Inhaled nitric oxide, right ventricular efficiency, and pulmonary vascular mechanics: selective vasodilation of small pulmonary vessels during hypoxic pulmonary vasoconstriction.
OBJECTIVE
In the setting of acute pulmonary artery hypertension, techniques to reduce right ventricular energy requirements may ameliorate cardiac failure and reduce morbidity and mortality. Inhaled nitric oxide, a selective pulmonary vasodilator, may be effective in the treatment of pulmonary artery hypertension, but its effects on cardiopulmonary interactions are poorly understood.


METHODS
We therefore developed a model of hypoxic pulmonary vasoconstriction that mimics the clinical syndrome of acute pulmonary hypertension. Inhaled nitric oxide was administered in concentrations of 20, 40, and 80 ppm.


RESULTS
During hypoxic pulmonary vasoconstriction, the administration of nitric oxide resulted in a significant improvement in pulmonary vascular mechanics and a reduction in right ventricular afterload. These improvements were a result of selective vasodilation of small pulmonary vessels and more efficient blood flow through the pulmonary vascular bed (improved transpulmonary vascular efficiency). The right ventricular total power output diminished during the inhalation of nitric oxide, indicating a reduction in right ventricular energy requirements. The net result of nitric oxide administration was an increase in right ventricular efficiency.


CONCLUSIONS
These data suggest that nitric oxide may be beneficial to the failing right ventricle by improving pulmonary vascular mechanics and right ventricular efficiency.
Hillman
N D
ND
Department of Pediatrics, Duke University Medical Center, Durham, N.C. 27710, USA.
Cheifetz
I M
IM
Craig
D M
DM
Smith
P K
PK
Ungerleider
R M
RM
Meliones
J N
JN
D000818:Animals; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D006976:Hypertension, Pulmonary / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology*; D009569:Nitric Oxide / Q000494:pharmacology*; D011652:Pulmonary Circulation / Q000187:drug effects*; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D013552:Swine; D014661:Vasoconstriction / Q000502:physiology*; D016278:Ventricular Function, Right / Q000187:drug effects*
D009569:Nitric Oxide