Breath of fresh air

Schwarzer Precision by Bürkert has supplied Corscience, a manufacturer of CO₂ analysers for clinical use, with a miniature eccentric diaphragm pump for its capnometer modules. Fast customisation, as well as compact size and quiet operation, were also key requirements for the medical device.

Capnometry is a method for monitoring (various) respiratory gas parameters of patients and its introduction has led to a significant reduction of complications in those who are on ventilators. A capnometer measures the CO₂ content of exhaled breath to present data to clinicians to ensure patient health and help prevent life-threatening situations. As a result, capnometers are vital medical devices in anaesthesiology, intensive care units and for emergency services.

Capnometry essentials

Capnometry devices can monitor CO₂ with a mainstream method, where the patient’s breathing creates the flow, or by a side-stream method, used, for example, when a patient is under anaesthetic. With a tube connected to the breathing circuit (eg, endotracheal tube or nasal cannulae), a diaphragm pump draws the breath down the tube and through an infrared sensor that continuously measures the CO₂ content.

To establish accurate measurement results for patient safety, it’s vital that the flow is continuous and achieves the required flow rate. For this reason, reliability was the most important factor in pump specification for Corscience, which develops capnometry devices (CAP201). Corscience turned to Schwarzer Precision to provide the miniature vacuum pump, based on the company’s reliable design and manufacturing, as well as its rapid customisation ability.

“One of the most important things is pump reliability,” says Nils Kerlin, product manager, Schwarzer Precision. “Frequently, the patient is in a critical condition where monitoring is crucial, therefore it’s vital that the capnometer is able to provide continuous, accurate measurement.”

Quiet reliability

Schwarzer Precision specified its SP 100 EC miniature eccentric diaphragm pump with EPDM elastomers and long-life bearings. Required to draw a continuous flow of 80 ml per minute, this rate also remains stable. Installed in a patient environment, it’s also important that the pump should allow quiet, low-noise operation with low vibration. It was also crucial that the pump occupied a small footprint within the capnometer’s compact board, which it achieved thanks to its micro dimensions.

To fulfil Corscience’s precise specification, Schwarzer Precision’s customisation capability was essential and every aspect of the pump can be adapted to suit the specification. For Corscience, the pump was equipped with special elastomers to enable safe operation at higher temperatures in emergency operations.

The elastomers were selected for their reliability, with various types of hardness and shape available. For the motor, a premium brushed DC motor was specified for its long lifetime. This level of customisation to create a sample is provided to the customer within a week and following customer testing.

“Customisation is often based on a balancing of the customer’s requirements, be that flow rate, noise level, power consumption, or other factors,” adds Kerlin. “A real differentiator for Schwarzer is our ability to customise every aspect of the pump and provide a customer sample, ready for their lab and field tests, within just days.”

Simple customisation

Corscience also supplies its CAP201 capnometer board for integration in wider medical devices. One use is for battery-powered mobile emergency devices that demand high energy efficiency.

“Set-up of the pump is critical in order to minimise energy consumption,” he explains. “It requires design expertise to reach the optimum level, often by adjusting the stroke of the pump and the elastomer design, balanced with aspects such as flow rate. It’s our customisation capability that ensures we can achieve the right pump attributes for the customer’s application.”

While the SP 100 EC series pump served as the basis for this capnometer, the slightly larger SP 270 EC eccentric diaphragm pump could also be used for this application. Schwarzer also supplies pumps such as rotary, miniature vane and linear diaphragm, as well as pumps for liquid applications. Schwarzer Precision’s range of micro pumps are offered alongside Bürkert’s fluid and gas control systems, which can be specified by Bürkert’s UK team.