CHEST Guidelines-Response_chest

Response_chest_13

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This correspondence between Drs. Kumar and Chandra and Dr. Baria and colleagues discusses the assessment of diaphragm function in COPD patients using B-mode ultrasound, as studied by Baria et al. Drs. Kumar and Chandra raised concerns about the hypothesis of diaphragm hypertrophy in COPD due to compensatory overuse, noting that oxidative stress and sarcomeric injury can lead to diaphragm atrophy instead. They highlighted that even in mild to moderate COPD, there is evidence of myosin loss and protein degradation, impacting force-generating capacity without necessarily changing diaphragm thickness. They questioned the measurement approaches used by Baria et al., suggesting that factors such as lung volume can non-linearly influence diaphragm thickness, potentially leading to misinterpretations.<br /><br />In response, Dr. Baria and colleagues acknowledge this complexity, clarifying that while the diaphragm may not demonstrate hypertrophy in structural terms, their original study did not display a reduction in the cross-sectional area of diaphragm fibers. They emphasized that their study sought to establish normal diaphragm thickness metrics in COPD patients to aid in diagnosing neuromuscular disorders. They acknowledged that diaphragm thickness does not change uniformly with lung volume, and the variability in diaphragm thickening during breathing is significant across individuals. They pointed out methodological differences in ultrasound techniques and urged for further careful evaluation of diaphragm function beyond simple thickness measurement, suggesting that thickening ratio and fraction analysis may provide better insights.<br /><br />Both sides seem to agree on the complexity and under-explored nature of diaphragm structural changes in COPD, advocating for careful methodological considerations in ultrasound studies to improve COPD assessments. This collaboration exemplifies how clinical hypotheses can be debated constructively, contributing to a deeper understanding of COPD pathophysiology.

Keywords

COPD

diaphragm function

B-mode ultrasound

diaphragm hypertrophy

oxidative stress

sarcomeric injury

myosin loss

lung volume

thickness measurement

neuromuscular disorders