Response to inhaled nitric oxide in focal versus diffuse lung disease

Purpose: Inhaled nitric oxide (NO) is a selective pulmonary vasodilator that decreases shunt and pulmonary artery pressures in patients with adult respiratory distress syndrome (ARDS). Whether inhaled NO would be equally effective in focal lung disease with severe hypoxia is an open question. Accordingly, we evaluated the effect of nitric oxide in hypoxic patients with focal versus diffuse disease on chest radiographs. Methods: Thirty one intubated patients had acute hypoxic respiratory failure defined as requiring a fraction of inspired oxygen (FIO2) greater than 50% and a positive end expiratory pressure (PEEP) greater than 5 mmHg. These patients were divided into two groups as having either one to two quadrant versus three to four quadrant involvement by chest radiograph. Baseline measurements were taken, including mean pulmonary artery pressure (PAP), the ratio of arterial oxygen pressure to fraction of inspired oxygen (PaO2/FIO2) and oxygen saturation (O2SAT). Inhaled NO was then incrementally increased every twenty minutes from 5 ppm to 80 ppm and patients was titrated to the optimal dose of NO. All patients were monitored for NO, nitrogen dioxide and methemoglobin levels. Results: Approximately, 59% (13/22) of patients with 3-4 quadrant involvement and 67% (6/9) of patients with 1-2 quadrant involvement showed an improvement of at least 10 mmHg in PaO2 with NO. Table 1 shows the average degree of improvement in both patient populations on inhaled NO. 3-4 quadrant 1-2 quadrant on CXR on CXR Δ in PaO2/FIO2 +29±30 +44±46 (mmHg) Δ in O2SAT (%) +4.0±3.1 +5.0±7.7 Δ in PAP -2.9±3.1 -3.6±3.7 (mmHg) Conclusions: Our findings demonstrate similar magnitude of improvement in oxygenation in patients with focal versus diffuse pulmonary infiltrates. PAP decreased minimally in both groups. Clinical Implications: These results indicate that inhaled NO therapy may benefit hypoxic patients with focal lung disease, in addition to patient with ARDS.