The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

EVALUATION OF THE ACCURACY IN DELIVERING NITRIC OXIDE USING THE DRAGER Pac II ANALYZER.

Joanne J. Nicks, RRT: Michael A. Becker, RRT; Ronald E. Dechert, MS, RRT; Kenneth P. Bandy, BS, RRT. Department of Critical Care Support Services, University of Michigan Medical Center, Ann Arbor, Michigan.

Background: A bench study was performed evaluating the accuracy of Nitric Oxide (NO), analyzed by the Drager Pac II Analyzer (DR), using two comparison methods; a mathematically derived calculation of the NO concentration (CALC) and analyzation with the Thermo Environmental Chemiluminescence Analyzer Model 42 H (TE)

Methods: Two different bench studies were performed on two separate occasions, Phase 1 and Phase 2. Phase 1 compared NO concentrations analyzed with both the DR and TE analyzers to the mathematically derived calculation of delivered NO parts per million (ppm). The formula for the calculated NO is as follows:

Delivered NO ppm = source NO ppm X source NO flowrate (lpm) bias flowrate (1pm)

NO at a tank concentration of 800 ppm was delivered into an open reservoir (12 ft length of aerosol tubing) through which a constant bias flow of non-humidified oxygen was running. The DR and TE analyzers were calibrated according to manufacturers recommendation and inserted in line. The flow of NO was adjusted to achieve various concentrations of NO between 5 and 50 ppm. Flowrates for the bias flow and the NO flow were measured using the Timeter Instrument RT 200 Calibration Analyzer. The calculated ppm of NO and the measurements of NO analyzed using the DR and TE were documented. Twenty paired observations, CALC vs DR and CALC vs TE, were compared. Phase 2 compared NO concentrations ranging between 5-80 ppm analyzed with both DR and TE analyzers. NO at a tank concentration of 800 ppm was introduced at the outlet of the Bird VIP. Ventilator at various flowrates. The gas from the ventilator was heated and humidified (36 degrees C). The analyzers were calibrated and inserted in-line on inspiration before the proximal patient connector. The patient connector was attached to an infant test lung with a compliance of 1 cc/cmH_{2}O. The ventilator was adjusted to deliver continuous flow, pressure limited ventilation with an FiO_{2} 1.0, f 40, IT 0.4 sec, FR 10 lpm, PIP and PEEP of 30 and 5 cm H_{2}O, respectively. Nine paired observations, DR vs TE, were compared.

Results: All paired observations were statistically analyzed using Student's T-test. Values are reported as Mean ± S.D. Significance was reached at p < =0.05.

Phase 1: Comparison of 20 paired samples: CALC vs TE 30.3 ± 14.39 vs 30 ± 14.16 p = 0.055 CALC vs DR 30.3 ± 14.39 vs 31.15 ± 14.83 p < 0.001^{*}

Phase 2: Comparison of 9 paired samples: TE vs DR 38.78 ± 24.82 vs 40.33 ± 26.24 p = 0.015^{*}

Experience: Nitric Oxide has been used in our NICU as part of an NIH regulated clinical study. Prior to using the DR analyzer clinically, training and bench testing were performed.

Conclusion: There was a statistically significant difference between the CALC and DR NO in Phase 1 and between the TE and DR in Phase 2. While the differences were statistically significant, it is doubtful that they are clinically relevant. The DR overestimated the NO levels by a maximum of 2 ppm at levels > 40 ppm. The usual therapeutic level of NO is < =40 ppm. There was no difference at levels below 40 ppm.

Reference: OF-96-141

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