Transpulmonary plasma catecholamines in acute high-altitude pulmonary hypertension.

Objective: High altitude leads to an increase in sympathetic nervous system (SNS) activity and pulmonary arterial pressure (PAP). We assessed whether the SNS contributes to this increase in PAP.

Methods: Sympathetic discharge to the pulmonary vasculature was assessed by measuring plasma norepinephrine concentrations in central venous blood entering the lung and systemic arterial blood leaving the lung (arterial-central venous difference; a - cv(diff)).