Anaes Vivas · Medical gases & gas supply
Data viva — the N2O cylinder pressure gauge
A data viva on the N2O cylinder pressure — the 52 bar stays constant until the liquid is exhausted (the saturated vapour pressure). The gauge is useless for the content. Weigh the cylinder.
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ANZCAFRCAABAEDAIC
Prompt
A nitrous oxide cylinder on the anaesthetic machine. The pressure gauge reads 52 bar (the full-cylinder pressure). The cylinder has been in use for 30 minutes at 3 L/min. The anaesthetist believes the cylinder is still full because the gauge has not moved.
Stimulus
An N2O cylinder on the machine. The pressure gauge reads 52 bar — the same as at the start of the case, 30 minutes ago. The N2O has been flowing at 3 L/min for 30 minutes (90 litres used). The anaesthetist concludes the cylinder is still full. Is this reasoning correct?
References1ShowHide
- [2]Tiviraj S, et al. Development of An Assessment Test for An Anesthetic Machine. J Med Assoc Thai, 2016.PMID 27501622