Cause of Device-Related Incident
Support system failures; User errors

Clinical Specialty or Hospital Department
Anesthesia; Clinical/Biomedical Engineering; Nursing; Pulmonary / Respiratory Therapy

Device Factors
*Not stated

Document Type
Hazard Reports

External Factors
*Not stated

Mechanism of Injury or Death

Support System Failures
Failure to train and / or credential; Use of inappropriate devices

Tampering and/or Sabotage
*Not stated

User Errors
Improper connection

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]

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 connections."(4)

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:


  1. 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.
  2. 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.)
  3. 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.
  4. Use locking connectors for applications (e.g., fresh gas hoses) that must remain tight. "Mechanical fusing" is unacceptable for these applications.


  1. American National Standards Institute (ANSI). American national standard for tracheal tube connectors and adapters. ANSI Z79.2-1976.
  2. Cooper JB et al. Accidental breathing system disconnections (A.D. Little: Interim report to Food and Drug Administration, October 1983).
  3. Neufeld PD, Johnson DL, deVeth J. Safety of anesthesia breathing circuit connectors. Can Anaesth Soc J 1983;30:646-52.
  4. Ibid.
  5. Cooper JB et al. Supra note 2.
  6. Standards Council of Canada. Tracheal tube connectors. CAN3-Z168.2-M82.
  7. British Standards Institution. Breathing attachments for anaesthesia apparatus, British Standard 3849:1965.
  8. 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


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