Partial Flow Volume Curve in Patients with Obstructive Ventilatory Disorder

Lim, Ho; Choi, In Seon; Jung, Ik Joo

Abstract

Obsructive ventilatory disorders such as bronchial asthma and COPD are characterized by a decreased expiratory flow rate due to airway obstruction. Forced expiratory volume in one second(FEV1) has been used widely for diagnosis, and for evaluation of clinical course and prognosis of obstructive ventilatory disorders. FEV1 is measured by forced vital capacity(FVC) maneuver starting from total lung capacity(maximal expiratory flow volume, MEFV, curve), which often causes asthmatic attack. The aim of this study was to determine whether partial flow volume(PEFV) curve instead of MEFV curve is helpful in evaluating obstructive ventilatory disorders. Four patients with bronchial asthma, 6 COPD, and 20 normal subjects were studied. The results were as follows: 1) All measurements on PEFV curve were significantly related to the respective one on MEFV curve. Among them, the correlation coefficient was highest in FEV1/FVC(r=0.98, p>0.001). 2) PEFV/MEFV(P/M) ratios of measurements expressed as a relative value to the respective vital capacity were close to 1 in both control and obstructive groups, which represents PEFV curve to be a miniature of MEFV curve. 3) The P/M ratio of the corrected values obtained by adjusting the residual volumes of both curves was close to 1 in control group, but it was higher than 1 in patients with obstructive ventilatory disorders. 4) The P/M ratio in Vmax50 was significantly related to FEV1(p>0.01). These results indicate that PEFV curve instead of MEFV curve may be useful in evaluating patients with obstructive ventilatory disorders. And, FVC maneuver-induced bronchoconstriction depends on the severity of airflow obstruction.