Causes of Concern for External Defibrillators
The following are examples of safety concerns:
Engineering Design Practices
Review of past recalls suggests that manufacturers of external defibrillators sometimes use design practices that lead to inconsistent device performance. In one example, a manufacturer designed its voltage-monitoring circuit to draw power from the same source it was intended to monitor. Because of this design, a momentary drop in the voltage caused a false signal to shut down the AED and the device was unable to deliver a shock, which may have caused a patient’s death. In another case, a manufacturer used the wrong kind of component in one of the circuits, causing the device to be susceptible to interference from noise coming from the device’s power line. Good engineering design practices also require user interfaces (like dials, monitors, alarms, and connectors) that meet users’ needs. Recent surveys suggest that improvements in user interfaces may be warranted.
The FDA’s analysis of recalls and inspections identified problems in how manufacturers test and incorporate components used in the manufacture of external defibrillators, as well as how they evaluate changes to the device before they are implemented to assure that device modifications do not adversely impact the safety and effectiveness of the technology. Between 2005 and 2010, the FDA issued nine warning letters to external defibrillator manufacturers, seven of which cited failures to appropriately control these aspects of their manufacturing process.
Communicating Systemic Problems to Users
The FDA has observed cases where external defibrillator manufacturers have used a “fix-on-fail” strategy to deal with the problems they find. “Fix-on-fail” refers to the industry practice of identifying and trending problems on a case-by-case basis and repairing individual devices rather than communicating the problem to all users as part of the recall process.
The FDA has also observed different industry practices for communicating the risk of device malfunctions to users. Some firms calculate these risks as the number of device failures out of the total number of months of device use, while others calculate the number of failures or deaths out of the number of products in distribution. These differences make it difficult for users to understand how common a problem is.
Adverse Event Reporting
From January 2005 through May 2010 the FDA received more than 28,000 adverse event reports for external defibrillators, including malfunctions, patient injuries and deaths. The FDA found the amount and quality of information in these reports to be highly variable across manufacturers. For some, a significant proportion of their malfunction reports failed to contain adequate information about the root cause of the problem, which limits the FDA’s ability to identify, track, and address device safety problems and suggests that these manufacturers may not have conducted appropriate follow up in some cases.
Between 2005 and 2010, the FDA issued nine warning letters to external defibrillator manufacturers, four of which cited the firms for failing to appropriately report events.