Cerebral Tissue Oxygenation Index Research Articles

Short apneas and periodic breathing in preterm infants in the neonatal intensive care unit-Effects of sleep position, sleep state, and age.

This observational study investigated the effects of sleep position and sleep state on short apneas and periodic breathing in hospitalized preterm infants longitudinally, in relation to postmenstrual age. Preterm infants (25-31 weeks gestation, n = 29) were studied fortnightly after birth until discharge, in prone and supine positions, and in quiet sleep and active sleep. The percentage of time spent in each sleep state (percentage of time in quiet sleep and percentage of time in active sleep), percentage of total sleep time spent in short apneas and periodic breathing, respectively, the percentage of falls from baseline in heart rate, arterial oxygen saturation and cerebral tissue oxygenation index during short apneas and periodic breathing, and the associated percentage of total sleep time with systemic (arterial oxygen saturation < 90%) and cerebral hypoxia (cerebral tissue oxygenation index < 55%) were analysed using a linear mixed model. Results showed that the prone position decreased (improved) the percentage of falls from baseline in arterial oxygen saturation during both short apneas and periodic breathing, decreased the proportion of infants with periodic breathing and the periodic breathing-associated percentage of total sleep time with cerebral hypoxia. The percentage of time in quiet sleep was higher in the prone position. Quiet sleep decreased the percentage of total sleep time spent in short apneas, the short apneas-associated percentage of falls from baseline in heart rate, arterial oxygen saturation, and proportion of infants with systemic hypoxia. Quiet sleep also decreased the proportion of infants with periodic breathing and percentage of total sleep time with cerebral hypoxia. The effects of sleep position and sleep state were not related to postmenstrual age. In summary, when sleep state is controlled for, the prone sleeping position has some benefits during both short apneas and periodic breathing. Quiet sleep improves cardiorespiratory stability and is increased in the prone position at the expense of active sleep, which is critical for brain maturation. This evidence should be considered in positioning preterm infants.

IMPACT OF HIGH-DOSE VASOPRESSOR DURING ENDOTOXIC SHOCK ON THE CEREBRAL, LINGUAL, HEPATIC, AND RENAL MICROCIRCULATION EVALUATED BY NEAR-INFRARED SPECTROSCOPY IN SWINE.

Background: High-dose vasopressors maintain blood pressure during septic shock but may adversely reduce microcirculation in vital organs. We assessed the effect of high-dose norepinephrine and vasopressin on the microcirculation of the brain, tongue, liver, and kidney during endotoxic shock using near-infrared spectroscopy (NIRS). Methods: Thirteen pigs (24.5 ± 1.8 kg) were anesthetized, and an NIRS probe was attached directly to each organ. Approximately 0.2, 0.5, 1, and 2 μg/kg/min of norepinephrine were administered in a stepwise manner, followed by 0.5, 1, 2, and 5 μg/kg/min of sodium nitroprusside in normal condition. Moreover, 1 μg/kg/h of lipopolysaccharide was administered continuously after 100 μg bolus to create endotoxic shock and after 1,000 mL of crystalloid infusion and high-dose norepinephrine (2, 5, 10, and 20 μg/kg/min) and vasopressin (0.6, 1.5, 3, and 6 U/min) were administered in a stepwise manner. The relationship between the MAP and each tissue oxygenation index (TOI) during vasopressor infusion was evaluated. Results: Three pigs died after receiving lipopolysaccharides, and 10 were analyzed. An increase of >20% from the baseline MAP induced by high-dose norepinephrine during endotoxic shock reduced the TOI in all organs except the liver. The elevation of MAP to baseline with vasopressin alone increased the kidney and liver TOIs and decreased the tongue TOI. Conclusion: Forced blood pressure elevation with high-dose norepinephrine during endotoxic shock decreased the microcirculation of vital organs, especially the kidney. Cerebral TOI may be useful for identifying the upper limit of blood pressure, at which norepinephrine impairs microcirculation.

Differences in Cerebral Oxygenation in Cardiogenic and Respiratory Cardiac Arrest Before, During, and After Cardiopulmonary Resuscitation.

We compared the changes in cerebral oxygen saturation (ScO2) levels during cardiac arrest (CA) events using porcine models of ventricular fibrillation CA (VF-CA) and asphyxial CA (A-CA). Twenty female pigs were randomly divided into VF-CA and A-CA groups. We initiated cardiopulmonary resuscitation (CPR) 4 min after CA and measured the cerebral tissue oxygenation index (TOI) using near-infrared spectroscopy (NIRS) before, during, and after CPR. In both groups, the TOI was the lowest at 3-4 min after pre-CPR phase initiation (VF-CA group: 3.4 min [2.8-3.9]; A-CA group: 3.2 min [2.9-4.6]; p = 0.386). The increase in TOI differed between the groups in the CPR phase (p < 0.001); it increased more rapidly in the VF-CA group (16.6 [5.5-32.6] vs. 1.1 [0.6-3.3] %/min; p < 0.001). Seven pigs surviving for 60 min after the return of spontaneous circulation in the VF-CA group recovered limb movement, whereas only one in the A-CA group (p = 0.023) achieved movement recovery. The increase in the TOI did not differ significantly between the groups in the post-CPR phase (p = 0.341). Therefore, it is better to monitor ScO2 concomitantly with CPR initiation using NIRS to assess the responsiveness to CPR in clinical settings.

Wavelet Analysis of Cerebral Oxygenation Signal Measured by Near-Infrared Spectroscopy in Moyamoya Disease.

Spontaneous low-frequency oscillations (LFOs) have been widely studied in cerebrovascular disease, but little is known about their role in moyamoya disease (MMD). The objective of this study was to assess the value of spontaneous LFOs in MMD based on wavelet analysis of near-infrared spectroscopy signals. Sixty-four consecutive idiopathic adult patients were prospectively enrolled. The regional tissue oxygenation index (TOI) obtained from continuous near-infrared spectroscopy signals. Five frequency intervals of spontaneous LFOs (I, 0.0095-0.02Hz; II, 0.02-0.06Hz; III, 0.06-0.15Hz; IV, 0.15-0.40Hz; and V, 0.40-2.00Hz) were extracted based on wavelet analysis. The data were compared between the patients and healthy control groups. Clinical features, cognitive function, and disease progression of MMD were analyzed using TOI and frequency interval data. Compared with the healthy control group, patients with MMD had a higher cerebral TOI in both hemispheres. Based on wavelet analysis, the spontaneous LFO of TOI was found to be significantly lower for patients with MMD in frequency intervals II to IV than that for the controls. The spontaneous LFO of TOI is also related to the Suzuki stages in intervals II to IV, stroke in interval III, and cognitive impairment in intervals III to Ⅳ. There were significant differences in spontaneous LFO between patients with MMD and healthy controls. The change in spontaneous LFO in MMD is related to Suzuki stage, cerebral infarction, and cognitive impairment. This might be an effective method for evaluating the severity and monitoring the progression of MMD.

There is no evidence that carbon dioxide-enriched oxygen before apnea affects the time to arterial desaturation, but it might improve cerebral oxygenation in anesthetized obese patients: a single-blinded randomized crossover trial

PurposeCarbon dioxide (CO2) increases cerebral perfusion. The effect of CO2 on apnea tolerance, such as after anesthesia induction, is unknown. This study aimed to assess if cerebral apnea tolerance can be improved in obese patients under general anesthesia when comparing O2/Air (95%O2) to O2/CO2 (95%O2/5%CO2).MethodsIn this single-center, single-blinded, randomized crossover trial, 30 patients 18–65 years, with body mass index > 35 kg/m2, requiring general anesthesia for bariatric surgery, underwent two apneas that were preceded by ventilation with either O2/Air or O2/CO2 in random order. After anesthesia induction, intubation, and ventilation with O2/Air or O2/CO2 for 10 min, apnea was performed until the cerebral tissue oxygenation index (TOI) dropped by a relative 20% from baseline (primary endpoint) or oxygen saturation (SpO2) reached 80% (safety abortion criterion). The intervention was then repeated with the second substance.ResultsThe safety criterion was reached in all patients before cerebral TOI decreased by 20%. The time until SpO2 dropped to 80% was similar in the two groups (+ 6 s with O2/CO2, 95%CI -7 to 19 s, p = 0.37). Cerebral TOI and PaO2 were higher after O2/CO2 (+ 1.5%; 95%CI: from 0.3 to 2.6; p = 0.02 and + 0.6 kPa; 95%CI: 0.1 to 1.1; p = 0.02).ConclusionO2/CO2 improves cerebral TOI and PaO2 in anesthetized bariatric patients. Better apnea tolerance could not be confirmed.

Cerebral tissue oxygenation response to brain irradiation measured during clinical radiotherapy.

Cancer therapy treatments produce extensive changes in the physiological and morphological properties of tissues, which are also individual dependent. Currently, a key challenge involves developing more tailored cancer therapy, and consequently, individual biological response measurement during therapy, such as tumor hypoxia, is of high interest. This is the first time human cerebral haemodynamics and cerebral tissue oxygenation index (TOI) changes were measured during the irradiation in clinical radiotherapy and functional near-infrared spectroscopy (fNIRS) technique was demonstrated as a feasible technique for clinical use in radiotherapy, based on 34 online patient measurements. Our aim is to develop predictive biomarkers and noninvasive real-time methods to establish the effect of radiotherapy during treatment as well as to optimize radiotherapy dose planning for individual patients. In particular, fNIRS-based technique could offer an effective and clinically feasible online technique for continuous monitoring of brain tissue hypoxia and responses to chemo- and radiotherapy, which involves modulating tumor oxygenation to increase or decrease tumor hypoxia. We aim to show that fNIRS is feasible for repeatability measuring in patient radiotherapy, the temporal alterations of tissue oxygenation induced by radiation. Fiber optics setup using multiwavelength fNIRS was built and combined with a medical linear accelerator to measure cerebral tissue oxygenation changes during the whole-brain radiotherapy treatment, where the radiation dose is given in whole brain area only preventing dosage to eyes. Correlation of temporal alterations in cerebral haemodynamics and TOI response to brain irradiation was quantified. Online fNIRS patient measurement of cerebral haemodynamics during clinical brain radiotherapy is feasible in clinical environment, and results based on 34 patient measurements show strong temporal alterations in cerebral haemodynamics and decrease in TOI during brain irradiation and confirmed the repeatability. Our proof-of-concept study shows evidently that irradiation causes characteristic immediate changes in brain tissue oxygenation. In particular, TOI seems to be a sensitive parameter to observe the tissue effects of radiotherapy. Monitoring the real-time interactions between the subjected radiation dose and corresponding haemodynamic effects may provide important tool for the researchers and clinicians in the field of radiotherapy. Eventually, presented fNIRS technique could be used for improving dose planning and safety control for individual patients.

Does physiological-based cord clamping improve cerebral tissue oxygenation and perfusion in healthy term neonates? - A randomized controlled trial.

To evaluate cerebral tissue oxygenation index (cTOI) during neonatal transition in a group of healthy full-term neonates receiving either a physiological-based approach of deferred cord clamping (CC) after the onset of stable regular breathing (PBCC group) or a standard approach of time-based CC < 1 min (control group). Secondary aim was to evaluate changes in cerebral blood volume (ΔCBV), peripheral arterial oxygen saturation (SpO2) and heart rate (HR) in those neonates. We conducted a randomized controlled trial (clinicaltrials.gov: NCT02763436) including vaginally delivered healthy full-term neonates. Continuous measurements of cTOI and ΔCBV using near-infrared spectroscopy, and of SpO2 and HR using pulse oximetry were performed within the first 15 min after birth. Data of each minute of the PBCC group were compared to those of the control group. A total of 71 full-term neonates (PBCC: n = 35, control: n = 36) with a mean (SD) gestational age of 40.0 (1.0) weeks and a birth weight of 3,479 (424) grams were included. Median (IQR) time of CC was 275 (197-345) seconds and 58 (35-86) seconds in the PBCC and control group, respectively (p < 0.001). There were no significant differences between the two groups regarding cTOI (p = 0.319), ΔCBV (p = 0.814), SpO2 (p = 0.322) and HR (p = 0.878) during the first 15 min after birth. There were no significant differences in the course of cTOI as well as ΔCBV, SpO2 and HR during the first 15 min after birth in a group of healthy full-term neonates, who received either deferred CC after the onset of stable regular breathing or standard CC < 1 min. Thus, deferring CC ≥ 1 min following a physiological-based approach offers no benefits regarding cerebral tissue oxygenation and perfusion after uncomplicated vaginal delivery compared to a time-based CC approach.

The influence of short-term high-altitude acclimatization on cerebral and leg tissue oxygenation post-orthostasis.

Orthostasis at sea level decreases brain tissue oxygenation and increases risk of syncope. High altitude reduces brain and peripheral muscle tissue oxygenation. This study determined the effect of short-term altitude acclimatization on cerebral and peripheral leg tissue oxygenation index (TOI) post-orthostasis. Seven lowlanders completed a supine-to-stand maneuver at sea level (450m) and for 3 consecutive days at high altitude (3776m). Cardiorespiratory measurements and near-infrared spectroscopy-derived oxygenation of the frontal lobe (cerebral TOI) and vastus lateralis (leg TOI) were measured at supine and 5-min post-orthostasis. After orthostasis at sea level, cerebral TOI decreased [mean Δ% (95% confidential interval): - 4.5%, (- 7.5, - 1.5), P < 0.001], whilst leg TOI was unchanged [- 4.6%, (- 10.9, 1.7), P = 0.42]. High altitude had no effect on cerebral TOI following orthostasis [days 1-3: - 2.3%, (- 5.3, 0.7); - 2.4%, (- 5.4, 0.6); - 2.1%, (- 5.1, 0.9), respectively, all P > 0.05], whereas leg TOI decreased [days 1-3: - 12.0%, (- 18.3, - 5.7); - 12.1%, (- 18.4, - 5.8); - 10.2%, (- 16.5, - 3.9), respectively, all P < 0.001]. This response did not differ with days spent at high altitude, despite evidence of cardiorespiratory acclimatization [increased peripheral oxygen saturation (supine: P = 0.01; stand: P = 0.02) and decreased end-tidal carbon dioxide (supine: P = 0.003; stand: P = 0.01)]. Cerebral oxygenation is preferentially maintained over leg oxygenation post-orthostasis at high altitude, suggesting different vascular regulation between cerebral and peripheral circulations. Short-term acclimatization to high altitude did not alter cerebral and leg oxygenation responses to orthostasis.

Cardiac Output and Cerebral Oxygenation in Term Neonates during Neonatal Transition.

The immediate transition from foetus to neonate includes substantial changes, especially concerning the cardiovascular system. Furthermore, the brain is one of the most vulnerable organs to hypoxia during this period. According to current guidelines for postnatal stabilization, the recommended parameters for monitoring are heart rate (HR) and arterial oxygen saturation (SpO2). Recently, there is a growing interest in advanced monitoring of the cardio-circulatory system and the brain to get further objective information about the neonate’s condition during the immediate postnatal transition after birth. The aim of the present study was to combine cardiac output (CO) and brain oxygenation monitoring in term neonates after caesarean section in order to analyse the potential influence of CO on cerebral oxygenation during neonatal transition. This was a monocentric, prospective, observational study. For non-invasive cardiac output measurements, the electrical velocimetry (EV) method (Aesculon Monitor, Osypka Medical, CA, USA) was used. The pulse oximeter probe for SpO2 and HR measurements was placed on the right hand or wrist. The cerebral tissue oxygen index (cTOI) was measured using a NIRO-200NX monitor with the near-infrared spectroscopy (NIRS) transducer on the right frontoparietal head. Monitoring started at minute 1 and was continued until minute 15 after birth. At minutes 5, 10, and 15 after birth, mean CO was calculated from six 10 s periods (with beat-to-beat analysis). During the study period, 99 term neonates were enrolled. Data from neonates with uncomplicated transitions were analysed. CO showed a tendency to decrease until minute 10. During the complete observational period, there was no significant correlation between CO and cTOI. The present study was the first to investigate a possible correlation between CO and cerebral oxygenation in term infants during the immediate neonatal transition. In term infants with uncomplicated neonatal transition after caesarean section, CO did not correlate with cerebral oxygenation.

Cerebral Oxygenation in Preterm Infants With Necrotizing Enterocolitis

Preterm infants with necrotizing enterocolitis (NEC) are known to have worse neurodevelopmental outcomes, but there is no substantial evidence to support an underlying pathophysiology. We aimed to examine whether cerebral oxygenation differs in those infants who develop NEC compared to cerebral oxygenation in those who do not. We examined 48 infants <30 weeks' gestation admitted to a tertiary level NICU from October 2016 to May 2018. Infants with birth weight less than or equal to the second percentile, abnormal antenatal dopplers or twin-to-twin-transfusion-syndrome were excluded. Cerebral oximetry measurements were performed by using a near-infrared spectroscopy (NIRS) monitor weekly for 60 minutes, allowing measurement of cerebral tissue oxygenation index from the first week of life to 36 weeks postconceptional age. Weekly clinical status was also recorded. NEC was defined as greater than or equal to Bell stage 2. The median birth weight was 884 g (range of 460-1600 g), the median weeks' gestational age was 26 + 3/7 (23 + 0/7 to 29 + 6/7), and 52% were girls. In total, 276 NIRS measurements were completed, and 7 infants developed NEC. NIRS measurements from 1 infant with NEC and 4 infants without NEC who developed hemorrhagic parenchymal infarcts were excluded from analysis. Infants who developed NEC had significantly lower cerebral tissue oxygenation index than those who did not (P = .011), even when adjusted for confounders, including gestational age, birth weight, patent ductus arteriosus, enteral feeds, sex, ethnicity, and hemoglobin. Infants with NEC have significantly lower cerebral tissue oxygenation throughout their neonatal intensive care stay in comparison with those who did not develop NEC. This is a novel finding and could explain their worse neurodevelopmental outcome.

Cerebral and peripheral muscle oxygenation and perfusion: Course in moderate and late preterm neonates during the first day after birth.

To investigate the ratio of cerebral tissue oxygenation index (cTOI) to peripheral muscle tissue oxygenation index (pTOI) measured by near-infrared spectroscopy (NIRS) in cardio-circulatory stable preterm neonates without signs of inflammation/infection on the first day after birth. Observational study analysing secondary outcome parameters of the 'Avoiding Hypotension in Preterm Neonates (AHIP)' trial (ClinicalTrials.gov identifier: NCT01910467). Preterm neonates, who had cTOI and pTOI measurements during 24 h after birth, were included. In each neonate the mean of the cTOI/pTOI-ratio, cTOI, pTOI and routine monitoring parameters were calculated for each hour and for the 24-h measuring period. Courses of all measured parameters were analysed. Eighty-seven stable preterm neonates (33.1 [32.1-34.1] weeks of gestation) were included. The mean value over the 24-h measuring period for the cTOI/pTOI-ratio was 0.96 ± 0.02, for cTOI 70.1 ± 1.4 and for pTOI 73.4 ± 0.9. Routine monitoring parameters were in the normal ranges over 24 h. The courses of the cTOI/pTOI-ratio and cTOI showed significantly lower values from hour 5 to 15 compared to the first hours after birth. Heart rate decreased significantly over time, whereas mean arterial blood pressure increased significantly. pTOI, arterial oxygen saturation and body temperature showed no significant change over time. We are the first to report on cTOI/pTOI-ratios for cardio-circulatory stable preterm neonates over a 24-h period after birth, showing significantly lower values from hour 5 to 15 compared to the first hours after birth.

Continuous reduction in cerebral oxygenation during endurance exercise in patients with pulmonary arterial hypertension.

BackgroundPatients with pulmonary arterial hypertension (PAH) have lower cerebral blood flow (CBF) and oxygenation compared to healthy sedentary subjects, the latter negatively correlating with exercise capacity during incremental cycling exercise. We hypothesized that patients would also exhibit altered CBF and oxygenation during endurance exercise, which would correlate with endurance time.MethodsResting and exercise cardiorespiratory parameters, blood velocity in the middle cerebral artery (MCAv; transcranial doppler) and cerebral oxygenation (relative changes in cerebral tissue oxygenation index (ΔcTOI) and cerebral deoxyhemoglobin (ΔcHHb); near‐infrared spectroscopy) were continuously monitored in nine PAH patients and 10 healthy‐matched controls throughout endurance exercise. Cardiac output (CO), systemic blood pressure (BP) and oxygen saturation (SpO2), ventilatory metrics and end‐tidal CO2 pressure (PETCO2) were also assessed noninvasively.ResultsDespite a lower workload and endurance oxygen consumption, similar CO and systemic BP, ΔcTOI was lower in PAH patients compared to controls (p < .01 for interaction). As expected during exercise, patients were characterized by an altered MCAv response to exercise, a lower PETCO2 and SpO2, as wells as a higher minute‐ventilation/CO2 production ratio (V˙E/V˙CO2 ratio). An uncoupling between changes in MCAv and PETCO2 during the cycling endurance exercise was also progressively apparent in PAH patients, but absent in healthy controls. Both cHHb and ΔcTOI correlated with V˙E/V˙CO2 ratio (r = 0.50 and r = −0.52; both p < .05 respectively), but not with endurance time.ConclusionPAH patients present an abnormal cerebrovascular profile during endurance exercise with a lower cerebral oxygenation that correlate with hyperventilation but not endurance exercise time. These findings complement the physiological characterization of the cerebral vascular responses to exercise in PAH patients.

Assessment of the benefits of head-up preoxygenation using near-infrared spectroscopy with pulse oximetry in a swine model.

Compared with supine positioning, head-up positioning improves preoxygenation and prolongs the time to oxygen desaturation. We reevaluated benefits of head-up positioning using near-infrared spectroscopy (NIRS) with pulse oximetry in a pig model. Six pigs (mean ± SD weight: 25.3 ± 0.6 kg) were anesthetized with isoflurane and evaluated in four positions—supine, head-up, head-down, head-up to supine—just before apnea (positions’ order after “supine” was randomized). In each position, after 5 min of preoxygenation with 100% oxygen, apnea was induced and the time to SpO2 < 70% measured. Hemodynamic and blood-gas variables and the cerebral tissue oxygenation index (TOI) were evaluated using NIRS and recorded. Hypovolemia was induced by collecting 600 mL blood. Apnea experiment was performed again in each position. The times (seconds) ± SD to SpO2 < 70% were 108 ± 13 (supine), 138 ± 15 (head-up; P < 0.0001 vs all other positions); 101 ± 12 (head-down) and 106 ± 15 (head-up to supine) during normovolemia, and 110 ± 29, 120 ± 7 (not significant vs all other positions), 101 ± 16, and 106 ± 11, respectively, during hypovolemia. Although the TOI was not associated with the positions during normovolemia, the head-up position during hypovolemia decreased TOI from 62% ± 6% (supine) to 50% ± 9% (head-up; P = 0.0019) before preoxygenation, and it remained low during apnea. The head-up position improves preoxygenation, but repositioning to supine negates the benefits. Head-up positioning during evident hypovolemia should be avoided because the cerebral oxygenation could decrease.

Remote Ischemic Conditioning Improves Attention Network Function and Blood Oxygen Levels in Unacclimatized Adults Exposed to High Altitude.

Remote ischemic conditioning (RIC) confers protection on major organs from hypoxic/ischemic injuries; however, its impacts on attention network function and blood oxygen levels in unacclimatized adults exposed to high altitudes have yet to be elucidated. In this study, we recruited 120 healthy male volunteers, of which one was exposed to high altitude and the other was exposed to low altitude. The two cohorts were further divided into RIC and sham control groups. The attentional network test (ANT) was performed to evaluate cognitive function before and after RIC treatment. Other outcomes such as heart rate, blood pressure, blood oxygen saturation, cerebral tissue oxygenation index (CTOI), and cerebrovascular hemodynamic indices were also evaluated. Prior to RIC treatment, there were no significant differences in orienting or executive function between the treatment and control arms of either cohort. Alerting function was significantly lower in the high-altitude cohort than in the low-altitude cohort. There were significant reductions in both blood oxygen and CTOI in the high-altitude cohort relative to the low-altitude cohort, while the pulse index (PI) of the former cohort was significantly increased. After RIC treatment, there was a significant difference in alerting function between the high-altitude RIC group and its associated control. The CTOI of the treatment group increased from 60.39±3.40% to 62.78±4.40%, and blood oxygenation also improved. Furthermore, this group showed a significant reduction in its PI. Exposure to high-altitude environments had a significant impact on alerting function, blood oxygen, CTOI, and PI. RIC ameliorated changes in attentional function, as well as blood oxygen and CTOI, suggesting that it potentially alters cerebrovascular compliance upon exposure to high altitude.

Different Patterns of Cerebral and Muscular Tissue Oxygenation 10 Years After Coarctation Repair.

The purpose of this study was to assess whether the lower exercise tolerance in children after coarctation repair is associated with alterations in peripheral tissue oxygenation during exercise. A total of 16 children after coarctation repair and 20 healthy control subjects performed an incremental ramp exercise test to exhaustion. Cerebral and locomotor muscle oxygenation were measured by means of near infrared spectroscopy. The responses of cerebral and muscle tissue oxygenation index (cTOI, mTOI), oxygenated (O2Hb), and deoxygenated hemoglobin (HHb) as a function of work rate were compared. Correlations between residual continuous wave Doppler gradients at rest, arm-leg blood pressure difference and local oxygenation responses were evaluated. Age, length, and weight was similar in both groups. Patients with aortic coarctation had lower peak power output (Ppeak) (72.3 ± 20.2% vs. 106 ± 18.7%, P < 0.001), VO2peak/kg (37.3 ± 9.1 vs. 44.2 ± 7.6 ml/kg, P = 0.019) and %VO2peak/kg (85.7 ± 21.9% vs. 112.1 ± 15.5%, P < 0.001). Cerebral O2Hb and HHb had a lower increase in patients vs. controls during exercise, with significant differences from 60 to 90% Ppeak (O2Hb) and 70% to 100% Ppeak (HHb). Muscle TOI was significantly lower in patients from 10 to 70% Ppeak and muscle HHb was significantly higher in patients vs. controls from 20 to 80% Ppeak. Muscle O2Hb was not different between both groups. There was a significant correlation between residual resting blood pressure gradient and Δmuscle HHb/ΔP at 10–20W and 20–30W (r = 0.40, P = 0.039 and r = 0.43, P = 0.034). Children after coarctation repair have different oxygenation responses at muscular and cerebral level. This reflects a different balance between O2 supply to O2 demand which might contribute to the reduced exercise tolerance in this patient population.

Cerebral Oxygenation During Respiratory Events in Children with Sleep-Disordered Breathing and Associated Disorders

To evaluate changes in cerebral oxygenation by means of near-infrared spectroscopy during respiratory events in children with sleep-disordered breathing (SDB) and associated disorders. Sixty-five children suspected of having SDB underwent a respiratory polygraphy with simultaneous recording of cerebral oxygenation indices. Respiratory events were analyzed by type of event, duration, variations of pulse oximetry (oxygen saturation [SpO2]), cerebral tissue oxygenation index (TOI), and heart rate. Data were categorized according to the severity of SDB and age. There were 540 obstructive and mixed apneas, 172 central apneas, and 393 obstructive hypopneas analyzed. The mean decreases in SpO2 and TOI were 4.1±3.1% and 3.4±2.8%, respectively. The mean TOI decrease was significantly smaller for obstructive hypopnea compared with apneas. The TOI decrease was significantly less in children with mild SDB as compared with those with moderate-to-severe SDB and in children >7years as compared with those <7years old. TOI decreases correlated significantly with SpO2 decreases, duration of event, and age, regardless of the type of event. In a multivariable regression model, predictive factors of TOI decreases were the type of respiratory event, SpO2 decrease, apnea-hypopnea index, and age. In children with SDB and associated disorders, cerebral oxygenation variations depend on the type of respiratory event, severity of SDB, and age.

The association of the cerebral oxygenation during neonatal sepsis with the Bayley-III Scale of Infant and Toddler Development index scores at 18–24 months of age

BackgroundNeonatal sepsis has been associated with poor neurodevelopmental outcome, however the evidence regarding the exact mechanism of the inflammation to the developing neonatal brain are inconclusive. AimsTo investigate association between cerebral oxygenation during neonatal sepsis and neurodevelopmental outcome. Study designFollow-up assessment of a previously described prospective case-control study. SubjectsA cohort of late preterm (34–37 weeks' gestation) and preterm (<34 weeks' gestation) infants with sepsis and healthy controls, evaluated at 18–24 months of corrected gestational age with Bayley-III Scales for Infant and Toddler Development (BSID-III). Outcome measuresTo evaluate the association between cerebral tissue oxygenation index (cTOI) and fractional tissue oxygen extraction (FTOE), measured with near-infrared spectroscopy, during sepsis and the composite cognitive and motor index scores. ResultsThirty-one infants with blood culture confirmed neonatal sepsis and thirty-five controls were recruited. The cerebral oxygenation was significantly lower in septic neonates, compared to controls (61 ± 7 compared to 72 ± 5; p < 0.001). Infants with sepsis had significantly lower cognitive and motor index scores and higher proportion of suboptimal cognitive (16% compared to 3%, p = 0.045) and motor (16% compared to none, p = 0.008) index score. The low mean cTOI and FTOE noted in septic infants were significantly associated with worse cognitive and motor composite index scores. ConclusionsInfants with lower cerebral oxygenation during neonatal sepsis are at increased risk of worse cognitive and motor scores in the neurodevelopmental assessment.

Assessment of cerebral and renal autoregulation using near-infrared spectroscopy under normal, hypovolaemic and postfluid resuscitation conditions in a swine model: An observational study.

The impact of blood pressure changes on tissue oxygenation differs between vital organs and with blood volume conditions. To assess cerebral and renal autoregulation simultaneously and compare the impact of blood pressure, hypovolaemia and fluid resuscitation on tissue oxygenation using near-infrared spectroscopy. Animal observational study. An animal laboratory in Hamamatsu University School of Medicine, Hamamatsu, Japan, from April 2018 to August 2018. Fifteen pigs, (mean ± SD) 25.2 ± 0.4 kg. The pigs were anaesthetised with 2.5% isoflurane and phenylephrine 0.5, 1, 2 and 5 μg kg min was administered in a stepwise fashion at 10-min intervals (baseline), followed by similar administration of sodium nitroprusside. Hypovolaemia was induced by a 600-ml bleed (33% of estimated total blood volume). Then phenylephrine was administered again (same protocol). Hypovolaemia was reversed by infusion of 600-ml hydroxyethyl starch. Phenylephrine and sodium nitroprusside were then administered again (same protocol). Average of the relation between mean arterial pressure (MAP) and cerebral or renal tissue oxygenation index (TOI) and individual TOI response during vasoactive drug infusions. The average relationship between MAP and cerebral or renal TOI both showed classic autoregulation patterns, whereas the renal TOI was more pressure-dependent than the cerebral TOI. Hypovolaemia shifted the relationship downward, reducing the cerebral and renal TOIs by approximately 5 and 20%, respectively, at similar MAPs. Subsequent fluid resuscitation preserved the autoregulatory pattern in both organs, not changing cerebral TOI but reducing renal TOI to 10% under baseline. TOI responses in both organs included paradoxical changes (tissue oxygenation changed inversely with MAP) in 60% of animals. Animals with paradoxical reactions maintained more stable cerebral and renal oxygenation. Renal oxygenation is more pressure-dependent than pressure-tolerant cerebral oxygenation, and autoregulation is not robust. Renal oxygenation decreased four-fold compared with cerebral oxygenation during hypovolaemia and two-fold during isovolaemic anaemia. Thus, paradoxical responses are part of normal autoregulatory function and beneficial for maintaining stable oxygenation.

Functional near infrared spectroscopy using spatially resolved data to account for tissue scattering: A numerical study and arm-cuff experiment.

Functional Near‐Infrared Spectroscopy (fNIRS) aims to recover changes in tissue optical parameters relating to tissue hemodynamics, to infer functional information in biological tissue. A widely‐used application of fNIRS relies on continuous wave (CW) methodology that utilizes multiple distance measurements on human head for study of brain health. The typical method used is spatially resolved spectroscopy (SRS), which is shown to recover tissue oxygenation index (TOI) based on gradient of light intensity measured between two detectors. However, this methodology does not account for tissue scattering which is often assumed. A new parameter recovery algorithm is developed, which directly recovers both the scattering parameter and scaled chromophore concentrations and hence TOI from the measured gradient of light‐attenuation at multiple wavelengths. It is shown through simulations that in comparison to conventional SRS which estimates cerebral TOI values with an error of ±12.3%, the proposed method provides more accurate estimate of TOI exhibiting an error of ±5.7% without any prior assumptions of tissue scatter, and can be easily implemented within CW fNIRS systems. Using an arm‐cuff experiment, the obtained TOI using the proposed method is shown to provide a higher and more realistic value as compared to utilizing any prior assumptions of tissue scatter.

Cerebral Hemodynamics During Neonatal Cerebrospinal Fluid Removal

BackgroundStandard treatment of neonatal posthemorrhagic hydrocephalus is cerebrospinal fluid removal. The aim of this study was to assess how much cerebrospinal fluid volume removal, by ventricular reservoir taps, is needed to improve cerebral hemodynamics and oxygenation in neonatal posthemorrhagic hydrocephalus. MethodsCerebral hemodynamics and oxygenation were continuously monitored by near-infrared spectroscopy in four newborns (one term and three preterm) during 28 ventricular reservoir taps. At each tap, 10 mL/kg of cerebrospinal fluid was removed. Near-infrared spectroscopy detected changes in the concentration of oxy-hemoglobin and total hemoglobin, considered as estimates of cerebral blood flow and volume, respectively. Cerebral tissue oxygenation index was also measured. During cerebrospinal fluid removal, variation in cerebral blood flow, volume, and oxygenation were analyzed by repeated measures analysis of variance. The associations between changes in cerebral hemodynamics and oxygenation, during cerebrospinal fluid removal and after its conclusion, were analyzed by Pearson's r correlation coefficient. ResultsA significant increase in cerebral blood flow and volume was already evident at 50% of targeted cerebrospinal fluid volume removal (P < 0.001). Although cerebral tissue oxygenation index absolute value remained unchanged, variations in cerebral blood flow and oxygenation were positively correlated, both during cerebrospinal fluid removal and after its conclusion (r = 0.57; P = 0.002). ConclusionsOn the basis of the results from this small cohort, the volume of cerebrospinal fluid removal associated with an improvement in cerebral hemodynamics and perfusion seems to be less than the traditional 10 mL/kg. Further research is needed to define the potential role of near-infrared spectroscopy monitoring to individualize cerebrospinal fluid removal.