We see patients who present with spirometry airflow limitation despite their forced expiratory volume in one second (FEV 1) as well as forced vital capacity (FVC) to be supernormal (FEV 1/FVC < 70%, both the %FEV 1 and the %FVC ≧100%) in asymptomatic healthy non-smokers. Based on previous studies, we hypothesized these spirometry conditions (results measured with spirometry) could be suitably used as a practical surrogate marker of pulmonary dysanapsis: the condition of disproportionate but physiologically normal growth between airways and lung parenchyma.
We compared the conventional surrogate marker of dysanapsis, maximum mid-expiratory flow to FVC (MMF/FVC), in SUBJECTS (FEV 1/FVC < 70%, both the %FEV 1 and the %FVC ≧100% in healthy non-smokers) (n = 25), in EMPHYSEMA (CT confirmed pulmonary emphysema, same spirometry results with SUBJECTS) (n = 55), and in CONTROLS (age- and height- matched, normal spirometry results) (n = 25). Next we added imaging analysis to evaluate the relationship between the cross sectional airway luminal area (X-Ai) and the lung volume results among the three groups.
The MMF/FVC was significantly lower in SUBJECTS and in EMPHYSEMA compared to CONTROLS. However, percent predicted peak expiratory flow (%PEFR) was significantly lower only in SUBJECTS and not in EMPHYSEMA compared to CONTROLS. The ratio of the X-Ai of the trachea and right apical bronchus to lung volume was significantly lower in SUBJECTS compared to CONTROLS.