title: Frequency-domain vs continuous-wave near-infrared spectroscopy devices: a comparison of clinically viable monitors in controlled hypoxia.
abstract: The Near-infrared spectroscopy (NIRS) has not been adopted as a mainstream monitoring modality in acute neurosurgical care due to concerns about its reliability and consistency. However, improvements in NIRS parameter recovery techniques are now available that may improve the quantitative accuracy of NIRS for this clinical context. Therefore, the aim of this study was to compare the abilities of a continuous-wave (CW) NIRS device with a similarly clinically viable NIRS device utilising a frequency-domain (FD) parameter recovery technique in detecting changes in cerebral tissue saturation during stepwise increases of experimentally induced hypoxia. Nine healthy individuals (6M/3F) underwent a dynamic end-tidal forced manipulation of their expiratory gases to induce a stepwise induced hypoxia. The minimum end-tidal oxygen partial pressure (EtO2) achieved was 40 mm Hg. Simultaneous neurological and extra-cranial tissue NIRS reading were obtained during this protocol by both tested devices. Both devices detected significant changes in cerebral tissue saturation during the induction of hypoxia (CW 9.8 ± 2.3 %; FD 7.0 ± 3.4 %; Wilcoxon signed rank test P < 0.01 for both devices). No significant difference was observed between the saturation changes observed by either device (P = 0.625). An observably greater degree of noise was noticed in parameters recovered by the FD device, and both demonstrated equally variable baseline readings (Coefficient of variance 8.4 and 9.7 % for the CW and FD devices, respectively) between individuals tested. No advantageous difference was observed in parameters recovered from the FD device compared with those detected by CW.
authors: National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre (NIHR SRMRC), University Hospitals Birmingham NHS Foundation Trust, Heritage Building (Old Queen Elizabeth Hospital), Edgbaston, Birmingham, B15 2TH, UK. David.Davies@uhb.nhs.uk.|Department of Neurosurgery, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK. David.Davies@uhb.nhs.uk.
authors: David James
authors: DJ
authors: Davies
authors: PSIBS Doctoral Training Centre, University of Birmingham, Birmingham, UK.
authors: Michael
authors: M
authors: Clancy
authors: School of Chemistry, University of Birmingham, Birmingham, UK.
authors: Daniel
authors: D
authors: Lighter
authors: School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.
authors: George M
authors: GM
authors: Balanos
authors: School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.
authors: Samuel John Edwin
authors: SJE
authors: Lucas
authors: PSIBS Doctoral Training Centre, University of Birmingham, Birmingham, UK.
authors: Hamid
authors: H
authors: Dehghani
authors: National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre (NIHR SRMRC), University Hospitals Birmingham NHS Foundation Trust, Heritage Building (Old Queen Elizabeth Hospital), Edgbaston, Birmingham, B15 2TH, UK.|School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK.
authors: Zhangjie
authors: Z
authors: Su
authors: Department of Neurosurgery, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK.
authors: Mario
authors: M
authors: Forcione
authors: National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre (NIHR SRMRC), University Hospitals Birmingham NHS Foundation Trust, Heritage Building (Old Queen Elizabeth Hospital), Edgbaston, Birmingham, B15 2TH, UK.|Department of Neurosurgery, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK.|School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK.
authors: Antonio
authors: A
authors: Belli
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging*; D003201:Computers; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D000860:Hypoxia; D008297:Male; D010100:Oxygen; D010101:Oxygen Consumption; D010313:Partial Pressure; D011446:Prospective Studies; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
chemical_list: D010100:Oxygen
keywords: Cerebral blood flow; Continuous-wave near-infrared spectroscopy; Frequency-domain near-infrared spectroscopy; Head injury