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Vital signs without handling or animal prep
A potential new method for non-invasively monitoring physiological parameters in small animals takes advantage of radio frequency near-field coherent sensing technology.
The assessment of physiological parameters, such as respiration rate, heart rate, blood pressure, or body temperature, is crucial in small animal veterinary practice and for many animal experiments. Monitoring vital signs is important during anesthesia as well as the post-surgical recovery phase, and the measurements can be used to detect cardiovascular diseases or to assess experimental treatments, e.g. during drug discovery and testing. Physiological parameters are also relevant for refinement research, as changes in these parameters are known to be indicators of stress and pain in animals1.
Traditionally applied techniques to measure these physiological parameters are invasive or require immobilization of the animal. Examples include radiotelemetry, electrocardiogram (ECG), ultrasound, or the use of other monitoring systems equipped with clips or electrodes to be attached to the animal’s surface. Radiotelemetry is capable of continuous data acquisition for a number of weeks in freely moving animals, but requires a transmitter device to be implanted surgically. The latter techniques offer data acquisition for short time periods during which the animal needs to be anaesthetized and prepared specifically (e.g. hair removal, which may cause thermoregulatory issues, or the use of tape, clamps, or gel for optimal skin contact, which may cause discomfort). All of these methods yield valuable information about the animal’s physiological and affective state but may induce discomfort, stress and pain.
At the moment, physiological parameters are hard to obtain non-invasively in conscious and freely moving animals, and techniques offering this are therefore of high relevance with regard to refinement of animal experiments. Currently available non-contact techniques include optical methods like infrared thermography, vibrocardiography and photoplethysmography, or radio- and micro- wave based methods like radar. None are yet used routinely in small animals.
A study performed by Xiaonan Hui and Edwin Kan at Cornell University demonstrates that radio frequency near-field coherent sensing (NCS) allows non-contact, non-invasive, real-time monitoring of physiological parameters in undisturbed animals, either in their home cage environment or during anesthesia2. The NCS method uses an antenna, placed near the animal’s cage or body, and microchip tags that measure mechanical motion by emitting radio waves; these are reflected from the body surface and the internal organs and detected by an electronic reader. Vital signs can be collected without preparing or restraining the animal or implanting transmitter devices (Fig. 1). Therefore, NCS does not affect the animals’ wellbeing or behavior, induces no pain, and likely causes less stress compared to existing methods. Thus, it also allows more physiological data to be collected.