Measurement of pressure in a medical ventilator

Getting the measure of medical ventilator pressure

Patients with respiratory failure often require assistance from a ventilator to help move air in and out of their lungs. Sadly, due to the events we have all witnessed over the past two years, the reliability of ventilators has never been under more scrutiny. When an air tube leaks, the ventilator cannot measure the pressure build up and flow rate, a potentially disastrous situation for the patient. For this reason, the ventilator requires a way of taking high accuracy, rapid measurements using reliable sensor and valve technologies. Here at Yokogawa, we have a solution that ticks all of these boxes.

The demand for ventilators is currently extremely high. These complex medical devices move air, often mixed with higher levels of oxygen, into and from a patient's lungs when they cannot breathe adequately unaided. Here, ventilator manufacturers have a clear responsibility for meeting the needs of both patients and healthcare providers by ensuring the sensing elements used to measure pressure and flow are precise, rapid, and reliable. For this critical application, a device is needed that checks the pressure loss between the supply pressure and the pressure sensor (which must give accurate measurements of the patient’s breathing). The device must also ensure the sensor accurately measures the timing of switching to guarantee proper valve operation when switching between expiration (exhalation) and inspiration (inhalation). In addition, it is necessary to check the pressure level when valves are opened or closed, and periodically calibrate several measurement devices to maintain equipment performance over a long period of time. There is little margin for error or failure. Experience tells us that the Yokogawa MT300 digital manometer meets the needs of this demanding application because of its high accuracy and ability to take rapid measurements. The measurement sensor and valve that we’ve built into the device are highly accurate and reliable to ensure faithful capture of the signal from the patient. 

Silicon-based resonant sensor

So what exactly helps to deliver this high level of accuracy? Well, the secret is our proprietary silicon-based resonant sensor. The sensor has excellent characteristics that allow it to meet the needs of critical ventilator applications, where attributes such as stability, reproducibility and sensitivity achieve the accurate measurements required. Our MT300-G03 (200 kPa gauge) is proven to be the best model for this application. One of its main advantages is that it displays the same units of mmHg and mmH2O used in medical equipment, meaning values can be read and compared directly. The MT300 has a measurement accuracy of 0.01%, making it suitable for everything from verifying device performance and small pressure losses in the equipment, through to conducting tests in product development and during production line inspection. When developing, manufacturing, inspecting and calibrating ventilators, OEMs have to measure and control pressure values to ensure correct performance.

High sampling rate
Importantly, the MT300 has a high enough sampling rate to capture respiration as a standard function. What’s more, we should point out that by selecting the high-speed measurement mode, our MT300 not only captures the open-close pressure of the valve, but any sudden pressure changes during opening and closing. As the synchronous measurement function can measure the inhale and exhale pressure in synchronization, it’s an effective way of checking how the pressure changes at the time of switching. Users can store measured data to the MT300’s internal memory and transfer it to a PC via a USB connection, while further advantages include battery operation for portable measurements, and a color dot matrix LCD that displays measurement data and analysis with high resolution and visibility.
Ultimately, we can confirm that the Yokogawa MT300 digital manometer is ideal for the needs of testing medical ventilators as it delivers both high accuracy and long-term stability - the device offers a guaranteed accuracy of pressure measurement (to within 0.01%) for a period of 12 months. The color display, combined with high-speed measurement and synchronous measurement functions, make our MT300 highly suitable for this high-precision application, while its leak test, scaling, and statistical processing functions promote the efficient working that customers need.

To discover more about our MT300 digital manometer, please read the application note.