Respiratory insufficiency in chest injuries

1. Arterial blood gas tensions have been studied in 50 cases of chest crush injuries. Hypoxia was present in most of these cases, but raised PCO 2 was present in only six cases and in no case was it grossly abnormal. In most cases the PCO 2 was below normal limits. Standard bicarbonate was normal in most cases. 2. The alveolar-arterial oxygen tension difference was increased in all nine cases studied but the ratio of dead space/tidal volume was within normal limits in four out of seven cases where this was estimated. 3. Ten patients treated with 100% oxygen for 20 min failed to show a normal rise in oxygen tension, suggesting that the hypoxia in many cases of chest injury is from a true shunt presumably due to blood perfusing atelectatic areas of lung or to pulmonary oedema. 4. These shunts persisted in many cases for a considerable time, even though there was no radiological evidence of atelectasis, and some were present for as long as 6 weeks after the injury.