruce David Johnson

Research output: Contribution to journalArticle

Abstract

The purpose of this report was to illustrate how thoracic gas compression (TGC) artifact, and differences in air density, may together conflate the interpretation of changes in the forced expiratory flows (FEFs) at high altitude (>2400 m). Twenty-four adults (10 women; 44 ± 15 year) with normal baseline pulmonary function (>90% predicted) completed a 12-day sojourn at Mt. Kilimanjaro. Participants were assessed at Moshi (Day 0, 853 m) and at Barafu Camp (Day 9, 4837 m). Typical maximal expiratory flow-volume (MEFV) curves were obtained in accordance with ATS/ERS guidelines, and were either: (1) left unadjusted; (2) adjusted for TGC by constructing a “maximal perimeter” MEFV curve; or (3) adjusted for both TGC and differences in air density between altitudes. Forced vital capacity (FVC) was lower at Barafu compared with Moshi camp (5.19 ± 1.29 L vs. 5.40 ± 1.45 L, P < 0.05). Unadjusted data indicated no difference in the mid-expiratory flows (FEF25–75%) between altitudes (∆ + 0.03 ± 0.53 L sec−1; ∆ + 1.2 ± 11.9%). Conversely, TGC-adjusted data revealed that FEF25–75% was significantly improved by sojourning at high altitude (∆ + 0.58 ± 0.78 L sec−1; ∆ + 12.9 ± 16.5%, P < 0.05). Finally, when data were adjusted for TGC and air density, FEFs were “less than expected” due to the lower air density at Barafu compared with Moshi camp (∆–0.54 ± 0.68 L sec−1; ∆–10.9 ± 13.0%, P < 0.05), indicating a mild obstructive defect had developed on ascent to high altitude. These findings clearly demonstrate the influence that TGC artifact, and differences in air density, bear on flow-volume data; consequently, it is imperative that future investigators adjust for, or at least acknowledge, these confounding factors when comparing FEFs between altitudes.

Original languageEnglish (US)
Article numbere13576
JournalPhysiological Reports
Volume6
Issue number6
DOIs
StatePublished - Mar 1 2018

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Thorax
Gases
Lung
Air
Maximal Expiratory Flow-Volume Curves
Artifacts
Data Compression
Vital Capacity
Research Personnel
Guidelines

Keywords

  • Airflow density dependence
  • forced expiratory flows
  • high altitude
  • thoracic gas compression

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

Cite this

The influence of thoracic gas compression and airflow density dependence on the assessment of pulmonary function at high altitude. / Cross, Troy J.; Wheatley, Courtney; Stewart, Glenn M.; Coffman, Kirsten; Carlson, Alex; Stepanek, Jan; Morris, Norman R.; Johnson, Bruce David.

In: Physiological Reports, Vol. 6, No. 6, e13576, 01.03.2018.

Research output: Contribution to journalArticle

Cross, Troy J. ; Wheatley, Courtney ; Stewart, Glenn M. ; Coffman, Kirsten ; Carlson, Alex ; Stepanek, Jan ; Morris, Norman R. ; Johnson, Bruce David. / The influence of thoracic gas compression and airflow density dependence on the assessment of pulmonary function at high altitude. In: Physiological Reports. 2018 ; Vol. 6, No. 6.
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