Lung stiffness in states of abnormal pulmonary blood flow and pressure.

The suspicion that pulmonary function in general and pulmonary compliance in particular might be disturbed by hyperkinetic pulmonary hypertension (increased pulmonary flow in the presence of increased pulmonary arterial pressure) arose from a study of the incidence of chest deformities in congenital heart disease (Davies, 1959). It was then observed that hyperkinetic pulmonary hypertension was often associated with a bilaterally increased antero-posterior chest diameter, sternal protrusion, and indrawing of the lower ribs on inspiration. Since hyperkinetic pulmonary hypertension occurs most commonly with ventricular septal defect, it is in conjunction with this lesion that such a deformity is usually seen (Fig. 1), although it occurs with other anomalies that disturb the pulmonary circulation in similar fashion (Fig. 2). In uncomplicated atrial septal defect of the secundum variety and in the Eisenmenger situation this type of chest deformity is rarely seen (Fig. 3). It was suggested that the abnormal shape of the chest might be due to altered pulmonary mechanics related to a combination of high pressure and high flow, but not to one or the other of these factors independently. Since increased stiffness of the lung seemed the most likely disturbance of pulmonary mechanics to cause a thoracic deformity of the kind described, we measured the pulmonary compliance in 34 patients with congenital heart disease causing high pressure, high flow, or both.