Dosage of inhaled nitric oxide: a simple method for experimental studies

Few studies on treatment with inhaled nitric oxide (NOi) have been carried out in small laboratory animals yet? since commercially available dosing de vices are not appropriate in this setting for technical or financial reason s. The aim of our study was to establish and validate a simple, cost-effect ive system for the application of NOi in small animals. The system mixes NO i with constant-flow inspiratory gas. A gas blender allows for a mixture of nitrogen, oxygen, and NO dissolved in nitrogen. A formula using the desire d inspiratory oxygen fraction and the desired concentration of NOi as indep endent variables derives a somewhat higher inspiratory oxygen fraction, whi ch is preset using an oximeter. Then the flow of NO in nitrogen is started, lowering the inspiratory oxygen fraction to the initially desired value, t hereby adding NOi in the desired concentration. The method was validated by 153 adjustments, covering a variety of oxygen fractions and concentrations of NOi. NOi was measured by chemiluminescence as reference method. A close correlation (R=0.994) was found, and the regression line was close to the line of identity with y=-0.0994+1.048x. No systematic errors could be ident ified. We conclude that the method described may serve as a simple, cost-ef fective way to administer NOi to small animals.