Abstract
Chronic obstructive emphysema is the clinically important form of emphysema. It is not caused by long continued blowing of wind instruments or by glass blowing as was formerly believed but is probably brought about by chronic disease of the bronchial tree and lungs such as chronic bronchitis, asthma, silicosis, etc. The mechanism responsible appears to be repeated insults to the alveolar walls caused by sudden repeated increases in intra-alveolar and intra-bronchiolar pressure during the act of coughing, with the additional important factor of the partial obstruction of these bronchioles owing to the presence.of mucus and to-scarring from fibrosis and pulmonary arteriolar sclerosis. This obstruction is such that air gets in, since the bronchial tree is dilated on inspiration, but can not get out because of its contraction on expiration. Alveolar walls long distended lose their elasticity and rupture. Large air sacs or bullae form which get larger and larger as additional groups of alveoli rupture into them.

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