Nitric oxide delivery to the lung: a model

Dedicated nitric oxide equipped ventilators are now available commercially but are not yet common in clinical practice. With other ventilators, there is no standardized procedure for the administration or monitoring of nitric oxide. We describe the use of nitric oxide in conjunction with a simple ti me-cycled, pressure regulated, flow generating ventilator attached to a mod el infant-sized lung. The measured nitric oxide concentrations were always less than calculated. Infusion site, minute ventilation and sampling port a ll affected nitric oxide concentration (P < 0.05). Increasing minute ventil ation lowered measured nitric oxide concentration exponentially. Mixing of gases improved when nitric oxide was infused closer to the ventilator. Acid contamination was found in water samples from humidifier, water trap and v entilator gas outlet. Acidification was reduced, without change in measured nitric oxide delivery, when infused prehumidifier. We recommend, when used as therapy, nitric oxide levels in inspired gases should always be measure d.