Photopletismography in dogs: identification of spectral elements and application in a surgical setting

This pilot study aimed to assess cardiac and respiratory activity in dogs using photopletismography (PPG) during the presurgical period and to determine the spectral elements composing the measured PPG signal. The studied sample comprised four dogs, two males and two females, ranging from 7 months to 6 years old, from different breeds under anesthetic premedication. PPG signal was obtained at the tail using a PPG sensor connected to a Bitalino hardware board (Plux, Portugal) before and after premedication with 5 µg/kg dexmedetomidine and 0.35 mg/kg methadone by intramuscular injection. The data obtained was analyzed using Matlab (MathWorks, USA) and the PPG signal decomposed into its various frequencies by the Wavelet transform. The estimated minimum and maximum values of heart and respiratory activity were then identified. Seven waves were found. Correspondence with the cardiac and respiratory activities was determined after comparing its frequency with the normal heart and respiratory frequencies in dogs. This study demonstrated that the PPG technique is a valuable diagnostic tool to record both heart and respiratory frequencies in a clinical setting using a wireless system.