Comparison of work of breathing on high gas flow and demand valve continuous positive airway pressure systems.

Using on-line computer analysis, the work of breathing (WOB) was measured in ten normal subjects breathing through four continuous positive airway pressure (CPAP) circuits. Two systems (Emerson ventilator) and MGH elastic loaded reservoir bag (ELRB) were high continuous flow systems and two (Puritan-Bennett MA-2 and Bourns Bear Ventilators) were demand valve circuits. Mean values for the WOB were similar with either of the two continuous high flow systems (Emerson 0.41 +/- .21 kg . m . L-1; ERLB 0.49 +/- .29 kg . m . min-1) and significantly lower than with the two demand valve systems (MA-2 0.89 +/- .40 kg . m . min-1; Bourns .71 +/- .30 kg . m . min-1).