Physiologic implications of helium as a carrier gas for inhaled nitric oxide in a neonatal model of Bethanecol-induced bronchoconstriction.
OBJECTIVE
To compare heliox to nitrogen-oxygen (nitrox) as a carrier gas for inducible nitric oxide (iNO) in the presence of pharmacologically inhaled bronchoconstriction. We hypothesized that respiratory resistance and gas exchange would improve when iNO is delivered with heliox.


METHODS
Interventional laboratory study.


METHODS
An academic medical research facility in the northeastern United States.


METHODS
Sedated, ventilated newborn piglets.


METHODS
Newborn piglets (n = 16; 2.3 +/- 0.1 kg) were placed on a flow-controlled ventilator and given intravenous Bethanecol (2 x 1 mg/kg followed by 1 mg/kg/hr) to induce bronchoconstriction. Piglets were randomized to heliox or nitrox (Fio2 = 0.3) and given 80 ppm iNO.


RESULTS
Hemodynamics, blood chemistry, and pulmonary mechanics were recorded at 30-min intervals for 2 hrs. Bethanecol dosing increased inspiratory respiratory resistance (cm H2O/L/min; p < .01) and decreased respiratory compliance (mL/cm H2O/kg; p < .01). Following carrier gas assignment, hemodynamics and respiratory compliance were similar between groups and respiratory resistance decreased (p < .01) in the heliox group. Over 2 hrs with iNO therapy, Paco2 increased (p < .01) whereas blood pH decreased (p < .01) in the heliox group. Respiratory resistance trended downward, oxygenation index improved (p < .01), and blood methemoglobin levels trended higher for nitrox compared with heliox.


CONCLUSIONS
The INOvent was effective for controlling heliox delivery of iNO. Despite marked reduction in respiratory resistance with heliox gas ventilation in a neonatal model of pharmacologic bronchoconstriction, nitrox might perform better as a delivery vehicle for iNO.
Nemours Research Lung Center, Nemours Children's Clinic-Wilmington of the Nemours Foundation, Alfred I. duPont Children's Hospital, Wilmington, DE, USA.
Thomas L
TL
Miller
Clifford J
CJ
Singhaus
Tami I
TI
Sherman
Jay S
JS
Greenspan
Thomas H
TH
Shaffer
D000818:Animals; D000831:Animals, Newborn; D018723:Bethanechol; D016084:Bronchoconstriction / Q000187:drug effects*; D016085:Bronchoconstrictor Agents; D001993:Bronchodilator Agents / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004337:Drug Carriers; D006371:Helium; D006439:Hemodynamics; D009569:Nitric Oxide / Q000008:administration & dosage*; D009584:Nitrogen; D010100:Oxygen; D011897:Random Allocation; D013552:Swine
D016085:Bronchoconstrictor Agents; D001993:Bronchodilator Agents; D004337:Drug Carriers; D018723:Bethanechol; D006371:Helium; D009569:Nitric Oxide; C041364:nitrox; C038949:heliox; D009584:Nitrogen; D010100:Oxygen