The Science Journal of the American Association for Respiratory Care

1995 OPEN FORUM Abstracts

RESPONSE OF CHEMILUMINESCENT ANALYZERS ON THE MEASURED VALUE OF NITRIC OXIDE (NO)

Masaji Nishimura, MD, Chikara Tashiro, MD, Yuji Fujino, MD, Hideaki Imanaka, MD, Dean Hess, RRT, PhD, Robert M Kacmarek, RRT, PhD. Hyogo College of Medicine, Hyogo, Japan. Massachusetts General Hospital, Boston, MA.

It has become increasingly common to use inhaled nitric oxide (NO) for patients with acute lung injury. The gold standard for NO measurements is chemiluminescence. However, its response is very slow because it is designed to neglect noise during investigation of air pollution. This slow response of the analyzer causes problems when it is used for a clinical setting. In this study, we investigated the response time of two NO chemiluminescent analyzers, and compared the measured values of each analyzer when NO concentration fluctuated.



Methods: Two chemiluminescent analyzers (Model 270B NOA, Sievers Instruments, Inc, Boulder, CO, and CLA 510S, Horiba, Kyoto, Japan) were employed. The transport delay and dynamic response time were measured by a balloon puncture in a glass chamber (Noguchi et al, J Appl Physiol 52:79-84,1982). Then fluctuation of NO concentrations was created by delivering 100 mL/min of NO gas (92 ppm in nitrogen) into 4 L/min of nitrogen gas stream. NO concentration inside a ventilator circuit was also measured at 20 inch both upstream and downstream of the airway opening and at "Y" between a patient and the circuit.



Results: 90% response time of each analyzer was 0.20±0.02 sec for 270B NOA, and 8.42±1.13 sec for CLA 510S. When NO concentration fluctuated between 0 and 2.3 ppm, 270B NOA gave a correct value of 0 and 2.3 ppm, while CLA 510S gave a value between 0.93 and 1.15 ppm. When NO was measured at the airway opening of a patient, 270B NOA and CLA 510S exhibited 84.0% and 45.3% of NO concentration measured at inspiratory limb, respectively. The analyzer with a long response time gave us a value of mean inhaled and exhaled NO concentration and therefore it was not a real value of inhaled NO. Figure shows NO concentration measured at the airway opening.

Conclusion: NO analyzers showed significant difference in response time. When NO was analyzed at the airway opening, NO value was less than half of the true value with a long response time analyzer. Inhaled NO should be measured at the inspiratory limb

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