In today’s medical device industry, there is strong demand for smaller, sleeker designs and speed to the market with the newest breakthrough products. Engineers designing respiratory equipment, such as ventilators and anesthesia machines, are challenged by a host of critical factors. Users demand top performance and compliance with evolving regulatory standards. Medical device original equipment manufacturers (OEMs) must address these challenges by producing equipment that meets design specifications and performance expectations while also controlling costs. To do this, resources need to be identified to help meet these needs and expedite the design process.
A direct acting proportional valve, integral to the design of an inspiratory flow system, provides precision control for the flow of gas. Specialized proportional valves are available for application in ventilators and anesthesia machines and provide accurate and safe delivery of precise gases to patients.
In this blog, we will focus on proportional valves and the key factors OEM design engineers should consider when selecting them to meet ventilator and anesthesia machine design requirements, including:
- Installation and component functions.
- Application considerations and requirements.
- New proportional valve technologies.
Installation and component functions
There can be on the order of a dozen components in an inspiratory flow system. Proportional valves are often located in the middle of the system and provide flow control of the gases employed and prevent over-pressure in lines. Other components may include: inlet filters, pressure transducers, auto zero or calibration valve switches, check valves, pressure regulators, mass flow sensors, relief valves, oxygen sensors and fittings and tubing. The various components can be categorized as safety elements and control elements. Proportional valves are considered control elements.
Application considerations and requirements
The following application and design specifications should be considered when selecting a proportional valve:
Air source: Most ICU/Operating room and general ward ventilators use hospital plumbed air which can be prone to significant pressure variations. A proportional valve will balance the variation of pressure. Depending on the application, using a high-pressure proportional valve can eliminate the need for a pressure-reducing regulator.
Safety: When a pressure reducing regulator is installed for safety purposes, then a proportional valve is necessary to maintain consistent flow rates.
Device size: Trends are towards smaller systems. Employing a proportional valve with pressure regulation can reduce the number of pressure management components needed, thus reducing system size.
Gas compatibility: Careful selection of proportional valves with compatible elastomers is important, particularly in anesthesia applications.
Life and reliability: Documented life testing across varied temperatures and conditions is important to the prevention of premature aging of valves.
Compliance: It is important to select a valve that meets the most recent directives and regulations pertaining to the manufacturing of medical device products and components such a RoHS and REACH.
Mounting style: Proportional valves have several mounting options. The most common are manifold and cartridge. Selection should be based on the best fit for the designed system.
Customization: If customization is a requirement, choosing a supplier that offers flexible design capabilities such as lead wires, calibration and mounting options is ideal.
The specifics of the installation location, physical size constraints, type of gases being used, the extent of use anticipated and operating conditions are variable and should be reviewed on a case-by-case basis. Once a clear picture has been drawn, the following considerations should be evaluated, specific to the proportional valve selection:
- Flow and pressure requirements
- Media compatibility
- System voltage
- Current control
- Mount size, weight and orientation
- Control capability
- Power profile
New proportional valve technologies
Parker Precision Fluidics has recently expanded its line of proportional valves for respiratory equipment such as ventilators and anesthesia machines as well as other life science applications. The VSO® MAX HP line consists of two models that offer a combination of flow performance, operating pressure range, controllability and power efficiency.
- High valve-to-valve consistency.
- Reduced power consumption profiles and lower heat generation.
- Cleaned for oxygen service.
- Reach and RoHS compliant.
When specifying proportional valves for medical equipment such as ventilators and anesthesia machines, it's important to consider component functions, application requirements and system specifications to ensure the valve you choose optimizes the performance and design of the device while keeping costs in check.
For additional information on choosing proportional valves for ventilators and anesthesia machines, download the guide "Selecting a High Flow Proportional Valve for Ventilators & Anesthesia Machines".
This blog was contributed by Sam Ruback, marketing development manager, Parker Precision Fluidics Division.