2000 OPEN FORUM Abstracts
Verification of Flow-Inflating Manual Bag Resuscitator for Nitric Oxide Delivery
Miller CC, Fairbanks S, Miller JWR. University of British Columbia, Department of Experimental Medicine
Introduction: Abrupt interruption of inhaled nitric oxide (NO) delivery during mechanical ventilation is associated with a rapid deterioration in physiological status known as "rebound effect." Many routine procedures, such as bronchial hygiene maneuvers, changing out NO cylinders, during transports, or as a back-up during break down of NO delivery devices require that the patient be removed from the ventilator. During such times, a manual bag resuscitator is utilized to maintain ventilation. A system is needed to provide a stable NO dosage during these procedures. The purpose of this study is to evaluate the Pulmonox flow-inflating manual bag resuscitator (INObag). Method: The INObag was set-up according to the attached test set-up Figure 1. NO was provided from either one of two AeroNOx delivery devices or a Pulmonox back-up cylinder with a fix flow rate of 0.25 LPM. These sources were isolated from one another with a three-way stop-cock. A pressure gauge was attached to the pressure port and the INObag was attached to a test lung. The suggested sample site on the INObag was connected to a rapid response chemiluminescence NO analyzer (280 NOA, Sievers, USA) or one of two AeroNOx delivery devices (Pulmonox Medical Corp, Alberta, Canada). Additional sample locations included a site within the test lung and another within the reservoir of the INObag. A standard oxygen flow meter was attached to the INObag delivery line. NO and nitrogen dioxide (NO2) data were recorded from these various sites during testing conditions. A standard flow of 9-10 LPM oxygen was used with 0.25 LPM of NO to attain a desired delivery dosage of 20-25 parts per million (ppm). Ventilatory conditions were varied as follows: respiratory rate (RR) 0-150 bpm; peak inspiratory pressure (PIP) 0-40 cmH2O; positive end expiratory pressure (PEEP) of 0-5 cmH2O; and inspiratory wave pattern spiked and square. Also, a possible clinical condition was simulated to evaluate NO2 accumulation within the device between use if the device was not flushed out with a fresh gas flow as recommended by the manufacturer.
Results: RR, PIP, PEEP and wave pattern had no significant effect on NO delivery (p>0.05) See Figures 2-4. There was good correlation between the chemiluminescence NO analyzer and both AeroNOx devices (r=0.86). In all simulated conditions during ventilation the NO2 remained below 0.2 ppm. The deadspace reservoir showed a NO2 concentration profile as shown in Figures 5-7. The peak NO2 at 80, 40 and 20 ppm NO and 100% oxygen over an hour period of time without flushing was 6.3 ppm (SD=1.74), 1.3 ppm (SD=0.42) and 0.2 ppm (SD=0.08) respectively. This was removed within 20 s with 10 LPM of fresh oxygen gas flow (Figure 8). Actual data is recorded ii Table 1. Conclusion: Use of the INObag for delivery of NO at 20-25 ppm under the clinical conditions tested does not pose any increased risk to patients receiving NO therapy during mechanical ventilation. We recommend that the system be flushed for 20 s before and after each use to ensure that NO2 is not allowed to build up within the systems dead space and reservoir.
Funding provided by Pulmonox Medical Corporation