Breathing Circuit Set Correction: Hamilton Medical Updates Use Instructions for Breathing Circuit Set

The affected products and recommendations for what to do with the devices below have not changed.

This recall involves updating instructions for using certain devices, and does not involve removing them from where they are used or sold. The FDA has identified this recall as the most serious type. This device may cause serious injury or death if you continue to use it without following the updated instructions.

Affected Product

The FDA is aware that Hamilton Medical has issued a letter to affected customers recommending certain coaxial breathing circuit sets used with HAMILTON-C1, HAMILTON T-1, and HAMILTON-MR1 ventilators have updated use instructions.

Affected devices:

Full List of Affected Lots

What to Do

Users should review and follow the pre-operative test instructions and troubleshooting instructions prior to continued use.

On May 18, 2026, Hamilton Medical sent all affected customers a letter recommending the following actions:

• Verify unimpeded expiratory gas flow prior to use by ventilating a test lung using the settings provided by Hamilton Medical after performing the pre-operative test.
  • If no “exhalation obstruction” alarm is issued, the expiratory valve is safe to use.
  • If the “exhalation obstruction” alarm is triggered, do not use the coaxial breathing circuit set. The coaxial breathing circuit set must be discarded and replaced.
• If the “Exhalation Obstructed” alarm is triggered on the ventilator, users should perform the following steps:
  • Disconnect the patient from the ventilator and ensure alternative means of ventilation (e.g. alternative ventilator, hand bagging, etc.).
  • Once patient safety is ensured, remove the expiratory valve set and overcome the membrane adhesion by detaching the membrane from the expiratory valve body once.
  • Place the membrane back onto the body. Then, ensure the membrane is aligned with the expiratory valve body with the metal facing up (do not press onto the metal) and install the expiratory valve set into the exhaust port on the ventilator.
  • Alternatively, use a new expiratory valve set.
• Inform all potential users of affected coaxial breathing circuit sets about this issue and post the provided notice in your facility. Make sure recommended actions are followed.
• Affected products may continue to be used with the risk mitigations provided above.

Reason for Correction

Hamilton Medical stated that certain lots of coaxial breathing circuit sets preassembled with an expiratory valve set do not perform as intended. In some cases, the expiratory valve membrane adhered to the sealing ring on the body of the expiratory valve, impairing valve opening and expiratory gas flow. The issue is not detected during the pre-operative test of the ventilator unless a test lung is actively ventilated. If the expiratory valve membrane is adhered to the sealing ring, the malfunction appears within the first breaths after ventilation is initiated.

When the expiratory gas flow is impeded, the end-expiratory pressure is too high, or the end-expiratory flow is too low. This will trigger the ventilator’s “Exhalation Obstructed” alarm.

An obstruction of expiratory flow results in inadequate ventilation and impaired gas exchange. Acute respiratory compromise due to impaired exhalation may result in inadequate ventilation and oxygen desaturation (hypoxemia).

As of May 13, Hamilton Medical has reported four serious injuries and no deaths associated with this issue.

Device Use

Hamilton Medical, Inc. ventilator coaxial breathing circuits are intended to connect HAMILTON-C1/T1/MR1 ventilators to a patient tube or respiratory mask during ventilation.

Contact Information

Customers in the U.S. with adverse reactions, quality problems, or questions about this issue should contact Hamilton Medical at complaints@hamiltonmedical.com or call 1-800-426-6331.

Additional FDA Resources  

1. FDA Enforcement Report
2. CDRH Medical Device Recall Database

Unique Device Identifier (UDI)  

The unique device identifier (UDI) helps identify individual medical devices sold in the United States from manufacturing through distribution to patient use. The UDI allows for more accurate reporting, reviewing, and analyzing of adverse event reports so that devices can be identified, and problems potentially corrected more quickly.  

• How do I recognize a UDI on a label?
• AccessGUDID database - Identify Your Medical Device
• Benefits of a UDI System

How do I report a problem?  

Health care professionals and consumers may report adverse reactions or quality problems they experienced using these devices to MedWatch: The FDA Safety Information and Adverse Event Reporting Program.

Timeline of Communication Updates