Ventilators provide critical airflow to patients whose natural breathing is insufficient to sustain life. They are also utilized as a preventative measure to counteract the imminent failure of other bodily functions or ineffective gas exchange in the lungs. The widespread use of mechanical ventilation has significantly enhanced the survival rates of patients undergoing surgeries, experiencing lung issues due to accidents, or suffering from acute and chronic pulmonary ailments. A critical aspect of the effective functioning of ventilators is the micro motion system, which powers the ventilation system. This article will focus on the use and benefits of brushless DC micro motors in ventilators.

Types of Medical Ventilators

Medical ventilators are categorized based on the specific drive mechanism that generates the airflow. These include ventilators driven by compressed air, as well as those driven by turbines.

Compressor-Based Ventilators

The compressed air or oxygen is usually fed through hospital supply lines or via a tank that is directly fed by a compressor. The air is then supplied to the patient with the help of bellows, vents, or regulation valves. Another type of compressor- based ventilator uses pistons to compress air that is generally actuated by electric motors. In this case, there is no need for compressed air or oxygen drawn from hospital supply lines or a compressor.

Turbine-Driven Ventilators

Similar to piston-based ventilators, turbine-based ventilators do not require supply lines from hospitals or compressors. Rather, the airflow and pressure are generated by a turbine driven at high speed that has autonomous pressure and flow control and is easily transported. These high-speed micro-turbine blower ventilators require powerful brushless DC motors to achieve reliable operation, ensure a lifetime of more than 15,000 hours, and provide high speeds up to 60,000 RPM.

Turbine-driven solutions are becoming more widely adopted by medical device manufacturers due to a few key advantages. One example is their pneumatic performance is not only equal to, but perhaps better than, compressor- based ventilators for ICU respirators. A second advantage is the independence of compressed air during patient transport, providing freedom of patient movement. A third is the increased efficiency of its design, which allows for a more compact mechanical footprint and downsizing of batteries based on lower power requirements.

Anesthesia Ventilators: The Impact of Application Requirements on Micro Motor Performance

One particular type of ventilator delivers anesthesia, where the air is recycled and operated in a closed loop to prevent polluting the operating room with anesthesia gas, which would negatively impact surgeons and other medical staff. Additionally, substances used for anesthesia are typically chlorofluorocarbons (CFCs), which are harmful to the environment if released into the atmosphere. These gases also act as a solvent for most plastics, making material selections critical, including the motor design.

Anesthesia ventilators may be operated in an environment with 100% oxygen, which has implications for motor performance and lifetime. Placing a motor in an environment with a high concentration of oxygen for a long period can oxidize the ball bearings' lubricant. Given that the motor operates at high speeds up to 60k RPM, this can have a significant impact on the lifetime of the motor.

Brushless DC Motors for Ventilators

Turbine-driven ventilators' performance requirements align with brushless DC slotless technology based on the primary application needs: high performance, long life, and low noise. Let’s review how the BLDC technology solves these requirements:

-    High Performance. The slotless design provides low inertia to achieve rapid step response, precisely following the dynamic needs of the patient. The design also enables high speed, torque, and efficiency, matching the demanding needs of the turbine.

-    Long Life. Brushless DC motors are electronically commutated and come with ball bearings as standard, producing or exceeding the required life expectancy for the ventilator.

-    Low Noise. The slotless design enables quiet operation, ideal for medical environments.

Portescap has a full range of 16 mm – 22 mm Ultra ECTM brushless DC motors that match the different power requirements for turbine-based ventilators. These include:

?    22ECS60 Ultra EC BLDC motors for Intensive Care Unit (ICU) ventilators

?    22ECA60 Ultra EC BLDC motors for anesthesia ventilators

?    22ECS45 or 22ECP35 Ultra EC BLDC motors for transport ventilators

?    22ECS45 or 22ECP35 Ultra EC BLDC motors for home care ventilators

?    16ECP36, 16ECS36, 16ECP52, and 16ECS52 Ultra EC BLDC motors for neonatal ventilators

Brushless DC Motors for Sterilized Ventilators

The micro motors used in anesthesia ventilators must feature long lifetimes, high speed and dynamic acceleration, as well as the lubrication’s resistance to oxidation. In some applications, the ventilators need the ability to survive hundreds of sterilization cycles. Brushless DC motors are uniquely suited to meet these challenging requirements.

In anesthesia ventilators, pathogens may come in contact with the blower unit (which includes the miniature motor), meaning that it must be able to withstand hundreds of sterilization cycles over the machine's service life. During the sterilization cycle, the machine can see 100% humidity, 135°C temperatures, and pressures ranging between 80 mbar and 2.5 bar. Sterilization can also be performed with hydrogen peroxide H2O2, which may be less stressful on the machine. While the motor is contained within the ventilator, the ability of the motor alone to withstand sterilization cycles is a benefit.

Portescap’s 22 mm slotless brushless DC motor, the 22ECA60, is well-suited for sterilizable ventilator applications. It benefits from the proprietary Ultra EC coil technology and can withstand more than 200 autoclave cycles; it can also operate at high speeds up to 60,000 RPM with a low amount of iron losses, hence generating low heat. This contributes to improving the motor’s lifetime by keeping the ball bearing’s lubricant at a lower temperature. The 22ECA60’s low mechanical time constant value (in the range of one millisecond) allows for quick accelerations, which facilitates the fast pressure and flow adjustment of the ventilator, improving patient acceptance and comfort. It also features an integrated thermistor for thermal performance monitoring and control.

It’s critical for design engineers working on ventilator applications to engage early with motion engineers to ensure the right micro motor and ball bearings are selected for these machines. Portescap engineers have decades of experience in customizing device designs for improved motor integration, as well as easier assembling of the impeller.