A 45-year-old woman with progressive pulmonary fibrosis maintains her alveolar ventilation by adopting a rapid, shallow breathing pattern rather than deep slow breaths. Which change in the components of the work of breathing best explains this strategy?

• A Decreased elastic recoil favors deeper breaths
• B Increased resistive work favors larger tidal volumes
• C Increased elastic work favors smaller tidal volumes ✓
• D Unchanged total work regardless of pattern

Explanation

Fibrosis stiffens the lungs, raising elastic work, which increases proportionally with tidal volume squared. Resistive work instead rises with airflow velocity, hence with respiratory rate. In stiff lungs the cheapest strategy is a small tidal volume at a higher rate, minimizing elastic cost at the expense of modestly higher resistive cost. In obstructive disease the opposite holds, where slow deep breathing reduces the dominant resistive component.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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