Objectives: We evaluated the Ohmeda INOvent Nitric Oxide Delivery System, which uses an inspiratory flow sensor to inject a synchronized and proportional nitric oxide (NO) flow into the mechanical ventilator circuit. This system should deliver a constant NO concentration independent of ventilator mode, minute ventilation, fraction of inspired oxygen, or ventilator brand. It should also minimize nitrogen dioxide (NO2) formation.
Methods: NO delivery by the INOvent and a premixing NO delivery system were compared using two ventilators (Puritan-Bennett 7200 and Servo 900C). NO concentration was measured within the trachea of an attached lung model using a fast-response chemiluminescence NO analyzer. NO concentration was also measured in the inspiratory limb using the electrochemical analyzer of the INOvent. For three NO concentrations (2, 5, and 20 ppm), the ventilators were set for constant flow volume control ventilation, pressure control ventilation, and spontaneous breathing with pressure support ventilation or synchronized intermittent mandatory ventilation. Different tidal volumes (300, 500, 750, and 1,000 mL) and inspiratory times (1 and 2 s) were evaluated. NO2 formation for both ventilators and delivery systems were evaluated at 20 ppm and 95% O2-.
Results: Regardless of ventilatory pattern, both systems delivered a constant NO concentration. The error between the target and the delivered NO dose for the INOvent was -1.3+/-3.6% with the Puritan-Bennett 7200 and -3.9+/-4.3% with the Servo 900C. For the premixing system, the error was -5.5+/-4.8% with the Puritan-Bennett 7200 and -6.7+/-6.2% with the Servo 900C. NO2 concentrations were 0.5+/-0.1 ppm during NO delivery by the INOvent, 5.8+/-1.6 ppm when NO was premixed with air, 0.3+/-0.1 ppm when NO was premixed with N2.
Conclusion: The INOvent provides a constant NO concentration independent of the ventilatory pattern, and NO2 formation is minimal.