Crepitation

CREPITATION (from Latin crepitus - crackling), a sound reminiscent of crackling roasting salt (Laennec), hair rubbing against each other, etc. In the lungs, crepitation is caused by the penetration of a strong stream of air into the alveoli, the walls of which have adhered due to compression or the presence of an insignificant but viscous exudate. Therefore, it is auscultated only during a sufficiently deep breath and specifically in the second half of the inspiration or at its peak. When the patient breathes superficially, to reveal crepitation, they should be asked to cough slightly: the deep breath accompanying the cough will end in the corresponding case with crepitation. After a prolonged stay in bed, especially in the mornings, during the first breaths, crepitation may be auscultated even in a completely healthy person due to the resulting minor atelectasis of the lower lobes of the lungs. In severely ill patients spending almost all their time in the supine position, such atelectatic crepitation is common even in the absence of actual pulmonary disease. The same crepitation appears in areas of the lung compressed by a tumor located in the chest cavity, pleural effusion (near its upper boundary), aortic aneurysm, diaphragm pushed upwards, etc., as well as in various kinds of spinal curvatures and chest deformations preventing the lung from expanding. Crepitation associated with exudation into the alveoli is observed primarily in pneumonic processes. In lobar pneumonia, crepitation is auscultated over the affected lobe at the very beginning of the disease, when there is still comparatively little exudate and it has not yet clotted (crepitatio indux), and at the end of the disease, when the exudate liquefies and resolves (crepitatio redux). In catarrhal bronchopneumonia, crepitation is auscultated throughout the entire disease. In pulmonary tuberculosis, crepitation is encountered at the beginning of caseous pneumonia, in tuberculous bronchopneumonia, at the periphery of disseminated foci (perifocal inflammation), in congestive pneumonia (Bard). Furthermore, crepitation is auscultated at the onset of pulmonary edema, in hemorrhagic infarction of the lungs, and finally in decompensated heart defects (especially mitral lesions) when stasis develops in the lesser circulation (crepitation is auscultated in this case predominantly in the lower lobes). Crepitation should be distinguished from subcrepitant rales (heard throughout the entire inspiration) and from pleural friction rub (heard during inspiration and expiration, intensifying upon pressure on the chest wall); but this distinction is far from always possible. Among extraneous sounds that can simulate crepitation, one should note the cracking of muscles and fascia (trying to fix them with a finger if possible), the friction of hairs covering the chest and back (moistening them), the crunch in the scapular and clavicular joints (pulling the shoulder downwards). Besides the lungs, crepitation is observed in the subcutaneous tissue in skin emphysema and at the sites of bone fractures due to the friction of contacting surfaces of the fragments. Crepitation in fractures, see Fractures.