Size trends in medical sensing; compact technology meets patient needs

April 17, 2014 // By EDN
Medical device design engineers face unprecedented opportunities and challenges; one of the most pressing challenges is to create sensor elements which keep pace with the miniaturisation occurring in nearly all medical devices, from simple blood pressure monitors to complex heart-lung machines.

Applications range from patient transport, through the operating theatre to home-care;

- Patient transport, intake and ambulatory care environments - the smaller the equipment is, the earlier it can reach the patient and the greater the likelihood it can be deployed directly at first-response sites. Likewise, smaller respirators, infusion pumps and vital sign monitors help hospitals to improve the quality of in-room and ICU care.

- The operating theatre - space in an operating theatre is always at a premium. Compact monitors, pumps, and suction equipment give a scrub team better access to both the patient and the monitors, life support and treatment equipment.

- Patient mobility and home-care - highly portable equipment is critical for patients recovering in hospital and returning home where mobility will give them greater autonomy and comfort and, in many cases, a speedier recovery.

Modern medical devices, such as these infusion pumps, require compact sensors compliant with the stringent standards which govern medical materials safety.

Sensor technology meets compact design requirements

A key focus of R & D at Honeywell Sensing and Control is space-saving sensors and the integration of multiple sensor elements in a single package. Advanced integration techniques have allowed sensors to be placed within small surgical devices and other applications, in configurations which were previously considered impossible. A number of technology developments are contributing to meeting medical needs.

Board-mountable sensor packages

Sensor platforms that offer several options for mechanical interfaces, mounting, packaging, and I/O options to give medical equipment designers new degrees of freedom when designing medical equipment are critical. For example, pressure sensors that provide several options for mating connections (port styles), packaging (DIP, SIP, surface mount), and outputs (analogue or digital) which can be used to satisfy their application demanding functional, cost and board space requirements.

The multiple benefits offered by sensors presented as board-mountable packages have made them one of the most popular space-saving components for medical and industrial designs. In the case of sensors which measure fluid pressure or flow, board-mount packaging enables the sensing element to be firmly attached to the device’s printed circuit board (PCB) as close as possible to the patient and/or the liquid media being sensed (e.g. blood, chemicals or water).

This is especially important in certain applications, such as dialysis machines, which require precise and accurate measurement of dialysate (one of the fluids involved in the dialysis process) and venous pressure to ensure a patient’s safety and comfort during treatment. Accurate measurement of pressures in the fluid and blood flows helps ensure that an over-or-under pressure situation does not occur, conditions which can result in either burst blood vessels or air bubbles in the dialysis feed line. For these types of applications a board-mounted package can help provide the close proximity the pressure sensor needs to produce accurate, precise measurements and better response times to changes in the system.

Besides ensuring accurate and precise measurements, board-mounted sensors enable simpler, more reliable designs which can be quickly assembled using automated equipment. Pressure and flow sensors are typically available in several board-mount package styles, many of which offer options for different orientations for their integrated ports. This can be very helpful for a design that needs a clear path for the tubes which connect the sensor with whatever medium it is monitoring.