Characterization of tissue oxygen saturation and the vascular occlusion test: influence of measurement sites, probe sizes and deflation thresholds

INTRODUCTION: Tissue oxygen saturation (StO2) and the vascular occlusion test (VOT) can identify tissue hypoperfusion in trauma and sepsis. However, the technique is neither standardized nor uses the same monitoring site. We hypothesized that baseline and VOT StO2 would be different in the forearm (F) and thenar eminence (TH) and that different minimal StO2 values during the VOT would result in different reoxygenation rates (ReO2). METHODS: StO2 and its change during the VOT were simultaneously measured in the F and TH, with 15 mm and 25 mm probes, using the 325 InSpectra monitor in 18 healthy, adult volunteers. Two VOTs were done to a threshold thenar StO2 of 40% interchanging the 15 mm and 25 mm probes between sites. Two additional VOTs were done to thresholds of 50% and 30%. Baseline StO2 (BaseO2), the deoxygenation rate (DeO2) and ReO2 were compared between sites, probes and (%O2/minute) thresholds. Results are presented as the median (interquartile range), P-value. RESULTS: BaseO2, DeO2, ReO2, area under the curve and hyperemia duration values were different when comparing TH vs. F and 15 mm vs. 25 mm probes. ReO2 was different between different thresholds for the TH and 15 mm probes. TH15 mm vs. F15 mm: BaseO2, 90.4 (85.2, 93.5) vs. 85.2 (80.7, 90.2), P = 0.031; DO2, -12.1 (-16.2, -11.3) vs. -8.5 (-10.3, -7.8), P = 0.011; ReO2, 297.2 (213.7, 328.6), P < 0.0001; 15 mm vs. 25 mm probe: BaseO2, 97.2 (89.4, 94.7) vs. 87.3 (81.7, 90.9), P = 0.016; DeO2, -18.0 (-24.1, -14.8) vs. -9.9 (-15.3, -6.5), P < 0.0001; and ReO2, 401.6 (331.7, 543.2) vs. 160.5 (132.3, 366.9), P = 0.012, respectively. TH15 mm vs. TH25 mm: BaseO2, P = 0.020; DeO2, P < 0.0001; and ReO2, P < 0.0001. Threshold StO2 values (15 mm probe only): ReO2, P = 0.003; DeO2, P = 0.60. ReO2 at 40% and 50% StO2 thresholds, P = 0.01. CONCLUSIONS: BaseO2, DeO2 and ReO2 were different when measured in different anatomical sites (F and TH) and with different probe sizes, and ReO2 was different with differing VOT release StO2 threshold values. Thus, standardization of the site, probe and VOT challenge need to be stipulated when reporting data

Peripheral microcirculatory alterations are associated with the severity of acute respiratory distress syndrome in COVID-19 patients admitted to intermediate respiratory and intensive care units

COVID-19; Endothelial dysfunction; MicrocirculationCOVID-19; Disfunción endotelial; MicrocirculaciónCOVID-19; Disfunció endotelial; MicrocirculacióBackground COVID-19 is primarily a respiratory disease; however, there is also evidence that it causes endothelial damage in the microvasculature of several organs. The aim of the present study is to characterize in vivo the microvascular reactivity in peripheral skeletal muscle of severe COVID-19 patients. Methods This is a prospective observational study carried out in Spain, Mexico and Brazil. Healthy subjects and severe COVID-19 patients admitted to the intermediate respiratory (IRCU) and intensive care units (ICU) due to hypoxemia were studied. Local tissue/blood oxygen saturation (StO2) and local hemoglobin concentration (THC) were non-invasively measured on the forearm by near-infrared spectroscopy (NIRS). A vascular occlusion test (VOT), a three-minute induced ischemia, was performed in order to obtain dynamic StO2 parameters: deoxygenation rate (DeO2), reoxygenation rate (ReO2), and hyperemic response (HAUC). In COVID-19 patients, the severity of ARDS was evaluated by the ratio between peripheral arterial oxygen saturation (SpO2) and the fraction of inspired oxygen (FiO2) (SF ratio). Results Healthy controls (32) and COVID-19 patients (73) were studied. Baseline StO2 and THC did not differ between the two groups. Dynamic VOT-derived parameters were significantly impaired in COVID-19 patients showing lower metabolic rate (DeO2) and diminished endothelial reactivity. At enrollment, most COVID-19 patients were receiving invasive mechanical ventilation (MV) (53%) or high-flow nasal cannula support (32%). Patients on MV were also receiving sedative agents (100%) and vasopressors (29%). Baseline StO2 and DeO2 negatively correlated with SF ratio, while ReO2 showed a positive correlation with SF ratio. There were significant differences in baseline StO2 and ReO2 among the different ARDS groups according to SF ratio, but not among different respiratory support therapies. Conclusion Patients with severe COVID-19 show systemic microcirculatory alterations suggestive of endothelial dysfunction, and these alterations are associated with the severity of ARDS. Further evaluation is needed to determine whether these observations have prognostic implications. These results represent interim findings of the ongoing HEMOCOVID-19 trial. Trial registration ClinicalTrials.gov NCT04689477. Retrospectively registered 30 December 2020.The study has received funding from Fundació CELLEX Barcelona, Fundació Mir-Puig, Ajuntament de Barcelona, Agencia Estatal de Investigación (PHOTOMETABO, PID2019-106481RB-C31/10.13039/501100011033), the "Severo Ochoa" Programme for Centers of Excellence in R&D (CEX2019-000910-S), the Obra social “La Caixa” Foundation (LlumMedBcn), Generalitat de Catalunya (CERCA, AGAUR-2017-SGR-1380, RIS3CAT-001-P-001682 CECH), European Commission Horizon 2020 (FEDER, 688303/LUCA, 101016087/VASCOVID, 87114/LASERLAB-EUROPE V). We also acknowledge the collaboration and an instrument loan from Artinis (Netherlands)

Near-infrared spectroscopy StO monitoring to assess the therapeutic effect of drotrecogin alfa (activated) on microcirculation in patients with severe sepsis or septic shock

Sepsis is a leading cause of death despite appropriate management. There is increasing evidence that microcirculatory alterations might persist independently from macrohemodynamic improvement and are related to clinical evolution. Future efforts need to be directed towards microperfusion monitoring and treatment. This study explored the utility of thenar muscle oxygen saturation (StO) and its changes during a transient vascular occlusion test (VOT) to measure the microcirculatory response to drotrecogin alfa (activated) (DrotAA) in septic patients. A prospective, observational study was performed in three general intensive care units at three university hospitals. We studied 58 patients with recent onset of severe sepsis or septic shock and at least two organ dysfunctions. Thirty-two patients were treated with DrotAA and 26 were not treated because of formal contraindication. StO was monitored using near-infrared spectroscopy (NIRS), and VOT was performed to obtain deoxygenation (DeOx) and reoxygenation (ReOx) slopes. Measurements were obtained before DrotAA was started and were repeated daily for a 96-hour period. Patients' characteristics, outcome, severity, and baseline values of StO, DeOx, and ReOx did not differ between groups. Treated patients significantly improved DeOx and ReOx values over time, whereas control patients did not. In treated patients, ReOx improvements were correlated to norepinephrine dose reductions. Early clinical response (SOFA improvement after 48 hours of treatment) was not associated to changes in VOT-derived slopes. In the treated group, the relative improvement of DeOx within 48 hours was able to predict mortality (AUC 0.91, p < 0.01). In patients with severe sepsis or septic shock, DrotAA infusion was associated with improvement in regional tissue oxygenation. The degree of DeOx amelioration after 2 days in treated patients predicted mortality with high sensitivity and specificity. Thus, StO derived variables might be useful to evaluate the microcirculatory response to treatment of septic shock

Near-infrared spectroscopy StO2 monitoring to assess the therapeutic effect of drotrecogin alfa (activated) on microcirculation in patients with severe sepsis or septic shock

BACKGROUND: Sepsis is a leading cause of death despite appropriate management. There is increasing evidence that microcirculatory alterations might persist independently from macrohemodynamic improvement and are related to clinical evolution. Future efforts need to be directed towards microperfusion monitoring and treatment. This study explored the utility of thenar muscle oxygen saturation (StO(2)) and its changes during a transient vascular occlusion test (VOT) to measure the microcirculatory response to drotrecogin alfa (activated) (DrotAA) in septic patients. METHODS: A prospective, observational study was performed in three general intensive care units at three university hospitals. We studied 58 patients with recent onset of severe sepsis or septic shock and at least two organ dysfunctions. Thirty-two patients were treated with DrotAA and 26 were not treated because of formal contraindication. StO(2) was monitored using near-infrared spectroscopy (NIRS), and VOT was performed to obtain deoxygenation (DeOx) and reoxygenation (ReOx) slopes. Measurements were obtained before DrotAA was started and were repeated daily for a 96-hour period. RESULTS: Patients’ characteristics, outcome, severity, and baseline values of StO(2), DeOx, and ReOx did not differ between groups. Treated patients significantly improved DeOx and ReOx values over time, whereas control patients did not. In treated patients, ReOx improvements were correlated to norepinephrine dose reductions. Early clinical response (SOFA improvement after 48 hours of treatment) was not associated to changes in VOT-derived slopes. In the treated group, the relative improvement of DeOx within 48 hours was able to predict mortality (AUC 0.91, p < 0.01). CONCLUSIONS: In patients with severe sepsis or septic shock, DrotAA infusion was associated with improvement in regional tissue oxygenation. The degree of DeOx amelioration after 2 days in treated patients predicted mortality with high sensitivity and specificity. Thus, StO(2) derived variables might be useful to evaluate the microcirculatory response to treatment of septic shock

Alterations in tissue oxygen saturation measured by near-infrared spectroscopy in trauma patients after initial resuscitation are associated with occult shock

Acord transformatiu CRUE-CSICPurpose: Persistent occult hypoperfusion after initial resuscitation is strongly associated with increased morbidity and mor- tality after severe trauma. The objective of this study was to analyze regional tissue oxygenation, along with other global markers, as potential detectors of occult shock in otherwise hemodynamically stable trauma patients. Methods: Trauma patients undergoing active resuscitation were evaluated 8 h after hospital admission with the measure- ment of several global and local hemodynamic/metabolic parameters. Apparently hemodynamically stable (AHD) patients, defined as having SBP ≥ 90 mmHg, HR < 100 bpm and no vasopressor support, were followed for 48 h, and finally classified according to the need for further treatment for persistent bleeding (defined as requiring additional red blood cell transfusion), initiation of vasopressors and/or bleeding control with surgery and/or angioembolization. Patients were labeled as "Occult shock" (OS) if they required any intervention or "Truly hemodynamically stable" (THD) if they did not. Regional tissue oxygenation (rSO2) was measured non-invasively by near-infrared spectroscopy (NIRS) on the forearm. A vascular occlu- sion test was performed, allowing a 3-min deoxygenation period and a reoxygenation period following occlusion release. Minimal rSO2 (rSO2min), Delta-down (rSO2-rSO2min), maximal rSO2 following cuff-release (rSO2max), and Delta-up (rSO2max-rSO2min) were computed. The NIRS response to the occlusion test was also measured in a control group of healthy volunteers. Results: Sixty-six consecutive trauma patients were included. After 8 h, 17 patients were classified as AHD, of whom five were finally considered to have OS and 12 THD. No hemodynamic, metabolic or coagulopathic differences were observed between the two groups, while NIRS-derived parameters showed statistically significant differences in Delta-down, rSO2min, and Delta-up. Conclusions: After 8 h of care, NIRS evaluation with an occlusion test is helpful for identifying occult shock in apparently hemodynamically stable patients

In vivo characterization of the optical and hemodynamic properties of the human sternocleidomastoid muscle through ultrasound-guided hybrid near-infrared spectroscopies

Objective. In this paper, we present a detailed in vivo characterization of the optical and hemodynamic properties of the human sternocleidomastoid muscle (SCM), obtained through ultrasound-guided near-infrared time-domain and diffuse correlation spectroscopies. Approach. A total of sixty-five subjects (forty-nine females, sixteen males) among healthy volunteers and thyroid nodule patients have been recruited for the study. Their SCM hemodynamic (oxy-, deoxy- and total hemoglobin concentrations, blood flow, blood oxygen saturation and metabolic rate of oxygen extraction) and optical properties (wavelength dependent absorption and reduced scattering coefficients) have been measured by the use of a novel hybrid device combining in a single unit time-domain near-infrared spectroscopy, diffuse correlation spectroscopy and simultaneous ultrasound imaging. Main results. We provide detailed tables of the results related to SCM baseline (i.e. muscle at rest) properties, and reveal significant differences on the measured parameters due to variables such as side of the neck, sex, age, body mass index, depth and thickness of the muscle, allowing future clinical studies to take into account such dependencies. Significance. The non-invasive monitoring of the hemodynamics and metabolism of the sternocleidomastoid muscle during respiration became a topic of increased interest partially due to the increased use of mechanical ventilation during the COVID-19 pandemic. Near-infrared diffuse optical spectroscopies were proposed as potential practical monitors of increased recruitment of SCM during respiratory distress. They can provide clinically relevant information on the degree of the patient's respiratory effort that is needed to maintain an optimal minute ventilation, with potential clinical application ranging from evaluating chronic pulmonary diseases to more acute settings, such as acute respiratory failure, or to determine the readiness to wean from invasive mechanical ventilation.</p

Optical imaging and spectroscopy for the study of the human brain: status report.

This report is the second part of a comprehensive two-part series aimed at reviewing an extensive and diverse toolkit of novel methods to explore brain health and function. While the first report focused on neurophotonic tools mostly applicable to animal studies, here, we highlight optical spectroscopy and imaging methods relevant to noninvasive human brain studies. We outline current state-of-the-art technologies and software advances, explore the most recent impact of these technologies on neuroscience and clinical applications, identify the areas where innovation is needed, and provide an outlook for the future directions

Saturació tenar d’oxigen (Sto2). Validació de la tècnica i anàlisi de la seva utilitat en pacients crítics amb sèpsia

El present treball de tesi doctoral s'ha dirigit a aprofundir en el coneixement de la utilitat d'un paràmetre d'avaluació de la oxigenació regional, la saturació tissular d'oxigen (StO2), obtingut mitjançant una tecnologia d'espectrofotometria de llum propera a l'infraroig (Near-Infrared Spectroscopy,o NIRS), en el pacient crític amb sèpsia greu i xoc sèptic. Tot i tractar-se de quatre publicacions, la temàtica d'aquesta tesi doctoral es pot tractar en tres blocs: (1) Validació i protocol·lització de la mesura de StO2; (2) Estudi del valor de la StO2 com a predictor ràpid i no-invasiu d'alteracions en variables hemodinàmiques i oximètriques de caràcter global utilitzades al procés de reanimació; (3) Anàlisi del valor pronòstic de les variables de StO2 en els pacients en xoc sèptic. En un primer treball, realitzat en voluntaris sans, i amb l'objectiu de proposar uns paràmetres de mesura de la StO2 menys subjectes a variabilitat entre individus, es van comparar els valors de StO2 en diferents localitzacions musculars i a diferents profunditats de sensat. Donat que, a més del valor basal de StO2, l'avaluació de la resposta de la StO2 a un test d'isquèmia transitòria dóna informació sobre l'estat metabòlic i la funcionalitat endotelial del teixit estudiat, la mesura s'ha de fer en zones distals de les extremitats. En el present treball, la cara ventral de l'avantbraç i l'eminència tenar van ser les regions escollides per a la seva anàlisi. Els resultats obtinguts suggereixen que, en el procés de mesura de la StO2 i de les seves variables derivades d’un test d’oclusió vascular transitori, la combinació de la utilització de l’eminència tenar, amb un sensor de 15 mm i un test de provocació d’isquèmia amb un llindar de StO2 del 40% estan menys subjectes a variabilitat i donarien, per tant, resultats més consistents i comparables en els estudis clínics. El segon i tercer treballs es van dirigir a avaluar la correlació entre la StO2 i diferents variables oximètriques de caràcter global utilitzades com a objectius en el procés de reanimació del xoc. L'objectiu principal d'aquests treballs va ser testar la capacitat de predicció de la StO2 de l'alteració en variables d'oxigenació global, totes elles de caràcter invasiu. Els resultats obtinguts demostren que el valor absolut de StO2 és poc sensible a l’hora de descartar hipoperfusió global i, per tant, no seria una variable idònia per guiar la reanimació del xoc en substitució de les actuals variables d'oxigenació global. Tanmateix, la especificitat amb que la seva alteració es correlaciona amb la insuficient oxigenació dels teixits, juntament amb el seu caràcter ràpid i no-invasiu, podria fer de la tecnologia NIRS un sistema d’ajuda en la detecció precoç d’estats de hipoperfusió en situacions en les que no disposem encara de variables més invasives i/o de laboratori per a la detecció d’aquesta hipoperfusió tissular. Finalment, un quart treball va pretendre avaluar el valor pronòstic de les variables derivades de la StO2 en el procés de reanimació hemodinàmica, un cop s’haguessin restaurat els valors de pressió arterial mitjana. Els resultats obtinguts mostren que les variables de StO2 derivades d'un test d'isquèmia transitòria (tant la taxa de desoxigenació com la de reoxigenació) tenen valor pronòstic, independentment de l’estat macrocirculatori i/o d’oxigenació global. Per tant, la incorporació d’aquestes variables en el procés de reanimació, de forma complementària a les variables globals d'oxigenació, podria ser beneficiosa. Tanmateix, l'avaluació de la resposta d'aquestes variables als diferents tipus d'intervencions hemodinàmiques, així com l'anàlisi de l'impacte sobre el pronòstic de la seva inclusió en els algoritmes de reanimació, seran passes necessàries en el futur immediat per tal d'acostar aquesta tecnologia a la pràctica clínica.The present thesis project has pretended to improve our knowledge on the usefulness of a regional oxygenation parameter, the tissue oxygen saturation (StO2), obtained by means of a novel spectroscopic technology (Near-Infrared Spectroscopy, or NIRS), in critically ill patients suffering from severe sepsis or septic shock. Although four publications complete this thesis, three main subjects might be depicted: (1) Validation and characterization of StO2 measurement; (2) Study of the StO2 value as a rapid and non-invasive predictor of alterations in global hemodynamic and oxygenation variables; (3) Analysis of the prognostic value of StO2 variables in septic shock patients. In a first study, in healthy volunteers, we aimed to propose a StO2 measurement process less subject to inter-individual variability. Therefore, we compared StO2 measurements in different muscular sites, and using different sensed depths. Since, in addition to StO2 steady-state value, StO2 changes in response to a transient ischemic challenge provide information about tissue metabolic state and endothelial integrity, its measurement needs to be performed on distal areas of the limbs. In the present study, the forearm and the thenar eminence were chosen for their analysis. The obtained results suggest that the combination of thenar eminence, a 15-mm probe and using a StO2 ischemic threshold of 40% is less subject to variability and, therefore, might result in more robust and comparable results in clinical studies. The second and third publications aimed to evaluate the correlation between StO2 and several global oxygenation variables used as septic shock resuscitation endpoints in clinical practice. The main objective of the study was to test the ability of StO2 to non-invasively predict alterations in global oxygenation variables. The observed results demonstrate that StO2 sensitivity is poor in order to rule out global tissue hypoperfusion, and therefore, might not be a reliable parameter to guide septic shock resuscitation process in substitution of current global oxygenation parameters. However, since StO2 alterations correlate with high specificity with tissue dysoxia, together with its rapid and non-invasive nature, NIRS technology might be a helpful tool in early detection of hypoperfusion states, when invasive or lab variables are not available yet. Finally, our fourth study was designed to evaluate the prognostic value of StO2 variables in the hemodynamic resuscitation process, once mean arterial pressure values have been normalized. The results of the study show that StO2 variables obtained during a transient ischemic challenge (both de-oxygenation and re-oxygenation rates) have prognostic implications, independently from the macrocirculatory state. Therefore, including these StO2 variables within the resuscitation process, complimentary to global oxygenation variables, might prove useful in terms of patients' outcome. However, StO2 response to further resuscitation interventions, as well as the impact of StO2 integration in future resuscitation algorithms, are mandatory in order to bring this technology closer to clinical practice

Desenvolupament de plataforma de transport a molt altes velocitats a baixes pressions amb superconductors

El següent projecte suposa l’intent d’estudiar el fenomen de la superconductivitat i la possibilitat de desenvolupar una aplicació, consistent en un transport a molt altes velocitats a baixes pressions, utilitzant les característiques electromagnètiques dels materials superconductors. El coneixement i l’aprofundiment necessari de les teories superconductores, per tal de portar aquest objectiu a terme, seran conceptes clau durant tota la primera part del treball, ja que es parteix de zero en quan a coneixements previs. Posteriorment, assentarem les bases dels desenvolupaments teòrics i pràctics que existeixen o han existit fins a l’actualitat. I finalment, plantejarem un disseny teòric, amb les seves consideracions i els seus aspectes tècnics. Així, com un seguit de conclusions, que seran les que realment serviran de cara a les futures investigacions d’aplicacions d’aquest enigmàtic fenomen, que des de 1911 s’ha convertit en un dels grans reptes de la física moderna

Anàlisi del model organitzatiu des d'una perspectiva inclusiva del IES Ramon Llull

[cat] El present document és un estudi sobre el model organitzatiu de l’Institut d’Estudis de Secundària Ramon Llull situat a Palma, Mallorca. Mitjançant aquest treball, tractarem d’analitzar les mesures inclusives que caracteritzen el model organitzatiu d’aquests centre educatiu. Presentarem l’estat de la qüestió al voltant de l’educació inclusiva per tractar de definir les variables en què es sustenten, centrades sobretot en l’alumnat estranger. Finalment, extraurem una sèrie de conclusions i propostes de bones pràctiques, fonamentades en la participació i la organització escolar del centre