Open AccessThe influence of thoracic gas compression and airflow density dependence on the assessment of pulmonary function at high altitude
Author(s) -
Cross Troy J.,
Wheatley Courtney,
Stewart Glenn M.,
Coffman Kirsten,
Carlson Alex,
Stepanek Jan,
Morris Norman R.,
Johnson Bruce D.
Publication year - 2018
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.13576
Subject(s) - medicine , altitude (triangle) , effects of high altitude on humans , pulmonary function testing , vital capacity , cardiology , zoology , perimeter , nuclear medicine , lung function , mathematics , anatomy , lung , biology , geometry , diffusing capacity
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 ( FEF s) 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 ( FEF 25–75% ) between altitudes (∆ + 0.03 ± 0.53 L sec −1 ; ∆ + 1.2 ± 11.9%). Conversely, TGC ‐adjusted data revealed that FEF 25–75% 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, FEF s 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 FEF s between altitudes.