Decreased pulmonary compliance has which effect on ventilation?

• A. It makes inhalation harder, reducing tidal volume and increasing work of breathing
• B. It makes exhalation harder, increasing tidal volume
• C. It increases lung compliance and reduces work
• D. It has no effect on ventilation

Answer: (A)

Pulmonary compliance is how easily the lungs and chest wall expand when pressure is applied. When compliance decreases, the lungs become stiffer and harder to expand.

During inspiration, your inspiratory muscles must overcome that stiffness to stretch the lungs. If the lungs are less compliant, more pressure is needed to achieve the same volume, so inhalation is harder. As a result, tidal volume falls for a given effort, and the work of breathing increases because the respiratory muscles must do more work to bring air in.

Exhalation is usually driven by elastic recoil and is not made harder by reduced compliance in the same way; it mainly relies on the lungs returning to their resting size rather than needing to be actively expanded. So the primary effect is on inhalation, not exhalation.