Non-invasive assessment of periodontal inflammation by continuum-removal hemodynamic spectral indices.

BACKGROUND: Hyperspectral techniques have aroused great interest in non-invasively measuring periodontal tissue hemodynamics. However, current studies mainly focused on three typical inflammation stages (healthy, gingivitis and periodontitis) and practical approaches for using optical spectroscopy for early and precisely detection of periodontal inflammation at finer disease stages have not been well studied. METHODS: This study provided novel spectroscopic insights into periodontitis at different stages of disease, and developed six simple but physically meaning hemodynamic spectral indices (HSIs) including four spectral absorption depths of oxyhemoglobin ( D HbO 2 ), deoxyhemoglobin ( D Hb ), total hemoglobin ( t Hb ) and tissue water ( D water ), and two normalized difference indices of oxyhemoglobin( N D HbO 2 I ) and deoxyhemoglobin ( N D Hb I ) from continuum-removal spectra (400-1700 nm) of periodontal tissue collected from 47 systemically healthy subjects over different severities from healthy, gingivitis, slight, moderate to severe periodontitis for early and precision diagnostics of periodontitis. Typical statistical analyses were conducted to explore the effectiveness of the proposed HSIs. RESULTS: D Hb and t Hb exerted significant increasing trends as inflammation progressed, whereas D HbO 2 exhibited significant difference (P < 0.05) from the healthy sites only at moderate and severe periodontitis and D water presented unstable sensitives to disease severity. By contrast, N D HbO 2 I and N D Hb I showed more steadily downward trends as severity increased, and demonstrated the highest correlations with clinical gold standard parameters. Particularly, the proposed normalized HSIs ( N D HbO 2 I and N D Hb I ) yielded high correlations of - 0.49 and - 0.44 with probing depth, respectively, far outperforming results achieved by previous studies. The performances of the HSIs were also confirmed using the periodontal therapy group. CONCLUSIONS: These results indicated great potentials of combination optical spectroscopy and smart devices to non-invasively probe periodontitis at earlier stages using the simple and practical HSIs. Trial registration This study was retrospectively registered in the Chinese Clinical Trial Registry on October 24, 2021, and the clinical registration number is ChiCTR2100052306.

Measuring and imaging of transcutaneous bilirubin, hemoglobin, and melanin based on diffuse reflectance spectroscopy.

Significance: Evaluation of biological chromophore levels is useful for detection of various skin diseases, including cancer, monitoring of health status and tissue metabolism, and assessment of clinical and physiological vascular functions. Clinically, it is useful to assess multiple different chromophores in vivo with a single technique or instrument. Aim: To investigate the possibility of estimating the concentration of four chromophores, bilirubin, oxygenated hemoglobin, deoxygenated hemoglobin, and melanin from diffuse reflectance spectra in the visible region. Approach: A new diffuse reflectance spectroscopic method based on the multiple regression analysis aided by Monte Carlo simulations for light transport was developed to quantify bilirubin, oxygenated hemoglobin, deoxygenated hemoglobin, and melanin. Three different experimental animal models were used to induce hyperbilirubinemia, hypoxemia, and melanogenesis in rats. Results: The estimated bilirubin concentration increased after ligation of the bile duct and reached around 18 mg/dl at 50 h after the onset of ligation, which corresponds to the reference value of bilirubin measured by a commercially available transcutaneous bilirubin meter. The concentration of oxygenated hemoglobin and that of deoxygenated hemoglobin decreased and increased, respectively, as the fraction of inspired oxygen decreased. Consequently, the tissue oxygen saturation dramatically decreased. The time course of melanin concentration after depilation of skin on the back of rats was indicative of the supply of melanosomes produced by melanocytes of hair follicles to the growing hair shaft. Conclusions: The results of our study showed that the proposed method is capable of the in vivo evaluation of percutaneous bilirubin level, skin hemodynamics, and melanogenesis in rats, and that it has potential as a tool for the diagnosis and management of hyperbilirubinemia, hypoxemia, and pigmented skin lesions.

Developmental changes in neonatal hemodynamics during tactile stimulation using whole-head functional near-infrared spectroscopy.

Neural-activity-associated hemodynamic changes have been used to noninvasively measure brain function in the early developmental stages. However, the temporal changes in their hemodynamics are not always consistent with adults. Studies have not evaluated developmental changes for a long period using the same stimuli; therefore, this study examined the normalized relative changes in oxygenated hemoglobin (Δ[oxy-Hb]) in full-term infants and compared them with neonates up to 10 months of age during the administration of tactile vibration stimuli to their limbs using whole-head functional near-infrared spectroscopy. The time to peak of normalized Δ[oxy-Hb] was not affected by age. The amplitude of normalized Δ[oxy-Hb] showed an effect of age in broader areas, including sensorimotor-related but excluding supplementary motor area; the amplitude of normalized Δ[oxy-Hb] decreased the most in the 1-2-month-old group and later increased with development. We hypothesized that these results may reflect developmental changes in neural activity, vasculature, and blood oxygenation.

Developing a novel device based on a new technology for non-invasive measurement of blood biomarkers irrespective of skin color.

Background: Human hemoglobin is a tetrameric metalloporphyrin. The heme part contains iron radicle and porphyrin. The globin part consists of two pairs of amino-acid chains. The absorption spectrum of hemoglobin spans from 250 nm to as high as 2,500 nm, with high coefficients reported in blue and green color zone. The visible absorption spectrum of deoxyhemoglobin has one, while the visible absorption spectrum of oxyhemoglobin shows two peaks. Objective: (1) To study absorption spectrometry of hemoglobin in 420 to 600 nm range; (2) to conduct preclinical experiments to validate a new device and technology based on green color absorption by hemoglobin; (3) to use this new technology and device for phase 1 study in healthy human volunteers for confirmation. Design material and methods: (1) Checking absorption spectrometry of hemoglobin in venous blood. We measured absorption spectrometry of 25 mother-baby pairs as an observational study. Readings were plotted from 400 nm to 560 nm. These included peaks, flat lines and deeps. Graph tracings of all samples - cord blood and maternal blood - showed similar patterns. (2) Preclinical experiments were set up (a) to correlate the reflection of green light by hemoglobin and concentration of hemoglobin, (b) to correlate concentration of O2 and reflection of green light related to oxyhemoglobin, (c) to correlate concentration of melanin in upper and the hemoglobin in lower layer of tissue phantom and to check the sensitivity of new device with green light for measuring Hb in presence of high levels of melanin, and lastly (d) to check if the new device can measure changes in oxy-hemoglobin and deoxy-hemoglobin, again in presence of high levels of melanin with normal as well as with low levels of hemoglobin. The experiments using bilayer tissue phantom were conducted with horse blood in lower cup as dermal tissue phantom and synthetic melanin in upper layer as epidermal tissue phantom. (3) Phase 1 observational studies following a protocol approved by the institutional review board (IRB) were done in two cohorts. Readings were taken using our device and a commercially available pulse oximeter. In the comparison arm we had Point of Care (POC) Hb test (HemoCu or iSTAT blood test). We had 127 data points of POC Hb test and 170 data points for our device and pulse oximeters. This device uses two wavelengths from the visible spectrum of light and uses reflected light. Light of specific wavelengths is shone on the skin of the individual, and the reflected light is collected as 'optical signal'. This optical signal - after conversion to electrical signal - is processed and finally analysed with a digital display on the screen. Melanin is accounted using Von Luschan's chromatic scale (VLS) and a specially designed algorithm. Results: In this set of various preclinical experiments using different concentrations of hemoglobin and melanin, we indeed demonstrated good sensitivity of our device. It could pick up signals from hemoglobin despite high levels of melanin. Our device is a non-invasive device to measure hemoglobin like a pulse oximeter. Results of our device and pulse oximeter were compared with those by POC Hb test like HemoCu and iSTAT. Our device showed better trending linearity and concordance than a pulse oximeter. Since the absorption spectrum of hemoglobin is the same is new-borns and adults, we could develop one device for all age groups and for people of all colors. Furthermore, the light is shone on the wrist of the individual and is then measured. So, in future this device has the potential of being incorporated in a wearable or smart watch technology.

Physiological Effects of Visual Stimulation by a Japanese Low Wooden Table: A Crossover Field Experiment.

The purpose of this study was to evaluate the physiological effects of visual stimulation by a unique Japanese low wooden table on the prefrontal cortex and autonomic nervous activities. A within-participants experiment with 26 male university students was conducted in a Japanese-style room. The visual stimuli were a low wooden table (WT) made of Japanese cypress and a low cloth-covered table (control) for an exposure time of 90 s. Near-infrared spectroscopy was used to measure the prefrontal cortex activity in the left and right prefrontal cortices as an indicator of oxyhemoglobin (oxy-Hb) concentration. Autonomic nervous activity was measured as an indicator of sympathetic (low-frequency/high-frequency component ratio, LF/HF), and parasympathetic (high-frequency components, HF) nervous activities were assessed by heart rate variability. Furthermore, the modified semantic differential method and the Profile of Mood States 2nd edition were used to measure psychological responses. Physiologically, the oxy-Hb concentration in the left prefrontal cortex and ln (LF/HF) were significantly lower during visual exposure to the WT than to the control. Psychologically, more comfortable, relaxed, and natural impressions, as well as improved mood states, were reported during visual stimulation to the WT than to the control. This study demonstrated that viewing a WT led to physiological relaxation and had a positive psychological effect on the participants.

Hemodynamic alterations response to Chinese acupuncture therapy monitored by a custom near-infrared spectroscopy probe with an open hole.

Traditional acupuncture, a popular traditional Chinese medicine (TCM) technique, has demonstrated potential in relieving various ailments' symptoms. However, its black-box feedback loop model has limited proper evaluation and use by unskilled practitioners. This study aimed to analyze hemodynamic signals around acupoints during acupuncture to identify significant parameter changes. We designed hollow near-infrared spectroscopy (NIRS) probes for real-time measurements during acupuncture at acupoints, monitoring oxy-hemoglobin (HbO), deoxy-hemoglobin (Hb), and blood volume (HbT) changes. Acupuncture was performed on the "Xuehai" acupoint in 17 healthy subjects, with NIRS measuring hemodynamic alterations. Results showed significant and consistent increases in Hb and HbT around the acupoint, returning to baseline values after needle removal. One case of fainting revealed a significant Hb increase and HbO decrease. Acupuncture may induce tissue vasodilation and enhance oxygen consumption. This research provides a potential explanation for acupuncture's mechanism and emphasizes NIRS's potential in TCM.

Differences in the prefrontal cortex responses of healthy young men performing either water-based or land-based exercise at light to moderate intensity.

Cerebral blood flow increases more during water-based exercise than land-based exercise owing to the effects of end-tidal CO2 (PETCO2) and mean arterial pressure (MAP) changes due to water immersion. However, it is unclear whether oxygenated hemoglobin (oxy-Hb) concentrations in the prefrontal cortex (PFC) are increased more by water-based or land-based exercise. We hypothesized that oxy-Hb concentrations in the PFC are higher during water-based exercise than land-based exercise when the exercise intensity is matched. To test this hypothesis, 10 healthy participants (age: 24.2 ± 1.7 years; height: 1.75 ± 0.04 m; weight: 69.5 ± 5.2 kg) performed light- to moderate-intensity cycling exercise in water (water-based cycling (WC); chest-high water at 30 °C) and on land (LC). Stroke volume, cardio output, heart rate, MAP, respiratory rate, PETCO2, and oxy-Hb in the PFC were assessed during 15 min of exercise, with exercise intensity increased every 5 min. Both WC and LC significantly increased oxy-Hb concentrations in the PFC as exercise intensity was increased (intensity effect: p < 0.001). There was no significant difference in oxy-Hb concentrations during WC and LC in most prefrontal areas, although significant differences were found in areas corresponding to the left dorsolateral PFC (exercise effect: p < 0.001). Thus, WC and LC increase oxy-Hb concentrations in the PFC in a similar manner with increasing exercise intensity, but part of the PFC exhibits enhanced oxy-Hb levels during WC. The neural response of the PFC may differ during water-based and land-based exercise owing to differences in external information associated with water immersion.

Correctly Establishing and Interpreting Oxygenation Status in Sickle Cell Disease.

BACKGROUND: As hypoxemia and hypoxia are central elements of disease pathophysiology and disease-related morbidity and mortality in individuals affected by sickle cell disease (SCD), clinical management aims to optimize oxygenation. CONTENT: Hypoxemia is primarily screened for with pulse oximetry. However, in SCD pulse oximetry can inaccurately reflect arterial saturation, posing the risk of undetected (occult) hypoxemia. Solely relying on pulse oximetry might therefore lead to misdiagnosis or mismanagement, with devastating effects on tissue oxygenation. The interpretation of oxygenation status is multifaceted, and "oxygen saturation" is often used as an umbrella term to refer to distinctly different measured quantities-estimated oxygen saturation (O2Sat), hemoglobin oxygen saturation (SO2) by either pulse oximetry or co-oximetry, and fractional oxyhemoglobin (FO2Hb). While in many clinical situations this ambiguous use is of little consequence, O2Sat, SO2, and FO2Hb cannot be used interchangeably in the setting of SCD, as dyshemoglobins, anemia, cardiopulmonary comorbidities, concomitant medications, and frequent transfusions need to be accounted for. This article describes the parameters that determine blood and tissue oxygen concentration, discusses laboratory method performance characteristics and the correct interpretation of currently available clinical laboratory testing, and reviews the literature on noninvasive vs invasive oxygenation measurements in SCD. SUMMARY: By correctly establishing and interpreting oxygenation parameters, clinical and laboratory teams can ensure high-quality, equitable healthcare, counteracting systemic exacerbations of health disparities frequently experienced by individuals with SCD.

Resting-state coupling between HbO and Hb measured by fNIRS in autism spectrum disorder.

To distinguish between children with autism spectrum disorder (ASD) and typically developing (TD) children, we have uncovered a new discriminative feature, hemoglobin coupling. Functional near-infrared spectroscopy (fNIRS) was used to record resting-state hemodynamic fluctuations in the bilateral temporal lobes in 25 children with ASD and 22 TD children, in which the coupling between low frequency oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (Hb) fluctuations was evaluated by Pearson correlation coefficient. The results showed significantly weak coupling in children with ASD in both the left and right, and throughout the whole temporal cortex. To explain this observation, a simulation study was performed using a balloon model, in which we found four related parameters could impact the coupling. This study suggested that hemoglobin coupling might be applied as a new cerebral hemodynamic characteristic for ASD screening or diagnostics.

The Intramuscular Circulation Is Affected by Neck and Shoulder Pain.

The purpose of this study was to investigate the effects of neck and shoulder pain (NSP) and the position of the head and neck on the intramuscular circulation of the cervical muscles such as the trapezius and levator scapulae muscles in young females. Ten NSP subjects (mean age: 20.9 ± 0.5 years) and ten non-NSP subjects (mean age: 20.6 ± 0.7 years) were recruited to this study. Near-infrared spectroscopy (NIRS) was used to non-invasively measure total haemoglobin (Total-Hb), oxygenated haemoglobin (Oxy-Hb), and deoxygenated haemoglobin (Deoxy-Hb) of the trapezius and levator scapulae muscles. The measurements of Total-Hb, Oxy-Hb, and Deoxy-Hb were taken in the neutral position, immediately after the maximally flexed (extended) position, and after 30 s in the maximally flexed (extended) position. In flexion, no significant main effect or interaction was observed with Total-Hb and Oxy-Hb. A significant interaction was observed with Deoxy-Hb (p < 0.01). There was no significant difference in the changes over time in the NSP group (p = 0.91). However, in the non-NSP group, a significant increase was noted at the neutral position to immediately after the maximally flexed position (p < 0.01) and at the end of maintaining the maximally flexed position (p < 0.01). In extension, no significant main effect or interaction was observed with Total-Hb and Oxy-Hb. A significant interaction was observed with Deoxy-Hb (p < 0.01). In the NSP group, no significant difference was observed in the changes over time (p = 0.91). In the non-NSP group, however, a significant decrease was observed from the neutral position to immediately after the maximally extended position (p < 0.01). The results of this study indicate that maintaining either maximal cervical flexion or extension may affect venous blood flow on non-NSP group. However, no effect on NSP group was observed due to existing diminished intramuscular circulation.

Intramuscular Circulation of the Lumbar Multifidus in Different Trunk Positions on Standing.

A deficiency in lumbar muscle blood circulation is considered to be a major risk factor for non-specific low back pain. The aim of this study was to investigate changes in relative circulation over time in the lumbar multifidus in different positions on sitting.Twelve healthy subjects (7 males, 5 females, average age: 20.9 years) without low back pain for the past 12 months were recruited. Near-infrared spectroscopy (NIRS) was used to non-invasively measure total haemoglobin (Total-Hb) and oxygenated haemoglobin (Oxy-Hb) in the lumbar multifidus at the L5-S1 segment. Subjects were asked to move into either 60-degree trunk-flexed or 20-degree trunk-extended position from the starting (standing in neutral) position in 3 s, timed by a metronome, and to maintain these positions for 30 s. The measurements of Total-Hb and Oxy-Hb were compared at -3 (neutral position), 0, 10, 20, and 30 s in each flexed and extended position on sitting.In flexion, Total-Hb and Oxy-Hb of the lumbar multifidus were significantly decreased from a neutral (-3 s) to flexed (0 s) position (Total-Hb: p = 0.002, Oxy-Hb: p = 0.004); however, there were no significant differences in the flexed position. In extension, Total-Hb and Oxy-Hb of the lumbar multifidus were significantly increased from 0 to 10 s (Total-Hb: p < 0.001, Oxy-Hb: p < 0.001); however, there were no significant differences from the neutral (-3 s) to extended (0 s) position, or from 10 to 30 s.The results of this study indicate that the intramuscular circulation of the lumbar multifidus decreases immediately once the trunk starts moving into a flexed position on sitting. On the other hand, the intramuscular circulation of the lumbar multifidus increases for up to 10 s once the trunk starts moving into an extended position.

Three-dimensional representation of triple spectral line imaging data as an option for noncontact skin diagnostics.

SIGNIFICANCE: Skin malformations in dermatology are mostly evaluated subjectively, based on a doctor's experience and visual perception; an option for objective quantitative skin assessment is camera-based spectrally selective diagnostics. Multispectral imaging is a technique capable to provide information about concentrations of the absorbing chromophores and their distribution over the malformation in a noncontact way. Conversion of spectral images into distribution maps of chromophores can be performed by means of the modified Beer-Lambert law. However, such distribution maps represent only single specific cases, therefore, some extensive method for data comparison is needed. AIM: This study aims to develop a more informative approach for identification and characterization of skin malformations using three-dimensional (3D) representation of triple spectral line imaging data. APPROACH: The 3D-representation method is experimentally tested on eight different skin pathology types, including both benign and malignant pathologies; an imaging device ensuring uniform three laser line (448, 532, and 659 nm) illumination is used. Three spectral line images are extracted from a single snapshot RGB image data, with subsequent calculation of attenuation coefficients for each working wavelength at every image pixel and represented as 3D graphs. Skin chromophore content variations in malformations are represented in a similar way. RESULTS: Clinical measurement results for 99 skin pathologies, including basal cell carcinomas, melanoma, dermal nevi, combined nevi, junctional nevi, blue nevi, seborrheic keratosis, and hemangiomas. They are presented as 3D spectral attenuation maps exhibiting specific individual features for each group of pathologies. Along with intensity attenuation maps, 3D maps for content variations of three main skin chromophores (melanin, oxyhemoglobin, and deoxyhemoglobin), calculated in frame of a model based on modified Beer-Lambert law, are also presented. Advantages and disadvantages of the proposed data representation method are discussed. CONCLUSIONS: The described 3D-representation method of triple spectral line imaging data shows promising potential for objective quantitative noncontact diagnosis of skin pathologies.

Interpretation of Oxygen Saturation in Congenital Heart Disease: Fact and Fallacy.

Oxygen saturation is the percentage of hemoglobin that is saturated with oxygen, converting it to oxyhemoglobin. Oxygen saturation is a critical part of the physical examination of children with congenital heart disease (CHD). The expected oxygen saturation of a patient with CHD depends on their anatomical lesion, their previous surgeries, and any additional pulmonary or systemic pathology that may derange their saturation. Oxygen saturation can be noninvasively measured using pulse oximetry. Pulse oximetry is based on the differential absorption of infrared and red light by oxyhemoglobin and deoxyhemoglobin, with the former absorbing more infrared than the latter. Pulse oximetry readings may be inaccurate in settings of low cardiac output, peripheral vasoconstriction, arrhythmia, hypothermia, and venous pulsations. The use of pulse oximetry in the care of a child with CHD begins with the newborn critical CHD screen. A failed screen indicates a need for further investigation, such as repeated pulse oximetry or echocardiography. The oxyhemoglobin dissociation curve may be used to estimate the partial pressure of oxygen in the blood at various oxygen saturations. It is also a marker of the affinity of hemoglobin for oxygen, with a right-shifted curve indicating a higher oxygen tension needed to saturate hemoglobin. This is a helpful adaptation of the body to situations of stress such as fever, acidosis, and hypercapnia. An understanding of these concepts is paramount for providers caring for patients with known or potential CHD in any setting to appropriately interpret and respond to abnormal saturations for each child.

Fetal Hemoglobin and Cerebral Tissue Oxygenation during Immediate Postnatal Transition.

INTRODUCTION: Concentration of fetal hemoglobin (HbFc) in human neonates determines oxygen-carrying capacity of blood and the position of oxyhemoglobin dissociation curve. Near-infrared spectroscopy enables the measurement of regional cerebral tissue oxygen saturation (rScO2) and in combination with measurements of pulsatile arterial oxygen saturation (SpO2), the calculation of cerebral fractional tissue oxygen extraction (cFTOE). METHODS: We aimed to investigate the impact of HbFc on rScO2, cFTOE, and SpO2 in preterm and term neonates during the first 15 min after birth. Blood analyses provided total blood hemoglobin (Hb) and HbFc measurements. Correlations between HbFc, Hb and rScO2, cFTOE, and SpO2 in each minute were analyzed. RESULTS: Ninety term and 19 preterm neonates without medical support were included. HbFc was significantly higher in preterm neonates, whereas there were no significant differences in Hb between the groups. In preterm neonates, we found positive correlations of both HbFc and Hb with rScO2 and negative correlations of HbFc and Hb with cFTOE in the first minutes after birth. In contrast, there were no significant correlations between the same parameters in term neonates. Correlations between HbFc or Hb and SpO2 were either insignificant, negligible, or very low in both groups. DISCUSSION/CONCLUSION: In preterm neonates, higher HbFc was associated with higher rScO2 and lower cFTOE in the first minutes after birth. This phenomenon could not be confirmed in term neonates and might reflect immature autoregulation of oxygen delivery to the brain or lower oxygen consumption in preterm neonates in the first minutes of immediate postnatal transition.

Effect of Indoor Forest Bathing on Reducing Feelings of Fatigue Using Cerebral Activity as an Indicator.

We created an indoor forest bathing environment in a sunlight-type environmentally controlled chamber and both physiological and psychological measurements were conducted for the evaluation of mental fatigue reduction. At first, a working memory load experiment was performed among 10 participants in a space without plants to identify an indicator correlating with feelings of fatigue, using the cerebral activity of the prefrontal cortex. Then, the indicator was used to evaluate whether a 20-min exposure to an indoor forest bathing environment reduced the level of the feeling of fatigue. The working memory load experiment demonstrated that, when mental fatigue increased, the amount of oxygenated hemoglobin (oxy-Hb) in the right prefrontal cortex and the right-left difference in oxy-Hb (ΔRL oxy-Hb) in the prefrontal cortex increased. These were proposed as indicators of mental fatigue. In the indoor forest bathing experiment, staying in an indoor green space showed that the subjective values of feeling of fatigue decreased and ΔRL oxy-Hb decreased. Since these results demonstrated an opposite effect to the increase in ΔRL oxy-Hb related to the feeling of fatigue, it was inferred that the decrease in ΔRL oxy-Hb reflected the fatigue reduction in the indoor forest bathing environment.

Infants' brain activity to cartoon face using functional near-infrared spectroscopy.

In this study, to investigate whether infants showed face-specific brain activity to a cartoon human face, we conducted a functional near-infrared spectroscopy (fNIRS) experiment and a behavioral experiment. In the fNIRS experiment, we measured the hemodynamic responses of 5- and 6-month-old infants to cartoon female and cartoon character faces using fNIRS. The results showed that the concentration of oxy-Hb increased for cartoon female faces but not for cartoon character faces. This indicates that face-specific brain activity occurred for cartoon female faces but not cartoon character faces, despite the fact that both are faces. In the behavioral experiment, we examined whether the 5- and 6-month-old infants preferred cartoon female faces to cartoon character faces in the upright and inverted conditions. The results showed a preference for cartoon female faces in the upright but not in the inverted condition. This indicates that 5- and 6-month-old infants can perceive cartoon female faces, but not cartoon character faces, as faces. The results of the two experiments indicated that face-specific brain activity occurred for cartoon female faces. This indicates that infants can perceive cartoon female faces as faces.

Broadband absorption spectroscopy of heterogeneous biological tissue.

Absorption spectra (∼600 to 1064 nm) of six tissues in three healthy volunteers were measured by combining dual-slope continuous-wave broadband spectroscopy with self-calibrated frequency-domain measurements of scattering at two wavelengths (690 and 830 nm). The spectral fit with a linear combination of oxy- and deoxyhemoglobin, water, and lipids extinction spectra is improved by a wavelength-independent absorption background. The need to introduce this background is assigned to the inhomogeneous distribution of absorbers in tissue. By using a two-layer model, the relationship between recovered concentrations and their two-layer values was investigated, and the implications for non-invasive tissue spectroscopy are discussed.

Cerebral Oxygenation Responses to Aerobatic Flight.

BACKGROUND: Aerobatic pilots must withstand high and sudden acceleration forces (Gz) up to 10 Gz. The physiological consequences of such a succession of high and abrupt positive and negative Gzon the human body over time remain mostly unknown. This case report emphasizes changes in physiological factors such as cerebral oxygenation and heart rate dynamics collected in real aerobatic flights. CASE REPORT: A 37-yr-old man, experienced in aerobatic flying, voluntarily took part in this study. During two flight runs (1520 min), the pilot performed aerobatic maneuvers with multiple high (10 Gz) positive and negative accelerations. During the flights he wore a Polar heart rate sensor while cerebral oxygenation was measured continuously over his prefrontal cortex via near-infrared spectroscopy (NIRS). NIRS allows for measurement of the relative concentration changes of oxygenated hemoglobin (O2Hb) and deoxygenated hemoglobin (HHb), making it possible to determine cerebral oxygenation and hemodynamic status. DISCUSSION: The continuous in-flight monitoring of O2Hb and HHb revealed the large effects of successive positive and negative Gz exposures on cerebral hemodynamics alterations. The results showed a significant and positive correlation between changes in Gz exposures and O2Hb concentration. This case report highlights that NIRS provides some valuable and sensitive indicators for the monitoring of cerebral hemodynamics during aerobatic flights exposed to multiple and high acceleration forces. To our knowledge, this first study quantifying cerebral oxygenation changes in aerobatics opens the way for the assessment of individual physiological responses and tolerance in pilots to repeated high Gz during real flights. Fresnel E, Dray G, Pla S, Jean P, Belda G, Perrey S. Cerebral oxygenation responses to aerobatic flight. Aerosp Med Hum Perform. 2021; 92(10):838842.

Magnetophoretic and spectral characterization of oxyhemoglobin and deoxyhemoglobin: Chemical versus enzymatic processes.

A new method for hemoglobin (Hb) deoxygenation, in suspension or within red blood cells (RBCs) is described using the commercial enzyme product, EC-Oxyrase®. The enzymatic deoxygenation method has several advantages over established deoxygenation methodologies, such as avoiding side reactions that produce methemoglobin (metHb), thus eliminating the need for an inert deoxygenation gas and airtight vessel, and facilitates easy re-oxygenation of Hb/RBCs by washing with a buffer that contains dissolved oxygen (DO). The UV-visible spectra of deoxyHb and metHb purified from human RBCs using three different preparation methods (sodium dithionite [to produce deoxyHb], sodium nitrite [to produce metHb], and EC-Oxyrase® [to produce deoxyHb]) show the high purity of deoxyHb prepared using EC-Oxyrase® (with little to no metHb or hemichrome production from side reactions). The oxyHb deoxygenation time course of EC-Oxyrase® follows first order reaction kinetics. The paramagnetic characteristics of intracellular Hb in RBCs were compared using Cell Tracking Velocimetry (CTV) for healthy and sickle cell disease (SCD) donors and oxygen equilibrium curves show that the function of healthy RBCs is unchanged after EC-Oxyrase® treatment. The results confirm that this enzymatic approach to deoxygenation produces pure deoxyHb, can be re-oxygenated easily, prepared aerobically and has similar paramagnetic mobility to existing methods of producing deoxyHb and metHb.

Oxyhemoglobin concentrations do not support hemoglobinopathy in COVID-19.

Based on computerized modeling studies, it has been postulated that the severe hypoxemia in COVID-19 may result from impaired oxygen carrying capacity on hemoglobin. Standard pulse oximetry may not detect hypoxemia resulting from hemoglobinopathy, therefore hemoglobin co-oximetry is needed to evaluate this divergence. In a clinical data analysis of a multicenter cohort of hospitalized patients with COVID-19, we found a minimal effect, less than 1%, on the correlation between oxyhemoglobin concentration and predicted oxygen saturation in the presence of COVID-19 infection. This effect is unlikely to explain the clinically significant hypoxia in COVID-19 patients.