The purpose of this report is to describe a potentially hypoxic event
which occurred during mask induction with the Bain circuit in a health
y, ASA I boy. Failure of induction occurred because a pop-off weight f
rom a bubble bottle was lodged in the elbow connecting the Bain circui
t to the mask and prevented gas flow. Pethick and Foex-Crampton Smith
tests of the Bain circuit could also have missed this condition. Such
an anaesthetic mishap could occur with any breathing circuit which is
re-used. Although there war no serious misadventure, the potential for
an hypoxic complication with either intra-venous induction of anaesth
esia, or dislodging of the weight into the airway was significant. We
conclude that the standard rests of system patency do not ensure safet
y.