The agency cites failures in corrective actions, design validation, and reporting for ventilators, defibrillators, and sensors.
The US Food and Drug Administration (FDA) issued a warning letter to Zoll Medical Corp following an inspection that revealed significant quality system and medical device reporting violations involving several of the company’s critical care products.
The inspection, conducted at the company’s Chelmsford, Massachusetts, facility between February and April 2025, identified issues with X Series/Advanced automated external defibrillators, 731 Series ventilators, OneStep electrodes, and Accuvent Sensors. According to the FDA, these devices are considered adulterated because the methods and controls used for their manufacture do not conform to current good manufacturing practice requirements.
Failures in Corrective and Preventive Action
A primary violation cited in the letter is the failure to maintain adequate procedures for corrective and preventive action (CAPA). The agency says Zoll failed to identify actions needed to prevent the recurrence of quality problems, citing an instance of burnt pediatric electrodes where a request for corrective action was rejected despite the potential for patient injury.
The FDA also found that the company’s trend analysis was ineffective at detecting recurring issues with 731 Series ventilators. These ventilators were subject to a Class I recall in 2024, yet the agency says the company’s internal processes failed to escalate related complaints properly, even after the associated CAPA was closed.
MRI Compatibility and Design Validation Issues
The warning letter details failures in design validation for MRI-compatible ventilators. The FDA says the company failed to adequately test the Z Vent Ventilator for use with 1.5T MRI scanners despite labeling the device for use with both 1.5T and 3T scanners. The agency noted a complaint where a customer reported imaging quality discrepancies when using the ventilator near a 1.5T magnet.
Additionally, Zoll failed to follow internal risk management procedures for X Series defibrillators and did not assess the risk of corrosion on OneStep electrodes, the agency says. In one case, a customer reported visible corrosion on a posterior electrode pad after a cardioversion procedure.
Reporting Violations and Software Concerns
The FDA also cited a medical device reporting violation involving a ventilator malfunction near an MRI. Zoll reportedly became aware of the event in June 2024 but did not submit a report to the FDA until March 2025, exceeding the 30-day requirement for life-supporting devices.
The agency also raised concerns regarding supplier controls and software. The letter states that Zoll failed to correctly categorize suppliers for critical components like the Accuvent Sensor. Furthermore, the FDA says Zoll’s RescueNet Live software may be considered an unapproved medical device if it generates secondary alarms rather than simply displaying alarms from a monitoring device.
While the company has submitted several responses since the initial inspection, the FDA says those responses are currently inadequate or lack enough information to determine if the systemic problems have been resolved. The warning letter was signed by Barbara C Marsden, director of the office of product evaluation and quality at the FDA Center for Devices and Radiological Health.
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