It has been shown clearly in animal and human subjects that structural changes of the bony thorax occur in emphysema. In hamsters, Snider and Sherter were able to demonstrate by roentgenogram a marked increase in the AP diameter of an emphysematous animal (compared with normal animals) 1 year after induction of emphysema. Likewise, Thomas et al showed significantly greater circumference, AP, transverse, and rostral-caudal dimensions of the thorax in emphysematous hamsters (compared with control animals) 6 months after induction of emphysema.
In humans, Gilmartin and Gibson, using plain roentgenograms and linearized magnetometers, found an increased AP diameter at FRC in patients with COPD. In addition, Cassart et al, using CT scans, demonstrated that COPD patients have a more circular configuration of their bony thorax (compared with controls) because of increases in AP diameter.
Roentgenographic indexes have been shown to correlate well with airflow obstruction in COPD patients. Simon et al assessed CXRs of 101 patients with chronic airflow obstruction and found good correlations between roentgenographic and pulmonary function abnormalities. Flattened diaphragm, increased retrosternal airspace, and roent-genographic estimation of TLC were all highly specific for having an FEV1 < 1 L. Similarly, using 189 CXRs of patients with COPD, Burki and Krumpel-man demonstrated that a depressed level of the diaphragmatic dome, increased retrosternal airspace, and decreased transverse diameter of the heart all correlated with the degree of airflow obstruction. canadian health care mall
To address whether postoperative changes in the bony thorax configuration actually improve respiratory mechanics, one may use the model of COPD patients undergoing lung transplantation. In patients with COPD undergoing single-lung transplantation, Brunsting et al demonstrated a correlation between lung volume and spirometry and concluded that “chest wall factors” determine postoperative pulmonary function. Scott et al found the physiologic improvements after single-lung transplantation in patients with COPD to be related to increases in lung elastic recoil and suggested that these findings implied a postoperative reduction in chest wall distention. Guignon et al demonstrated the opposite effect on thoracic dimensions in heart-lung transplant recipients for cystic fibrosis, with a persistent increase in FRC after transplantation, and concluded that the persistent hyperinflation was owing to the AP rib cage expansion. The persistent hyperinflation may have been related to the en bloc insertion used during heart-lung implantation, which differs from the technique of single- or double-lung transplantation.