A ventilation/perfusion mismatch is most commonly associated with which condition?

A ventilation/perfusion mismatch is most commonly associated with which condition?

• A. Pulmonary embolism
• B. Asthma
• C. Pneumonia
• D. COPD

Answer: (A)

V/Q mismatch happens when part of the lung is ventilated but not adequately perfused, or vice versa. A pulmonary embolism blocks blood flow to portions of the lung while ventilation continues, so the affected areas have a very high V/Q ratio (approaching dead space). This selective perfusion loss is the classic reason PE is associated with V/Q mismatch. In contrast, asthma mainly reduces ventilation (low V/Q in parts of the lung), pneumonia reduces ventilation due to alveolar filling, and COPD causes broader, chronic mismatches from both airway obstruction and parenchymal destruction, but not the acute, regionally perfused-but-ventilated pattern seen with PE.

V/Q mismatch happens when part of the lung is ventilated but not adequately perfused, or vice versa. A pulmonary embolism blocks blood flow to portions of the lung while ventilation continues, so the affected areas have a very high V/Q ratio (approaching dead space). This selective perfusion loss is the classic reason PE is associated with V/Q mismatch. In contrast, asthma mainly reduces ventilation (low V/Q in parts of the lung), pneumonia reduces ventilation due to alveolar filling, and COPD causes broader, chronic mismatches from both airway obstruction and parenchymal destruction, but not the acute, regionally perfused-but-ventilated pattern seen with PE.