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(A)/Q) 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 NO with 1 microg/kg per min ALM, 3) 1 microg/ kg per min ALM. For each condition, gas exchange, hemodynamics and V(A)/Q 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(A)/Q 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(A)/Q relationships.