Leak Testing Ventilator Tubes & Assemblies

Mechanical ventilators are used as interventional therapy when a patient has a condition or incident that has or will threaten their ability to breathe. Also known as Acute Respiratory Distress Syndrome (ARDS), which can occur for numerous reasons.  Ventilators are responsible for assisting the patient with gas exchanges (up taking oxygen, ridding of CO2), keeping an open airway (ie: from someone who has a severe allergic reaction and their airway closes), to protect against choking (ie: pneumonia patient choking on saliva), or if the patient has some sort of trauma or life threatening illness that would eventually lead to respiratory failure.

Mechanical ventilators control the rate, depth, mixture of air, flow rates, tidal volumes, total pressures, and min and max pressure limits. Depending on the patients history of illness and specific needs, a clinician can program the ventilator to suit the individual needs of each patient. For example, if a patient has a lung injury or a preexisting respiratory condition (COPD, pneumonia, etc.) it is vital to control the total and min and max peak pressures of the air a ventilator is pushing in and out of the lungs, as well as the pressure on the lungs, to ensure that the ventilator doesn’t cause any further lung complications to the already compromised patient. Also, for patients with pneumonia, ventilators are incredibly instrumental in not only providing airway protection and breathing assistance, but also allowing the clinician to program the min and max pressures to fully inflate and deflate the lungs, which assists in moving debris (sputum, phlegm) out of the lungs, allowing for uptake of more oxygen, which typically results in more ventilator-free days. These two examples are an the numerous ways that a programable ventilator can meet the exponentially changing needs of critically ill patients.

More information on ventilator management.3
 

How Do You Leak Test Ventilator Tubes and Assemblies?

When leak testing a ventilator tubing assembly there are two primary defects to look for:

• Proper (non-leaking) Seals Between Assembled Parts
• No Obstructions in the Airway

The fastest and most inexpensive way to test tubing walls and assembly connections is a Pressure Decay test. In a PD test, one side of the tube or tubing set is attached to a leak tester while the other side is sealed. The assembly is pressurized to set value. With the incoming supply shut off, the part settles to reduce the thermodynamic and elastomeric effects on the part. During the test step, any decrease in air pressure over time signifies a leak. If the assembly does not leak/decay past its predetermined reject value, it is a good part.

To check for obstructions in a ventilator tubing set, it is best to use a Back-Pressure Flow test. The BP Flow test measures the back pressure created by the part at a specific flow rate. Obstructions will cause the pressure to increase or decrease from the nominal value. This pressure change is compared to the programmed tolerance for pass/fail status. These flow values are very specific to each tubing set design. Variables like filters, tube diameter, and tube length can affect what an acceptable value is for one tube design but not for another.
 

How to Save Time

Unlike the ventilator device itself that can be used multiple times with many patients, the tubing assembly is a consumable product that can only be used by one patient. This makes high throughput essential to production.

The two best ways to reduce leak test cycle time for ventilator tube sets are:

• Minimizing the test circuit volume
• Use a multi-function leak tester that has both pressure decay and back-pressure flow as well as multiple test ports.
• Ensure that the part is the choke of the system, not the test pneumatics.
• Establish accurate but efficient test times.