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

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.

Ventilatory function among healthy young Saudi adults: a comparison with Caucasian reference values

Background: Ethnic differences in lung function are recognized. However, most of the modern lung function equipments are pre-programmed with Caucasian reference values.

Objective: Measure spirometric values among healthy Saudi male and female adults and compare with the Caucasian reference values in a standard spirometer.

Methods: Thirty healthy Saudi young adults (15 males and 15 females; mean age 25 years) participated in this study. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC (%), and maximal voluntary ventilation (MVV) were recorded using a portable digital spirometer.

Results: Mean values of FVC, FEV1, FEV1/FVC (%) and MVV for the Saudi subjects were significantly lower than the Caucasians predicted values.

Conclusion: Interpretation of lung function tests of Saudi subjects based on the Caucasian prediction equations is generally not valid, as the parameters of lung function tests in Saudi subjects are lower than the Caucasian reference values. The present results underline an urgent need for larger studies to develop prediction equations based on normative spirometric values for Saudi population involving subjects of all ages and both genders living in different climates of the country.