The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

NOPORT - A PORTABLE NITRIC OXIDE DELIVERY SYSTEM

Kliewer K. RRT, Hill W. BSc. RRT King Faisal Specialist Hospital & Research Center, Riyadh, Kingdom of Saudi Arabia.

Background: The delivery of inhaled nitric oxide (NO) presents a challenge to facilities involved in therapeutic trials, because no commercial delivery system is yet available. Methods of delivery are generally developed and fabricated in-house and may differ significantly from hospital. In a recent oditorial in Respiratory Care, the "ideal" NO delivery system was described as follows: It should: 1) be simple and dependable, 2) deliver precise and stable doscs of NO, 3) limit NO_{2} productio, 4) be capable of monitoring both NO and NO_{2}, 5) permit scavenging of NO, and 6) maiain proper ventilator function. Method: The NOPORT nitric oxide delivery system has been developed by our department over a two year period. NOPORT is built around a modified cylinder truck, which provides structural support for all control and analysis equipment. Storage containers on the cart hold all neccessary equipment for bedside application. Two suction outlets and a power source are the only peripheral requirements. The unit is easily transported by a single person and provides a compact (4 ft^{2}) and stable platform for bedside NO delivery. NOPORT utilizes inspiratory limb titration of NO. During intermittent flow modes of ventilation, we use a noncompliant mixing chamber between the NO inlet and the humidification chamber to ensure complete mixing of constant flow NO gas with the intermittent gas flow of the ventilator. NOPORT provides continuous sidestream sampling and analysis of mixed, inspired gas by an electrochemical NO/NO_{2} analyzer (Pulmonox II, Pulmonox Research & Development Corporation) and a fuel cell oxygen analyzer. Sampling rate is controlled by the Pulmonox external flow control (EFC), powered by low suction. Exhaled gases are scavenged by isolation of exhalation valves or exhalation ports. The scavenger circuit, powered by-140 mmHg suction, is open to ambient air distally to avoid compromising ventilator function. Results / Experience: We have used this method of NO delivery in 55 adult and pediatric patients since October 1994 (PPHN 23, Cardiac surgical 25, ARDS 7). Inspiratory limb NO_{2} production has been limited to 0.1 -2.0 ppm at NO concentrations up to 60 ppm. The highest NO_{2} concentration measured was 4.7 ppm at a NO dose of 75 ppm. Methemoglobin levels have been less than 5% in all cases. We have delivered 2 - 80 ppm NO, in minute ventilation ranges from 8-16 L/min in both constant flow (pediatric) & intermittent flow ventilators in A/C, SIMV & PS, PCV, PC-IRV & HFOV modes. Conclusion: NOPORT application is done at the bedside using a small number of common adapters and can generally be accomplished in just a few minutes. System components are easily accessed and monitored, allowinng for case in both application and troubleshooting. NOPORT has proven itself, under a variety of conditions, to be adaptable and technically reliable, the key to its success being its evolution towards simplicity. The evolution continues, but NOPORT currently meets and exceeds all conditions of the "ideal" NO delivery system.

Reference: OF-96-079

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