Noninvasive Tissue Oxygen Research Articles

Tissue Perfusion and the Braden Scale as Predictors of Pressure Injury Risk in the Intensive Care Unit Patient

Purpose: The national rate of pressure injury (PI) in the intensive care unit (ICU) 2016-2018 was 5.97%, while at one hospital in Honolulu, Hawaii it averaged 13%. The Braden scale is the gold standard PI risk assessment tool. Researchers have reported the Braden scale has limited value in the ICU setting and consider tissue perfusion to be the better indicator. The aim was to determine if tissue perfusion, as measured by noninvasive transcutaneous tissue oxygen levels, was a predictor of PI risk development.Methods: Electronic medical records of 161 patients admitted from January 1, 2017 to June 30, 2019 were retrospectively reviewed. Patients’ characteristics were summarized using descriptive statistics. Bivariate associations with the development of PI were examined using Fisher’s exact test for the categorical variables, and Wilcoxon rank-sum test for the continuous variables. A multivariable logistic model was fitted for the development of PI with adjustments for potential confounders.Results: Of 161 patients, 125 met the inclusion criteria. Length of stay, Acute Physiology and Chronic Health Evaluation II score, use of vasopressors, and the Braden score were statistically significant predictors of PI risk development; tissue perfusion was not significant.Conclusion: ICU patients have a higher mortality and severity of illness. The Braden score guides implementation of PI preventative measures. The relationship between tissue perfusion and PI development may warrant further research. A broader clinical picture to incorporate the Braden scale and other risk factors in PI development such as Acute Physiology and Chronic Health Evaluation II score and use of vasopressors should be considered.

Assessment of Anastomotic Viability With Spectroscopic Real-time Oxygen Saturation Measurement in a Porcine Study.

Anastomotic leakage (AL) is a severe complication following intestinal procedures. Intra.Ox™ by ViOptix Inc (Newark, CA, USA) is a novel, FDA-approved spectroscopic device which enables real-time measurement of mixed tissue oxygen saturation (StO2). Using a porcine model, this study explores the correlation between StO2 measurements and AL formation as well as investigates the applicability of Intra.Ox™ in the clinical setting. Eleven female swine were divided into 3 groups to explore AL formation in different ischemic conditions. Group 1: 100% mesenteric-vascular ligation, n = 3; Group 2: 50% ligation, n = 5; Group 3: No mesenteric ligation, n = 3. StO2 at the anastomotic line was measured before and after vessel ligation and anastomosis. Measurements were taken at 6 distinct locations along afferent and efferent loops. AL was evaluated on postoperative day 5 by re-laparotomy. AL rate was 100%, 60% and 0% in groups 1, 2 and 3, respectively. Post-anastomotic StO2 in group 1 (22.9 ± 18.5%) and 2 (39.2 ± 20.1%) were significantly lower than in group 3 (53.1 ± 8.3%, p<.0001). Post-anastomotic StO2 readings ≤40% indicated AL potential with 100% sensitivity,+ 80% specificity, positive predictive value of 85.7% and negative predictive value of 100%. This study demonstrates the value of Intra.Ox™ in assessing local perfusion and indicate the association between low StO2 and AL by providing accurate, real-time, noninvasive tissue oxygenation measurements at anastomotic sites. Further studies are required to investigate the clinical application of this novel device in intestinal surgery.

Noninvasive Measurement of Oxygen Saturation in Human Retinal Blood Vessels and Tissues With Multispectral Confocal Imaging.

Proof of concept for the first system of noninvasive human retinal vessel and tissue oxygenation measurement in axial and radial directions. A confocal imaging system capable of calculating and mapping relative retinal blood oxygenation in radial and axial directions from three eyes of two healthy subjects was built. The relationship between oxygenation and retinal depth in vivo was analyzed to illustrate application of this novel system. The system shows capacity for measuring oxygenation along retinal depth for the first time. (1) Arteriovenous oxygenation difference decreases with blood vessel diameter. (2) Artery-tissue oxygenation difference is greater than vein-tissue oxygenation difference in the same region. (3) Intravascular-extravascular oxygenation difference decreases with blood vessel diameter. (4) Oxygenation data reported with a 95% CI are as follows: A1 91.5% ± 18.2%, V1 32.8% ± 18.6%, A2 97.3% ± 17.8%, V2 64.4% ± 11.2%, A3 73.2% ± 19.1%, V3 52.9% ± 15.3%, and Tissue 56.6% ± 00.4%. This article demonstrates proof of concept for retinal oxygenation calculation in radial and axial dimensions for the first time. Initial results provide biological validity to this method. Future aims include further characterization of this system's results in healthy subjects and subsequent comparison of oxygenation between diseased and healthy retinae. [Ophthalmic Surg Lasers Imaging Retina. 2022;53:275-283.].

Noninvasive Monitoring of Deep Tissue Oxygenation in Buried Flaps by Time-Resolved Near-Infrared Spectroscopy in Pigs.

Flap monitoring in reconstructive surgery is particularly important because flap failure is a dramatic event for the patient and for the medical team. Noninvasive deep tissue oxygenation monitoring is a challenge. The aim of this experimental study was to assess the performance of time-resolved near-infrared spectroscopy compared with continuous-wave near-infrared spectroscopy and with invasive oxygen partial pressure measurement in pigs. Thirty fasciocutaneous flaps based on the superficial epigastric inferior pedicle were harvested and buried under the transcutaneous dorsal muscle (approximately 1 cm thick). An optical probe was placed on the skin above each buried flap. For each pig, two buried flaps were performed, one submitted to arterial occlusion and one to venous occlusion. Oxyhemoglobin and deoxyhemoglobin concentrations were observed for over 40 minutes before clamping, almost 20 minutes during clamping and during a period of release of approximately 20 minutes. Variations in time-resolved near-infrared spectroscopy were compared to the oxygen partial pressure and continuous-wave near-infrared spectroscopy variations. All vascular events were detected by the time-resolved near-infrared spectroscopy. During arterial clamping, oxyhemoglobin decreased rapidly, whereas deoxyhemoglobin increased moderately. The divergence of oxyhemoglobin and deoxyhemoglobin curves indicated arterial occlusion. During venous clamping, deoxyhemoglobin increased, whereas oxyhemoglobin increased briefly then remained stable or decreased moderately. The initial increases in the oxyhemoglobin and deoxyhemoglobin curves indicated venous occlusion. Oxygen partial pressure failed to detect vascular events in three cases. Continuous-wave near-infrared spectroscopy could not clearly identify vascular occlusions. Thus, the authors demonstrated the relevance of time-resolved near-infrared spectroscopy to buried flap monitoring. Time-resolved near-infrared spectroscopy could differentiate between arterial occlusion and venous occlusion.

Changes in Optical Path Length Reveal Significant Potential Errors of Muscle Oxygenation Evaluation during Exercise in Humans.

Near-infrared spectroscopy (NIRS), performed with a commonly available noninvasive tissue oxygenation monitoring device, is based on the modified Beer-Lambert law (MBLL). Although NIRS based on MBLL (NIRSMBLL) assumes that the optical path length (PL) is constant, the effects of changes in PL during exercise on muscle oxygenation calculated by MBLL are still incompletely understood. Thus, the purposes of this study were to examine the changes in optical properties during ramp incremental exercise and to compare muscle oxygen dynamics measured by time-resolved NIRS with those calculated based on MBLL. Twenty-two healthy young men performed ramp incremental cycling exercise until exhaustion. Optical properties (reduced scattering coefficient and PL) and absolute oxygenated, deoxygenated, and total hemoglobin and myoglobin concentrations (oxy[Hb + Mb], deoxy[Hb + Mb], and total[Hb + Mb], respectively) at the vastus lateralis were continuously monitored by a three-wavelength (763, 801, and 836) time-resolved NIRS device. The values of oxy-, deoxy-, and total[Hb + Mb] were then recalculated by assuming constant PL. PL at all wavelengths statistically significantly shortened during exercise. In particular, PL at 763 nm was greatly shortened, and the average changes during exercise were a 9.8% ± 3.1% reduction. In addition, significant differences in the kinetics of oxy-, deoxy-, and total[Hb + Mb] between directly measuring PL and assuming constant PL were found. The average changes in measured PL and assuming constant PL-deoxy[Hb + Mb] were increases of 28.8 ± 16.0 μM and increases of 16.4 ± 9.3 μM, respectively. Assuming constant PL in NIRSMBLL significantly underestimated actual muscle oxy/deoxygenation as compared with measurements obtained by real-time PL determination. The percent degree of the underestimated oxy/deoxygenation was greater than the percent degree of the changes in PL.

Noninvasive Cerebral Perfusion and Oxygenation Monitoring Augment Prolonged Field Care in a Non-Human Primate Model of Decompensated Hemorrhage and Resuscitation.

Decompensated hemorrhagic shock (DHS) is the leading cause of preventable death in combat casualties. "Golden hour" resuscitation effects on cerebral blood flow and perfusion following DHS in prolonged field care (PFC) are not well investigated. Using an established non-human primate model of DHS, we hypothesized noninvasive regional tissue oxygenation (rSO2) and Transcranial Doppler (TCD) would correlate to the invasive measurement of partial pressure of oxygen (PtO2) and mean arterial pressure (MAP) in guiding hypotensive resuscitation in a PFC setting. Ten rhesus macaques underwent DHS followed by a 2 h PFC phase (T0-T120), and subsequent 4 h hospital resuscitation phase (T120-T360). Invasive monitoring (PtO2, MAP) was compared against noninvasive monitoring systems (rSO2, TCD). Results were analyzed using t tests and one-way repeated measures ANOVA. Linear correlation was determined via Pearson r. Significance = P < 0.05. MAP, PtO2, rSO2, and mean flow velocity (MFV) significantly decreased from baseline at T0. MAP and PtO2 were restored to baseline by T15, while rSO2 was delayed through T30. At T120, MFV returned to baseline, while the Pulsatility Index significantly elevated by T120 (1.50 ± 0.31). PtO2 versus rSO2 (R2 = 0.2099) and MAP versus MFV (R2 = 0.2891) shared very weak effect sizes, MAP versus rSO2 (R2 = 0.4636) displayed a low effect size, and PtO2 versus MFV displayed a moderate effect size (R2 = 0.5540). Though noninvasive monitoring methods assessed here did not correlate strongly enough against invasive methods to warrant a surrogate in the field, they do effectively augment and direct resuscitation, while potentially serving as a substitute in the absence of invasive capabilities.

Use of Tissue Oxygen Saturation Levels as a Vital Sign in the ED Triage

Objectives: The utilization of vital signs as triage tools remains a mainstay ofemergency patients. The evolution of monitoring technologies, including the noninvasive tissue oxygen saturation devices has improved our ability to monitor the critically ill patients. The aim of the present study was to determine the tissue oxygen saturation (StO2) levels of the patients as a vital sign during emergency triage. Methods: Approximately 30-35 patients present to our emergency department each day and the triage of these patients are performed by a nurse at admission time. A three level system (1: red, 2: yellow, 3: green) is used to determine the triage level of the patients presenting to our department. We examined 150 patients during five days. Age gender, triage levels and hospitalization status of the patients were noted. For the StO2 level measurement, an Inspectra device was placed to the right thenar muscle for 10 s and mean of the first, fifth and 10th second values were noted at the admission time. Results: In our study 73 females (48.6%), 77 males (51.4%) totally 150 patients were included. We determined a significant difference between green and yellow (p=0.00), green and red (p=0.00), yellow and red (p=0.001) according to StO2 levels. We couldn’t find a significant difference between females and males in triage groups (p=0.13 for green, p=0.71 for yellow, p=0.86 for red). There was correlation between StO2 - triage level (p=0.00, r=0.609) and StO2-hospitalization status (p=0.00, r=0.449). Conclusion: StO2 level measurement may be helpful in determining the triage level of the patients presenting to the ED. Keywords: emergency, tissue oxygen saturation, triage

Measuring Flap Oxygen Using Electron Paramagnetic Resonance Oximetry.

To determine if electron paramagnetic resonance (EPR) oximetry is a viable technology to aid in flap monitoring. Prospective cohort. This was a cohort study assessing accuracy and speed of EPR oximetry in detecting ischemia of a saphenous artery-based flap in a rat model, using transcutaneous oximetry as a control. Measurements were obtained under both resting and ischemic conditions for nine Sprague Dawley rats (18 flaps), for 3 postoperative days following flap elevation. The mean partial pressure of oxygen prior to tourniquet application was 66.9 ± 8.9 mm Hg with EPR oximetry and 64.7 ± 5.2 mm Hg with transcutaneous oximetry (P = .45). Mean partial pressures of oxygen during tourniquet application were 8.9 ± 3.2 mm Hg and 8.5 ± 2.9 mm Hg for EPR oximetry and transcutaneous oximetry, respectively (P = .48), and 67.2 ± 6.9 mm Hg and 65.3 ± 6.1 mm Hg after tourniquet release for EPR oximetry and transcutaneous oximetry, respectively (P = .44). The mean ischemia detection time of EPR oximetry was 49 ± 21 seconds. Offering timely, accurate, and noninvasive tissue oxygen measurements, EPR oximetry is a promising adjunct in flap monitoring. NA Laryngoscope, 129:E415-E419, 2019.

Novel optical assessments of tissue composition and viability using fluorescence spectroscopy and tissue oxygenation spectrophotometry in patients with systemic sclerosis: a pilot study

Objective: Patients with systemic sclerosis (SSc) experience significant morbidity and mortality, therefore, the development of tests to aid its early diagnosis are very important. The aim of this pilot study was to assess the diagnostic value of novel optical non-invasive skin fluorescence spectroscopy (FS) and tissue oxygen saturation (TOS) viability measurements in patients with established SSc. Approach: Two groups were studied, comprising 14 SSc patients and nine healthy controls (93% and 73% females, respectively). FS and TOS measurements were collected from three body sites: the forearm, chest, and calf. Fluorescence intensities at wavelengths attributed to collagen, elastin, and L-tryptophan were computed, with adjustment for melanin, and a normalised combined fluorescence score (NCFS) was determined. Main results: The NCFS was significantly higher (p < 0.001) and the combined TOS significantly lower (p < 0.001) in the SSc group. TOS measurements alone showed good classification accuracy (95.7%) at separating SSc from healthy control participants, with some clustering of values close to the 50% oxygenation level in both groups. When the composition and viability measures were combined and modelled using binary logistic regression, excellent results for the sample were obtained following leave one out cross validation (100%). Significance: The results of this pilot study demonstrate the potential diagnostic utility of FS and TOS assessments in SSc patients and further work is now needed to validate these techniques prospectively in a larger group of SSc patients across the spectrum of the disease, and also patients with other types of vasculopathy and conditions that can cause skin fibrosis.

Non-invasive tissue oximetry following unilateral DIEP-flap reconstruction: A pilot evaluation

IntroductionPost-operative monitoring of a free flap transplant in the form of a deep inferior epigastric perforator flap (DIEP-flap) is crucial for early detection of vascular compromise. The aim of the current study, therefore, is to gain insight whether non-invasive tissue oximetry is suitable for the assessment of tissue perfusion following DIEP-flap surgery and whether it can serve as an early marker for vascular compromise. MethodsPatients (n = 29) undergoing secondary unilateral DIEP-flap surgery were included in this prospective explorative study. Non-invasive tissue oxygen saturation (StO2) measurements were performed using one sensor positioned on the DIEP-flap and another positioned on the native breast. Measurements were performed directly after the surgical procedure until 24 h post-operatively. ResultsTissue oxygenation response was swift in the native breast (on average 11.9%/h for 84 min, n = 28), whereas the DIEP-flap showed a lower and more extended tissue recovery phase of approximately 7.5%/h for 6 h (n = 23). In some of these latter cases (n = 14), an acute and second more prolonged response was observed in the DIEP-flap. The average difference between the DIEP-flap and native breast StO2 was 4% across the entire measurement (p = 0.043). Two patients underwent post-operative re-exploration of the DIEP-flap, in which an immediate and constant enlarged difference between DIEP-flap and native breast StO2 (≥38%) and a decreased DIEP-flap StO2 (≤43%) was observed. ConclusionContinuous non-invasive tissue oxygen saturation is suitable for postoperative monitoring of DIEP-flaps, and StO2 pattern may aid in early identification of vascular compromise in DIEP-flaps.

Toward translating near-infrared spectroscopy oxygen saturation data for the non-invasive prediction of spatial and temporal hemodynamics during exercise.

Image-based computational fluid dynamics (CFD) studies conducted at rest have shown that atherosclerotic plaque in the thoracic aorta (TA) correlates with adverse wall shear stress (WSS), but there is a paucity of such data under elevated flow conditions. We developed a pedaling exercise protocol to obtain phase contrast magnetic resonance imaging (PC-MRI) blood flow measurements in the TA and brachiocephalic arteries during three-tiered supine pedaling at 130, 150, and 170% of resting heart rate (HR), and relate these measurements to non-invasive tissue oxygen saturation [Formula: see text] acquired by near-infrared spectroscopy (NIRS) while conducting the same protocol. Local quantification of WSS indices by CFD revealed low time-averaged WSS on the outer curvature of the ascending aorta and the inner curvature of the descending aorta (dAo) that progressively increased with exercise, but that remained low on the anterior surface of brachiocephalic arteries. High oscillatory WSS observed on the inner curvature of the aorta persisted during exercise as well. Results suggest locally continuous exposure to potentially deleterious indices of WSS despite benefits of exercise. Linear relationships between flow distributions and tissue oxygen extraction calculated from [Formula: see text] were found between the left common carotid versus cerebral tissue [Formula: see text] and the dAo versus leg tissue [Formula: see text]. A resulting six-step procedure is presented to use NIRS data as a surrogate for exercise PC-MRI when setting boundary conditions for future CFD studies of the TA under simulated exercise conditions. Relationships and ensemble-averaged PC-MRI inflow waveforms are provided in an online repository for this purpose.

A systematic review of human and veterinary applications of noninvasive tissue oxygen monitoring.

To describe the methodology for and utilization of tissue oxygen monitoring by near infrared spectroscopy, and to review the current literature on the use of this monitoring modality in human and veterinary settings. Scientific reviews and original research found using the PubMed and CAB Abstract search engines with the following keywords: "tissue oxygen monitoring," "near-infrared tissue spectroscopy," and "tissue oxygen saturation (StO2 )." Tissue oxygen monitors have been evaluated in a wide variety of human clinical applications including trauma and triage, surgery, sepsis, and septic shock, and early goal-directed therapy. StO2 more rapidly identifies occult shock in human patients compared to traditional methods, which can lead to earlier intervention in these patients. Veterinary studies involving tissue oxygen monitoring are limited, but the technology may have utility for identification of hemorrhagic shock earlier than changes in base excess, blood lactate concentration, or other traditional perfusion parameters. Tissue oxygen monitoring is most commonly performed utilizing a noninvasive, portable monitor, which provides real-time, continuous, repeatable StO2 measurements. A decline in StO2 is an early indicator of shock in both human and veterinary patients. Low StO2 values in human patients are associated with increased morbidity, mortality, and length of hospitalization, as well as the development of multiple organ system dysfunction and surgical site infections.

Development of non-invasive tissue oxygen consumption measurement method based on arterio-venous photoplethysmography

Development of non-invasive tissue oxygen consumption measurement method based on arterio-venous photoplethysmography

Effect of Transfusion of Red Blood Cells With Longer vs Shorter Storage Duration on Elevated Blood Lactate Levels in Children With Severe Anemia: The TOTAL Randomized Clinical Trial.

Although millions of transfusions are given annually worldwide, the effect of red blood cell (RBC) unit storage duration on oxygen delivery is uncertain. To determine if longer-storage RBC units are not inferior to shorter-storage RBC units for tissue oxygenation as measured by reduction in blood lactate levels and improvement in cerebral tissue oxygen saturation among children with severe anemia. Randomized noninferiority trial of 290 children (aged 6-60 months), most with malaria or sickle cell disease, presenting February 2013 through May 2015 to a university-affiliated national referral hospital in Kampala, Uganda, with a hemoglobin level of 5 g/dL or lower and a lactate level of 5 mmol/L or higher. Patients were randomly assigned to receive RBC units stored 25 to 35 days (longer-storage group; n = 145) vs 1 to 10 days (shorter-storage group; n = 145). All units were leukoreduced prior to storage. All patients received 10 mL/kg of RBCs during hours 0 through 2 and, if indicated per protocol, an additional 10 mL/kg during hours 4 through 6. The primary outcome was the proportion of patients with a lactate level of 3 mmol/L or lower at 8 hours using a margin of noninferiority equal to an absolute difference of 25%. Secondary measures included noninvasive cerebral tissue oxygen saturation during the first transfusion, clinical and laboratory changes up to 24 hours, and survival and health at 30 days after transfusion. Adverse events were monitored up to 24 hours. In the total population of 290 children, the mean (SD) presenting hemoglobin level was 3.7 g/dL (1.3) and mean lactate level was 9.3 mmol/L (3.4). Median (interquartile range) RBC unit storage was 8 days (7-9) for shorter storage vs 32 days (30-34) for longer storage without overlap. The proportion achieving the primary end point was 0.61 (95% CI, 0.52 to 0.69) in the longer-storage group vs 0.58 (95% CI, 0.49 to 0.66) in the shorter-storage group (between-group difference, 0.03 [95% CI, -0.07 to ∞], P < .001), meeting the prespecified margin of noninferiority. Mean lactate levels were not statistically different between the 2 groups at 0, 2, 4, 6, 8, or 24 hours. Kaplan-Meier analysis and global nonlinear regression revealed no statistical difference in lactate reduction between the 2 groups. Clinical assessment, cerebral oxygen saturation, electrolyte abnormalities, adverse events, survival, and 30-day recovery were also not significantly different between the groups. Among children with lactic acidosis due to severe anemia, transfusion of longer-storage compared with shorter-storage RBC units did not result in inferior reduction of elevated blood lactate levels. These findings have relevance regarding the efficacy of stored RBC transfusion for patients with critical tissue hypoxia and lactic acidosis due to anemia. clinicaltrials.gov Identifier: NCT01586923.

Effect of moderate hyperventilation and induced hypertension on cerebral tissue oxygenation after cardiac arrest and therapeutic hypothermia

AimImproving cerebral perfusion is an essential component of post-resuscitation care after cardiac arrest (CA), however precise recommendations in this setting are limited. We aimed to examine the effect of moderate hyperventilation (HV) and induced hypertension (IH) on non-invasive cerebral tissue oxygenation (SctO2) in patients with coma after CA monitored with near-infrared spectroscopy (NIRS) during therapeutic hypothermia (TH). MethodsProspective pilot study including comatose patients successfully resuscitated from out-of-hospital CA treated with TH, monitored with NIRS. Dynamic changes of SctO2 upon HV and IH were analyzed during the stable TH maintenance phase. HV was induced by decreasing PaCO2 from ∼40 to ∼30mmHg, at stable mean arterial blood pressure (MAP∼70mmHg). IH was obtained by increasing MAP from ∼70 to ∼90mmHg with noradrenaline. ResultsTen patients (mean age 69 years; mean time to ROSC 19min) were studied. Following HV, a significant reduction of SctO2 was observed (baseline 74.7±4.3% vs. 69.0±4.2% at the end of HV test, p<0.001, paired t-test). In contrast, IH was not associated with changes in SctO2 (baseline 73.6±3.5% vs. 74.1±3.8% at the end of IH test, p=0.24). ConclusionsModerate hyperventilation was associated with a significant reduction in SctO2, while increasing MAP to supra-normal levels with vasopressors had no effect on cerebral tissue oxygenation. Our study suggests that maintenance of strictly normal PaCO2 levels and MAP targets of 70mmHg may provide optimal cerebral perfusion during TH in comatose CA patients.

Correlation of a Novel Noninvasive Tissue Oxygen Saturation Monitor to Serum Central Venous Oxygen Saturation in Pediatric Patients with Postoperative Congenital Cyanotic Heart Disease

Using a novel noninvasive, visible-light optical diffusion oximeter (T-Stat VLS Tissue Oximeter; Spectros Corporation, Portola Valley, CA) to measure the tissue oxygen saturation (StO2) of the buccal mucosa, the correlation between StO2 and central venous oxygen saturation (ScvO2) was examined in children with congenital cyanotic heart disease undergoing a cardiac surgical procedure. Paired StO2 and serum ScvO2 measurements were obtained postoperatively and statistically analyzed for agreement and association. Thirteen children (nine male) participated in the study (age range, 4 days to 18 months). Surgeries included Glenn shunt procedures, Norwood procedures, unifocalization procedures with Blalock-Taussig shunt placement, a Kawashima/Glenn shunt procedure, a Blalock-Taussig shunt placement, and a modified Norwood procedure. A total of 45 paired StO2-ScvO2 measurements was obtained. Linear regression demonstrated a Pearson’s correlation of .58 (95% confidence interval [CI], .35–.75; p &lt; .0001). The regression slope coefficient estimate was .95 (95% CI, .54–1.36) with an interclass correlation coefficient of .48 (95% CI, .22–.68). Below a clinically relevant average ScvO2 value, a receiver operator characteristic analysis yielded an area under the curve of .78. Statistical methods to control for repeatedly measuring the same subjects produced similar results. This study shows a moderate relationship and agreement between StO2 and ScvO2 measurements in pediatric patients with a history of congenital cyanotic heart disease undergoing a cardiac surgical procedure. This real-time monitoring device can act as a valuable adjunct to standard noninvasive monitoring in which serum ScvO2 sampling currently assists in the diagnosis of low cardiac output after pediatric cardiac surgery.

Sleep Apnea Detection And Non-Invasive Brain Tissue Oxygen Monitoring

This paper introduces a non-invasive method for monitoring the respiratory patterns of the patients and the specifications of apnea monitor hardware. The microcontroller based apnea monitor consists of a sensor system interfaced with a microcontroller to detect the apnea from the heat changes in the oro-nazal air flow and simultaneously measure the brain tissue oxygen level by Near Infrared spectroscopy(NIRS).Near-infrared spectroscopy (NIRS) has the potential to noninvasively monitor brain tissue oxygen saturation (SO2), and changes in concentration of oxyhemoglobin [O2Hb], deoxyhemoglobin [HHb] and total haemoglobin [tHb] with real-time resolution. We hypothesized that brain tissue oxygenation would be worse during sleep in OSA relative to controls and sought to determine the practical use of NIRS in the sleep laboratory.

Noninvasive tissue oxygen saturation determined by near‐infrared spectroscopy following peripheral nerve block

Noninvasive physiologic measurement of cutaneous tissue oxygenation using near-infrared spectroscopy (NIRS) has become increasingly common in cardiovascular and plastic surgery. The aim of this study was to determine whether clinically available NIRS-based monitors could detect changes in tissue oxygen saturation (rSO(2)) following a variety of peripheral nerve blocks. We hypothesize that peripheral nerve blocks will produce detectable changes in cutaneous tissue oxygenation levels that can be measured by noninvasive NIRS-based oximetry. Forty adult patients scheduled for pre-operative peripheral nerve block placement were enrolled. Prior to block placement, NIRS sensors were placed on the operative and nonoperative (control) limb. Baseline tissue oxygen saturation values were obtained prior to dosing of the nerve block, and measurements were recorded every 5 min thereafter. Initial rSO(2) values were higher in the operative vs. control limbs prior to nerve block placement. Tissue oxygen saturation increased in the blocked, but not control, limbs with time. Subgroup analysis suggested statistically significant differences in rSO(2) values in blocked vs. control limbs for cervical paravertebral, infraclavicular, and femoral nerve blocks. Our results demonstrated sustained increases in tissue rSO(2) values following peripheral nerve block placement, in addition to higher initial rSO(2) values in operative limbs prior to block placement. Further investigations are necessary to define the expected baseline rSO(2) values in operative and control limbs. Future efforts utilizing NIRS-based detection of tissue ischemia should consider the small but significant changes in rSO(2) resulting from a successful nerve block.

500 ml of blood loss does not decrease non-invasive tissue oxygen saturation (StO2) as measured by near infrared spectroscopy - A hypothesis generating pilot study in healthy adult women

BackgroundThe goal when resuscitating trauma patients is to achieve adequate tissue perfusion. One parameter of tissue perfusion is tissue oxygen saturation (StO2), as measured by near infrared spectroscopy. Using a commercially available device, we investigated whether clinically relevant blood loss of 500 ml in healthy volunteers can be detected by changes in StO2 after a standardized ischemic event.MethodsWe performed occlusion of the brachial artery for 3 minutes in 20 healthy female blood donors before and after blood donation. StO2 and total oxygenated tissue hemoglobin (O2Hb) were measured continuously at the thenar eminence. 10 healthy volunteers were assessed in the same way, to examine whether repeated vascular occlusion without blood donation exhibits time dependent effects.ResultsBlood donation caused a substantial decrease in systolic blood pressure, but did not affect resting StO2 and O2Hb values. No changes were measured in the blood donor group in the reaction to the vascular occlusion test, but in the control group there was an increase in the O2Hb rate of recovery during the reperfusion phase.ConclusionStO2 measured at the thenar eminence seems to be insensitive to blood loss of 500 ml in this setting. Probably blood loss greater than this might lead to detectable changes guiding the treating physician. The exact cut off for detectable changes and the time effect on repeated vascular occlusion tests should be explored further. Until now no such data exist.

携帯型近赤外線組織酸素モニタシステムによる高速サンプリング計測の検討

Non-invasive tissue oxygenation monitoring system based on Near-InfraRed Spectroscopy (NIRS) is expected to be used in the various applications such as medical field and brain studies. We have developed the new instrument which incorporates the wireless communication system so that unconstrained measurements can be done. The instrument consists of 3 different wavelengths LEDs as light sources and one photo-diode as a detector. The measured data were sent to personal computer through wireless communication system up to 60 data per second. We demonstrated that the system could monitor the high-speed sampling measurement of the hemoglobin concentration change in an unconstraint subject. We found the pulsation of measurement data in the hemoglobin concentration change due to heart beat. These results indicate that the NIRS technology system can evaluate blood circulation by local oxygen metabolism information and a pulse rate measurement that reflects general circulation at the same time. This NIRS system can be used as the oxygenation monitor not only for existing medical applications but also for new applications.