Considerations for leak testing ventilator tubes and circuits
Ventilator tubes and respiratory breathing tubes provide a crucial function in healthcare. Respiratory breathing tubes are primarily used to provide an umbilical connection between a ventilator and the patient for inhalation and exhalation gas management. In some cases, they are also used for anesthetic delivery.
Leak testing 100% of the tubes in production for proper functioning in the field is essential. Most frequently manufactured from corrugated polymer tubing, common variants include single limb, dual limb, and coaxial in both heated and non-heated variants. The flexible nature of the tubing provides some challenges for leak testing.
Leak test method and instrumentation for ventilator tubes
Medical device manufacturers typically use dry positive pressure mass flow leak testing with a single-channel Sentinel Blackbelt or multi-channel Blackbelt Pro instrument. For most applications, the test is executed using clean and dry compressed air at approximately 60 cmH2O (0.85 psig) positive pressure. This pressure is largely driven by the audit testing specifications prescribed under ISO-5367.
Leak test process for breathing tubes
Various factors, defined in the next section of this post, may affect the approach to the test but following are the typical steps in the process of leak testing breathing circuits using a CTS Blackbelt or Blackbelt Pro instrument.
1. Sealing the tube
The proximal (inlet) end of the ventilator breathing tube is mated to the test port on the leak test instrument while the distal (outlet) is sealed to atmosphere.
CTS provides medical-grade inside and outside diameter Connects that can be controlled by the Blackbelt instruments and provide a reliable seal. Learn more>
2. Pressurization of the tube
The instrument pressurizes the tube with regulated compressed air, inflating it to the desired test pressure for a user-defined Fill time.
This pressure is measured by the instrument’s pressure transducer and compared to min/max limits, enabling it to detect improperly adjusted pressure supply or gross leaks on the part under test.
3. Leak Rate Measurement
After the Fill timer expires, the source air is routed through the instrument’s mass flow transducer where actual flow (leak) through the part to atmosphere is recorded at the end of the user-defined Test time and compared to min/max flow limits to determine whether fine leaks are present, typically in leak rate units of standard cubic centimeters per minute (sccm).
4. Exhaust and Test Result
After the Test time, source pressure is disconnected from the mass flow measurement circuit and any pressure trapped inside the breathing tube is vented to atmosphere for a user-defined Exhaust time.
After Exhaust, the final variable test result data is displayed on the instrument. Highly visible indicators on the display and front panel make it obvious to the operator which tubes have passed or failed, allowing them to disconnect from the Sentinel instrument and properly move the parts down the production line or into reject containers.
For more specifics on the test process, see our Application Note: “How to Leak Test Respiratory Breathing Tubes/Circuits” >
Consider factors that will affect cycle time
Total test cycle time required is dependent upon many factors, however most critically:
- Reject limit
- Volume of the pressurized/evacuated area of the part under test
- Temperature stability of part and testing environment
- Dimensional stability of the part while under test
- Repeatability requirements defined by the user
- Accuracy, precision, and resolution of the instrument executing the test
When you need to boost throughput, it requires a careful balance of optimizing for the above factors. Search through our blog for one of our many articles on how to improve a leak test >
Reliable leak test solutions for medical device leak testing
Millions of disposable medical devices are leak and blockage tested using CTS instrumentation and know-how. Are you leak testing respiratory breathing tubes or breathing circuits, or other medical devices? Contact us to discuss the most efficient and trusted test methods.