A simple method for monitoring the concentration of inhaled nitric oxide

Nitric oxide is a potent endogenous vasodilator involved in the homeostatic control of systemic blood pressure. It has also recently been demonstrated that when inhaled in low concentrations it acts as a specific pulmonary vasodilator. The concept of inhaled nitric oxide as a form of therapy is almost an anathema to anaesthetists. However, nitric oxide is being used increasingly for the treatment of persistent pulmonary hypertension of the neonate and in the adult respiratory distress syndrome. One major limitation to its frequent and widespread use is the problem of measuring the concentration of nitric oxide delivered. Currently, the gold standard technique used is chemiluminesence. However, the equipment required is costly and can be difficult to use. If the use of inhaled nitric oxide increases and it develops a therapeutic role then its applications may be limited only to centres which can afford such equipment. Others may be prevented from using a potentially valuable therapy due to lack of a controlled delivery system for nitric oxide. An inexpensive, simple alternative technique to chemiluminesence is described, which will allow most intensive care units the freedom to use inhaled nitric oxide if necessary.