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A leading medical device customer approached us at a conference to learn more about how they could use a disc pump in their ABPM system.
We were able to show the customer, then & there, a working demonstration of a BPM system that incorporated the disc pump. We then worked with the customer to create a detailed resource outlining how to set up a basic BPM system for laboratory testing, utilizing the application note AN006: Blood Pressure Monitoring – whilst also providing a pump & valve manifold for ease of integration.
The customer was able to create a novel, fully integrated, arm-worn pump module for ABPM, optimised for patient comfort to deliver enhanced measurement accuracy.
During a 24-hour ABPM observation, a patient’s blood pressure is measured at regular intervals throughout the day and night as they go about their normal daily business. The measurements taken help healthcare professionals build an accurate patient health profile and diagnosis.
Current ABPM devices involve the patient wearing a cuff around their arm that is connected via tubing to a portable device, worn around the neck or waist. These ABPM systems commonly use traditional motor-driven diaphragm pumps that rely on the bulk compression of air within a cavity to create pressure, which, in turn, creates a pulsed flow, noise and vibration.
Resulting devices can be bulky, noisy, and uncomfortable. They also can skew readings through design fault – for example, kinks in the tubing when the patient is sleeping can interrupt cuff inflation and void measurements.
Early on, here at The Lee Company, we identified that incorporating a disc pump into an ABPM system provided opportunities for our customers to elevate their device design.
This is because, in contrast to conventional air pumping mechanisms, the disc pump doesn’t rely on the bulk compression of air within a cavity.The pump runs at a frequency of around 21kHz, a frequency above the range of human hearing and as it cycles at over 21,000 times per second, the resultant air flow is effectively pulsation free. The piezo drive also has very little mass and inertia so the pump can respond to set point changes within just a few milliseconds, helping to improve system response times and control.
As a result, it is possible to measure the oscillometric signal whilst inflating the cuff. The cuff pressure need not exceed the systolic pressure by much, minimising the compression forces applied to the patient.
Figure 1. Schematic of a BPM system integrating a disc pump (US series)
By taking the measurement on inflation, you remove the need for a check valve to hold the pressure as seen in traditional BPM systems. Using a disc pump can also remove the need for a proportional valve that are often used to control the vent speed in the cuff.
Figure 2. A disc pump and valve manifold for compact integration
To further help with the integration and reduction of system size, we created a manifold that incorporated a disc pump and a valve for a ‘plug ‘n’ play’ solution so our customer was able to integrate with other components quickly & easily.
Due to the silent operation and the lack of mechanical vibration with disc pump, our customer was able to:
Figure 3. Current ABPM system vs. wholly arm-worn cuff system
Our first steps were to encourage the customer to evaluate the technology for themselves with our Development Kit. With the development kit you can test both the disc pump and valves to be up and running with a test BPM system in no time at all.
From that point onwards, we walked the customer through a typical design journey integrating a disc pump and valves, working with them every step of the way, and providing direct and sustained engineering support as well as freely available resources to help with all aspects of development.
If you have a project you are interested in using disc pump in, get in touch, or if you would like to learn more about our Development Kit, click here. Or, if you want to learn more about developing your own BPM prototype with disc pump, access our Application Note on Blood Pressure Monitoring here.
Always verify flow calculations by experiment.
*There are many parameters to consider when determining V-Factor. Click here for more information.
