Objective: To discuss the mechanism of severe hypoxemia that induced with acute respiratory distress syndrome (ARDS) by way of observing the effective local blood perfusion in different lung areas of ARDS rabbits.
Methods: ARDS rabbit models were established by injecting oleic acid through central vein, and the results of effective local blood perfusion in different areas of rabbit lung (upper area, abdominal area, and dorsal area of right lung)with PIM-II laser perfusion imager and arterial blood gas under different ventilation modes [large tidal volume ventilation, low tidal volume ventilation + positive end-expiratory pressure (PEEP), prone position + large tidal volume ventilation, and prone position + low tidal volume ventilation + PEEP] were measured.
Results: The results of oxygenation index were significantly getting worsen after lung injury, and after receiving lung protective ventilation (including low tidal volume + PEEP, prone position + low tidal volume + PEEP), the indexes were taking a turn to the better. After lung injury, the results of effective local lung blood perfusion index (including upper area, abdominal area, and dorsal area) under right lung of ARDS rabbits decreased in the experimental ARDS groups. The results of experimental dorsal area group decreased most significantly, and the results of experimental upper area group changed most lightly. We observed that the effects of receiving low tidal volume + PEEP ventilation were not as good as prone position + low tidal volume + PEEP ventilation in the dorsal area of the rabbit lung compared to the results of effective local area lung blood perfusion index between two ventilation modes, there showed significantly differences in statistics.
Conclusion: We indicated that the one of the main mechanisms of severe hypoxemia in ARDS might be caught by the shunt between pulmonary artery and pulmonary vein just like physiological right to left shunt, which caused severe ventilation/perfusion disturbance. Both low tidal volume ventilation + PEEP and prone position + low tidal volume ventilation + PEEP had good effects on ameliorating local blood perfusion, and the effects of ventilation mode of prone position + low tidal volume ventilation +PEEP might be better.