The concept of structural changes of the bony thorax leading to hyperinflation in COPD originated in the early 20th century. Traditionally, it has been believed that patients with COPD accommodate an increased lung volume by expanding the anteroposterior (AP) diameter of their rib cage, thus resulting in a “barrel-chest” configuration. This observation has been demonstrated in animal and human subjects.
This alteration of the bony thorax can have detrimental implications for respiratory mechanics. The hyperinflated thorax of an emphysematous patient passively shortens the diaphragm to a suboptimal operating length and reduces its area of apposition with the rib cage, thus placing it at a mechanical disadvantage to generate force. The enlarged rib cage may also contribute to an impairment in chest wall elastic recoil. ventolin inhaler
Because roentgenographic indices correlate well with airflow obstruction in COPD patients,- we thought that by lessening the severity of obstruction, there would be changes in bony thorax configuration. It has been shown that lung volume reduction surgery (LVRS) improves spirometry, lung volumes, and diaphragm strength in select patients with severe COPD. Also, two recent studies evaluated lung volume and thoracic dimensions after LVRS. They suggested that lung height and coronal diameter are reduced shortly after LVRS, as measured by plain chest roentgenograms (CXRs), and that all thoracic dimensions during expiration are decreased after LVRS, as measured by MRI. To date, it has not been determined whether these changes in thoracic dimensions after LVRS maintain long-term stability, or whether they are significant enough to improve respiratory mechanics (ie, respiratory muscle function).
The purpose of this investigation is to determine whether (1) the configuration of the bony thorax in patients with severe COPD is altered after LVRS, as measured by plain CXRs and CT scans; and (2) the postoperative improvements in hyperinflation correlate with improvements in respiratory mechanics.