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