Speckle Vibrometry for Instantaneous Heart Rate Monitoring

Instantaneous heart rate (IHR) has been investigated for sleep applications, such as sleep 1 apnea detection and sleep staging. To ensure the comfort of the patient during sleep, it is desirable for 2 IHR to be measured in a contact-free fashion. In this work, we use Speckle Vibrometry (SV) to perform 3 on-skin and on-textile IHR monitoring in a sleep setting. Minute motions on the laser-illuminated 4 surface can be captured by a defocused camera, enabling the detection of cardiac motions even on 5 textiles. We investigate supine, lateral, and prone sleeping positions. Based on Bland-Altman analysis 6 between SV cardiac measurements and electrocardiogram (ECG), with respect to each position, we 7 achieve the best limits of agreement with ECG of [-8.65, 7.79] bpm, [-9.79, 9.25] bpm, and [-10.81, 10.23] 8 bpm respectively. The results indicate the potential of using Speckle Vibrometry as a contact-free 9 monitoring method for instantaneous heart rate in a setting where the participant is allowed to rest 10 in a spontaneous position while covered by textile layers.