Key Instrumentation Considerations in Medical Gas Delivery Systems

European Pharmacopoeia sets forth stringent definitions for the maximum allowable and stability concentrations of delivered patient oxygen. Without exception, medical gas OEMs and integrators must specify instrumentation in strict conformance with these standards. Smaller and more mobile healthcare environments, such as ambulances and temporary triage centres, rely upon portable, replaceable supply cylinders for patient inhaled oxygen delivery. Due to the wide external temperature ranges over which portable changeover systems must operate, cylinder setups are also instrumented with safety alarms. High-pressure alarms signal higher temperatures and increased risk of gas store depletion caused by evaporation. Low-pressure alarms can signal pending cylinder changeover requirements. Pressure monitoring ranges vary, depending upon medical gas type. Thus, careful attention to proper sensor selection criteria is essential. Specified instrumentation, such as Gems 3100 Series pressure transducers, can accurately monitor the cylinder pressure levels of oxygen, nitrous oxide, and other medical gases. Typically installed between the cylinders and gas delivery system, they also help to determine proper cylinder supply changeover criteria and timing. One transducer is used to measure incoming delivered gas supply pressure. Another measures supply feed pressure to the distribution system. This process ensures that consistent pressure levels are maintained within a specified range.

Surgical and medical air are essential for safe operating theatre, patient hospital ward and intensive care unit functionality. Compressed air helps medical professionals to deliver proper surgical anaesthesia and inhaled patient oxygen concentrations. It also powers diagnostic and surgical equipment, dental drills, and other non-critical medical devices. Medical and surgical air is typically produced via specialty water- or air-cooled compressor systems. In order to remain effective, a compressor must be clean and dry, as well as dust-, mould- and oil-free, throughout its operation. It also must reliably perform to varying set pressure levels. To ensure this, compressors are instrumented with both an automatic manifold panel and a manifold reserve, each programmed to a predefined set buffer pressure range. In the event that an automatic manifold is exhausted, a secondary emergency reserve manifold engages, ensuring uninterrupted airflow. Both manifolds require accurate, continuous pressure level monitoring. The Gems 3100 Series, a family of rugged stainless steel pressure sensors, is often specified within these generator systems. The sensors form part of a control circuit that activates and deactivates the compressor, allowing it to automatically monitor supply pressure. In doing so, the 3100 Series helps to ensure that buffer pressure remains within its predefined set range. These sensors can reliably operate over a variety of pressure settings, with low thermal errors and a wide temperature compensation range. Sensors may also be customised with application-specific pressure ranges, ports, connectors, cables and electrical outputs. In addition, the 3100 Series acts as an alarm, should levels fall below acceptable values. Data from these sensors also provide important overall compressor health assessments. Medical vacuum systems, like compressed air, operate from a centrally controlled source. The systems are essential for surgical suction, as well as for generating negative pressure conditions within environmental chambers. Here, pressure transducers are used for critical level monitoring, alarm activation, and support of the central vacuum generator control circuit. The Gems 3500 Series pressure transducer presents a unique advantage within these applications. In its compound form, it can accurately cover a range of -1 bar to +1 bar. This allows for the specification of one pressure transducer model for the effective support of a multitude of vacuum systems.

Medical gas pipeline systems (MGPS) are used to transport a variety of often-combustible medical gases, including oxygen, medical air, and anaesthesia, from central and secondary stores into designated areas. Standards for these systems are maintained and installed as set forth in “UK Health Technical Memorandum 02-01: Medical gas pipeline systems.” In North America, medical gas pipelines are also designed for conformance to National Fire Protection Association (NFPA) guidelines. Typically constructed of copper, MGPS support high- and low-pressure medical gas delivery within hospitals, laboratories and other clinical environments.

Basic medical gas pipeline infrastructure consists of a main line, connecting the gas media supply to the risers; risers, which connect the main line to lateral pipelines; and lateral pipelines, which feed into a branch room, or set of rooms, within the medical care environment. These pipes are installed in plain view within the healthcare setting.

All MGPS must be extensively tested prior to use. This is to ensure adequate gas delivery pressure, supply regulation and control. Particularly, gas supplies to anesthesia ventilators are most critical, as those rely upon sufficiently high pressure levels for proper functionality. To ensure such functionality, MGPS must also be continuously monitored for pressure and temperature variations and extremes. Sensors implemented within these environments are used to provide critical early warning of impending pressure drops or overpressures.

The highly corrosive nature of certain gas media makes MGPS prone to corrosion, moisture, mould, pressure stresses and other mechanical damages. Over time, these factors can contribute to pipe leakages. Within an oxygen delivery environment, such leaks can pose an especially high risk of fire or combustion, as well as patient health damage caused by depleted oxygen stores. Any cross-leakage can further increase patient hypoxia risks.

Selected instrumentation must be able to withstand higher-than-typical pressure levels. Pressure sensors typically would operate at 12V or 24V, with 4-20 mA or 0.5 to 4.5V output. An IP67 rating ensures continued sensor reliability within possible splash environments.

Gems 3500 and 3100 Series pressure transducers, as well as associated switches, are recommended for MGPS applications. Their versatility and interchangeability effectively support a wide range of MGPS points. Gems is also able to customise individual sensor settings for specific gas media compatibility, as well as other requirements.

Both 3500 and 3100 Series sensors feature high-accuracy and reliability with low thermal errors and a wide temperature compensation. Their compact size facilitates ease of installation within the space constraints of a typical MGPS environment. All sensors are degreased prior to shipment, ensuring their compatibility with specialty monitored gases. In addition, Gems pressure switches are offered with a variety of pressure ranges, from miniature vacuum switches to units over 400 bar. Their highly favourable size-to pressure ratio allows them to effectively monitor pipeline infrastructure within confined spaces. All switches are also available with custom set points.

All Gems standard catalogue products are available for immediate customer order. Standard OEM volumes can be produced within just a few business days. The rapid customisation of medical gas sensors and switches is also possible, as well as close customer collaboration on custom manifold designs to help meet specific regulatory compliance standards.

Ensuring Absolute Compliance

The specialty nature of medical gas delivery systems, along with their critical end use, creates often-complex requirements. As the burdens of stringent regulatory compliance are left to the OEMs, integrators, and health care facilities themselves, effective system monitoring is essential. Specified sensors and switches must be fully gas media compatible, as well as highly robust, accurate, and compact. Instrumentation must be free of contamination risks. It must also have the option for rapid customisation. Gems, with their longtime proven expertise, unique technical capabilities and rapid customer response, can serve as highly competent partners.