Low levels of nitric oxide as contaminant in hospital compressed air: Physiologic significance?

OBJECTIVES To determine whether the levels of nitric oxide found in hospital compressed air have a clinically relevant effect on oxygenation in intubated patients with normal lungs. DESIGN Prospective study. SETTING Cardiothoracic and surgical intensive care unit in a university hospital. PATIENTS Twelve postoperative patients receiving mechanical ventilation. INTERVENTIONS Pure nitrogen and oxygen were substituted for hospital compressed air as a source of blending for correct FIO2. MEASUREMENTS AND MAIN RESULTS Hemodynamics and PaO2 were measured in nitrogen and oxygen used for blending oxygen during stable FIO2 levels. Inhaled nitric oxide was measured with a nitric oxide-chemiluminescence detector. There was no clinically relevant change in systemic hemodynamics. However, the PaO2 decreased significantly when nitrogen was used for blending. Inhaled nitric oxide levels varied from 2 to 550 parts per billion during use of hospital compressed air; no nitric oxide was detectable during use of nitrogen. CONCLUSIONS The low concentration of nitric oxide in hospital compressed air improves oxygenation in patients with normal lungs receiving mechanical ventilation. (Crit Care Med 1997; 25:1143-1146)