The COVID-19 pandemic has created havoc globally, putting more and more people in hospitals. The demand for ventilators is so high that doctors are creating makeshift ventilators to meet the demand. Many companies are contributing to the cause in various ways, including opening up their IPs. Renesas is also helping this global cause by designing ready-to-assemble electronic boards for ventilators.

This is a ventilator system reference design to provide a portable ventilator used in hallway or non-ICU use cases. This machine can provide high pressure oxygen to patients in assist control and pressure control modes. The assist control mode provides a certain tidal volume of gas to a patient with each inhale. The flow sensor (FS1023) would monitor the gas flow rate at the inhale tube and the tidal volume would be calculated by the MCU using the rate integrated with time. The oxygen valve would be controlled by the MCU and manage the oxygen ratio. The pressure control mode provides a certain pressure to the patient with each inhale. There is one proximal air pressure sensor connected to the mask to monitor the inhale pressure and send that information to the RX23W MCU. The blower, which provides pressure and blows air into the system, is driven by a motor control board that is controlled by the RX23T MCU. It uses I2C communication with the RX23W. A humidifier is added to the system to provide moist gas to the patient.

The system is using two MCUs for higher safety, so these devices can monitor and reset each other.

System Benefits

  • Secure system using two MCUs to monitor each other
  • System available for assist control mode and pressure control mode
  • Hardware is capable of providing low tidal volume, peak pressure, disconnect, and apnea alarms
  • Both gas volume and flow rate are monitored by the FS1023
  • The oxygen ratio is controlled by the valve, which is controlled by the MCU, and monitored by the flow sensor
  • The exhale pressure is controlled by MCU through the exhale valve
  • The oxygen sensor is used to test FiO2 (fraction of inspired oxygen)
  • The blower is controlled via pressure/flow sensor feedback
  • The LCD brightness is controlled by the light sensor monitoring ambient light
  • Features a battery balance monitor to extend battery lifetime
System Block Diagram

Ventilator System

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