A 44-year-old woman has developed calf pain during a transatlantic flight. She is extremely short of breath upon arrival at her
destination. She was subsequently diagnosed with a pulmonary embolism (PE) that resolved with anticoagulant therapy. Which statement best characterizes the underlying problem of her PE?
"Ventilation was occurring, but perfusion was inadequate causing shortness of breath. "
Explanation:
Uneven changes in airflow resistance, the resulting uneven distribution of air, and alterations in circulation from increased intra-alveolar pressure due to hyperinflation all lead to ventilation-perfusion mismatch. Vasoconstriction due to alveolar hypoxia also contributes to this mismatch. For effective gas exchange to occur, alveoli must be ventilated and perfused. Ventilation (V) refers to the flow of air into and out of the alveoli, while perfusion (Q) refers to the flow of blood to alveolar capillaries.
