Pulmonary hypertension turns the right ventricle into a high-risk chamber. The right ventricle is designed to eject blood into a low-pressure pulmonary circulation. When pulmonary vascular resistance rises, the RV may dilate, lose contractile efficiency, and fail.
Critical illness can worsen pulmonary hypertension quickly. Hypoxemia causes hypoxic pulmonary vasoconstriction. Acidosis increases pulmonary vascular resistance.
Hypercapnia can increase pulmonary vasoconstriction. High airway pressures and excessive PEEP may overdistend alveoli and compress pulmonary capillaries. Pulmonary embolism, ARDS, pneumonia, sepsis, and chronic pulmonary vascular disease can all push the RV toward failure.