RESUMO
The AMBU bag is a useful equipment at the cardiopulmonary resuscitation (CPR) or the respiratory therapy. The AMBU bag eonsists simply of a self-reflating bag, a patient valve and a inlet valve. The patient valve is a non-rebreathing valve and the self-inflating bag is a recoiled rubber bag. The inlet valve on the posterior site of self-inflstion bag is closed during the bag is squeezed, and opened during the bag is released. During reflation of bag, fresh room air through the one-way valve and fresh oxygen through the orifice for oxygen supply will mix. Therefore the inspiratory oxygen concentration is decided by a speed of re- flation of the self-reflating bag. We measured inspiratory oxygen concentration during AMBU bag ventilation under different inspiration : expiration (I:E) ratio, frequency of venti- lation, ventilatory volume and flow rate of oxygen. The results were that factors increase a inspirstory oxygen concentration are 1) decrease of I:E ratio, 2) decrease of frequency of ventilation, 3) decrease of ventilatory volume, 4) inerease of flow rate. We found that haste of physician makes frequent squeezing of AMBU bag and the haste results a decrease of inspiratory oxygen concentration.