Chest
Volume 113, Issue 6, June 1998, Pages 1650-1657
Journal home page for Chest

Laboratory and Animal Investigations
Delivery of Inhaled Nitric Oxide Using the Ohmeda INOvent Delivery System

https://doi.org/10.1378/chest.113.6.1650Get rights and content

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.

Section snippets

Lung Model

The experimental set-up was used as previously described1 and is shown in Figure 1. A two-chamber lung model (Training Test Lung model 1600; Michigan Instruments; Grand Rapids, Mich) was configured to separate inspired and expired gases. A valve system ensured that the ventilator inflated one chamber during inspiration, while the second chamber was lifted and aspirated room air. At expiration, the NO-containing inspiratory gas was released to atmosphere, and the room air from the second chamber

RESULTS

No differences in the NO delivery patterns were observed between the two delivery systems with the Puritan-Bennett 7200 and Servo 900C. The NO waveform always demonstrated a nearly constant concentration regardless of inspiratory flow pattern. Simulating spontaneous breathing resulted in irregular inspiratory flow patterns without any change in NO delivery pattern. Sample tracings obtained during use of the INOvent and the Puritan-Bennett 7200 are shown in Figure 2. To demonstrate the

DISCUSSION

The INOvent Delivery System reliably delivered NO over a wide range of NO concentrations and ventilator settings. This system provided a constant NO dose regardless of the ventilatory pattern. Premixing NO proximal to the ventilator also resulted in a constant NO delivery, but produced an error as great as 20%, compared with the 11% error observed with the INOvent. When NO was premixed with N2, NO2 formation was low for both systems.

CONCLUSION

The INOvent Delivery System provides an accurate and stable NO concentration. The NO2 production was low, even at high FIo2.

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Supported in part by Ohmeda, Inc., maker of the INOvent Delivery System. Dr. Kirmse was supported in part by a grant from the Deutsche Forschungsgemeinschaft (Ki582/1-1).

Reprint requests: Dean Hess, PhD, RRT, FCCP, Respiratory Care, Ellison 401, Massachusetts General Hospital, Boston, MA 02114

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