Inverse ratio ventilation in adult respiratory distress syndrome: an experimental study in dogs regarding gasometric and hemodynamic aspects

Cardiorespiratory values were measured in 14 mongrel dogs with adult respiratory distress syndrome (ARDS), before and following the pressure controlled inverse ratio ventilation (IRV) at an inspiratory to expiratory ratio of 2:1. After the administration of oleic acid, the dogs developed metabolic acidosis, arterial hypoxemia, decreased compliance and cardiac index. There were no significant changes in any hemodynamic or arterial blood gases with the institution of inverse ratio ventilation. We concluded that the IRV with I:E of 2:1 and respiratory ratio of 12 bpm did not improve the arterial blood gases in ARDS. We speculate that to get better oxygenation in this model of mechanical ventilation we'll need increase the respiratory ratio to decrease the expiratory time and provoke the intrinsic positive end expiration pressure (PEEP).