NITRIC-OXIDE (NO) MEASUREMENT ACCURACY

Background. Evaluation of the clinical utility of NO requires accurate assessment of inspired [NO]. Currently, chemiluminescence analyzers a re the clinical standard for analysis; however, their performance in t he clinical setting has not been systemically evaluated. Methods. We e valuated the performance of four chemiluminescence analyzers (270B NOA , Sievers Instruments, Inc.; CLA 510S, Horiba Co., Led.; CLD 700 AL, E co Physics Corp.; Model 42, Thermo Environmental Instruments Inc.) in simulated clinical settings. Transport delay and dynamic 95% response time were measured by the balloon in a glass chamber puncture techniqu e. Fluctuating [NO] in a continuous flow of gas and [NO] during mechan ical ventilation, where NO was premixed prior to entering the ventilat or, were evaluated. Results, Transport delay ranged from 1.02 +/- 0.02 to 24.36 +/- 2.47 s (p < 0.05) and the 95% response time ranged from 0.22 +/- 0.04 to 70.03 +/- 0.03 s (p < 0.05). Accurate analysis of[NO] in a continuous flow system was only possible with the most rapid res ponse analyzer (270B NOA). All other analyzers under reported the maxi mum [NO] (p < 0.05) and over reported the minimum [NO] (p < 0.05), All analyzers accurately determined [NO] in the inspiratory limb of the v entilator circuit, but none accurately determined [NO] ae the airway o pening. Conclusions, Measurements of inhaled [NO] can vary greatly, de pendent upon the performance characteristics of the analyzer and the l ocation of NO analysis. Ail studies evaluating the clinical use of NO should fully describe the technical gas delivery methodology and the r esponse time and transport delay of the chemiluminescence analyzer use d.