Pulmonary oedema reduces the effectiveness of HBO (pulmonary shunt effect) and in turn HBO may even aggravate it (hyperoxic cardiac decompensation).
In a 4-year series of 1,850 cases of CO poisoning, 120 patients (6.5%) suffered pulmonary oedema. These patients could be divided into two groups:
- cardiac-related: This included 92 cases (77%); patients were older (aged 71 + 13 years), had frequently a previous history of heart failure. For these patients, pulmonary oedema was an indication for HBO, since HBO accelerates myoglobin detoxification. - non-cardiac related: The 2nd group included 28 younger patients (aged 18 + 11 years), usually without previous heart pathology. The mechanism of pulmonary oedema was non-cardiogenic -either by toxic effect of the CO, or aspiration of gastric content (in 20 out of 28 patients). In these cases, the risk-benefit decision regarding HBO was made on the basis of reducing neurological risk in exchange for possibly increasing the pulmonary problems.
In our experience, comatose patients were always provided HBO without aggravating existing pulmonary oedema. However, the proviso is that only multi-place hyperbaric chambers that are equipped for intensive care should be used for such treatment so that potential complications can be managed (e.g., ventilation with positive end expiratory pressure; continuous positive pressure ventilation; haemodynamic monitoring, etc).
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