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STMicroelectronics

Mechanical Ventilation Solutions From STMicroelectronics

By Francisco de Molina and Adriano Basile

Medical artificial ventilators are machines supporting patient breath by providing mechanical ventilation to push air into and out of the patient’s lungs, supporting a patient who is tangibly unable to breathe or breathing insufficiently.

Mechanical ventilators are used in a variety of settings, mainly Intensive Care Unit (ICU), in Emergency Medical Service (as standalone units or transport vehicles) and in Anesthesiology (as a component of an anesthesia machine). Although similar in basic functions, we will focus on ICU ventilators as it is a topic of high importance at the moment.
 

Ventilator Topology

In its most basic topology, modern ventilators are computerized medical devices where the user (physician or nurse) sets breathing parameters such as respiratory rate, tidal volume, set pressure and inspiratory time. The main processing unit executes the selected breathing curves based on the parameters and modes set by the user by controlling in real-time the air going into the patient and, the oxygen rate, acting on several valves, with a retro-feedback using pressure and flow sensors.
 

STMicroelectronics Mechanical Ventilation Solutions Figure 1

 

Sensing Elements

In order to perform an effective and safe ventilation, the system needs a variety of sensors such as pressure, air flow, oxygenation, humidity and temperature.

In mechanical ventilators, accurate control of pressure and air flow allows the processing unit to accurately deliver air to the patient based on the user’s input. Pressure sensors perform a variety of critical checks on the system, from controlling input pressure from hospital lines, reading mixing chamber pressure, to the most important ones, checking pressure of air delivered to patient as well as reading the pressure of patient’s exhalation. Verifying flow is equally important, from controlling air to O2 ratio mixing, to ensure air going to the patient is delivered accurately and safely. STMicroelectronics offers barometric pressure sensors [LPS22HH] and water-resistant pressure sensors [LPS27HHW, LPS33HW] that can be used for some of these functions. Cost effective, reliable flow metering can be achieved by combining two pressure sensors.

Temperature and humidity sensors can be used in ventilators that offer active humidification. This feature is very important during invasive mechanical ventilation to prevent a variety of negative side effects related to cold and/or dry air. STMicroelectronics offering covers this need with Temp sensors such as such as STTS22H or combo temperature and humidity HTS221.
 

Reference Component Function Board Additional on-board components
Pressure Sensor [LPS22HH]
Humidity [HTS221]
Pressure & Humidity sensors X-NUCLEO-IKS01A1 MEMS 3D accelerometer and 3D gyroscope [LSM6DSO]
MEMS 3D accelerometer [LIS2DW12]
MEMS 3D magnetometer [LIS2MDL]
Temperature Sensor [STTS751]

 

Moreover, further sensors can be considered in the use of advanced masks: an accelerometer (IIS2DLPC) to capture the face movements and, a microphones (IMP34DT05) could be used to monitor sleep apnea.
 

Motor Control

Ventilators generally do not mechanically compress air to push it into the patient, they however control the release of pre-compressed air/O2 mix. In most cases, ventilators are connected to two high pressure lines coming from the hospital infrastructure, one with pure O2 and one with compressed air. Both lines are pressurized around 50 psi. However, in field operations or large-scale emergencies as seen during the COVID-19 crisis, ventilators are deployed outside of normal hospital conditions, connected to just a compressed O2 tank. In this case, the ventilator must compress external air to match the pressure of the O2 tank.

STMicroelectronics offers a comprehensive portfolio of motion control suited for a variety of motor architectures. In this case, many customers prefer to consider 3phase motors for reliability in this critical application.
 

STMicroelectronics Mechanical Ventilation Solutions Figure 2
 

Reference Component Function Board
3-phase BLDC [STSPIN830] Motor control X-NUCLEO-IHM09M1
Dual brushed DC [STSPIN840] Motor control X-NUCLEO-IHM15A1
Brushless DC [L6230] Motor control X-NUCLEO-IHM07M1
3-phase Brushless DC Motor control STEVAL-SPIN3201

 

Processing Unit

At the core of the ventilator sits a processing unit that utilizes its various sensors controls for the overall operation. The processor must be able to provide an effective and easy interface with the user and execute the different breathing algorithms for a safe and accurate ventilation. For systems that require a feature rich User Interface, you will need an MCU/MPU that can perform such tasks. The STM32H7 series is available with a dual-core MCU with an accelerated graphics capability will meet your needs. For a more cost-conscious approach, ST has products ideal for applications requiring MCUs that offer advanced and rich analog peripherals such as the STM32L5 and STM32G4 series.

Below is a selection of ST’s evaluation boards

Reference Component Board Additional on-board components
STM32G4 series NUCLEO-G431RB 64-pin package, 128 KBytes of Flash memory and 32 Kbytes of SRAM
STM32G4 series NUCLEO-G474RE 64-pin package, 512 KBytes of Flash memory and 128 Kbytes of SRAM
STM32L5 series NUCLEO-L552ZE-Q 144-pin package, 512 KBytes of Flash memory and 256 Kbytes of SRAM
Internal SMPS
STM32H7 series NUCLEO-H743ZI 144-pin package, 2 Mbytes of Flash memory and 1 Mbytes of SRAM
STM32H7 series NUCLEO-H7A3ZI-Q 144-pin package, 2 Mbytes of Flash memory and 1.4 Mbytes of SRAM
Internal SMPS
STM32H7 series NUCLEO-H745ZI-Q 144-pin package, 2 Mbytes of Flash memory and 1 Mbytes of SRAM
Internal SMPS
STM32H7 series NUCLEO-H753ZI 144-pin package, 2 Mbytes of Flash memory and 1 Mbytes of SRAM
STM32H7 series NUCLEO-H755ZI-Q 144-pin package, 2 Mbytes of Flash memory and 1 Mbytes of SRAM
Internal SMPS

 

Wireless Solutions

The different usages of these ventilators can change to have different connectivity. In fact, in hospitals the Artificial Ventilators are often paired with a Patient Monitor System capturing ECG, SpO2 and other parameters from patients, these are shown on a wide screen beside the patient bed. In other cases, the Ventilators are remotely controlled outside the ICU rooms.

STMicroelectronics is committed to offer a reliable and a comprehensive portfolio of wireless connectivity solutions. ST’s portfolio includes a variety of RF transceivers, network processors ICs and fully certified modules for key wireless connectivity technologies including sub-1GHz long-range networks, Bluetooth®, Bluetooth-Smart®, 802-15-4, OpenThread, LTE Cat 1 and Narrowband IoT.
 

Security

Any connections can request a security level to establish a secure connection between devices, in the medical field this requirement is more stringent, and ST can offer several Secure Elements for this purpose. One of it is STSAFE-A110 which enable identification of devices using a Unique ID in silicon, a software integrity of the device via a Secure Boot process and an integrity of patient data with a digital signature.
 

Longevity Commitment

STMicroelectronics offers a 10 or 15 years longevity commitment. When selected for new designs, you are guaranteed these parts have a production lifetime of at least 10 or 15 years, meaning they are a safe choice for medical applications where the in-market lifetime of your products is expected to be long.