Cause of Device-Related Incident
Device factors; External factors; Tampering and / or sabotage; User errors

Clinical Specialty or Hospital Department
Anesthesia; Obstetrics and Gynecology; OR / Surgery

Device Factors
Device interaction

Document Type
Hazard Reports

External Factors
Medical gas and vacuum supplies

Mechanism of Injury or Death
Barotrauma; Overdose; Suffocation; Underdose

Support System Failures
Lack or failure of incoming and pre-use inspections

Tampering and/or Sabotage

User Errors
Failure to perform pre-use inspection; Improper connection

Anesthesia Unit Gas Scavengers [10-142]; Anesthesia Units [10-134]; Breathing Circuits, Anesthesia [10-139]

Pre-Use Testing Prevents 'Helpful' Reconnnection of Anesthesia Components

Hazard [Health Devices May 1987;16(5):178]


A member hospital reported that a 19 mm scavenging transfer hose on an anesthesia machine became disconnected. Someone who was not familiar with anesthesia or scavenging circuits found the disconnection and, being well meaning, attached it to a 3/4-inch nut on the bottom of the absorber. This improper connection left the scavenging system open to the atmosphere; thus, the waste anesthesia gases could have discharged into the OR. Fortunately, pre-use inspection and testing of the anesthesia system revealed the hazardous situation.


ECRI has investigated and reported on incidents in other member hospitals in which inadvertent misconnections occasionally resulted in patient injury, as in two of the following examples:

  • A rubber bottle top for a vial of IV solution was found to be blocking a scavenging outlet of a breathing circuit adapter. It was removed, and no patients were harmed. Apparently, it had been dropped on the floor the day before and picked up by a member of the housekeeping staff, who inserted it into the nearest suitable-looking hole.
  • An exhalation valve disk was lost in the valve body but was not reported or retrieved and replaced. When a new disk was put in the correct position without first extricating the displaced disk, the patient suffered a pneumothorax. (See Health Devices 11:325-6.)
  • During anesthesia, an accidentally disconnected vacuum hose was misconnected directly to the scavenging fitting on the anesthesia ventilator. The high vacuum held the overflow valve shut, preventing discharge of excess anesthetic gas, and the patient suffered a pneumothorax. A similar hazard was previously reported in the literature.
  • Two anesthesia breathing circuit hoses were reversed, making it impossible for the ventilator to deliver any gas to a patient. The ventilator hose was misconnected to the inspiratory valve fitting. During use, the bellows could fill with fresh gas, but none could be delivered to the patient. The patient was not ventilated until the misconnections were discovered and the two hoses were reconnected to the proper fittings.

In the last three reports, the patients were not adequately ventilated until they were disconnected from the circuit or the problem was corrected. Two of the problems would have been found by adequate pre-use testing of the ventilators. The fact that the disconnection in the fourth case occurred during anesthesia underscores the need for users to know how scavenging circuits are connected and to check them for secure connections before using a system. In addition, unauthorized personnel should be instructed never to reconnect hoses.


  1. A disconnected hose end is easier to recognize than improperly connected or interchanged hoses. Therefore, personnel who work around anesthesia equipment, but are not qualified to connect and check circuits, should not try to reconnect a hose or other component that is found disconnected. Even those who inadvertently cause a disconnection while moving equipment should not attempt reconnection. Such conditions should be reported to a qualified individual, and anyone finding a disconnection should leave a note on the machine or tape the loose end conspicuously to the flat top panel.
  2. Pre-use checks of anesthesia equipment should include a general survey of the system for missing, misconnected, disconnected, or loosely connected hoses and other components. The equipment should also be checked for proper operating condition, including simulated ventilation of a lung, by a procedure such as the one outlined in ECRI's Pre-Use Checklist for Anesthesia Units.


  • Anesthesia Unit Gas Scavengers [10-142]
  • Anesthesia Units [10-134]
  • Breathing Circuits, Anesthesia [10-139]

Cause of Device-Related Incident

Device factor: Device interaction

User errors: Failure to perform pre-use inspection; Improper connection

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; Overdose; Suffocation; Underdose

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