FEF_25–75 as a Marker of Airway Obstruction in Asthmatic Children During Reduced Mite Exposure at High Altitude

Abstract

Sensitivity of forced expiratory flow between 25% and 75% of the vital capacity (FEF_25–75) in detecting airway obstruction was investigated in 14 children with mild-moderate asthma, allergic to house dust mites, while at high altitude (1756 m). Forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV₁), FEF_25–75, and peak expiratory flow (PEF) were measured every 2 weeks for 12 weeks (total, 84 measurements). The presence or absence of wheezing at the chest auscultation was ascertained before each test. During the study period, a significant improvement of both mean (SD) FEF_25–75 [61 (12)% vs. 68 (11)% of the predicted value, p = 0.005] and PEF [95 (16)% vs. 103 (1 3)%, p = 0.002] was observed. FEV₁ changed only marginally [82 (7)% vs. 86 (6)%, p = 0.05]. Wheezing was present on 12/84 occasions. Wheezing was associated with abnormal FEF_25–75 values on most occasions but not with abnormal FEV₁ or PEF. FEF_25–75 was decreased on 51% of days in which wheezing was absent. FEV₁ and PEF were, respectively, normal in 69% (p < 0.0001) and 92% (p < 0.0001) of measurements in which FEF_25–75 was abnormal. These results suggest that FEF_25–75 may be considered a good indicator of airflow obstruction and a sensitive marker of respiratory improvement in asthmatic children during reduced antigen exposure.

Key Words:

• Altitude
• Antigen avoidance
• Asthma
• Children
• FEF_25–75
• Lung function
• Wheezing