ventilator is a machine that provides mechanical ventilation by moving breathable air into and out of the lungs, to deliver breaths to a patient who is physically unable to breathe, or breathing insufficiently. Ventilators are primarily used in emergency care, intensive care, home care, and as a part of anesthesia machines

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Below is a reference design of a ventilator that can help you get started. The high-level system architecture of the medical ventilator system, in general, is an integrated system that consists of several valves, sensors, microcontroller unit (MCU), and converters to monitor, analyze, and control oxygen level. The complexity of the system can differ significantly, but standard elements in a medical ventilator system remain the same. Additionally, power converters, battery management, backlight, and remote monitoring unit provide necessary accustom to the system.

Block-Diagram for medical ventilator

  • Sensors

  • Some common variables under measurement in a medical ventilator system are oxygen level delivery, the flow of breaths, tidal volume, the pressure inside mask, temperature, and humidity. Pressure sensors play an essential role in respiration equipment by converting physical values such as airway pressure and flow into a differential signal. The air and oxygen flow sensors generate signals to help the MCU control the valves to deliver the desired inspiratory air and oxygen flows.  Sensors used in a ventilator are very cost-effective with large offset and offset drift causing the signals to be over or under scaled. Amplifiers with low offset voltage and drift over time and temperature, as well as low-noise and a high common-mode rejection ratio are ideal for signal conditioning.

  • MCU

  • MCU is the heart of the ventilator system. It performs multiple operations, including sampling the pressure signals, computing the desired airway pressure and total inspiratory flow level, and actuating the air and oxygen valves for each inspiratory cycle. To achieve these operations efficiently and in real-time, a high-speed, low-power, highly-integrated microcontroller is required. A 32-bit microcontroller is generally recommended.

  • Power

  • Power is a crucial consideration for medical devices. Commonly support multiple modes of supply, including mains AC input as well as rechargeable power pack and backup battery power is required to maintain uninterruptable operations. This flexibility requires suitable means of switching between different power sources without disrupting the performance of the ventilator machine, battery-charge management, and AC-DC conversion that is resilient to different voltage inputs to cater to the different world markets.

  • Connectivity

  • Further, for connecting to external data systems and hosts, several options like Wi-Fi module is available. Connectivity solutions also include multiple USB ports for connections to external drives, voice recognition hardware, internal display output with display drive, and backlight drive. The alarm system for critical events with amplification for the loudspeaker is a safety monitoring feature of ventilators. All aspects vital to safe operation can be monitored, including power-supply status, maximum and minimum inspiration pressures, and timing integrity.

To ensure the safety and effectiveness of the device, the FDA has three regulatory classes based on the level of control necessary, Class I, II, and III. Circuit protection is critical for both medical devices, and patient health, the device should not fail due to electrical transients on the power line, and electrostatic discharges can cause severe hazards to human safety. Using ESD device functionality of the device won't interrupt in regular operation, and it also reacts quickly for current and voltage spikes to the ground during surge and ESD. Consider leakage current and the capacitance have to be low enough when selecting ESD or TVS Diode.
Many of the devices and components supported for medical applications are automotive qualified, a benefit that is becoming popular within the medical device manufacturing community. These automotive-rated devices usually offer more durability and extended working temperature ranges, making these features and capabilities attractive to the medical industry as well for diagnostic features and fault protection functions for safety.