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Abstract
Sir,
We are reporting a rare but critical incident wherein water was detected in a nitrous
oxide (N2O) flowmeter. This incident occurred in the gynecology OR where the anaesthesiologist
used an O2 / N2O mixture with a volatile agent for maintenance of anaesthesia. After
about one to two minutes of opening the N2 O flowmeter control valve, a spurt of yellowish
colored fluid from the needle valve filled the flowmeter barrel and the bobbin jumped
erratically up and down on it. The fluid got accumulated over the bobbin making it
stick to the side of the barrel and cease its rotations [Figure 1]. The total flow
of the gas from the common gas outlet also decreased, as evidenced by the empty feel
of the ventilating reservoir bag. The N2O was immediately shut off and patient was
maintained on 100% O2 from the cylinder supply, while ventilating with a self-inflating
resuscitation bag. Fortunately, the fluid did not travel distally into the breathing
system. On disconnection of the N2O hose from the terminal unit and connecting yoke,
some water was found emerging from the yoke adapter [Figure 2]. On purging the terminal
units no contamination of gases with any fluid was observed. No problem was encountered
after using new hoses and a new anaesthesia machine.
Figure 1
Nitrous oxide flowmeter control valve showing the `stuck bobbin´nd water level on
top of the bobbin
Figure 2
Water emerging from the yoke adapter of the nitrous oxide hose
Subsequent investigation revealed that on the previous day gas hoses of the same OR
were disconnected for maintenance. Subsequently, only the O2hose was connected by
the maintenance staff and the N2O hose remained disconnected from the terminal unit
overnight. It was possible that the water vapour entering from the atmosphere could
have condensed under pressure on reconnection in the morning. A routine morning check
of the machine did not reveal any problem due to the small quantity of water, which
took some time to reach up to the flowmeter. A similar incident had been reported
earlier, where a central air pipeline was found contaminated by water condensation,
as it was kept open to atmosphere during maintenance.[1]We feel that purging of hoses
must be done with central pipeline dry gases before connecting the yoke adapter to
the machine for prevention of this problem. In addition to patient safety concerns,
any water in the gas supply would also lead to malfunction of vaporisers and a major
break down in the modern anaesthesia machines with electronic components.
Postgraduate Institute of Medical Education and Research, Chandigarh - 160 012, India
Author notes
Address for correspondence: Dr. Virendra Arya, Department of Anesthesia and Intensive Care, PGIMER, Chandigarh
- 160 012, India. E-mail:
aryavk_99@
123456yahoo.com
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