Delivery and monitoring of inhaled nitric oxide in patients with pulmonary hypertension.

OBJECTIVE

The development of a safe, portable, accurate, and adaptable system to deliver nitric oxide to patients with pulmonary hypertension.

DESIGN

A prospective, clinical study.

SETTING

Tertiary care pediatric intensive care unit and cardiac catheterization laboratory.

PATIENTS

One hundred twenty-three patients (median age 11 months, range 1 day to 72 yrs) with pulmonary hypertension who were administered nitric oxide between November 1991 and July 1993. Ninety-one patients were mechanically ventilated (volume-controlled ventilator, n = 53; pressure-controlled ventilator, n = 5; and a pressure-limited, time-cycled infant ventilator, n = 25). The system was adapted to allow high-frequency oscillator (n = 2) or hand ventilation, and for intraoperative use with an anesthesia machine (n = 6). Thirty-two patients were breathing spontaneously through a mask without assistance.

INTERVENTIONS

Nitric oxide was delivered at 10 to 80 parts per million (ppm); the dose was adjusted independently of the FIO2 without altering minute ventilation or tidal volume.

MEASUREMENTS AND MAIN RESULTS

Nitrogen dioxide was continuously monitored and exceeded 3 ppm in only four patients. Methemoglobin concentrations were < 5% in all but four patients. Nitric oxide doses remained stable, independent of minute ventilation and could be changed easily and quickly.

CONCLUSIONS

Inhaled nitric oxide can be administered precisely and reliably through a variety of delivery systems which can be used in patients of any size. Potential toxicity requires careful monitoring and continued improvement on apparatus design.