TY - JOUR
T1 - The influence of thoracic gas compression and airflow density dependence on the assessment of pulmonary function at high altitude
AU - Cross, Troy J.
AU - Wheatley, Courtney
AU - Stewart, Glenn M.
AU - Coffman, Kirsten
AU - Carlson, Alex
AU - Stepanek, Jan
AU - Morris, Norman R.
AU - Johnson, Bruce D.
N1 - Publisher Copyright:
© 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.
PY - 2018/3
Y1 - 2018/3
N2 - 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 (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, 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.
AB - 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 (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, 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.
KW - Airflow density dependence
KW - forced expiratory flows
KW - high altitude
KW - thoracic gas compression
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U2 - 10.14814/phy2.13576
DO - 10.14814/phy2.13576
M3 - Article
C2 - 29595881
AN - SCOPUS:85044790633
SN - 2051-817X
VL - 6
JO - Physiological reports
JF - Physiological reports
IS - 6
M1 - e13576
ER -