Resuscitation. 2000 Aug 1;45(3):221-4.
The text book of Pediatric Advanced Life Support of the American Heart Association recommends that a reservoir is used with a self inflating bag valve device. The figure in the book suggests that if such a device is connected to an oxygen supply, the oxygen will fill the bag first and then go on to fill the reservoir. However the valve structure of the self-inflating device does not permit active entry of oxygen into the bag, unless the bag is deflated and allowed to reinflate, drawing oxygen from the reservoir. We did this study to test the concentration of oxygen delivered in the first few breaths with the help of a Miniox-III oxygen monitor probe (MSA Medical Products, Pittsburgh, PA 15230) inserted into a self inflating bag (AMBU). Twenty-one percent oxygen is delivered with first breath and it rose to 42 and 58% with the second and third inflations, respectively. Eighty percent oxygen was achieved after eight reinflation cycles. We developed a formula to calculate the concentration of oxygen in the bag after each inflation effort, assuming that there was no passive diffusion of oxygen. We suggest that compressing the bag 8-12 times prior to putting the mask to the face of the patient will allow 80% oxygen to be delivered with first breath.