title: Investigation of photoplethysmographic signals  and blood oxygen saturation values obtained from human splanchnic organs using a fiber optic sensor.
abstract: OBJECTIVE
  A reliable, continuous method of monitoring splanchnic organ oxygen saturation could allow for the early detection of malperfusion, and may prevent the onset of multiple organ failure. Current monitoring techniques have not been widely accepted in critical care monitoring. As a preliminary to developing a continuous indwelling device, this study evaluates a new handheld fiber optic photoplethysmographic (PPG) sensor for estimating the blood oxygen saturation (SpO(2)) of splanchnic organs during surgery.
  
  
  METHODS
  A fiber optic splanchnic PPG sensor, instrumentation system and virtual instrument were developed to facilitate PPG and SpO(2) measurement from splanchnic organs. Following Local Research Ethics Committee approval, the sensor was evaluated on seventeen ASA 1 and 2 patients undergoing open laparotomy. PPG signals were obtained from the large bowel, small bowel, liver and stomach. Simultaneous PPG signals from the finger were also obtained using an identical fiber optic sensor.
  
  
  RESULTS
  Good quality PPG signals with high signal-to-noise (SNR) ratios were obtained from all splanchnic sites under investigation. Analysis of the ac and dc amplitudes of the red and infrared PPG signals showed there to be a statistically significant difference between PPG signals obtained from splanchnic organs with those obtained from the finger (using fiber optic sensors). Estimated SpO(2) values from the splanchnic organs show good agreement with those obtained from the finger using both a fiber optic sensor and a commercial device. Furthermore, the results of a Bland and Altman analysis indicate that fiber optic splanchnic pulse oximetry, particularly of the bowel, may provide a suitable method for monitoring splanchnic organ perfusion.
  
  
  CONCLUSIONS
  The evaluation of a new fiber optic sensor on anaesthetized patients undergoing laparotomy demonstrated that good quality PPG signals and SpO(2) estimates can be obtained from splanchnic organs. Such a sensor may provide a useful tool for the intraoperative assessment of splanchnic perfusion.
authors.affiliation: School of Engineering and Mathematical Sciences, City University London, Northampton Square, London, EC1V 0HB, UK. m.hickey@city.ac.uk
authors.forename: Michelle
authors.initials: M
authors.lastname: Hickey
authors.forename: Neal
authors.initials: N
authors.lastname: Samuels
authors.forename: Nilesh
authors.initials: N
authors.lastname: Randive
authors.forename: R M
authors.initials: RM
authors.lastname: Langford
authors.forename: P A
authors.initials: PA
authors.lastname: Kyriacou
mesh_terms: D000328:Adult; D001785:Blood Gas Monitoring, Transcutaneous / Q000295:instrumentation / Q000379:methods; D005260:Female; D005385:Fingers; D006801:Humans; D007259:Infrared Rays; D007813:Laparotomy; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation / Q000379:methods; D055100:Optical Fibers; D010092:Oximetry / Q000295:instrumentation* / Q000379:methods; D010100:Oxygen / Q000097:blood*; D017156:Photoplethysmography / Q000295:instrumentation* / Q000379:methods; D013152:Splanchnic Circulation
chemical_list: D010100:Oxygen