Nitric oxide administration using an oxygen hood: a pilot trial

Abstract

Background: We have shown earlier that inhaled nitric oxide (iNO) administered by oxygen hood reduces pulmonary hypertension in an animal model (J Perinatol 2002; 22:50-6). Our objective in this study was to determine feasibility of iNO by oxygen hood in neonates with elevated alveolar-arterial oxygen gradients (A-aDO(2)).

Methods/principal findings: Masked randomized controlled pilot trial. Inclusion criteria were: gestation>or=34 weeks, age<7 days, with post-ductal arterial line, and A-aDO(2) 400-600. Infants were randomized to study gas (iNO 20 ppm or equivalent O(2) flow) for 1 hr which was then weaned over the next 4 hours. Primary outcome was PaO(2) one hour post-randomization. Four infants each were randomized to iNO or O(2) (controls). Two of the four infants given iNO had an increase in PaO(2) of >100 torr, while oxygenation was unchanged in the controls. Methemoglobinemia and other adverse effects were not noted in any infant. Environmental levels of NO and NO(2) were minimal (<1 ppm) at >0.3 m from the hood.

Conclusions: Administration of iNO by oxygen hood is feasible. Larger randomized controlled trials are required to measure the efficacy and determine an appropriate target population for this technique.

Trial registration: ClinicalTrials.gov NCT00041548.

Figure 1. CONSORT flowchart

Figure 2. Delivery of inhaled nitric oxide into an oxygen hood using an INOvent®.

The injector module from the INOvent® is inserted into the gas delivery circuit proximal to the humidifier (on the dry side). The sample line from the INOvent® measures the oxygen concentration, nitric oxide, and nitrogen dioxide in the oxygen hood.

Figure 3. Change in PaO₂ with study gas.

Line graph showing change in PaO₂ from before initiation of study gas (nitric oxide or oxygen) to one hour after study gas. Two of the four infants receiving nitric oxide (dark circles connected by solid lines) had an increase in PaO₂ >100 torr, but none of the infants receiving O₂ alone (open circles connected by dashed lines) demonstrated a significant change.