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 μg/kg per min ALM, 3) 1 μg/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.