Introduction

The study aimed to estimate the association between thoracic injury severity as evaluated by computed tomography (CT) and arterial blood gas and acid base status in dogs sustaining natural, blunt trauma.

Methods

Twenty-four dogs were assessed by thoracic CT scan and arterial blood gas analysis between 4 and 24 hours after the traumatic incident. Extrathoracic injury did not play a large part in the status of this group. Fifteen clinically normal dogs were sampled as a comparison group for the trauma cases. Thorax injuries were classified as pleural space, rib cage or pulmonary and each of these three components of the thorax were scored according to severity. Dogs' blood gas and acid base status was evaluated for statistical difference from normal.

Results

There was a significant difference between normal controls and the trauma group with respect to arterial pO₂ (p < 0.001) and the calculated variables of arterial blood oxygenation: pO₂/FIO₂ (p = 0.033) and pAO₂–paO₂ (p = 0.015). There was also a significant correlation (Spearman rank correlation, p < 0.05) between the composite lung score and pleural score and the variables of arterial oxygen status. The pCO₂ was not significantly different from any of the thoracic injury variables indicating normal alveolar ventilation. Acid base imbalances were variable and considered clinically insignificant.

Conclusions

Pulmonary and pleural injury significantly affected blood oxygen status, and this was strongly correlated with what was observed on CT imaging. Trauma thus did not affect alveolar ventilation (pCO₂ was unaffected) but did cause a clinically significant ventilation perfusion mismatch (oxygen status was abnormal).