PURPOSE Impairment of diaphragmatic function is one of the main pathophysiological mechanisms of chronic obstructive pulmonary disease (COPD) and is known to be related to acute exacerbation. Ultrasonography (US) allows for a simple, non-invasive assessment of diaphragm kinetics. The purpose of this study was to investigate the changes in diaphragmatic function during acute exacerbation of COPD, by US.

METHODS This single-center, prospective study included patients with acute exacerbation of COPD symptoms. US measurements were performed within 72 hrs after exacerbation and after improvement of symptoms. Diaphragmatic excursion and its thickening fraction (TF) were measured as markers of diaphragmatic function. TF was calculated as (thickness at end inspiration - thickness at end expiration)/thickness at end expiration.

RESULTS Ten patients were enrolled. All patients were male, and the mean age was 79.8 years. The TF of the right diaphragm showed a significant increase from the initial to the follow-up values (80.1 ± 104.9 mm vs. 159.5 ± 224.6 mm, p = 0.011); however, the diaphragmatic excursion did not vary significantly between the initial and follow-up values (22 ± 6 mm vs 23 ±12 mm). The change in excursion between the stable and exacerbation periods was positively correlated with time to the next exacerbation and negatively correlated with the time taken to recover from the exacerbation.

CONCLUSION These data support the possibility that a defect in diaphragm thickening is related to acute exacerbation of COPD.