The Science Journal of the American Association for Respiratory Care

1998 OPEN FORUM Abstracts

LAB EVALUATION OF A NITRIC OXIDE BREATHING SYSTEM UTILIZING THE OHMEDA INO-VENT.

John Newhart RCP, Elsie M. Collado B.S. RRT RCP, F. Wayne Johnson RCP, R. N. Channick MD. UCSD Medical Center San Diego California.

BACKGROUND: The use of inhaled nitric oxide (INO) to treat pulmonary hypertension and hypoxia has been previously described in the literature. In our institution we utilize the Ohmeda INO-Vent to deliver INO to mechanically ventilated patients. We sought to adapt the INO-Vent for use on spontaneously breathing patients via facemask.

Methods: Selectable inspired oxygen concentrations were generated by a Bird 3800 air/O2 blender with available flow controlled by a 0-75 lpm flowmeter. The patient draws gas from a "T" piece through the INO-Vent flow/injector module where a proportionate amount of NO is injected into the inspired gas. This gas flows through a 6 inch length of 22mm corrugated tube, through a gas sample adapter and into a Vital Signs CPAP mask. Exhaled gas passes through the exhalation port in the mask. To bench test the system we attached the complete mask to an open 30mm port in one chamber of a Michigan Instruments TTL. The other chamber of the lung was driven by a NPB 7200 ventilator. A bar was attached to the ventilator driven side in such a way as to lift the mask side (simulating a patient breathing) when the ventilator cycles. We tested the system at different ventilator volume, respiratory rate and peak flow rates. In all runs, the ventilator was in CMV, square wave, and used a standard ventilator circuit. The INO-Vent was calibrated prior to use and an external oxygen analyzer (MSA Mini-Ox III) was used to determine FiO2.

Results:

Ventilator settings: Vt .5L, RR 12, 45 lpm

O2 % 10ppm 20ppm 40ppm

(NO/NO2) (NO/NO2) (NO/NO2)

50% 8.5/0 18/.1 37/.1

90% 8.2/0 18/0 37/.1

Ventilator settings: Vt .5L, RR 20, 45 lpm

O2 % 10ppm 20ppm 40ppm

(NO/NO2) (NO/NO2) (NO/NO2)

50% 8.7/0 18/0 38/0

90% 8.4/0 18/0 37/.1

Ventilator settings: Vt 1.0L, RR 20, 65 lpm

O2 % 10ppm 20ppm 40ppm

(NO/NO2) (NO/NO2) (NO/NO2)

50% 8.4/0 18/0 37/0

90% 8.5/0 18/0 37/0

In all runs, NO was held constant within the Ohmeda factory specifications (set vs. analyzed). Nitrogen dioxide was in all instances below the maximum OSHA limit of 5ppm as well as the commonly accepted clinical limit of 2ppm. CONCLUSION: Mask delivery of NO can be safely accomplished utilizing the INO-VENT, a CPAP mask and minimal additional hardware. Actual response of the system will require utilizing a rapid response NO analyzer.

The 44th International Respiratory Congress Abstracts-On-DiskĀ®, November 7 - 10, 1998, Atlanta, Georgia.

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