Body position affects ultrasonographic measurement of diaphragm contractility

Brown, Christopher
Tseng, Shih-Chiao
Mitchell, Katy
Roddey, Toni
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Wolters Kluwer Health, Inc.

PURPOSE: (1) Determine whether ultrasonography can detect differences in diaphragm contractility between body positions. (2) Perform reliability analysis of diaphragm thickness measurements in each test condition.

METHODS: We used a repeated-measures experimental design with 45 healthy adults where 3 B-mode ultrasound images were collected at peak-inspiration and end-expiration in supine, sitting, and standing. Mean diaphragm thickening fractions were calculated for each test position. Statistical significance was tested using 1-way repeated-measures analysis of variance with planned comparisons. For reliability analysis, the intraclass correlation coefficient (3, 3) was calculated.

RESULTS: Mean diaphragm thickening fraction increased from 60.2% (95% confidence interval [CI] 53.0%, 67.9%) in supine, to 96.5% (95% CI 83.2%, 109.9%) while seated and to 173.8% (95% CI 150.5%, 197.1%) while standing. Body position was a significant factor overall (P < .001), as were comparisons between each individual position (P < .001). Intraobserver reliability was excellent (>0.93) for all body positions tested.

CONCLUSION: Ultrasound imaging detected positional differences in diaphragm contractility. The effect of gravitational loading on diaphragm length-tension, and body position-mediated changes in intra-abdominal pressure may explain the differences found. Future research should address methodological concerns and apply this method to patients participating in early mobilization programs in the intensive care unit.

Article originally published in Cardiopulmonary Physical Therapy Journal, 29(4), 166–172. English. Published online 2018.
Ultrasonography, Diaphragm, Patient positioning
This is a published version of an article that is available at Recommended citation: Brown, C., Tseng, S.-C., Mitchell, K., & Roddey, T. (2018). Body position affects ultrasonographic measurement of diaphragm contractility. Cardiopulmonary Physical Therapy Journal, 29(4), 166–172. This item has been deposited in accordance with publisher copyright and licensing terms and with the author’s permission.