Effect of inhaled nitric oxide in combination with almitrine on ventilation-perfusion distributions in experimental lung injury

Objective:To investigate a possible additive effect of combined nitric oxide (NO) and almitrine bismesylate (ALM) on pulmonary ventilation-perfusion ((V) over dot(A)/(Q) over dot) ratio. Design: Prospective, controlled animal study. Setting: Animal research facility of a university hospital. Interventions: Three conditions were studied in ten female pigs with experimental acute lung injury (ALI) induced by repeated lung lavage: 1) 10 ppm NO, 2) 10 ppm WO with 1 mu g/kg per min ALM, 3) 1 mu g/ kg per min ALM. For each condition, gas exchange, hemodynamics and (V) over dot(A)/(Q) over dot distributions were analyzed using the multiple inert gas elimination technique (MIGET). Measurement and results: With NO + ALM, arterial oxygen partial pressure (PaO2) increased from 63 +/- 18 mmHg to 202 +/- 97 mmHg while intrapulmonary shunt decreased from 50 +/- 15% to 26 +/- 12% and blood flow to regions with a normal (V) over dot(A)/(Q) over dot ratio increased from 49 +/- 16% to 72 +/- 15%. These changes were significant when compared to untreated ALI (p < 0.05) and NO or ALM alone (p < 0.05), although improvements due to NO or ALM also reached statistical significance compared to ALI values (p < 0.05). Conclusions: We conclude that NO + ALM results in an additive improvement of pulmonary gas exchange in an experimental model of ALI by diverting additional blood flow from non-ventilated lung regions towards those with normal (V) over dot(A)/(Q) over dot relationships.