Abstract
Comparisons of flow-volume curve (V-V) with spirogram, residual volume, delta N2 Xe-133 inhalation scintigram and Tc-99m perfusion scintigram were made in 121 patients with pulmonray diseases. We calculated dV/dV of descent of V-V (slope). The curve had good correlation with FEV1/FVC (FEV1%). A gradient of less than 1.9 was equivalent to FEV1% less than 69% and a gradient less than 0.9 was eqivalent to FEV1% less than 54%. We calculated the descent curvature using the following formula; Curvature (%) is (S′-S) × 100/S′, where S is the area under the descending curve and S′ is the area under a line connecting the peak with endexpiratory position. The descent gradient was classified into 4 patterns; When the slope is less than 0.9, it is classified as flat. A slope over 1.0 and curvature of less than 29% is classified as straight. A slope over 1.0 with a curvature of over 30% and a descent gradient can be approximated to a bent double or triple line is classified as bent. The remainders are curved. As ventilatory disturbances advanced, the shape transformed from straight through bent or curved to flat and the frequency in abnormalities in residual volume and/or delta N2 increased.
We quantitated abnormalities on the inhalation scintigram and perfusion scintigram dividing the lung field into 6 areas (left or right, upper, middle and lower) and scoring each area as follows; 3 as total regional defect, 2 as patchy defect, 1 as other hypofunctions and 0 as no abnormality. The score increased when the shape transformed from straight through bent or curved to flat. We determined regional mean washout time (MTT) dividing the lung field into 6 areas. Then we calculated the coefficient of variance (CV) of regional MTT as an index for interregional nonhomogenity of ventilation. CV increased as the shape changed from straight through bent to curved. In bent cases, regional MTT could be separated into either normal or delayed. Delayed areas were put together. When we recalculated CV in normal areas and delayed areas respectively, revised CV in both areas were similar to those in strainght. Thus in bent case, poorly ventilated areas were considered to be put together and connected in parallel to well ventilated areas. Meanwhile, curved underventilated areas were patchy but scattered diffusely throughout total lung-field. CV in flat cases was rather small considering their scores. In most flat cases, ventilatory disturbances advanced throughout the lungfield so that interregional nonhomogenity became less remarkable. In rare flat cases, airway obstruction might be restricted merely to the central airway without nonhomogenity of ventilation.
It is concluded that the slope of the descent gradient of flow-volume curve indicates severity of obstruction and the curvature may reflect interregional nonhomogenity of ventilation.
