Diaphragm structure and function in elastase-induced emphysema

The present study indicates that alterations in diaphragmatic muscle structure occur in elastase-induced emphysema. These changes, which presumably result from hyperinflation-induced increases in load and decreases in length, augment force production. Reductions in sarcomere number allow the diaphragm to reestablish a favorable sarcomere length despite reductions in muscle fiber length. Muscle fiber hypertrophy results in an increase in cross-sectional area and in the force which can be developed at any given length. These changes resemble those in limb muscle exposed to chronic increases in load or decreases in length.