Oxygen enrichment of bag-valve-mask units during positive-pressure ventilation: a comparison of various techniques

Bag-mask devices are used frequently to provide patients with positive-pressure-assisted ventilation. To increase the percentage of oxygen delivered (FDO2) from the bag, supplemental oxygen must be provided by way of an oxygen inlet nipple attached to the unit. Using ten medical volunteers and a test lung with oxygen analyzer, we studied the effect of several variables on the FDO2 and determined the most effective reservoir that would provide the highest consistent FDO2 from the ventilating port of the bag. An FDO2 of 1.00 was consistently provided by the 2.5-L bag reservoir and a demand-valve set-up attached to the reservoir port of the ventilating bag. Bag refill time significantly affected the FDO2 when no reservoir or corrugated tube reservoirs were used. Corrugated tube reservoirs were found to be more sensitive to all variations in ventilatory technique and to oxygen flow rates. From our findings we recommend that corrugated tube reservoirs not be used for oxygen supplementation, as they are sensitive to variations in ventilatory technique and cannot alert clinicians to problems with oxygen flow. While both the 2.5-L bag reservoir and demand-valve provide a consistent FDO2 of 1.00, the demand valve has the advantage of audible filling of the ventilating bag as well as being compact and independent of ventilatory technique.