Hypercapnic acidosis transiently weakens hypoxic pulmonary vasoconstriction without affecting endogenous pulmonary nitric oxide production.

Purpose: Hypercapnic acidosis often occurs in critically ill patients and during protective mechanical ventilation; however, the effect of hypercapnic acidosis on endogenous nitric oxide (NO) production and hypoxic pulmonary vasoconstriction (HPV) presents conflicting results. The aim of this study is to test the hypothesis that hypercapnic acidosis augments HPV without changing endogenous NO production in both hyperoxic and hypoxic lung regions in pigs.

Methods: Sixteen healthy anesthetized pigs were separately ventilated with hypoxic gas to the left lower lobe (LLL) and hyperoxic gas to the rest of the lung.

Distant effects of nitric oxide inhalation in endotoxemic pigs.

Objective: Inhalation of nitric oxide (INO) has distant effects. By a blood- borne factor, INO down-regulates endogenous nitric oxide production in healthy pig lungs, resulting in vasoconstriction in lung regions not directly reached by INO. The aim of this study was to investigate whether INO has distant effects in endotoxemic pig lungs.