Effect of assuming constant tissue scattering on measured tissue oxygenation values during tissue ischemia and vascular reperfusion

The purpose of this study was to determine the effects of assuming constant tissue scattering properties on tissue oxygenation measurements during a vascular occlusion test (VOT). Twenty-one subjects (21.8 ± 1.9 yr) completed a VOT [1 min baseline (BL), 5 min of tissue ischemia (TI), and 3 min of vascular reperfusion (VR)]. Absolute concentrations of oxygenated heme (oxy-[heme]), deoxygenated heme (deoxy-[heme]), total heme (total [heme), tissue oxygen saturation (StO2), and heme difference [heme]diff) were measured using frequency domain near-infrared spectroscopy (FD-NIRS) while 1) continuously measuring and incorporating tissue scattering ([Formula: see text]) and 2) assuming scattering remained constant. FD-NIRS measured [Formula: see text] increased during TI at 692 nm ( P < 0.001) and decreased at 834 nm ( P < 0.001). During VR, [Formula: see text] decreased at 692 nm ( P < 0.001) and increased at 834 nm ( P < 0.001). When assuming constant scattering, oxy-[heme] was significantly less at TIpeak ( P < 0.05) while deoxy-[heme] and StO2 were significantly altered at BL, TIpeak, and VRpeak (all P < 0.001). Total [heme] did not change during the VOT. Absolute changes in deoxy-[heme], oxy-[heme], and StO2 in response to TI and VR were significantly exaggerated (all P < 0.001) and the rates of change during TI ( slope 1) and VR ( slope 2) in deoxy-[heme], oxy-[heme], StO2, and [heme]diff were significantly increased (all P < 0.05) when constant tissue scattering was assumed. These findings demonstrate the need for caution when interpreting NIRS data without continuously measuring tissue optical properties. Further, assuming tissue optical properties remain constant may have important consequences to experimental data and clinical conclusions made using NIRS. NEW & NOTEWORTHY NIRS measurements provide significant experimental and clinical insight. We demonstrate that absolute changes in tissue oxygenation measurements made with NIRS are overestimated and the kinetic responses of NIRS measurements are exaggerated by varying degrees among individuals if tissue scattering characteristics are assumed to remain constant during vascular occlusion tests.

Download Full-text

Evaluation of Different Near-Infrared Spectroscopy Devices for Assessing Tissue Oxygenation with a Vascular Occlusion Test in Healthy Volunteers

Journal of Vascular Research ◽

10.1159/000510072 ◽

2020 ◽

Vol 57 (6) ◽

pp. 341-347

Author(s):

Jaeyeon Chung ◽

Sang-Hwan Ji ◽

Young-Eun Jang ◽

Eun-Hee Kim ◽

Ji-Hyun Lee ◽

...

Keyword(s):

Infrared Spectroscopy ◽

Near Infrared Spectroscopy ◽

Near Infrared ◽

Pairwise Comparison ◽

Vascular Occlusion ◽

Tissue Oxygen Saturation ◽

Vascular Occlusion Test ◽

Occlusion Test ◽

Significant Difference ◽

Post Hoc

Near-infrared spectroscopy devices can measure peripheral tissue oxygen saturation (StO2). This study aims to compare StO2 using INVOS® and different O3™ settings (O325:75 and O330:70). Twenty adults were recruited. INVOS® and O3™ probes were placed simultaneously on 1 side of forearm. After baseline measurement, the vascular occlusion test was initiated. The baseline value, rate of deoxygenation and reoxygenation, minimum and peak StO2, and time from cuff release to peak value were measured. The parameters were compared using ANOVA and Kruskal-Wallis tests. Bonferroni’s correction and Mann-Whitney pairwise comparison were used for post hoc analysis. The agreement between StO2 of devices was evaluated using Bland-Altman plots. INVOS® baseline value was higher (79.7 ± 6.4%) than that of O325:75 and O330:70 (62.4 ± 6.0% and 63.7 ± 5.5%, respectively, p < 0.001). The deoxygenation rate was higher with INVOS® (10.6 ± 2.1%/min) than with O325:75 and O330:70 (8.4 ± 2.2%/min, p = 0.006 and 7.5 ± 2.1%/min, p < 0.001). The minimum and peak StO2 were higher with INVOS®. No significant difference in the reoxygenation rate was found between the devices and settings. The time to reach peak after cuff deflation was faster with INVOS® (both p < 0.001). Other parameters were similar. There were no differences between the different O3™ settings. There were differences in StO2 measurements between the devices, and these devices should not be interchanged. Differences were not observed between O3™ device settings.

Download Full-text

Impact of Changes in Tissue Optical Properties on Near-Infrared Diffuse Correlation Spectroscopy Measures of Skeletal Muscle Blood Flow

Journal of Applied Physiology ◽

10.1152/japplphysiol.00857.2020 ◽

2021 ◽

Author(s):

Miles F. Bartlett ◽

Scott M. Jordan ◽

Dennis M. Hueber ◽

Michael D. Nelson

Keyword(s):

Skeletal Muscle ◽

Blood Flow ◽

Optical Properties ◽

Near Infrared ◽

Muscle Blood Flow ◽

Reactive Hyperemia ◽

Correlation Spectroscopy ◽

Skeletal Muscle Blood Flow ◽

Diffuse Correlation Spectroscopy ◽

Tissue Optical Properties

Near-infrared diffuse correlation spectroscopy (DCS) is increasingly utilized to study relative changes in skeletal muscle blood flow. However, most diffuse correlation spectrometers assume that tissue optical properties- such as absorption (μa) and reduced scattering (μ's) coefficients- remain constant during physiological provocations, which is untrue for skeletal muscle. Here, we interrogate how changes in tissue μa and μ's affect DCS calculations of blood flow index (BFI). We recalculated BFI using raw autocorrelation curves and μa/μ's values recorded during a reactive hyperemia protocol in 16 healthy young individuals. First, we show that incorrectly assuming baseline μa and μ's substantially affects peak BFI and BFI slope when expressed in absolute terms (cm2/s, p<0.01) but these differences are abolished when expressed in relative terms (% baseline). Next, to evaluate the impact of physiologic changes in μa and μ's, we compared peak BFI and BFI slope when μa and μ's were held constant throughout the reactive hyperemia protocol versus integrated from a 3s-rolling average. Regardless of approach, group means for peak BFI and BFI slope did not differ. Group means for peak BFI and BFI slope were also similar following ad absurdum analyses, where we simulated supraphysiologic changes in μa/μ's. In both cases, however, we identified individual cases where peak BFI and BFI slope were indeed affected, with this result being driven by relative changes in μa over μ's. Overall, these results provide support for past reports in which μa/μ's were held constant but also advocate for real-time incorporation of μa and μ's moving forward.

Download Full-text

Noninvasive Assessment of Regional and Temporal Variations in Tissue Oxygenation by Near-Infrared Spectroscopy and Imaging

Applied Spectroscopy ◽

10.1366/0003702971939901 ◽

1997 ◽

Vol 51 (2) ◽

pp. 143-152 ◽

Cited By ~ 26

Author(s):

Michael G. Sowa ◽

James R. Mansfield ◽

Gordon B. Scarth ◽

Henry H. Mantsch

Keyword(s):

Infrared Spectroscopy ◽

Near Infrared Spectroscopy ◽

Near Infrared ◽

Tissue Oxygenation ◽

Infrared Imaging ◽

Temporal Variations ◽

Tissue Oxygen Saturation ◽

Venous Outflow ◽

Fuzzy C Means Clustering ◽

Time Courses

A combination of near-infrared spectroscopy and discrete wavelength near-infrared imaging is used to noninvasively monitor the forearm during periods of restricted blood outflow (venous outflow restriction) and interrupted blood inflow (ischemia). Multivariate analysis of image and spectral data time courses was used to identify highly correlated spectral and regional domains, while fuzzy C-means clustering of image time courses was used to reveal finer regional heterogeneities in the response of stressed tissues. Localized near-infrared spectroscopy was used to investigate the magnitude of the bulk changes in the tissue optical properties and the variation in tissue oxygenation saturation during venous outflow restriction and complete forearm ischemia. The imaging and spectroscopic analyses revealed highly localized regional variations in tissue oxygen saturation during forearm ischemia as compared to the more diffuse and global response of the forearm during venous outflow restriction.

Download Full-text

Accuracy and precision of tissue optical properties and hemodynamic parameters estimated by the BabyLux device: a hybrid time-resolved near-infrared and diffuse correlation spectroscopy neuro-monitor

Biomedical Optics Express ◽

10.1364/boe.10.002556 ◽

2019 ◽

Vol 10 (5) ◽

pp. 2556 ◽

Cited By ~ 2

Author(s):

Martina Giovannella ◽

Lorenzo Spinelli ◽

Marco Pagliazzi ◽

Davide Contini ◽

Gorm Greisen ◽

...

Keyword(s):

Optical Properties ◽

Near Infrared ◽

Correlation Spectroscopy ◽

Hemodynamic Parameters ◽

Time Resolved ◽

Diffuse Correlation Spectroscopy ◽

Tissue Optical Properties ◽

Accuracy And Precision

Download Full-text

Interindividual differences in the ischemic stimulus and other technical considerations when assessing reactive hyperemia

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00157.2019 ◽

2019 ◽

Vol 317 (4) ◽

pp. R530-R538 ◽

Cited By ~ 6

Author(s):

Ryan Rosenberry ◽

Darian Trojacek ◽

Susie Chung ◽

Daisha J. Cipher ◽

Michael D. Nelson

Keyword(s):

Near Infrared ◽

Reactive Hyperemia ◽

Vascular Occlusion ◽

Duplex Ultrasound ◽

Noninvasive Technique ◽

Close Link ◽

Interindividual Differences ◽

Tissue Ischemia ◽

Cardiovascular Morbidity And Mortality ◽

Wide Range

Reactive hyperemia is an established, noninvasive technique to assess microvascular function and a powerful predictor of all-cause and cardiovascular morbidity and mortality. Emerging evidence from our laboratory suggests a close link between reactive hyperemia and the metabolic rate of the ischemic limb and the existence of large interindividual differences contributing to markedly different stimuli to vasodilate. Here we relate forearm tissue desaturation (i.e., the ischemic stimulus to vasodilate, measured by near-infrared spectroscopy) to brachial artery hyperemic velocity and flow (measured using duplex ultrasound) across a wide range of ischemic stimuli. Twelve young and 11 elderly individuals were prospectively studied. To recapitulate conventional vascular occlusion testing, reactive hyperemia was first assessed using a standard 5-min occlusion period. Then, to evaluate the dose dependence of tissue ischemia on reactive hyperemia, we randomly performed 4-, 6-, and 8-min cuff occlusions in both groups. In all cases, peak velocity, as well as the 5-s average velocity, immediately after the cuff occlusion was significantly higher in the young than the elderly group; however, tissue desaturation was also much more pronounced in the young group ( P < 0.05), representing a greater ischemic stimulus. Remarkably, when reactive hyperemia was adjusted for the ischemic vasodilatory stimulus, group differences in reactive hyperemia were abrogated. Together, these data challenge conventional interpretations of reactive hyperemia and show that the ischemic stimulus to vasodilate varies across individuals and that the level of reactive hyperemia is often coupled to the magnitude of tissue desaturation.

Download Full-text

Near-Infrared Spectroscopy: A Tool for Diagnosing Necrotizing Enterocolitis at Onset of Symptoms in Preterm Neonates with Acute Gastrointestinal Symptoms?

American Journal of Perinatology ◽

10.1055/s-0040-1710033 ◽

2020 ◽

Author(s):

Julia Le Bouhellec ◽

Olivier Prodhomme ◽

Thibault Mura ◽

Aurélien Jacquot ◽

Clémentine Combes ◽

...

Keyword(s):

Infrared Spectroscopy ◽

Necrotizing Enterocolitis ◽

Near Infrared Spectroscopy ◽

Near Infrared ◽

Cerebral Oxygenation ◽

Gastrointestinal Symptoms ◽

Abdominal Distension ◽

Tissue Oxygen Saturation ◽

Preterm Neonates ◽

Nirs Data

Abstract Objective In premature neonates, bloody stools and/or abdominal distension with feeding intolerance may be inaugural signs of necrotizing enterocolitis (NEC). We assessed the ability of near-infrared spectroscopy (NIRS) to distinguish those neonates with NEC soon after the occurrence of these symptoms. Study Design We prospectively collected NIRS measurements of abdominal and cerebral regional tissue oxygen saturation (r-SO2), with values masked by an opaque cover. Two physicians, blinded to the NIRS data, determined whether the gastrointestinal symptoms were related to NEC 10 days after symptom onset. Results Forty-five neonates with mean (standard deviation [SD]) gestational, birth weight and postnatal ages of 31 (3.9) weeks, 1,486 (794) g, and 18 (14) days were enrolled over 30 months. Gastrointestinal symptoms were related to NEC in 23 patients and associated with other causes in 22. Analysis of the 48 hours of monitoring revealed comparable abdominal r-SO2 and splanchnic-cerebral oxygenation ratio (SCOR) in patients with and without NEC (r-SO2: 47.3 [20.4] vs. 50.4 [17.8], p = 0.59, SCOR: 0.64 [0.26] vs. 0.69 [0.24], p = 0.51). Results were unchanged after NIRS analysis in 6-hour periods, and restriction of the analysis to severe NEC (i.e., grade 2 and 3, 57% of the NEC cases). Conclusion In this study, NIRS monitoring was unable to individualize NEC in premature infants with acute gastrointestinal symptoms.

Download Full-text

SPECTRAL IMAGING AND ANALYSIS TO YIELD TISSUE OPTICAL PROPERTIES

Journal of Innovative Optical Health Sciences ◽

10.1142/s1793545809000528 ◽

2009 ◽

Vol 02 (02) ◽

pp. 123-129 ◽

Cited By ~ 12

Author(s):

STEVEN L. JACQUES

Keyword(s):

Optical Properties ◽

Rayleigh Scattering ◽

Spectral Imaging ◽

Biological Tissues ◽

Mie Scattering ◽

Tissue Oxygen Saturation ◽

Melanin Content ◽

Tissue Oxygen ◽

Spectral Image ◽

Tissue Optical Properties

An introduction to the basics of spectral imaging as applied to biological tissues is presented. An example of a spectral image of a face is used to demonstrate the data and spectral analysis that specify the melanin content (M), blood content (B), tissue oxygen saturation (S), water content (W), fraction of scattering due to Rayleigh scattering (f) and due to Mie scattering (1 - f), and the reduced scattering coefficient at 500-nm wavelength (μ′s 500 nm). The sensitivity of reflectance spectra to variation in the various parameters is illustrated.

Download Full-text

Assessment of tissue oxygen saturation during a vascular occlusion test using near-infrared spectroscopy: role of the probe spacing and measurement site studied in healthy volunteers

Critical Care ◽

10.1186/cc7408 ◽

2009 ◽

Vol 13 (Suppl 1) ◽

pp. P244

Author(s):

R Bezemer ◽

A Lima ◽

E Klijn ◽

J Bakker ◽

C Ince

Keyword(s):

Infrared Spectroscopy ◽

Near Infrared Spectroscopy ◽

Near Infrared ◽

Vascular Occlusion ◽

Tissue Oxygen Saturation ◽

Tissue Oxygen ◽

Vascular Occlusion Test ◽

Occlusion Test ◽

Probe Spacing

Download Full-text

Near-infrared monitoring of cerebral tissue oxygen saturation and blood volume in newborn piglets

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1997.273.2.h682 ◽

1997 ◽

Vol 273 (2) ◽

pp. H682-H686 ◽

Cited By ~ 2

Author(s):

N. C. Brun ◽

A. Moen ◽

K. Borch ◽

O. D. Saugstad ◽

G. Greisen

Keyword(s):

Blood Volume ◽

Near Infrared ◽

Cerebral Blood Volume ◽

Tissue Oxygenation ◽

Oxygenation Index ◽

Mean Value ◽

Tissue Oxygen Saturation ◽

Cerebral Tissue ◽

Newborn Piglets ◽

Sagittal Sinus

Near-infrared spectrophotometry (NIRS) potentially provides a tool for noninvasive tissue oxygenation and blood volume monitoring. Cerebral monitoring could be useful in the prevention of hypoxic ischemic brain injury in newborns. This study sought to validate such NIRS measurements in normoventilated, hypocapnic, and hypoxemic states in the brain of newborn piglets vs. arterial (SaO2) and sagittal sinus blood hemoglobin saturation (SssO2) and blood volume measurements with 99mTc-labeled erythrocytes. NIRS measurements of cerebral blood volume (CBV) were performed with both oxyhemoglobin and indocyanine green as tracers, and changes in CBV were monitored by following the change in the concentration of total hemoglobin (i.e., oxyhemoglobin + deoxyhemoglobin). NIRS CBV measurements did not correlate well with the radioactive measurements. NIRS measurements of oxygenation, however, correlated well with a weighted mean value of SaO2 and SssO2 (r = 0.90; P < 0.0001). Multiple linear regression of the oxygenation index (i.e., oxyhemoglobin - deoxyhemoglobin) on SaO2 and SssO2 suggested that NIRS sees hemoglobin in tissue in a venous-to-arterial ratio of 2:1. Therefore, in this study, NIRS reliably monitored changes in cerebral tissue oxygenation but not in CBV.

Download Full-text