Recording the heart beat of cattle using a gradiometer system of optically pumped magnetometers

Sutter, Jens U. and Lewis, Oliver and Robinson, Clive and McMahon, Anthony and Boyce, Robert and Bragg, Rachel and Macrae, Alastair and Orton, Jeffrey and Shah, Vishal and Ingleby, Stuart J. and Griffin, Paul F. and Riis, Erling (2020) Recording the heart beat of cattle using a gradiometer system of optically pumped magnetometers. Computers and Electronics in Agriculture, 177. 105651. ISSN 0168-1699 (https://doi.org/10.1016/j.compag.2020.105651)

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Abstract

Monitoring of heart rate has the potential to provide excellent data for the remote monitoring of animals, and heart rate has been associated with stress, pyrexia, pain and illness in animals. However monitoring of heart rate in domesticated animals is difficult as it entails the restraint of the animal (which may in turn affect heart rate), and the application of complex monitoring equipment that is either invasive or not practical to implement under commercial farm conditions. Therefore accurate non-invasive automated remote monitoring of heart rate has not been possible in domesticated animals. Biomagnetism associated with muscle and nerve action provides a promising emerging field in medical sensing, but it is currently confined to magnetically-shielded clinical environments. In this study, we use biomagnetic sensing on commercial dairy cattle under farm conditions as a model system to show proof-of-principle for non-contact magnetocardiography (MCG) outside a controlled laboratory environment. By arranging magnetometers in a differential set-up and using purpose-built low-noise electronics, we are able to suppress common mode noise and successfully record the heart rate, the heart beat intervals and the heart beat amplitude. Comparing the MCG signal with simultaneous data recorded using a conventional electrocardiogram (ECG) allowed alignment of the two signals, and was able to match features of the ECG including the P-wave, the QRS complex and the T-wave. This study has shown the potential for MCG to be developed as a non-contact method for the assessment of heart rate and other cardiac attributes in adult dairy cattle. Whilst this study using an animal model showed the capabilities of un-shielded MCG, these techniques also suggest potentially exciting opportunities in human cardiac medicine outside hospital environments.

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