Ambient oxygen concentrations during simulated cardiopulmonary resuscitation

Oxygen concentrations were measured at 12 points around a cardiopulmonary resuscitation practice mannequin following simulated ventilation with a self-inflating bag, a 'Waters' bag and a ventilator to determine whether increased oxygen concentrations may contribute to the risk of combustion from arcing defibrillator paddles. Ventilation was simulated using either a mask or via a tracheal tube fitted to the airway. The head of the mannequin rested upon a 10-cm-high pillow. Gas sampling took place after 5 min of ventilation with subsequent removal of the ventilatory device and placement on the pillow to the left of the mouth, with the tubing of the device removed to a point 1 m behind the mouth and with the device left connected to the tracheal tube. Gas was sampled after using all devices at oxygen flows of 10l.min-1 and 15l.min-1. Slightly increased oxygen concentrations were noted over the anterior chest after placement of all devices on the pillow at the higher flow. Concentrations of greater than 30% were measured in the left axilla after placement of all devices on the pillow at both flows. No increase in oxygen concentration was seen when the devices were either left connected to the tracheal tube or removed to a distance of 1 m. It would appear that leaving a patient connected to a ventilator poses no increase in risk of fire from ignition of combustible material in an oxygen-enriched atmosphere during defibrillation. Disconnecting any device which continues to discharge oxygen and leaving it on the pillow before defibrillation is dangerous.