TITLE: EVALUATION OF NITRIC OXIDE (NO) DELIVERY SYSTEM USING A MANUAL RESUSCITATOR BAG (MRB)

AUTHORS: Arthur J. Smerling, MD¹, James R. Beck, CCP¹, John Newhart, RCP², Eileen Barnwell, RRT¹
AFFILIATION: ¹Columbia University, New York, NY; ²UCSD Medical Center, San Diego, CA.

INTRODUCTION: Clinicians treat critically ill patients with inhaled NO to improve oxygenation and reduce pulmonary artery pressure. These patients often need to be transiently manually ventilated to facilitate suctioning or transport. Any temporary NO delivery system must be able to maintain the same concentration of NO that the patient previously required, generate a minimum of NO2 and allow for O2, NO2 and NO monitoring. We evaluated an inhaled NO delivery system using a MRB in-vitro.
METHODS: Oxygen flowed in series via the flow sensor/ injector module of an INOvent (Datex), through a mixing tube (8 cm corrugated) to the gas inflow of an adult MRB (Engineered Medical Systems, IN) and finally into a 1L test lung (Seimens #190). NO concentration was sampled distal to the mixing tube and proximal to the test lung. Oxygen flow was varied from 2-15 LPM, NO concentration was varied from 20-80 ppm and ventilation was varied from 6-12 BPM.
RESULTS: Although O2 flow rates of >2 LPM could deliver 20- 40 ppm NO distal to the mixing tube, only >10 LPM flow could accurately deliver 20-40 ppm NO to the test lung. Oxygen flow rates >8-10 LPM were required to deliver 80 ppm NO to both the mixing tube and the test lung. Delivering 80 ppm NO generated the highest concentration of NO2 (3.4 ppm ). Increasing the ventilation rate decreased the amount of generated NO2 without changing the concentration of NO delivered.
CONCLUSION: NO can be safely administered using a MRB and should be continuously monitored close to the patients' airway. Flow rates should be greater than 10 LPM and increasing the rate of ventilation can decrease the delivered NO2 concen- tration.