The Photoplethysmography Imaging Device for Non-contact Monitoring of Sympathetic Blocks

Transcription

1 The Photoplethysmography Imaging Device for Non-contact Monitoring of Sympathetic Blocks U.Rubins 1, A.Miscuks 2, I.Golubovska 2, M.Aron 3 and J.Spigulis 1 1 Institute of Atomic Physics and Spectroscopy, University of Latvia 2 Faculty of Medicine, Hospital of Traumatology and Orthopaedics, University of Latvia 3 Medical Centre D.A.P. Pain Clinics

2 Introduction The principle of photoplethysmography imaging Methods Results The prototype PPG imaging device The algorithm of PPG imaging Monitoring of quality of sympathetic blocks Summary

3 Introduction One of the main objectives of anaesthesia is to ensure a patient relief from pain quality of regional anesthesia (RA) There are some methods for objective control of RA: Mechanical contact simple but not objective Temperature monitoring limited to small skin surface/ expensive Pulse oximetry monitoring contact method Measurement of electrodermal activity unconfortable The main aim of our research was to find simple non-contact optical method for monitoring the quality of sympathetic block for invasive treatment of neuropathic pain

4 The principle of photoplethysmography imaging Stratum corneum Epidermis -Capillaries Dermis -Small arterioles Fat -Large arteries Photoplethysmography imaging is a non-invasive technique for detection of blood flow pulsations in skin using backscattered optical radiation.

5 Methods

6 The prototype PPG imaging device White light source (80 LED s 4W) Computer with custom designed software CMOS color video camera with optics (1280x1024pix 30fps) USB connection

7 The algorithm of PPG imaging Data from video camera Region of interest (green G color) Spatial analysis (object recognition, segmentation, blurring) Temporal analysis (band-pass filtering, heartbeat recognition) Intensity pulsations PPG image mapping

8 The algorithm of PPG imaging The temporal analysis 1. RoI is divided by sub-regions (16x16 pix.) 2. PPG signal from each sub-region has been analyzed: the mean value in specified sub-region, in every video frame; band-pass filtering ( Hz) highlights heartbeat component; only those regions are defined where heartbeats are recognized A j-1 A j T j-1 T j Successive sub-regions are defined where the waveforms of neighborhood beats are similar: 0.7 < A j-1 /A j < < T j-1 /T j < 1.5 A pulse amplitude, T pulse period in j-th beat

9 The algorithm of PPG imaging The calculation of PPG image 1. RoI has divided by sub-regions 2. PPG signal from each sub-region has been analyzed: the mean value in specified sub-region, in every video frame; band-pass filtering ( Hz) highlights heartbeat component; only those regions are defined where heartbeats are recognized 3. The AC amplitude and pulse rate has been calculated in every heartbeat (real-time) 4. PPG image map has been calculated from AC amplitudes of PPG in every pixel of RoI image Each color of PPGI represents the amplitude of PPG signal

10 Results

11 The software of PPG imaging

12 Monitoring of quality of regional anesthesia Immediately ater RA input 8 min. later 12 min. later 16 min. later After the administration of RA, due to sympathetic block, the temperature of palm skin increases; PPG amplitude increases too

13 Monitoring of quality of sympathetic blocks After the administration of lidocaine, PPG amplitude increases indicating successfull sympathetic block in leg Start contrast lidocaine fenol

14 Conclusion Our developed PPG imaging device could be usable for real-time monitoring of skin tissue blood perfusion. The PPGI technique could be usable for monitoring of quality of sympathetic block for invasive treatment of neuropathic pain.

15 Thank you