4 Diseases of Children, p. 570, 5th ed.
The chief differences between the two conditions are—1st, the color, which in collapsed lobules is purplish or livid, and in pneumonia reddish-brown; 2d, the microscopic appearance, showing the alveoli filled with cell-proliferation in pneumonia and free from change in collapse; and 3d, the state of the adjacent pleura, which is inflamed and often covered with lymph in pneumonia, while it is entirely healthy in non-complicated collapse.
The bronchial tubes present the appearances met with in bronchitis, being more or less congested, showing a softened state of their lining membrane, and containing liquid mucous secretion and sometimes firmer pledgets which have caused the obstruction.
As regards changes in the heart, extensive atelectasis may prevent closure both of the foramen ovale and of the ductus arteriosus. From the obstruction to the flow of venous blood offered by the collapsed portions of the lungs the right ventricle may become so distended that a portion of its blood may still be forced through the ductus arteriosus, and another portion backward into the auricle and through the foramen ovale, so that both of these channels may be kept pervious.
DIAGNOSIS.—Congenital atelectasis, if complete, cannot be mistaken for any other condition occurring at birth, and is sufficiently denoted by the signs already described.
Imperfect expansion of the lungs continuing for some days after birth might suggest patency of the foramen ovale from the purplish hue of the surface common to both conditions. The expansion of the chest and the resonance that it yields on percussion in the cardiac affection will be sufficient to discriminate them except in those cases in which they exist together.
Acquired atelectasis or collapse of the lung may require to be distinguished from bronchitis, from pleural effusion, and from catarrhal pneumonia.
Even uncomplicated bronchitis is in children sometimes accompanied with so much dyspnoea as to cause apprehension that collapse of lobules has taken place, but the absence of percussion dulness, either diffused or in patches, will exclude the supposition.
From pleural effusion collapse of the lung may be distinguished by the fact that the dulness due to pleurisy is generally on one side only, that it is more intense and diffused than that of collapse, and that its line of demarcation may often be made to shift with the position of the patient.
Catarrhal pneumonia is in general distinguishable from collapse by the history, course, and symptoms of the disease, especially the sudden rise of temperature that belongs to pneumonia; as also by the auscultatory signs. The percussion dulness of pneumonia is more extensive than that of collapse, and is accompanied with bronchial breathing; whereas in collapse the respiratory sounds are feeble and mingled with moist râles.