In clinical practice, FVC is used mostly for the evaluation
of large airway functions, FEV1 reflects airway obstruction
in large and small airways, whereas FEF25, FEF75, and
FEF25e75 are measures more indicative of peripheral small
airway functions. It has been suggested that small airways
are likely to receive the highest tissue doses of air pollutants, and might undergo preclinical structural changes
before the larger airways are affected. 21 As the small
airways may be the first part of the respiratory tract
affected by the adverse effects of air pollutants, early
detection would require a test sensitive to abnormalities of
the small airways. Abnormalities in FEF25e75 have been
observed before the decline in FEV1, 22 and the former has
been suggested to be a sensitive indicator of small airway
disease. 23 Alberts et al. reported that FEF25e75 was useful in
predicting the presence of airway hyperresponsiveness. 24
Ferguson pointed out that FEF25e75 was a more valuable
spirometric parameter than peak expiratory flow in
assessing chronic airflow obstruction. 25 Our findings
demonstrated that air pollution exposure had adverse
effects on both large and small airways, suggesting that the
effects of air pollution were long-standing
In clinical practice, FVC is used mostly for the evaluation
of large airway functions, FEV1 reflects airway obstruction
in large and small airways, whereas FEF25, FEF75, and
FEF25e75 are measures more indicative of peripheral small
airway functions. It has been suggested that small airways
are likely to receive the highest tissue doses of air pollutants, and might undergo preclinical structural changes
before the larger airways are affected. 21 As the small
airways may be the first part of the respiratory tract
affected by the adverse effects of air pollutants, early
detection would require a test sensitive to abnormalities of
the small airways. Abnormalities in FEF25e75 have been
observed before the decline in FEV1, 22 and the former has
been suggested to be a sensitive indicator of small airway
disease. 23 Alberts et al. reported that FEF25e75 was useful in
predicting the presence of airway hyperresponsiveness. 24
Ferguson pointed out that FEF25e75 was a more valuable
spirometric parameter than peak expiratory flow in
assessing chronic airflow obstruction. 25 Our findings
demonstrated that air pollution exposure had adverse
effects on both large and small airways, suggesting that the
effects of air pollution were long-standing
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