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Pulse oximetry is arguably the most impactful monitor ever introduced into respiratory care practice. Recently there has been increased attention to the problem of occult hypoxemia in which patients are hypoxemic despite an acceptable SpO2. Although occult hypoxemia might be greater in Black patients than white patients, it is not insignificant in whites. In a given population of patients, the bias between SpO2 and arterial oxygen saturation (SaO2) might be close to zero. However, the limits of agreement can be wide, meaning that SpO2 might overestimate SaO2 in many individual patients, which can result in occult hypoxemia in some. Manufactures report accuracy of SpO2 derived from normal individuals, which might differ from that in the clinical setting. That SpO2 overestimates SaO2 in an important number of individuals has caused some to recommend higher SpO2 targets to avoid occult hypoxemia. There is also evidence that suggests that SpO2 might not accurately trend SaO2. Additional research is needed to investigate strategies to mitigate the bias between SpO2 and SaO2. Clinicians must be cognizant of the limitations of pulse oximetry when clinically using SpO2. The aim of this paper is to provide an update on pulse oximetry. [ABSTRACT FROM AUTHOR]

We undertook the present study to investigate the cognitive status of patients with interstitial lung disease (ILD) and its relationship to pulmonary function and cardiovascular efficiency. Fifty-one patients with a diagnosis of ILD [mean duration = 3.13 years (SD = 3.01)] received a respiratory examination, including spirometry and the six-minute walk test, and completed a neuropsychological assessment including several cognitive domains. Eighty-eight healthy individuals matched on age, education, and gender, completed the neuropsychological test battery. Patients performed more poorly than their healthy peers on cognitive tasks related to verbal and visual memory, visual perception, and working memory, but not attention, processing speed and executive functioning. Stepwise linear regression analyses showed that exercise-related measures (heart rate, oxygen saturation and distance walked) predicted performance on neuropsychological tests of psychomotor speed, verbal memory and word production. Additionally, an index of pulmonary function, specifically, lung diffusion capacity, predicted performance on selective and sustained attention and word generation. The present preliminary findings may have implications for the quality of life and treatment compliance of patients with ILD and warrant further study with a larger sample of patients. [ABSTRACT FROM AUTHOR]

Photoacoustic imaging can be used to extract functional information at the molecular level for imaging the whole body of small animals in vivo. However, the use of a mechanical scanner to image the whole body involves acquiring the data for a period of time which can lead to breathing-related artifacts. Thus, the acquired three-dimensional data cannot be analyzed and visualized using two-dimensional projection rendering techniques unless the respiratory distortions are minimized. In this study, an ultrasound-guided breath-compensation method for the three-dimensional data of photoacoustic macroscopy to facilitate visualization and analysis in the depth direction is presented. Photoacoustic and ultrasound data of the whole body of mice were acquired in vivo, then the distorted skin layers were compensated in ultrasound data. The extracted distortion parameters were then applied to the corresponding photoacoustic data to compensate for the motion. The compensation method was successfully applied to visualize three-dimensional hemoglobin oxygen saturation in the whole body of mice in vivo by using multispectral photoacoustic data. The resulting three-dimensional images show that the developed methodology can be used in various biomedical studies, including monitoring drug delivery, imaging of tumors, and analysis of vasculature networks.

Quantitative BOLD (qBOLD) MRI permits noninvasive evaluation of hemodynamic and metabolic states of the brain by quantifying parametric maps of deoxygenated blood volume (DBV) and hemoglobin oxygen saturation level of venous blood (Yv), and along with a measurement of cerebral blood flow (CBF), the cerebral metabolic rate of oxygen (CMRO2). The method, thus should have potential to provide important information on many neurological disorders as well as normal cerebral physiology. One major challenge in qBOLD is to separate deoxyhemoglobin's contribution to R2′ from other sources modulating the voxel signal, for instance, R2, R2′ from non-heme iron (R′2,nh), and macroscopic magnetic field variations. Further, even with successful separation of the several confounders, it is still challenging to extract DBV and Yv from the heme-originated R2′ because of limited sensitivity of the qBOLD model. These issues, which have not been fully addressed in currently practiced qBOLD methods, have so far precluded 3D whole-brain implementation of qBOLD. Thus, the purpose of this work was to develop a new 3D MRI oximetry technique that enables robust qBOLD parameter mapping across the entire brain. To achieve this goal, we employed a rapid, R2′-sensitive, steady-state 3D pulse sequence (termed ‘AUSFIDE’) for data acquisition, and implemented a prior-constrained qBOLD processing pipeline that exploits a plurality of preliminary parameters obtained via AUSFIDE, along with additionally measured cerebral venous blood volume. Numerical simulations and in vivo studies at 3 T were performed to evaluate the performance of the proposed, constrained qBOLD mapping in comparison to the parent qBOLD method. Measured parameters (Yv, DBV, R′2,nh, nonblood magnetic susceptibility) in ten healthy subjects demonstrate the expected contrast across brain territories, while yielding group-averages of 64.0 ± 2.3 % and 62.2 ± 3.1 % for Yv and 2.8 ± 0.5 % and 1.8 ± 0.4 % for DBV in cortical gray and white matter, respectively. Given the Yv measurements, additionally quantified CBF in seven of the ten study subjects enabled whole-brain 3D CMRO2 mapping, yielding group averages of 134.2 ± 21.1 and 79.4 ± 12.6 μmol/100 g/min for cortical gray and white matter, in good agreement with literature values. The results suggest feasibility of the proposed method as a practical and reliable means for measuring neurometabolic parameters over an extended brain coverage.

We studied skin color in participants before and after a 100‐m sprint using a Konica Minolta CM‐2600d spectrophotometer. Four body positions (forehead, cheek, neck, and inner forearm) were measured for the approximately 30 students (non‐professional runners) who participated in the experiment. Skin reflectance was measured three times at each position before running and again soon afterward. Analysis of the data showed that average measurement repeatability (mean color difference from the mean [MCDM]) was 0.5, 0.4, 0.3, and 0.2 CIELAB units for forehead, cheek, neck, and inner forearm, respectively. However, average skin color differences produced by running were 1.8, 2.2, 2.0, and 1.7 CIELAB units for forehead, cheek, neck, and inner forearm positions, respectively, which are considerably higher than repeatability before or after running. Furthermore, appearance variation was analyzed in the CIELAB space, and it was found that sprinting for 100 m considerably changes the values of the red‐green a* coordinate, while the lightness L* and yellow‐blue b* coordinates remain almost constant. More specifically, on average, a* decreases after running for the forehead, cheek, and neck positions, while the opposite is true for the inner forearm position. The findings in this article may be useful to test previous physical models, achieve more realistic images of human skin after sprinting, and contribute to work of CIE TC 1‐92 on skin spectra database. [ABSTRACT FROM AUTHOR]

Alginate encapsulation reduces the risk of transplant rejection by evading immune-mediated cell injury and rejection; however, poor vascular perfusion results in graft failure. Since existing imaging models are incapable of quantifying the vascular response to biomaterial implants after transplantation, in this study, we demonstrate the use of in vivo laser speckle imaging (LSI) and wide-field functional imaging (WiFI) to monitor the microvascular environment surrounding biomaterial implants. The vascular response to two islet-containing biomaterial encapsulation devices, alginate microcapsules and a high-guluronate alginate sheet, was studied and compared after implantation into the mouse dorsal window chamber (N = 4 per implant group). Images obtained over a 14-day period using LSI and WiFI were analyzed using algorithms to quantify blood flow, hemoglobin oxygen saturation and vascular density. Using our method, we were able to monitor the changes in the peri-implant microvasculature noninvasively without the use of fluorescent dyes. Significant changes in blood flow, hemoglobin oxygen saturation and vascular density were noted as early as the first week post-transplant. The dorsal window chamber model enables comparison of host responses to transplanted biomaterials. Future experiments will study the effect of changes in alginate composition on the vascular and immune responses.

Severe hemostatic disorders against the background of COVID-19 have a significant effect on the state of dental status. The study aimed to improve the effectiveness of dental care for patients with COVID-19 disease. To study the dental status of patients with COVID-19 undergoing inpatient treatment, to compare the change in saliva pH with the results of SARS-CoV-2 detection in paired nasopharyngeal smears and saliva samples, to study the microcirculation and oxygenation level of periodontal tissues in patients with moderate and severe COVID-19 undergoing inpatient treatment. 194 people were examined, including 112 patients with the new COVID 19 coronavirus infection and 82 comparison group without concomitant pathology. All patients are divided into five age groups according to their recommendations. The complex of examination included assessment of dental status, determination of saliva pH, the study of microcirculation and oxygenation in the periodontium, and on the phalanx of the index finger of the right hand. Analysis of the results of the study shows that when assessing the dental status, the most characteristic complaints were dryness of the oral cavity, ageusia or hypogeusia, anosmia, or hyposmia. Gum bleeding was observed in two older age groups: in patients aged 45-54 years in 20% of cases, in 55-64 years -18.5% of cases. Less than a quarter of the patients complained of hypersensitivity of the teeth. The study of the saliva pH level revealed normal indicators of the acid-base balance of the oral cavity, which did not depend on the results of the PCR test for COVID-19. [ABSTRACT FROM AUTHOR]

Understanding the relationship between brain function and natural behavior remains a significant challenge in neuroscience because there are very few convincing imaging/recording tools available for the evaluation of awake and freely moving animals. Here, we employed a miniaturized head-mounted scanning photoacoustic imaging (hmPAI) system to image real-time cortical dynamics. A compact photoacoustic (PA) probe based on four in-house optical fiber pads and a single custom-made 48-MHz focused ultrasound transducer was designed to enable focused dark-field PA imaging, and miniature linear motors were included to enable two-dimensional (2D) scanning. The total dimensions and weight of the proposed hmPAI system are only approximately 50 × 64 × 48 mm and 58.7 g (excluding cables). Our ex vivo phantom experimental tests revealed that a spatial resolution of approximately 0.225 mm could be achieved at a depth of 9 mm. Our in vivo results further revealed that the diameters of cortical vessels draining into the superior sagittal sinus (SSS) could be clearly imaged and continuously observed in both anesthetized rats and awake, freely moving rats. Statistical analysis showed that the full width at half maximum (FWHM) of the PA A-line signals (relative to the blood vessel diameter) was significantly increased in the selected SSS-drained cortical vessels of awake rats (0.58 ± 0.17 mm) compared with those of anesthetized rats (0.31 ± 0.09 mm) (p < 0.01, paired t-test). In addition, the number of pixels in PA B-scan images (relative to the cerebral blood volume (CBV)) was also significantly increased in the selected SSS-drained blood vessels of awake rats (107.66 ± 23.02 pixels) compared with those of anesthetized rats (81.99 ± 21.52 pixels) (p < 0.01, paired t-test). This outcome may result from a more active brain in awake rats than in anesthetized rats, which caused cerebral blood vessels to transport more blood to meet the increased nutrient demand of the tissue, resulting in an obvious increase in blood vessel volume. This hmPAI system was further validated for utility in the brains of awake and freely moving rats, showing that their natural behavior was unimpaired during vascular imaging, thereby providing novel opportunities for studies of behavior, cognition, and preclinical models of brain diseases.

Objective: To evaluate the ability of arterial hemoglobin oxygen saturation measurement via pulse oximetry (SpO2) to serve as a surrogate for PaO2 in dogs. Design: Two‐part study: prospective observational and retrospective components. Setting: University teaching hospital. Animals: Ninety‐two dogs breathing room air prospectively enrolled on a convenience basis. Retrospective evaluation of 1,033 paired SpO2 and PaO2 measurements from 62 dogs on mechanical ventilation. Interventions: Dogs with concurrent SpO2 and PaO2 measured on room air had a data sheet completed with blood gas analysis. SpO2, PaO2, and FiO2 values were collected from medical records of dogs on mechanical ventilation. Measurements and Main Results: Predicted PaO2 was calculated from SpO2 using the dog oxyhemoglobin dissociation curve. The correlation coefficient between measured and predicted PaO2 was 0.49 (P < 0.0001) in room air dogs and 0.74 (P < 0.0001) in ventilated dogs. In room air dogs, Bland–Altman analysis between measured minus predicted PaO2 versus the average showed a mean bias of −6.0 mm Hg (95% limit of agreement, −35 to 23 mm Hg). The correlation coefficient between PaO2/FiO2 and SpO2/FiO2 ratios was 0.76 (P < 0.0001). After combining data sets, receiver operating characteristic curve analysis showed the optimal cutoff value for detecting hypoxemia (PaO2 < 80 mm Hg) was an SpO2 of 95%, with sensitivity and specificity of 77.8% and 89.5%, respectively. Using this cutoff, 6.9% of SpO2 readings failed to detect hypoxemia, whereas 7.2% predicted hypoxemia that was not present. Conclusions: The SpO2 was not clinically suitable as a surrogate for PaO2, though it performed better in mechanically ventilated dogs. As sensitivity for the detection of hypoxemia was poor, pulse oximetry does not appear to be an acceptable screening test. The SpO2/FiO2 ratio may have value for evaluation of anesthetized dogs on supplemental oxygen. Arterial blood gas analysis remains ideal for assessment of oxygenation. [ABSTRACT FROM AUTHOR]

Introduction and Aims: one of the most common complications after surgery is hypoxia and it can create a lot of problems and complications for patients. This study aimed to determine the effect of oxygen therapy with simple face mask over and nasal canola on the hemoglobin oxygen saturation after the surgery in the recovery room. Materials and Methods: This study was performed on 84 patients in the recovery room of Besat hospital in Sanandaj city and the patients were randomly divided into two groups. Both groups were treated with nasal cannula and oxygen mask and received 5 liters of oxygen. Then, before and after the intervention the hemoglobin saturated of oxygen was measured and then were compared together. SPSS 23 was used for data analysis. In order to compare the mean of hemoglobin saturated of oxygen before and after intervention in both methods of simple face mask and nasal canola paired t-test was used and for the comparison of means before and after the intervention independent t-test was used. Results: The results showed that there was a significant difference in hemoglobin oxygen saturation before and after the treatment with nasal cannula and oxygen simple face mask (0.0001 Conclusion: The results of the findings showed that oxygen therapy had no influence on hemoglobin oxygen saturation in the two groups of simple face mask and nasal canola and the longer the time of receiving oxygen, the more the percentage of hemoglobin oxygen saturation.

Quantitative BOLD (qBOLD), a non-invasive MRI method for assessment of hemodynamic and metabolic properties of the brain in the baseline state, provides spatial maps of deoxygenated blood volume fraction (DBV) and hemoglobin oxygen saturation (HbO 2 ) by means of an analytical model for the temporal evolution of free-induction-decay signals in the extravascular compartment. However, mutual coupling between DBV and HbO 2 in the signal model results in considerable estimation uncertainty precluding achievement of a unique set of solutions. To address this problem, we developed an interleaved qBOLD method (iqBOLD) that combines extravascular R 2 ʹ and intravascular R 2 mapping techniques so as to obtain prior knowledge for the two unknown parameters. To achieve these goals, asymmetric spin echo and velocity-selective spin-labeling (VSSL) modules were interleaved in a single pulse sequence. Prior to VSSL, arterial blood and CSF signals were suppressed to produce reliable estimates for cerebral venous blood volume fraction (CBV v ) as well as venous blood R 2 (to yield HbO 2 ). Parameter maps derived from the VSSL module were employed to initialize DBV and HbO 2 in the qBOLD processing. Numerical simulations and in vivo experiments at 3 T were performed to evaluate the performance of iqBOLD in comparison to the parent qBOLD method. Data obtained in eight healthy subjects yielded plausible values averaging 60.1 ± 3.3% for HbO 2 and 3.1 ± 0.5 and 2.0 ± 0.4% for DBV in gray and white matter, respectively. Furthermore, the results show that prior estimates of CBV v and HbO 2 from the VSSL component enhance the solution stability in the qBOLD processing, and thus suggest the feasibility of iqBOLD as a promising alternative to the conventional technique for quantifying neurometabolic parameters. [ABSTRACT FROM AUTHOR]

During surgical treatment for cerebrovascular diseases, cortical hemodynamics are often controlled by bypass graft surgery, temporary occlusion of arteries, and surgical removal of veins. Since the brain is vulnerable to hypoxemia and ischemia, interruption of cerebral blood flow reduces the oxygen supply to tissues and induces irreversible damage to cells and tissues. Monitoring of cerebral hemodynamics and alteration of cellular structure during neurosurgery is thus crucial. Sequential recordings of red-green-blue (RGB) images of in vivo exposed rat brains were made during hyperoxia, normoxia, hypoxia, and anoxia. Monte Carlo simulation of light transport in brain tissue was used to specify relationships among RGB-values and oxygenated hemoglobin concentration (CHbO), deoxygenated hemoglobin concentration (CHbR), total hemoglobin concentration (CHbT), hemoglobin oxygen saturation (StO2), and scattering power b. Temporal courses of CHbO, CHbR, CHbT, and StO2 indicated physiological responses to reduced oxygen delivery to cerebral tissue. A rapid decrease in light scattering power b was observed after respiratory arrest, similar to the negative deflection of the extracellular direct current (DC) potential in so-called anoxic depolarization. These results suggest the potential of this method for evaluating pathophysiological conditions and loss of tissue viability. [ABSTRACT FROM AUTHOR]

Oxygen therapy is the main treatment method for acute respiratory failure in children. The method consisting in the administration of oxygen therapy by head box to infants is frequently used in pediatric practice. Objectives. To evaluate the effi ciency of oxygen therapy administered by head box to infants suffering from pneumogenic acute respiratory failure by comparing two methods for measuring hemoglobin oxygen saturation: in arterialized capillary blood and by pulse oximetry. Material and method. 30 infants suffering from pneumogenic acute respiratory failure were studied. We used a clinical appraisal score for acute respiratory failure, which appraises respiratory rate, nasal fl aring, recession, cyanosis, sensorial, before and after oxygen therapy. In arterialized capillary blood we measured partial pressure of oxygen and hemoglobin oxygen saturation, and we used an Automatic Blood Gas System analyzer. We also measured hemoglobin oxygen saturation using a pulse oximeter. Determinations were made before the initiation of oxygen therapy, and 30 minutes and 60 minutes after the initiation of oxygen therapy. Results. As compared to the baseline values, determined before the initiation of oxygen therapy, we recorded a statistically signifi cant improvement in the clinical score both after 30 minutes and 60 minutes from the initiation of oxygen therapy (p

The global cerebral metabolic rate of oxygen (CMRO2), which reflects metabolic activity of the brain under various physiologic conditions, can be quantified using a method, referred to as 'OxFlow', which simultaneously measures hemoglobin oxygen saturation in a draining vein (Yv) and total cerebral blood flow (tCBF). Conventional OxFlow (Conv-OxFlow) entails four interleaves incorporated in a single pulse sequence - two for phase-contrast based measurement of tCBF in the supplying arteries of the neck, and two to measure the intra- to extravascular phase difference in the superior sagittal sinus to derive Yv [Jain et al., JCBFM 2010]. However, this approach limits achievable temporal resolution thus precluding capture of rapid changes of brain metabolic states such as the response to apneic stimuli. Here, we developed a time-efficient, multiplexed OxFlow method and evaluated its potential for measuring dynamic alterations in global CMRO2 during a breath-hold challenge. Two different implementations of multiplexed OxFlow were investigated: 1) simultaneous-echo-refocusing based OxFlow (SER-OxFlow) and 2) simultaneous-multi-slice imaging-based dual-band OxFlow (DB-OxFlow). The two sequences were implemented on 3 T scanners (Siemens TIM Trio and Prisma) and their performance was evaluated in comparison to Conv-OxFlow in ten healthy subjects for baseline CMRO2 quantification. Comparison of measured parameters (Yv, tCBF, CMRO2) revealed no significant bias of SER-OxFlow and DB-OxFlow, with respect to the reference Conv-OxFlow while improving temporal resolution two-fold (12.5 versus 25 s). Further acceleration shortened scan time to 8 and 6 s for SER and DB-OxFlow, respectively, for time-resolved CMRO2 measurement. The two sequences were able of capturing smooth transitions of Yv, tCBF, and CMRO2 over the time course consisting of 30 s of normal breathing, 30 s of volitional apnea, and 90 s of recovery. While both SER- and DB-OxFlow techniques provide significantly improved temporal resolution (by a factor of 3 - 4 relative to Conv-OxFlow), DB-OxFlow was found to be superior for the study of short physiologic stimuli. [ABSTRACT FROM AUTHOR]

During surgical treatment for cerebrovascular diseases, cortical hemodynamics are often controlled by bypass graft surgery, temporary occlusion of arteries, and surgical removal of veins. Since the brain is vulnerable to hypoxemia and ischemia, interruption of cerebral blood flow reduces the oxygen supply to tissues and induces irreversible damage to cells and tissues. Monitoring of cerebral hemodynamics and alteration of cellular structure during neurosurgery is thus crucial. Sequential recordings of red-green-blue (RGB) images of in vivo exposed rat brains were made during hyperoxia, normoxia, hypoxia, and anoxia. Monte Carlo simulation of light transport in brain tissue was used to specify relationships among RGB-values and oxygenated hemoglobin concentration (CHbO), deoxygenated hemoglobin concentration (CHbR), total hemoglobin concentration (CHbT), hemoglobin oxygen saturation (StO2), and scattering power b. Temporal courses of CHbO, CHbR, CHbT, and StO2 indicated physiological responses to reduced oxygen delivery to cerebral tissue. A rapid decrease in light scattering power b was observed after respiratory arrest, similar to the negative deflection of the extracellular direct current (DC) potential in so-called anoxic depolarization. These results suggest the potential of this method for evaluating pathophysiological conditions and loss of tissue viability.

Angiogenesis in a tumor region creates arteriovenous (AV) shunts that cause an abnormal venous blood oxygen saturation (sO2) distribution. Here, we applied optical-resolution photoacoustic microscopy to study the AV shunting in vivo. First, we built a phantom to image sO2 distribution in a vessel containing converged flows from two upstream blood vessels with different sO2 values. The phantom experiment showed that the blood from the two upstream vessels maintained a clear sO2 boundary for hundreds of seconds, which is consistent with our theoretical analysis using a diffusion model. Next, we xenotransplanted O-786 tumor cells in mouse ears and observed abnormal sO2 distribution in the downstream vein from the AV shunts in vivo. Finally, we identified the tumor location by tracing the sO2 distribution. Our study suggests that abnormal sO2 distribution induced by the AV shunts in the vessel network may be used as a new functional benchmark for early tumor detection. [ABSTRACT FROM AUTHOR]