Study objectives: To define anatomic landmarks
that can be used to predict insertions of the diaphragm on chest
radiographs and to estimate diaphragm length.
Prospective clinical trial with a parallel group design.
Setting: Laboratory investigations in normal volunteers
recruited by advertisement 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 groups, with a third group of 13 emphysema patients
matched for age and sex with the older group.
Measurements: Identification and between-group comparisons
were made of anatomic landmarks on anteroposterior and lateral chest
radiographs obtained at total lung capacity. Predicted landmarks were
generated from normal subjects. Within-subject and between-group
comparisons were made of diaphragm length index (DLI) based on observed
anatomic landmarks (DLIobs) and diaphragm length index based on
predicted anatomic landmarks (DLIpred) at functional residual
Results: Anatomic landmarks were not
different between the three groups or between male and female subjects,
and were not different before and after LVRS in emphysema patients. No
difference was found between DLIobs and DLIpred in normal subjects and
emphysema patients, but both were smaller in emphysema patients than in
normal subjects and increased after LVRS in emphysema patients.
Conclusion: This study validates the use of anatomic
landmarks to estimate DLI. Using these landmarks simplifies the
determination of diaphragmatic lengths and could be a useful tool for
the evaluation of the functional capacity of the diaphragm, and
possibly as a prognostic indicator of patients who are candidates for