A pathological accumulation of air in tissues. The air may derive from a skin laceration and be drawn in by the movements of muscles. A discontinuity of the tracheal mucosa is a common cause, either by way of laceration or ulceration. Extension from a pulmonary lesion is also common. The syndrome resulting depends on the location of the air. See also pulmonary emphysema and subcutaneous emphysema (below).
- acute bovine pulmonary e. — see atypical interstitial pneumonia.
- alveolar e. — see pulmonary emphysema (below).
- bullous e. — emphysema in which bullae form in areas of lung tissue so that these areas do not contribute to respiration.
- conjunctival e. — may occur after head trauma which permits escape of air from the paranasal sinuses.
- fetal e. — see emphysematous/putrescent fetus.
- generalized e. — widespread distribution of air, including subcutaneous tissues, seen with pneumomediastinum.
- hypoplastic e. — pulmonary emphysema due to a developmental abnormality, resulting in a reduced number of alveoli, which are abnormally large.
- interlobular e. — accumulation of air in the septa between lobules of the lungs.
- interstitial e. — presence of air in the peribronchial and interstitial tissues of the lungs.
- intestinal e. — a condition marked by accumulation of gas under the tunica serosa of the intestine.
- lobar e. — emphysema involving less than all the lobes of the affected lung.
- mediastinal e. — see pneumomediastinum.
- orbital e. — may occur after trauma to the head which permits escape of air from the paranasal sinuses; appears as swelling with crepitus under the conjunctiva or periocular skin.
- panacinar e., panlobular e. — generalized obstructive emphysema affecting all lung segments, with atrophy and dilatation of the alveoli and destruction of the vascular bed.
- pulmonary e. — distention of the lung caused by overdistention of alveoli and rupture of alveolar walls (alveolar emphysema) and in some cases escape of air into the interstitial spaces (interstitial emphysema). It is a common pathological finding in many diseases of the lung in all species, but also occurs independently, especially in horses, as a principal lesion in chronic obstructive pulmonary disease. It is also a prominent lesion in bovine atypical interstitial pneumonia. It is always secondary to a primary lesion which effectively traps an excessive amount of air in the alveoli. It is characterized clinically by cough, dyspnea, forced expiratory effort and poor work tolerance. A double expiratory effort is a characteristic sign—hence broken wind.
- subconjunctival e. — occurs with fractures involving the paranasal sinuses.
- subcutaneous e. — air or gas in the subcutaneous tissues. The characteristic lesion is a soft, mobile swelling which crackles like stiff paper when palpated. There is no pain, nor heat and no ill effects unless the pharyngeal area is sufficiently involved to cause asphyxia.
- surgical e. — subcutaneous emphysema following operation.
- unilateral e. — emphysema affecting only one lung, frequently due to congenital defects in circulation.
- vesicular e. — see panacinar emphysema (above).
