Diaphragmatic motion in the sitting and supine positions: Healthy subject study using a vertically open magnetic resonance system

PURPOSE: To determine the postural difference of diaphragmatic motion between the sitting and supine positions. MATERIALS AND METHODS: A total of 10 healthy men were examined using a vertically open 0.5-T magnetic resonance (MR) system. A total of 40 sequential MR images were obtained in both the sitting and supine positions during two to five respiratory cycles. The diaphragmatic excursions (DEs) were measured on three diaphragmatic points of six sagittal planes for both positions. The differences in DEs between the anterior and posterior parts of the diaphragm were also determined. RESULTS: DEs in the supine position were significantly greater than those in the sitting position at 15 of the 18 points. In five of the six sagittal planes, the difference of DE between posterior and anterior points was significantly larger in the supine position than in the sitting position. CONCLUSION: Diaphragmatic movement in the supine position is greater than that in the sitting position, especially in the posterior part of the diaphragm.