Normally, the bronchi dilate rapidly in inspiration and contract slowly in expiration, thus effecting a form of check-valve mechanism. Intra-and extra-bronchial occlusion, pulmonary infection, developmental bronchopulmonary malformations and pleural communications are pathologic processes which can disturb the check-valve mechanism and produce increased aeration. [See Figure in Source Pdf.]
The main bronchus and artery may be obstructed separately, or as a unit. Angiocardiograms should be analyzed for abnormal patterns, especially obstruction or atresia. A lack of vascular markings in the lungs can suggest pseudo-increased aeration.
On a regional basis, roentgenographic study of the vascular and air patterns can lead to recognition of certain entities. An angiogram in congenital lobar emphysema contrasts the vascular pattern in the involved and the remaining normal and unaffected lobes with pneumatocele, cystic disease, and atelectasis.
Reasons for support of the deficient-cartilage theory as a cause of lobar emphysema are cited, with emphasis on the localization of the emphysema to the anterior or upper lobes.
Bronchiolitis can give total compensatory emphysema, and the reasons given will help to understand the roentgenographic findings. Regional compensatory emphysema of the remaining lung, after total or partial collapse of a lobe by intrinsic or extrinsic factors, is illustrated. Basal pneumothorax is indicated to be a significant postoperative complication.
Although at times great similarity may exist in the appearance of plain films in conditions producing increased aeration of infants' lungs, it is hoped that this review will stimulate deeper analyses and wider recognition of the fundamentals.
Diagnosis and surgical strategy for sacral meningeal cysts with check-valve mechanism: technical note