Simplified Pulmonary Vasodilatory Testing in the Cardiac Catheterization Laboratory with Nasal Cannula Nitric Oxide

In patients with pulmonary hypertension, pulmonary vasodilator testing with inhaled nitric oxide (NO) during cardiac catheterization provides valuable data for defining future care plans. Previously, the use of delivery systems for spontaneously breathing individuals required a tight-fitting seal by face mask and an approved delivery and dilution device. We hypothesized that a simplified delivery system using nasal cannula could be utilized to effectively deliver NO during cardiac catheterization. We developed a simple delivery system to deliver through a nasal cannula a concentration of NO at 50 ppm at the nares along with supplemental oxygen (O₂) via face tent. We prospectively employed this system for 10-minute intervals on 11 patients (age range, 7 months to 41 years) with pulmonary hypertension undergoing scheduled cardiac catheterization. Mean pulmonary artery pressure (PA_p) decreased from 62 mmHg (range, 38–99) at room air testing to 45 mmHg (range, 36–91) with the addition of NO plus O₂ (p = 0.014). Pulmonary vascular resistance (PVR) decreased from 11.6 U · m² (range, 4.5–43.4) to 6.3 U · m² (range, 2.0–34.2) (p = 0.001). A response of 20% or more reduction in PVR was seen in all 11 patients. The initial ratio of pulmonary to systemic vascular resistance (R_p:R_s) was 0.49 (range, 0.25–3.5) and decreased to 0.35 (range 0.1–2.6) (p = 0.002). No adverse side effects were noted. We found this NO delivery system to be a simple and effective method of pulmonary vasodilatory testing that may have wide applicability in the cardiac catheterization laboratory.