In the midst of the COVID-19 pandemic, demand for ventilators is high. Ventilators are complex medical devices that move breathable air, sometimes mixed with higher levels of oxygen, into and out of a patient's lungs when they are physically unable to breathe.
The pressure and flow rate delivered by these ventilators is critical to the well-being of the patient. Healthcare providers must know the parameters to set for individual patients and conditions. Manufacturers of ventilators are responsible for meeting the needs of healthcare providers and patients by ensuring the sensing elements used to measure pressure and flow are accurate, fast, and reliable. A variety of sensing elements are present within these ventilators that need to be verified and calibrated periodically to maintain their performance.
There are many devices that can measure the flow of air, including ultrasonic time of flight sensors, thermal measurement devices based on the concept of convective heat transfer, and differential pressure flow meters.
Pressure Sensor Use in Ventilators
Differential pressure sensors are used for flow measurement in many devices. Flow of air is proportional to the pressure drop across a restriction in the flow path. The differential pressure sensor measures the pressure difference, and sends a signal to the ventilator display. A feedback loop within the ventilator controller allows the sensor to maintain and monitor the desired set of conditions. These sensors are placed in three critical areas that measure the effectiveness of the ventilator therapy:
- the respiratory flow path,
- the expiratory flow path, and
- proximal flow path.
The accuracy of this measuring method depends on the combination of the pressure sensor and the component used to obtain the pressure drop, which is usually an orifice or a linear flow element. It is critical these pressure sensors have a wide dynamic measuring range (typically from +/-6 in H2O to +/-60 in H2O), high measurement accuracy, and a short response time. They must also be robust and have the best long term stability to minimize re-calibration and maintenance.
Pressure Calibration in Ventilator Manufacturing
Production of ventilators requires testing of each device, as well as calibration of the internal pressure sensors. The demand for ventilators during the COVID crisis has risen substantially. This has led to an increasing need for ventilator manufacturing. Precision pressure measurement devices, such as Mensor transducers, digital pressure gauges or automated pressure controllers, are integrated into the ventilator production test stands to calibrate and adjust these internal pressure sensors. This process ensures accurate readings and optimally pressurized air and flow rates for the patient.
Verification of Existing Ventilators
Along with an necessitated increase in manufacturing these ventilators, there is a growing need for existing ventilators to be checked for proper functionality and performance against their specifications. This is typically carried out through test systems and fixtures that exercise the ventilators and other medical devices, like centrifuge systems and pumps, to ensure accuracy and reliability. A pressure controller's ability to automate and reliably generate precise pressures during the testing and verification process makes it a cost effective component in the verification and repair facility test stands.
During this time when the need for ventilators is escalating, the rapid construction of ventilators, their critical subsystems, integrated sensors and new test stands is also required. Fast turnaround of high accuracy test sensors and controllers is paramount to the successful delivery of test stands, which ensures rapid production and distribution of ventilators to healthcare providers and patients in the U.S. and around the world.