Abstract
The flow-volume curve adovocated by Hyatt in 1958, has been studied by obstructive changes of small airways in chronic obstructive lung disease. However, the evaluation of restrictive changes of the lung with the flow-volume curve has received little attention. We designed this study to evaluate restrictive changes of the lung in heart diseases with the flow-volume curve.
Flow-volume curves and compliance were measured in 12 normal subjects and in 53 patients with non-congenital heart diseases. The pulmonary hemodynamics of 20 subjects were examined during right cardiac catheterization as it seemed that restrictive lung changes due to pulmonary congestion existed in these patients.
There was a good correlation between the V50/V25 ratio and the dynamic compliance in 65 subjects (r=-0.74). In the same way, the V50/V25 ratio correlated significantly with the static compliance. There was a good correlation between the V50/V25 ratio and the mean pulmonary wedge pressure in 20 subjects (r=0.77). But the PF/V50 ratio and the V75/V50 ratio did not correlate significantly with the compliance and the mean pulmonary wedge pressure. Therefore, it was postulated that the V50/V25 ratio was a good index for detecting pulmonary congestion or restrictive lung changes.
Subsequently we studied the flow-volume curve in 10 patients with acute myocardial infarction every week from the first week to the fourth week.
The forced vital capacity and the forced expiratory volume per second and the peak flow of these patients returned to normal values in the second week following infarction. But, the V50/V25 ratio did not return to normal value in the fourth week following infarction and the compliance showed a marked decrease in these patients. Therefore, these results showed that there was pulmonary congestion or restrictive changes of the lung in these patients in the fourth week after acute myocardial infarction.
In conclusion, we suggest that the V50/V25 ratio is useful as an index of pulmonary congestion or restrictive change of the lung in heart diseases.
