Stabilizing function of the diaphragm: dynamic MRI and synchronized spirometric assessment

Abstract

The aim was to describe diaphragmatic behavior during postural limb activities and examine the ventilatory and stabilizing functions of the diaphragm. Thirty healthy subjects were examined in the supine position using a dynamic MRI system assessed simultaneously with specialized spirometric readings. The diaphragmatic excursions (DEs) were measured at three diaphragmatic points in the sagittal plane; the diaphragm positions (DPs) as related to a reference horizontal baseline were determined. Measurements were taken during tidal breathing (TB) and isometric flexion of upper or lower extremities against external resistance together with TB. Mean DE in both upper and lower postural limb activities was greater compared with the TB condition (P < 0.05), with the effect greater for lower limb activities. Inspiratory DPs in the upper and lower extremity activities were lower compared with TB alone (P < 0.01). Expiratory DP was lower only for lower extremity activities (P < 0.01). DP was most affected at the apex of the crescent and crural (posterior) portion of the diaphragm. DEs correlated strongly with tidal volume (Vt) in all conditions. Changes in DEs relative to the initial value were minimal for upper and lower extremities but were related to lower values of Vt (P < 0.03). Significant involvement of the diaphragm in the limb postural activities was found. Resulting DEs and DPs differed from the TB conditions, especially in lower extremity activities. The differences between the percent changes of DEs vs. Vt found for lower extremity activities were confirmed by both ventilatory and postural diaphragm recruitment in response to postural demands.

Postural Function of the Diaphragm in Persons With and Without Chronic Low Back Pain

“…27 Similarly, higher inspiratory pressures and hypertrophic changes in the diaphragm have been demonstrated during exercise. 1,6 It can be assumed that, in cases of postural instability, the insufficient stabilizers must be compensated by other muscles.…”

“…27 The diaphragm was imaged in the sagittal plane with the subject in supine, using a body coil. The imaging plane was placed sagittally in the axial topogram directed paravertebrally to the right, midway between the center of the vertebral body and the edge of the thoracic wall.…”

“…27 Tidal volumes were recorded with a spirometer (MasterScope Jaeger Version 4.67; Jaeger, VIASYS, Würzburg, Germany) by a specially designed pneumotachograph with a plastic isoresistive membrane. This device allowed safe and reliable respiratory recording while in a strong magnetic field.…”

“…The diaphragm is the muscle that contributes the intra-abdominal pressure modulation and plays an important role in spinal stability. 7,16,18,27,31 Insufficient function and poor coordination of postural, or stabilizing, muscles are considered to be important etiological factors in spinal disorders associated with low back pain, such as deformational spondyloarthrosis (with or without spinal disc herniation), spinal disc protrusion, and/or spondylolisthesis. 5,12,21,25 However, a study designed specifically to test the dynamics of the diaphragm in chronic spinal disorders is lacking.…”

“…In the first phase, a sample of 30 healthy participants was recruited as part of a previously published study of the stabilizing function of the diaphragm. 27 One participant was excluded due to insufficient data required for the present study. In the second phase, available volunteers with chronic low back pain due to vertebrogenic disorders were assessed (n = 18).…”