Patient Circuit Disconnections
Hazard [Health Devices Mar-Apr 1984;13(5-6):108-10]
For many years, tapered 15 and 22 mm connectors have been used in
breathing circuits to form joints between fittings and hoses; between various fittings in
ventilator, resuscitator, and anesthesia circuits; and for fresh gas hoses and reservoir
bags on anesthesia equipment. Through long experience, most users know that these
connectors are prone to accidental disconnections.
Until the time of this writing, these connectors and variations of them designed to prevent disconnection have
been based on standards such as American National Standards Institute (ANSI) ANSI Z79.2-1976.(1)
However, the ANSI standard, like its predecessor in 1961, is for metal fittings, not the
plastic fittings that are used more and more. For such fittings, no standard can include a
performance requirement to ensure a secure connection.
The U.S. Food and Drug Administration (FDA) and the Canadian Bureau of Medical
Devices reported the results of two extensive studies.(2,3) ECRI has also published an evaluation of disposable
anesthesia patient circuits (Health Devices Vol. 9, p. 3), which showed that
samples of all units failed our disconnect tests. The Canadian study, which showed the
same problem, stated, ". . . it is not evident that compliance with current
specifications as determined by gauge tests would improve the reliability of
An interim FDA-sponsored report by Arthur D. Little, Inc.,(5) which has been
widely distributed for comment, also finds that disconnections are not uncommon in
anesthesia and critical care.
Some users believe that connectors should separate before the tension
reaches a level sufficient to cause extubation. Thus, to satisfy all users, connectors
must lock, not leak; separate easily (when desired); and act as a mechanical
"fuse" by separating when tension approaches a level that would cause
extubation. The current standard would need more than "fine-tuning" to satisfy
these requirements. For example, the solution to one problem may not be a
"fuse," but rather a device that affixes the tracheal tube to the patient's head
and neck and transfers all stresses and torques from the breathing circuit to the patient,
not to the tracheal tube.
The Canadian report addresses the frequent use of adhesive tape to prevent
disconnections. Tape and adhesive residue can increase the seriousness of a disconnection
by making reconnection more difficult. However, the report finds that locking connectors,
although available and compatible with ANSI, Canadian,(6) and British(7) connection standards
and described by Spurring and Small,(8) are used infrequently.
Until a satisfactory connector system is developed and generally
available, we suggest the following:
- Provide in-service education that regularly
emphasizes how disconnections occur, case histories, risk analyses, and how
to anticipate and prevent these incidents. Repeat these points in other
appropriate patient care training programs (e.g., critical care, patient in
rotating bed, manipulation of patient with breathing circuit). Vigilance is
the key issue.
- Use monitor/alarm devices in all ventilator circuits to warn of
disconnections and other airway problems. Our evaluation of ventilation alarms (Health
Devices, Vol. 10, p. 204) recommends a unit that warns of low (disconnection) and high
airway pressures. Other recommended alarms monitor expired CO2 or expired
minute or tidal volume. Ensure that sensors for these alarms are in the correct position
in the breathing system and that controls are properly set to reduce false negative
indications. (The need for low pressure alarms to sense ventilator disconnections was
discussed in Health Devices, Vol. 12, p. 260.)
- Insist that your suppliers provide only breathing
circuit components (e.g., connectors, adapters, other fittings)
that meet the requirements of American Society of Testing
and Materials (ASTM) ASTM F1054-87. Also, use connectors with lugs or other
features that make them easy to grip for tightening and loosening without
causing injury to the patient. Standardize on fittings that you have tested
for ease of use with your own equipment, and discard all others that have
accumulated over the years.
- Use locking connectors for applications (e.g., fresh gas hoses) that
must remain tight. "Mechanical fusing" is unacceptable for these
- American National Standards Institute (ANSI).
American national standard for tracheal tube connectors and adapters. ANSI
- Cooper JB et al. Accidental breathing system
disconnections (A.D. Little: Interim report to Food and Drug Administration,
- Neufeld PD, Johnson DL, deVeth J. Safety of anesthesia breathing circuit
connectors. Can Anaesth Soc J 1983;30:646-52.
- Cooper JB et al. Supra note 2.
- Standards Council of Canada. Tracheal tube
- British Standards Institution. Breathing
attachments for anaesthesia apparatus, British Standard 3849:1965.
- Spurring PW, Small LFG. Breathing system disconnexions and
misconnexions. Anaesthesia 1983;38:683-8.
- Breathing Circuit Adapters [10-123]
- Breathing Circuits [15-562]
- Breathing Circuits, Anesthesia [10-139]
- Breathing Circuits, Oxygen Administration [16-987]
- Breathing Circuits, Ventilator [15-003]
Cause of Device-Related Incident
User error: Improper connection
Support system failures: Failure to train and/or credential; Use of inappropriate devices
Mechanism of Injury or Death