Hypertrophy of the accessory muscles is most commonly seen in patients with which condition?

Hypertrophy of the accessory muscles is primarily associated with chronic obstructive pulmonary disease (COPD), which includes emphysema and chronic bronchitis. In COPD, patients often experience persistent airflow limitation and increased work of breathing due to airway obstruction and reduction in lung function. Over time, to compensate for the decreased efficiency of the diaphragm and other primary muscles of respiration, patients may recruit and rely more on the accessory muscles of respiration, such as the sternocleidomastoid and scalene muscles. This leads to hypertrophy or enlargement of these muscles as they are used more frequently during breathing.

In contrast, while asthma can also lead to some use of accessory muscles during acute episodes of bronchospasm, it does not typically result in the same degree of muscle hypertrophy over time compared to the chronic nature of COPD. Pneumonia primarily causes inflammation and infection in the lungs, leading to symptoms that can affect breathing but does not result in the chronic use of accessory muscles. Similarly, bronchitis, particularly its acute form, is typically a temporary condition that does not lead to the prolonged respiratory effort and muscle hypertrophy seen in COPD.