Chest
Volume 146, Issue 3, September 2014, Pages 680-685
Journal home page for Chest

Original Research: Imaging
B-Mode Ultrasound Assessment of Diaphragm Structure and Function in Patients With COPD

https://doi.org/10.1378/chest.13-2306Get rights and content

BACKGROUND

Electromyographic evaluation of diaphragmatic neuromuscular disease in patients with COPD is technically difficult and potentially high risk. Defining standard values for diaphragm thickness and thickening ratio using B-mode ultrasound may provide a simpler, safer means of evaluating these patients.

METHODS

Fifty patients with a diagnosis of COPD and FEV1< 70% underwent B-mode ultrasound. Three images were captured both at end expiration (Tmin) and at maximal inspiration (Tmax). The thickening ratio was calculated as (Tmax/Tmin), and each set of values was averaged. Findings were compared with a database of 150 healthy control subjects.

RESULTS

There was no significant difference in diaphragm thickness or thickening ratio between sides within groups (control subjects or patients with COPD) or between groups, with the exception of the subgroup with severe air trapping (residual volume > 200%), in which the only difference was that the thickening ratio was higher on the left (P= .0045).

CONCLUSIONS

In patients with COPD presenting for evaluation of coexisting neuromuscular respiratory weakness, the same values established for healthy control subjects serve as the baseline for comparison. This knowledge expands the role of ultrasound in evaluating neuromuscular disease in patients with COPD.

Section snippets

Materials and Methods

This observational case-control study was carried out at a large, tertiary-referral, academic institution, after receiving institutional review board approval (IRB number 11-002744). All patients gave verbal consent and signed Healthcare Information Portability and Accountability Act authorization. Patients with COPD were recruited from the pulmonary function laboratory if they met the inclusion criteria and agreed to participate. Inclusion criteria for patients with COPD were an FEV1< 70% and

Results

The study population included 50 patients with COPD and 150 control subjects. Case and control subject demographics are presented inTable 1. Diaphragm muscle thickness and thickening ratio in normal subjects and in patients with COPD are presented inTable 2.

There was no significant difference in diaphragm thickness or thickening ratio between sides within groups (control subjects or patients with COPD), or between groups, with the exception of the subgroup of patients with severe air trapping

Discussion

Ultrasound has been used since the 1960s to evaluate diaphragm structure and function, primarily using M mode to measure excursion. In recent years, as technology has progressed and image resolution has improved markedly, B-mode sonography has become more readily available. The advantages of ultrasound over other imaging modalities include portability, which is particularly advantageous in the ICU setting, relatively low cost, and absence of contraindications. In comparison with other methods

Conclusions

The primary objective of this study was to establish normal values of diaphragmatic structure and function in patients with COPD as a means of facilitating the use of B-mode ultrasound as a diagnostic tool in the evaluation of neuromuscular respiratory failure in patients with COPD and in the identification of high-risk patients prior to general anesthesia, mechanical ventilation, or invasive procedures such as needle EMG of the diaphragm. In conclusion, lower limits of normal diaphragm

Acknowledgments

Author contributions: A. J. B. is the guarantor of this paper and certifies that the methods, data, and analysis set forth in this paper are truthful and accurate. E. J. S., J. A. S., and A. J. B. contributed to study concept; E. J. S., J. A. S., C. D. M., and A. J. B. contributed to study design; M. R. B., L. S., C. J. H., and A. J. B. contributed to data collection; E. J. S. and K. G. L. contributed to data analysis; K. G. L., C. D. M., and A. J. B. contributed to data interpretation; M. R.

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    This study was presented at the International Conference and Course on Neuromuscular Ultrasound, May 16-18, 2013, Charleston, SC.

    FUNDING/SUPPORT: This publication was made possible by the Mayo Clinic Center for Translation Science Activities [Grant UL1 TR000135] from the National Center for Advancing Translational Science, a component of the National Institutes of Health.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.

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