WARNING LETTER
ZOLL Medical Corporation
MARCS-CMS 711320 —
April 30, 2026
Delivery Method:
VIA Electronic Mail
Product:
Medical Devices
Recipient:
ZOLL Medical Corporation
269 Mill Road
Chelmsford
,
ME
01824
United States
jrennert@zoll.com
Issuing Office:
Center for Devices and Radiological Health
United States
WARNING LETTER
CMS # 711320
April 30, 2026
Dear Mr. Rennert:
During an inspection of your firm located in Chelmsford, MA from February 27, 2025 through April 15, 2025, an investigator from the United States Food and Drug Administration (FDA) determined that your firm manufactures X Series/Advanced automated external defibrillators (AEDs) (Class 3), Zoll MRI Compatible 731 Ventilators (Class 2), OneStep electrodes (Class 3), and Accuvent Sensors (Class 3). Under section 201(h) of the Federal Food, Drug, and Cosmetic Act (the Act), 21 U.S.C. § 321(h), these products are devices because they are intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, or to affect the structure or any function of the body.
Quality System Regulation Violations
This inspection revealed that these devices are adulterated within the meaning of section 501(h) of the Act, 21 U.S.C. § 351(h), in that the methods used in, or the facilities or controls used for, their manufacture, packing, storage, or installation are not in conformity with the current good manufacturing practice requirements of the Quality System regulation found at Title 21,
Code of Federal Regulations
(CFR), Part 820. We received responses from Paul Dias, Vice President of Service, Quality and Regulatory Affairs, dated May 6, 2025, from Brian Abbott, Principal Quality Assurance Compliance Engineer, dated June 8, 2025 and July 8, 2025, September 8, 2025, October 8, 2025, November 7, 2025, December 8, 2025, January 10, 2026, February 6, 2026, March 6, 2026, April 6, 2026 and from Jill McFadden, Principal Quality Assurance Compliance Engineer, dated August 8, 2025, concerning our investigator’s observations noted on the Form FDA 483 (FDA 483), List of Inspectional Observations, that was issued to your firm on April 15, 2025. We address these responses below, in relation to each of the noted violations. These violations include, but are not limited to, the following:
1) Failure to establish and maintain procedures for implementing corrective and preventive action, as required by 21 CFR 820.100(a). Specifically, your firm did not adequately establish your “Corrective and Preventive Action Procedure,” 5004-0002-RP, Revision W.
For example:
A. Your firm failed to identify the action(s) needed to correct and prevent recurrence of nonconforming product and other quality problems, as required by 21 CFR 820.100(a)(3). Specifically, your firm did not follow your Corrective and Preventive Action (CAPA) Procedure, 5004-0002-RP, section 7.3 which states “Quality Assurance and CAPA Committee Review Team will review the CAPA request and determine if a corrective action, preventive action, or no action is required. […] It will determine the potential impact of the problem and the risk to the company and/or customer will be determined. […] If the request is determined to be a CAPA, Quality Assurance will enter the information into the CAPA System and a CAPA number will be assigned.”
For example, DMR 12426 was initiated on February 11, 2025, for the Onestep Pediatric GC Electrode (P/N 8900-000252-05), documenting that the tin under the gel on the electrode was burnt and there were air pockets surrounding the burn location. As a result of the nonconformity, a CAPA request under CAR # 131 was made on March 5, 2025. The request form collected during the inspection was not completely filled out, and the CAPA request was rejected on March 5, 2025. The stated justification for the rejection was that this was the first-time instance of such an event, even though CAR # 131 identified that the nonconformance, which could cause “arcing and burning a patient carries an end severity of
(b)(4)
, which requires a CAPA request per SOP-682.”
B. Your firm failed to analyze complaints and other sources of quality data to identify existing and potential causes of nonconforming product, or other quality problems, as required by 21 CFR 820.100(a)(1). For example:
i. The failure trend analysis specified under Procedure, Field Data Analysis, 5004-0003-RP, Revision YE, is ineffective to detect and mitigate recurring quality problems related to “No Fault Found,” “No Product Returned,” and “User Attempted Repair.” Specifically, CAPA CA 90 was initiated on April 9, 2024, for 731 Series Ventilators with MRI compatibility nonconformances, resulting in a Class I recall that was not initiated until April 30, 2024. The CAPA CA 90 was escalated during the internal labeling review of the device as a result of recent MRI testing. Your firm was unable to detect the issue through the CAPA process as six of these complaints were coded as “User Errors,” nine as “No Fault Found,” seven as “No Product Returned” and two as “User Attempted Repairs.” These ventilator failures caused malfunctions and shutdowns that led to the stoppage of ventilatory support and the need for alternative means of ventilation. CAPA CA 90 was closed as effective September 20, 2024. You have received 6 complaints relating to the MRI compatibility issues from November 15, 2024, through January 16, 2025, after closure of the CAPA and no additional CAPAs have been initiated by your firm.
ii. Complaints were not further escalated to a CAPA if they failed to meet a specified threshold per Procedure, Field Data Analysis, Document Number 5004-0003-RP, Revision YE and as per Procedure, Health Risk Assessment, Document Number 5005-000149-RP, Revision P, Effective Date October 7, 2024. Your firm received complaints related to inaccurate and inconsistent end tidal CO2 readings for the X Series System Defibrillator; the decision, however, was not to open a CAPA for such complaints based on a determination that the complaint trends are reviewed monthly. The risk file of the X Series identified inaccurate CO2 monitoring measurement with a hazard of misdiagnosis with a severity level of
(b)(4)
, level
(b)(4)
, as per the risk management plan for X Series. Examples include Complaints 1065028, 956175, 970112, 971261, 970108, and 1064552.
iii. Your firm analyzes complaint trends for potential corrective/preventive actions and risk assessment based on the root cause code and does not consider the incident type. Your firm received at least 28 complaints from January 1, 2022, to February 27, 2025, where the BVM feature of the Accuvent Sensor was not working, with an incident code 038100, where 15 of 28 complaints were that the device was either not reading or not accurately reading tidal volume and/or ventilation rate. However, no CAPA was initiated as the complaints trend did not meet the escalation criteria where 16 out of 28 complaints were coded with “No fault found” and “No product was returned.” Therefore, only the remaining 10 complaints, where the issues were confirmed, were used in the trending analysis, resulting in the escalation criteria not being met.
The responses dated May 6, 2025, and June 8, 2025, are not adequate. Your May 6, 2025 response promises a revised complaint handling procedure that involves your firm reviewing complaint trends from a complaint mode perspective, continuing to review trends from a failure mode perspective, escalating complaint and failure modes that do not present a risk to a CAPA based on historical trends, escalating complaint and failure modes that present risk to a CAPA if their occurrence falls outside of the expectations of the product’s risk management files, and updating product risk management files when new hazards are identified from field data. Attachment 19 of your June 8, 2025, response addresses the review of the six additional complaints associated with MRI distance after your CAPA was closed on September 20, 2024, as promised on page 9 of your May 6, 2025, response, but your responses do not address completing a retrospective review of complaints. In addition, your firm’s responses did not provide enough information to determine whether your responses are adequate. Specifically, attachment 24 included with your June 8, 2025, response states “
(b)(4)
”. Your firm found that
(b)(4)
out of the 51 reports were attributed to a device component failure, and the remaining reports were attributed to something other than a component failure. Please provide additional information on the
(b)(4)
reports attributed to component failures and additional information on why this did not trigger a CAPA request.
We cannot determine the adequacy of your firm’s August 8, 2025, response since your next step will consist of performing further analysis of the complaint data collected over a
(b)(4)
period that has an indication of a potential statistically significant upward trend. Your firm promises to provide the results of this analysis as part of a monthly response update.
2) Failure to establish and maintain procedures for validating the device design, as required by 21 CFR 820.30(g). Specifically, your firm failed to verify and validate the labeling change of your 731 MRI compatible ventilators adequately as per your procedure, Design Verification and Validation Requirements, 5002-0005-SOP, Revision T, as per the following:
A. The Z Vent Ventilator is an MRI-compatible device intended to be used with 1.5T and 3T clinical scanners. Per MRI Compatibility of Zoll Medical Corporation’s Z Vent Ventilator Final Report, dated June 21, 2023, the Z Vent Ventilator was evaluated to test for MRI compatibility only by using the 3T MRI scanner. No rationale or justification for lack of testing with the 1.5T MRI scanner was documented. Based on the testing, it was determined that the ventilator should be placed behind the 130 Gauss field line (approximately
(b)(4)
to the bore opening of a 3T MRI magnet); however, the labeling fails to specify how far the ventilator should be placed when using 1.5T MRI. You received complaint 1102291 on July 18, 2024, for the use of the Z Vent Ventilator when using 1.5T MRI equipment where the customer experienced discrepancies in the imaging quality. The facility confirmed that the vent was used
(b)(4)
away from the MRI. The vent specification is for
(b)(4)
with a 3T MRI, no specifications were evaluated by your firm for a 1.5T MRI.
B. MRI Compatibility of Zoll Medical Corporation’s Z Vent Ventilator Final Report, dated June 21, 2023, shows that one Z Vent Ventilator was used for the evaluation of MRI compatibility of Zoll 731 Series Ventilators (which includes the Z Vent, Eagle 2, and EMV Plus ventilators) with MRI Compatibility. The justification provided states that the devices are identical mechanically and differ in cosmetic features only. However, 731 Series Ventilator Platform Validation Plan – Zoll Z Vent, Document Number 1731-000001-VP01, Revision 01, Page 5, identifies
(b)(4)
. These factors were not assessed when performing the MRI compatibility testing.
The responses dated May 6, 2025, and July 8, 2025, are not adequate. Your May 6, 2025, response states “
(b)(4)
.” However, the 731 Series Ventilator Platform Validation Plan – Zoll Z Vent, Document Number 1731- 000001-VP01, Revision 01, Page 5, identifies
(b)(4)
. These factors were not assessed when your firm performed the MRI compatibility testing. The 731 Series platform models include EMV, EMV+, AEV, and Eagle II included under part number 703-0731-04. This part number was not listed in table 1-731 Ventilator Configurations Overview provided in your response. The IFUs for EMV Plus indicate that when marked with an “MRI conditional” label, the ZOLL Ventilators are suitable for use in an MRI environment with appropriate precautions.
We cannot determine the adequacy of your May 6, 2025, or July 8, 2025, responses regarding not testing the MRI compatibility when used with 1.5T scanners. You state in your July 8, 2025, response that MRI compatibility testing of the Z Vent Ventilator in a 1.5
(b)(4)
environment in accordance with FDA-recognized ASTM standards has been completed; and “[t]he testing demonstrated that the device meets all applicable criteria for magnetic field interactions. Based on the results, the Z Vent Ventilator has been determined to be MR Conditional, with specific use conditions defined for both 1.5 T and 3 T MRI environments. The labeling is the same for 1.5T or 3T and there are no changes needed.” Please provide additional information on whether or not you conducted any additional reviews of complaint 1102291 which occurred on July 18, 2024 where a customer confirmed that the 731 Impact Z vent was used
(b)(4)
away from the 1.5T MRI equipment and the Z vent affected the imaging quality of the 1.5T MRI equipment and if you have received any additional complaints regarding 1.5T MRI equipment compatibility.
3) Failure to establish and maintain procedures for validating the device design which includes a risk analysis as required by 21 CFR 820.30(g). Specifically, Procedure, Health Risk Assessment, Document Number 5005-000149-RP, Revision P, Effective Date October 7, 2024, fails to require a complete assessment of potential
(b)(4)
and
(b)(4)
when calculating the adverse health risk assessment. Section 7.5.3 of this procedure requires a risk of harm investigation that includes calculating the occurrence of harm of the event by using product field data from a complaint history search to be included on a HRA form. However, your firm has failed to perform a complete complaint history search while performing a health risk assessment. In addition, your firm has failed to follow your Risk Management procedure, Document Number 5008-000011-SOP, Revision T for the risk analysis for the X Series defibrillators. For example:
A. For the 731 Ventilators MRI compatibility issue, the risk was calculated only by using the adverse events (24 malfunction reports) and complaints (27 complaints) that may be related to the device defect. Your Health Hazard Evaluation stated, “Although the risk is life-threatening, the likelihood of a potentially hazardous occurrence related to the omission of information, is considered remote”. However, during the inspection, the investigator reviewed the complaint analysis for CA 90 with
(b)(4)
employees from your firm and found there were 50 complaints, not 27, received from 2016 to 2024.
B. The risk analysis performed for X Series defibrillators is ineffective. You failed to follow your Risk Management procedure, Document Number 5008-000011-SOP, Revision T. Page 11 of the procedure requires your firm to follow the risk estimation criteria listed in the procedure for the products that were introduced after the initial release of the procedure in December 2011. The X series defibrillator was introduced after December 2011. It was originally cleared on March 21, 2012, as a Class III 510(k) product under K112432 and was later approved on December 27, 2017, through P160022. Your firm should therefore follow the risk estimation criteria listed in your Risk Management procedure for the X series defibrillator.
However, unlike the risk estimation criteria listed in your Risk Management procedure, the risk ranking for the X Series and Propaq products and accessories has an additional acceptable level of risk associated with the term Negligible (Occurrence Rank of
(b)(4)
for Legacy,
(b)(4)
for X series) occurrence classification as per Risk Management Plan, X Series/Propaq, Document Number 1127-0001-RMP, Revision 5. Where the occurrence has an estimated likelihood of
(b)(4)
and a probability of
(b)(4)
, the level of risk will always be considered
(b)(4)
despite the level of severity.
C. You have failed to assess the risk of visible corrosion spots larger than
(b)(4)
in diameter for the One Step electrode. Your design verification, VPN 1334R, dated 3/15/19, of OneStep Adult Electrodes for use for defibrillation, cardioversion, and ECG Monitoring, identified that corrosion spots as large as
(b)(4)
diameter can function as intended; however, your firm failed to assess the risk for corrosion larger than
(b)(4)
diameter when within the shelf life of
(b)(4)
. Your firm received complaint 895198, aware date 3/4/22, where it was reported that after a cardioversion, they were removing the pads from the patient and found corrosion at the center of the metal element of the posterior portion of the pad. This problem was reported on January 25, 2022, which was the day of the expiration for the pads. Your investigation determined that “Discoloration and air bubbles shown in these pictures are signs that will lead to a malfunction with the pads.”
The adequacy of your May 6, 2025, June 8, 2025, July 8, 2025, August 8, 2025, and September 8, 2025, responses cannot be determined at this time. Your firm’s May 6, 2025, response states that you did not share
(b)(4)
with the investigator during the inspection and have completed the testing and provided the testing in your response.
Your firm reviewed the initial Hazard Analysis documents for Pedi-Padz II Electrodes, ProPadz Radiolucent Solid Gel/ProPadz Radiolucent/HWD Electrodes, Pedi-Padz Radiolucent Electrodes, Pro-Padz Adult MFE LG Electrodes, Pedi-Padz LG Electrodes, Aspirator and G3/G3 Elite were finalized following Quality Assurance Management Review on July 3, 2025. Your August 8, 2025, September 8, 2025, October 8, 2025, November 7, 2025, responses, in alignment with the approach outlined in the Project Quality Plan, provided new
(b)(4)
documents in lieu of updating the existing
(b)(4)
documents. What is your rationale for risk acceptability (
(b)(4)
) determined since your risk categorization appears to be mostly
(b)(4)
and
(b)(4)
for all of your new Hazard Analysis documents received to date? For example, attachment 44 included with your August 8, 2025 response has a hazardous situation column with a delay in defibrillation causing a harm of clinically relevant delay contributed to irreversible harm or death receiving a risk categorization of
(b)(4)
for two out of
(b)(4)
with the same hazard of algorithm analysis incorrect but the
(b)(4)
hazardous situation (delay in defibrillation) has a different harm stating clinically relevant delay in patient receiving appropriate treatment receiving a risk categorization of
(b)(4)
not
(b)(4)
since the clinically relevant delay does not contribute to irreversible harm or death.
4) Failure to establish and maintain procedures to ensure that all purchased or otherwise received product and services conform to specified requirements as required by 21 CFR 820.50. Specifically, your firm failed to establish and maintain the requirements, including quality requirements, that must be met by suppliers, contractors, and consultants, as required by 21 CFR 820.50(a). For example:
A. Your firm failed to categorize two suppliers according to your Supplier Assessment and Qualification Procedure, Document Number 5004-2162-SOP, Revision YD. Per the procedure, suppliers that deliver materials, components or other services that shall influence the safety and effectiveness of the product are required to be classified as Level
(b)(4)
. The supplier of the AccuVent Sensor, a feature of your X series ventilator used to provide ventilation feedback on volume, breath rate and quality of ventilation of
(b)(4)
delivered breaths via Real BVM Help, was categorized as Level
(b)(4)
. Level
(b)(4)
suppliers are considered critical to business needs but not to the safety and effectiveness of the product. Similarly, your firm categorized the supplier that provides RescueNet software, including the RescueNet CaseReview that is used to review the performance of the device during a complaint investigation, as a Level
(b)(4)
supplier, which is defined as not directly impacting the production or quality of a device.
B. Your firm failed to establish a Supplier Change Control Agreement with the supplier that provides RescueNet software to your firm as required by your Supplier Assessment and Qualification Procedure, Document Number 5004-2162-SOP, Revision YD. RescueNet is the software that you describe on your website and in other marketing materials as allowing clinicians to remotely view real-time data from the monitor/defibrillators, optimizing care and driving efficiency from EMS to the hospital, and capturing clinical event information from AEDs to use in quality review, analysis and post-event debriefing.
Your responses dated May 6, 2025, June 8, 2025, July 8, 2025, and August 8, 2025, are not adequate, because your firm continues to not take into account the effect the suppliers that deliver materials, components or other services may have on the safety or effectiveness of your finished devices. This includes all suppliers that are Level
(b)(4)
and Level
(b)(4)
for components used in finished devices.
Medical Device Reporting (MDR) Violation(s)
Our inspection also revealed that your firm’s devices are misbranded under section 502(t)(2) of the Act, 21 U.S.C. § 352(t)(2), in that your firm failed or refused to furnish material or information respecting the device that is required by or under section 519 of the Act, 21 U.S.C. § 360i, and 21 CFR Part 803 - Medical Device Reporting. Significant violations include, but are not limited to, the following:
Failure to submit a report to FDA no later than 30 calendar days after the day that your firm receives or otherwise becomes aware of information, from any source, that reasonably suggests that a device that your firm markets has malfunctioned and this device or a similar device that it markets would be likely to cause or contribute to a death or serious injury, if the malfunction were to recur, as required by 21 CFR 803.50(a)(2).
For example, the information included for Incident No. 1095284 reasonably suggests that your firm’s ventilator malfunctioned (i.e. insufficient user instructions that led to an unexpected shutdown) while operating near an MRI. According to the preamble to the MDR final rule published on December 11, 1995 (60 FR 63578), a malfunction is reportable if the malfunction involves a device that is considered to be life‐supporting or life-sustaining and thus is essential to maintaining human life. Your firm’s ventilator is a life-supporting/life-sustaining device. The information included in the complaint reasonably suggests that the malfunction would be likely to cause or contribute to a death or serious injury, if it were to recur. Therefore, the referenced complaint represents an MDR reportable event as defined in 21 CFR 803.3(o). Your firm became aware of the event on June 20, 2024, and FDA received the MDR, 1220908‐2025‐00947, for the corresponding incident on March 10, 2025, which is beyond the 30‐calendar day timeframe.
The adequacy of your firm’s responses dated May 6, 2025, June 8, 2025, July 8, 2025, and August 8, 2025, cannot be determined at this time. Although an MDR for the corresponding incident was received by FDA on March 10, 2025, your firm states in its May 6, 2025, response that it plans to revise its reporting process and conduct a retrospective review based on further communication with the FDA clarifying the reportability determination. However, there has been no evidence provided documenting the completion of these activities. We acknowledge from your August 8, 2025, response that you have completed your updates to your risk management files and are continuing to work on your retrospective review based on your revised risk analysis.
Our understanding is that your firm’s RescueNet Live software analyzes data from a monitoring device and generates a secondary alarm and is not merely receiving and displaying alarms generated by the monitoring device. If that is the case, your software is a medical device and is adulterated under 501(f)(1)(B) of the Act, 21 U.S.C. § 351(f)(1)(B), because your firm does not have an approved application for premarket approval (PMA) in effect pursuant to section 515(a) of the Act, 21 U.S.C. § 360e(a), or an approved application for an investigational device exemption under section 520(g) of the Act, 21 U.S.C. § 360j(g). The device is also misbranded under section 502(o) the Act, 21 U.S.C. § 352(o), because your firm did not notify the agency of its intent to introduce the device into commercial distribution, as required by section 510(k) of the Act, 21 U.S.C. § 360(k).
Your firm should take prompt action to address any violations identified in this letter. Failure to adequately address this matter may result in regulatory action being initiated by the FDA without further notice. These actions include, but are not limited to, seizure, injunction, and civil money penalties.
Other federal agencies may take your compliance with the FD&C Act and its implementing regulations into account when considering the award of federal contracts. Additionally, should FDA determine that you have Quality System regulation violations that are reasonably related to premarket approval applications for Class III devices, such devices will not be approved until the violations have been addressed. Should FDA determine that your devices or facilities do not meet the requirements of the Act, requests for Certificates to Foreign Governments (CFG) may not be granted.
On February 2, 2024, the FDA issued a
final rule
amending the device current good manufacturing practice (CGMP) requirements of the Quality System (QS) Regulation under 21 CFR 820 to align more closely with the international consensus standard for Quality Management Systems for medical devices used by many other regulatory authorities around the world. The revised part 820, referred to as the Quality Management System Regulation (QMSR), became effective on February 2, 2026. Your most recent inspection on February 27, 2025, through April 15, 2025 was conducted pursuant to the QS Regulation, which was in effect at the time of the inspection. However, any corrective actions you propose or implement must be pursuant to the QMSR requirements in effect as of February 2, 2026. For more information on the QMSR please refer to our frequently asked questions webpage: https://www.fda.gov/medical-devices/quality-system-qs-regulationmedical-device-current-good-manufacturing-practices-cgmp/quality-management-system-regulation-final-rule-amending-quality-system-regulation-frequently-asked.
Please notify this office in writing within fifteen business days from the date you receive this letter of the specific steps your firm has taken to address the noted violations, as well as an explanation of how your firm plans to prevent these violations, or similar violations, from occurring again. Include documentation of the corrections and/or corrective actions (which must address systemic problems) that your firm has taken. If your firm’s planned corrections and/or corrective actions will occur over time, please include a timetable for implementation of those activities. If corrections and/or corrective actions cannot be completed within fifteen business days, state the reason for the delay and the time within which these activities will be completed. Your firm’s response should be comprehensive and address any violations included in this Warning Letter. If you believe that your products are not in violation of the FD&C Act, include your reasoning and any supporting information for our consideration as part of your response.
Your firm’s response should be sent via email to Establishment Assessment Team 1 Assistant Director Gina Brackett at CDRHEnforcement@fda.hhs.gov. Please include in the subject line, “CMS Case 711320” when replying. If you have any questions about the contents of this letter, please contact: Robert Maffei, Compliance Officer at robert.maffei@fda.hhs.gov.
Finally, you should know that this letter is not intended to be an all-inclusive list of the violations at your firm’s facility. It is your firm’s responsibility to ensure compliance with applicable laws and regulations administered by FDA. The specific violations noted in this letter and in the Inspectional Observations, FDA 483, issued at the close of the inspection may be symptomatic of serious problems in your firm’s manufacturing and quality management systems. Your firm should investigate and determine the causes of any violations and take prompt actions to address any violations and bring the products into compliance.
Sincerely,
/S/
Barbara C. Marsden
Director
Office of Product Evaluation and Quality
Center for Devices and Radiological Health
Content current as of:
06/16/2026
Regulated Product(s)
Medical Devices