Anatomic landmarks to estimate the length of the diaphragm from chest radiographs - Effects of emphysema and lung volume reduction surgery

Study objectives: To define anatomic landmarks that can be used to predict insertions of the diaphragm on chest radiographs and to estimate diaphragm length. Design: Prospective clinical trial with a parallel group design. Setting. Laboratory investigations in normal volunteers recruited by advert isement and in emphysema outpatients being evaluated for elective bilateral lung volume reduction surgery (LVRS). Patients: Twenty-six normal subjects classified into young and older age gr oups, with a third group of 13 emphysema patients matched for age and sex w ith the older group. Measurements: Identification and between-group comparisons were made of ana tomic landmarks on anteroposterior and and lateral chest radiographs obtain ed at total lung capacity. Predicted landmarks were generated from normal s ubjects. Within-subject and between-group comparisons were made of diaphrag m length index (DLI) based on observed anatomic landmarks (DLIobs) and diap hragm length index based on predicted anatomic landmarks (DLIpred) at funct ional residual capacity. Results: Anatomic landmarks were not different between the three groups or between male and female subjects, and were not different before and after L AIRS in emphysema patients. No difference was found between DLIobs and DLIp red in normal subjects and emphysema patients, but both were smaller in emp hysema patients than in normal subjects and increased after LAIRS' in emphy sema patients. Conclusion: This study validates the use of anatomic landmarks to estimate DLL Using these landmarks simplifies the determination of diaphragmatic len gths and could be a useful tool for the evaluation of the functional capaci ty of the diaphragm, and possibly as a prognostic indicator of patients who are candidates for LVRS.