Crossed Connections in Medical Gas Systems
Hazard [Health Devices Jul 1984;13(9):22]
ECRI received two reports of cross-connected medical gas lines. In both
reports, nitrous oxide and oxygen couplers had been unscrewed at the threaded fittings
that connect the back of the coupler housing to the gas supply hose. When reassembled, the
couplers were reversed. While both reports involved one brand of
quick-connect hose couplers, similar cross-connections can occur with virtually all other
manufacturers' systems. The purpose of this Hazard Bulletin is not simply to discuss the
two specific incidents, but to remind hospitals how easily (and innocuously) cross
connections can occur in any medical gas system.
The first incident occurred after attempted modification of an anesthesia
machine's gas supply lines and resulted in the deaths of two patients. Legal action
surrounding this incident was previously described in the literature (Biomed Saf
1984;14 [Feb 5]:15-6).
In the second incident, the quick-connect couplers had been removed so
that the cover plate of a ceiling-mounted gas hose reel system could be installed just
prior to occupancy of a new operating room suite. Although the gas system had already
undergone final inspection and certification, the seemingly trivial installation of the
cover plate required the couplers to be temporarily removed from the hoses.
Improper replacement of the couplers led to crossed connections.
Fortunately, a vigilant anesthesia department double-checked the medical gas system and
noticed the crossed connections before clinical use.
Many types of quick-connect couplers have these
threaded fittings. The threaded fittings are the same design for many manufacturer's couplers, and a
variety of crossed connections are possible between oxygen, vacuum, nitrous oxide, air,
and carbon dioxide.
The coupler face plates are usually color coded to
correspond with the color of the gas hose or outlet. While this decreases the risk of
misassembly and undetected crossed lines, it may not always be effective protection, as
demonstrated by the reported cases.
We believe that this hazard exists with other manufacturers' couplers, as
well as other types of medical gas system connectors. Any fittings that are accessible to
service personnel or users and are not gas-specific throughout their design (e.g., pin
indexed, unique threading) have the potential for crossed connections. We have also
investigated a similar problem involving crossed connections with duplex cover plates for
gas wall outlets (Health Devices
10:222, July 1981).
While the reported incidents occurred during system installation or
modification, many quick-connect couplers must also be disassembled at threaded fittings
to periodically replace O-rings in the connector. This increases the likelihood that they
may be reconnected to the wrong gas line or inadequately tightened.
We believe that many couplers or connectors in use may not be adequately
tightened. In a ECRI survey of a hospital's operating rooms, 13 of 160 couplers could be
loosened by hand. Loose or hand-tightened threaded fittings could be used improperly as
the primary disconnection point of the connector.
According to the
manufacturer or the incident couplers, some models of its quick-connect couplers now have
gas-specific fittings at the back of the coupler. Couplers that require disassembly to replace
O-rings are no longer available. New couplers allow access to the O-rings through
the front panel. Threaded fittings are factory tightened and cannot be unscrewed by hand.
The potential for these incidents underscores the importance of a complete final inspection of the gas
system (in accordance with National Fire Protection Association [NFPA] NFPA 56F) following any repair,
maintenance, or modification of a medical gas system. We believe that, ideally, the
threaded or internal design for all connectors should be unique for each type of gas or
secured so that the connectors cannot be removed by hand or with simple hand tools.
However, because many connectors with the potential for easy removal are in widespread use
and may continue to be used in the future, hospitals must ensure that these connectors are
reassembled correctly, tightened securely, and inspected after any disconnection prior to
- Immediately inspect every gas supply hose coupler
and connector throughout the hospital and ensure that threaded fittings
cannot be disassembled by hand. Mark all connectors with a surface sealant
(e.g., Glyptol) that will indicate (i.e., with a broken seal) if a threaded
connector has been disassembled. Also, ensure that all connectors and hoses
are color coded.
- Whenever any part of a medical gas system is
modified or serviced, alert the department using the equipment and ensure
that the system is inspected by qualified personnel before use. Inspect only
after all work on the system has been completed. If the system cannot be
inspected immediately, prominently label the connectors (e.g., place tape
over each outlet) to warn users that the system has been serviced and must
be inspected before use.
- When replacing O-rings in the connectors,
disassemble only one connector at a time. Retighten all fittings securely,
so that they cannot be removed by hand.
- In accordance with good clinical practice, always use an oxygen analyzer
during inhalation anesthesia.
- Fittings/Adapters [11-726]
- Fittings/Adapters, Pneumatic, Quick-Connect
- Medical Gas and Vacuum Systems [18-046]
Cause of Device-Related Incident
User errors: Accidental misconnection; Failure to perform pre-use inspection
External factor: Medical gas and vacuum supplies
Support system failure: Lack or failure of incoming and pre-use inspections
Mechanism of Injury or Death
Barotrauma; Suffocation; Wrong drug