Increased intrinsic work of breathing with decreased compliance is most associated with which condition?

• A. Pulmonary Edema
• B. Pulmonary Fibrosis
• C. Acute Bronchitis
• D. Pneumothorax

Answer: (B)

When the lungs are less compliant, the muscles of breathing must generate higher pressures to achieve the same tidal volume. This makes the intrinsic work of breathing increase because more effort is required to expand the chest and ventilate. Pulmonary fibrosis causes widespread scarring that stiffens the lung tissue, drastically reducing compliance. As a result, inspiratory muscles have to work harder, leading to marked dyspnea and rapid, shallow breathing with elevated work of breathing.

Other conditions can affect breathing, but not in the same clear way. Edema lowers compliance somewhat but is not as classic for the stiff, scarred lung pattern. Acute bronchitis is mainly an inflammatory/obstructive issue with increased airway resistance rather than a primary reduction in lung compliance. Pneumothorax alters mechanics by collapsing part of the lung, increasing effort, but the hallmark decreased compliance driving intrinsic work of breathing is most characteristic of pulmonary fibrosis.