Article

Assessment of diaphragm contraction may be useful for identifying
impairments in patients with movement dysfunction involving trunk stabilization,
respiration, or both. Real-time ultrasound imaging is a readily available
technology that can be used to quickly assess this aspect of diaphragm activity.
Although previous studies have examined diaphragm contraction in the supine
posture, a comparison of measurements between supine and upright postures has not
been made. OBJECTIVE: To examine whether diaphragm thickness measurements differ
among 3 different body postures in healthy subjects. DESIGN: Descriptive repeated
measures. SETTING: Clinical laboratory. PATIENTS (OR PARTICIPANTS): Twenty-four
healthy subjects (12 male and 12 female) aged 22-35 years old were recruited and
completed the study. METHOD: Diaphragm thickness was assessed in via B-mode
ultrasound imaging in supine, seated, and standing postures. Measurements of
diaphragm thickness were taken in the zone of apposition during maximal
inspiration to total lung capacity (TLC) and end-tidal expiratory lung volume
(EELV). A thickness ratio (inspiration thickness/expiration thickness) was
calculated to compare relative diaphragm contraction during each condition. MAIN
OUTCOME MEASUREMENTS: The primary dependent variable was diaphragm thickness
(mm). RESULTS: Average diaphragm thickness at EELV and maximum TLC were more than
20% greater in the seated and standing postures than in supine (P < .05).
Moreover, the diaphragm was approximately 205% thicker at TLC than at EELV (P <
.05). Relative inspiratory to expiratory thickness ratios (TLC/EELV) did not
differ among postures (P = .24). CONCLUSIONS: The diaphragm is thicker when the
body is in more upright postures (standing and sitting versus supine) perhaps due
to greater vertical gravitational load on the muscle and associated change in the
resting length of the muscle fibers. Thus it appears that ultrasound imaging may
be a sensitive tool to examine changes in diaphragm contraction during varying
postural tasks. LEVEL OF EVIDENCE: IV.
CI - Copyright (c) 2017 American Academy of Physical Medicine and Rehabilitation.
Published by Elsevier Inc. All rights reserved.

Langue : ANGLAIS