Cause of Device-Related Incident
Device factors

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

Device Factors
Improper maintenance, testing, repair, or lack or failure of incoming inspection; Improper modification

Document Type
Hazard Reports

External Factors
*Not stated

Mechanism of Injury or Death
Various

Support System Failures
*Not stated

Tampering and/or Sabotage
*Not stated

User Errors
*Not stated

UMDNS
Adhesives [10-034]; Anesthesia Unit Ventilators [10-145]

Damage to Plastic Components from Loctite



Hazard [Health Devices Jul-Aug 1989;18(7-8):288]

Problem

During a preventive maintenance check of an anesthesia ventilator, a member hospital found that a low-pressure alarm malfunctioned because of a broken pressure switch. Two other pressure switches in the unit were also found to be damaged. The damage apparently occurred after the previous preventive maintenance inspection. Although the low-pressure alarm problem would have been detected if ECRI's Pre-Use Checklist for Anesthesia Units had been used, the malfunction had not been brought to the attention of the clinical engineering department in the hospital. Proper operation of pressure alarms is essential to rapid detection of high pressure, which may cause barotrauma, or low pressure, which could indicate a disconnection.

Discussion

The manufacturer of the ventilator and alarms investigated the problem and found that it was caused by Loctite, which had been applied to the pressure-setting screws of the pressure switches. The Loctite, which had been used to hold screw settings, caused the polysulfone plastic body parts of the switches to deteriorate and crack, releasing the pressure-compensating spring under the set screw and causing the switches to fly apart. The manufacturer's experience has been that the screws hold their settings without Loctite.

Loctite, like other similar products, is available in different formulations for specific applications. For example, Loctite 404 can be used to join the ends of synthetic rubber O-rings. Removable Loctite Threadlocker 242 carries the warning "May attack some plastics." With any such compounds, users must know the materials on which they will be used and the possible adverse interactions.

Recommendations

  1. When using Loctite, be sure that it will contact only metal parts; or, if it will contact plastic parts, be sure that they are resistant to the formulation of Loctite being used. Loctite Corp. offers the guide How to Bond Plastics, which can be used to help users select the proper product. The guide states that Loctite's instant adhesives, such as SuperBonder materials, can be used with most plastics.
  2. Always check with the manufacturer of a device before adding a new maintenance step.

UMDNS Terms

  • Adhesives [10-034]
  • Anesthesia Unit Ventilators [10-145]

Cause of Device-Related Incident

Device factors: Improper maintenance, testing, repair, or lack or failure of incoming inspection; Improper modification

Mechanism of Injury or Death

Various


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