Administration of nitric oxide into open lung regions: delivery and monitoring.

BACKGROUND Pulsed administration of nitric oxide has proven effective in relieving pulmonary hypertension and in improving oxygenation. With this delivery method the nitric oxide administration to low ventilated lung regions is avoided with subsequent enhancement in oxygenation. This study presents (i) pulsed administration technique for nitric oxide during artificial ventilation, (ii) evaluation of the delivery in an animal model, and (iii) validation of the delivery device in a laboratory setting. METHODS Nitric oxide was delivered in four different pulse volumes synchronously with inspiration. The delivery was monitored with a fast responding high sensitivity nitric oxide monitor and nitric oxide uptake was calculated. Pulse delivery dose range, accuracy of the delivered dose, and stability of successive doses were analysed in a laboratory setting. RESULTS Uptake of the delivered nitric oxide was 87-92%. Measured nitric oxide pulse concentration was 1.6-fold the delivery concentration, calculated as the ratio of nitric oxide flow to inspiration flow. Dose accuracy and stability were both 5% or 3 nmol in the validated range of 3-1000 nmol. CONCLUSION With pulsed administration nitric oxide therapy can be directed to well-ventilated lung regions. Avoiding administration to the anatomic dead space eliminates nitric oxide exhalation effectively, which makes the method optimal for nitric oxide therapy in a rebreathing circuit. The required dose range from paediatric to adult is covered by the delivery device with a single nitric oxide gas supply.