Arterial Oxygenation was Determined by the Volume Partition of Normal Aeration Region after Sustained Inflation in Acute Respiratory Distress Syndrome

  Objective  To analyze the correlation of arterial blood gas with pulmonary CT scan image after sustained inflation (SI) with the attempt to explore the optimal recruitment maneuvers (RMs) in acute respiratory distress syndrome.

  Methods  Dynamic pulmonary CT scan was performed to monitor the intrapulmonary gas volume and distribution during increment and decrement of airway pressure gradually in 10 warm-saline-lavaged New Zealand rabbits. CT scan was analyzed by Images-J software. In order to explore optimal airway pressure for opening lung and optimal positive end-expiratory pressure (PEEP) for maintaining lung open, five different SIs were implemented individually and randomly, and rabbits' arterial blood gases were measured in 2 and 20 minutes after every SI. Pulmonary CT scan and PaO₂ under different airway pressure were combined to be analyzed.

  Results  After different airway pressure of SI and equal PEEP ventilation, PaO₂ was increased accompanied with airway pressure of SI both in 2 and 20 minutes after RMs (P < 0.05). When PaO₂ was combined with CT images, we found PaO₂ was positively correlated with the volume partition of normal aeration region (r=0.597, P=0.001), negatively correlated with the insufficient aeration region (r=-0.592, P=0.001) and nonaeration region (r=-0.475, P=0.012), while not correlated with the overdistension region (r=0.202, P=0.311). While after equal airway pressure of SI and different PEEP ventilation, the difference of PaO₂ was not significant in 2 minutes after RMs (P>0.05), and PaO₂ was increased accompanied with PEEP in 20 minutes (P < 0.05). In this situation, we found PaO₂ was positively correlated with the volume partition of normal aeration region (r=0.635, P=0.000), negatively correlated with the insufficient aeration region (r=-0.609, P=0.000) and nonaeration region (r=-0.544, P=0.002), while not correlated with the overdistension region (r=0.058, P=0.762).

  Conclusions  High airway pressure is needed for opening up the lung and keeping the lung open. Arterial oxygenation is determined by the volume partition of normal aeration region after SI.