To evaluate the influence of reservoir bag types, volumes and previous use on the
peak pressures (Pmax) and the times to develop 30 cmH2O pressure (P30) within a nonrebreathing system with a closed adjustable pressure-limiting
In vitro study using three-way factorial design with repeated measure on one factor.
A total of 75 new anesthesia reservoir bags (five types, three volumes, five bags
from each type × volume). The bag types were reusable latex (RL), disposable latex
(DL) and three disposable neoprene (DN-1, DN-2 and DN-3).
Each bag was tested three times (treatments): new, after prestretching and 1 week
later. The bags were attached to a Bain system and anesthesia machine with closed
APL valve and patient port with O2 flow 2 L minute–1 until Pmax was reached. The Pmax and time to reach P30 values were determined from
recorded pressure traces. General linear mixed model analysis was used to examine
the effects of bag type, volume and treatment. One-sided 95% upper prediction limits
of Pmax were calculated to test the null hypothesis that predicted Pmax of new bags
would be ≥ 50 cmH2O for each factor combination.
RL bags were the least and DN-3 bags were the most compliant. Prestretching increased
compliance in all bag types. Smaller bags of RL, DL and DN-1 were less compliant than
larger ones. The predicted Pmax values were < 50 cmH2O only for DN-3 bags after prestretching. The time to reach P30 was critically low
when using 0.5 L bags (median 17 seconds).
Conclusions and clinical relevance
To minimize the risk of barotrauma, highly compliant reservoir bags (e.g. DN-3) are
recommended and reusable bags should be avoided. Bags should be prestretched before
first use, 0.5 L bags should be avoided and fresh gas flow minimized.