[Inhaled nitric oxide test for patients with stable chronic obstructive pulmonary disease: value and feasibility]

Patients suffering from chronic lung disease (CLDP) often develop secondary pulmonary hypertension (HP), which contributes to right ventricular dysfunction and worsens their prognosis. In order to evaluate the severity of this HP, pharmacodynamics tests are periodically proposed to these patients. Therefore, the administration of vasodilators is limited by systemic and pulmonary side-effects. Inhaling nitric oxide gas (NO) has been reported to induce a selective pulmonary vasodilation. The purpose of this study was to evaluate the safety and efficacy of an inhaled NO test perfected in our service. Sixteen CLDP were investigated in the absence of acute pulmonary failure. All had severe pre-capillary HP, confirmed after placement of a thermodilution pulmonary-artery catheter (mean pulmonary artery pressure >20 mmHg, pulmonary capillary wedge pressure >12 mmHg). Each subject breathed spontaneously NO in a concentration of 10 ppm for 15 minutes. They were connected through a facial mask and a one-way valve put on the inspiratory connection of a ventilator (Drager-Evita), to a tank of nitrogen with a NO concentration of 900 ppm. Hemodynamic variables and gas exchange were measured before, during and after gas inhalation. The inspired fractions of NO and NO2 were determined using a Polytron analyser (Drager). The methemoglobin levels were measured with spectrophotometry (OSM3). Inhaled NO acts as a selective pulmonary arterial vasodilator, without systemic effect. The action on the shunt is variable. Methemoglobin levels are remained <0.01%. All the patients were satisfied with the way of NO administration. In view of the lack of systemic effects, its seems that the NO inhaled test proposed in this study may be used accurately to evaluate the HP of chronic lung disease patients.