Hamilton Medical issued a letter to affected customers regarding updated use instructions for certain coaxial breathing circuit sets used with Hamilton-C1, Hamilton T-1, and Hamilton-MR1 ventilators, according to an FDA alert.
The agency says users should review and follow the pre-operative test instructions and troubleshooting instructions prior to continued use.
Hamilton Medical has reported 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.
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.
| Product Name | Brand Name | Product Number | UDI-DI |
|---|---|---|---|
| T1 CIRCUIT 240 +VALVE B/10 | Hamilton Breathing circuit sets, coaxial | 260127 | 07630002802956 |
| T1 CIRCUIT 180 +VALVE B/20 | Hamilton Breathing circuit sets, coaxial | 260128 | 07630002802963 |
| MR1 CIRCUIT 300 +VALVE B/10 | Hamilton Breathing circuit sets, coaxial | 260167 | 07630002802970 |
| MR1 CIRCUIT 480 +VALVE B/8 | Hamilton Breathing circuit sets, coaxial | 260168 | 07630002802987 |
FDA Recommendations
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.
More information is available on the FDA website.
