Evaluation of North Sea saturation procedures through divers monitoring.

BACKGROUND: Saturation diving is a standard method of intervention for commercial diving during offshore operations. Current saturation procedures achieve a high level of safety with regards to decompression sickness but still put the divers under multiple stressors: 1) Environmental stress (long confinement, heat/cold, dense gases, high oxygen levels), 2) Work stress (muscular fatigue, psychological pressure, breathing equipment, etc.), 3) venous gas emboli associated with decompression, 4) Inflammation related to oxidative stress and microparticles. We present the results of a saturation divers monitoring campaign performed in the North Sea Danish sector, on the Tyra field, during 2022. The study was supported by TotalEnergies, the field operator, and performed by Boskalis Subsea Services, the diving contractor, onboard the diving support vessel Boka Atlantis. The objective was twofold: document the level of diving stress during saturation operations in the Danish sector, and compare the performances of two saturation procedures, the Boskalis and the NORSOK procedures. MATERIALS AND METHODS: Fourteen divers volunteered for the study. The monitoring package include weight and temperature measurements, psychomotor tests (objective evaluation) and questionnaires (subjective evaluation), Doppler bubble detection and bioimpedance. The results were presented in a radar diagram that provides a general view of the situation. RESULTS: The data were analysed along 3 dimensions: work and environmental, desaturation bubbles, oxidative stress and inflammation. The results showed little or no variations from the reference values. No bubbles were detected after excursion dives and the final decompression, except for two divers with a grade 1 after arriving at surface. No statistical difference could be found between the Boskalis and the NORSOK saturation procedures. CONCLUSIONS: At a depth of 40-50 msw corresponding to the Danish sector, the two saturation procedures monitored induce no or little stress to the divers. The divers know how to manage their diet, equilibrate their hydration and pace their effort. Data available on divers' post saturation period show a recovery over the 24-48 hours following the end of the decompression. Further research should focus on diving deeper than 100 msw where a greater stress can be anticipated.

[Correlation between arousal threshold and occurrence of hypertension in patients with obstructive sleep apnea hypopnea syndrome].

Objective: To investigate the relationship between arousal threshold (ArTH) and hypertension in patients with obstructive sleep apnea hypopnea syndrome (OSA). Methods: This study recruited 648 patients diagnosed with OSA at the Sleep Center of the Second Affiliated Hospital of Soochow University from January 2020 to August 2021, including 569 males and 79 females, aged 42(35,52) years. The basic demographic information and clinical data of all patients were collected, including blood pressure measurement, and relevant questionnaire scores, and nocturnal polysomnography (PSG) parameters. A clinical predictive model based on sleep apnea hypopnea index (AHI), lowest pulse oxygen saturation (LSpaO2) and hypopnea ratio (FHypopneas) was used to access the arousal threshold of OSA patients. Patients were divided into OSA group and OSA with hypertension group according to whether they were combined with hypertension. The differences in the above indexes between the two groups were analyzed to explore the relationship between arousal threshold and hypertension in OSA patients, using a binary logistic stepwise regression analysis. Results: A total of 648 OSA patients were enrolled, including 415 in the OSA with hypertension group and 233 in the OSA group. Compared with OSA group, OSA with hypertension group had older age, higher body mass index (BMI), higher blood pressure at bedtime and at awakening, higher AHI and lower proportion of hypopnea (all P<0.05). There were no significant differences between other general data and PSG parameters (all P>0.05). The proportion of patients with low arousal threshold (AHI<30 events per hour, LSpO2>82.5%, Fhypopneas>58.3%) in OSA with hypertension group was lower, and the proportion of phenotypic patients with low arousal threshold was significantly lower (30.1% vs. 52.4% P<0.001). Binary logistic stepwise regression analysis showed that the high arousal threshold (OR=1.930, 95%CI:1.326-2.808, P=0.001) was an independent risk factor for OSA complicated with hypertension. Conclusion: The arousal threshold is associated with the development of hypertension in OSA patients, and OSA patients with a high arousal threshold have a higher risk of developing hypertension.

Exercise-Induced Oxygen Desaturation Increases Arterial Stiffness in Patients with COPD During the 6WMT.

Objective: Given the established impact of exercise in reducing arterial stiffness and the potential for intermittent hypoxia to induce its elevation, this study aims to understand how oxygen desaturation during exercise affects arterial stiffness in individuals with COPD. Methods: We enrolled patients with stable COPD from China-Japan Friendship Hospital from November 2022 to June 2023. The 6-minute walk test (6-MWT) was performed with continuous blood oxygen saturation (SpO2) monitoring in these patients. The patients were classified into three groups: non-exercise induced desaturation (EID), mild-EID and severe-EID, according to the changes in SpO2 during the 6-MWT. The Cardio-Ankle Vascular Index (CAVI) and the change in CAVI (ΔCAVI, calculated as CAVI before 6MWT minus CAVI after the 6MWT) were measured before and immediately after the 6MWT to assess the acute effects of exercise on arterial stiffness. GOLD Stage, pulmonary function, and other functional outcomes were also measured in this study. Results: A total of 37 patients with stable COPD underwent evaluation for changes in CAVI (ΔCAVI) before and after the 6-MWT. Stratification based on revealed three subgroups: non-EID (n=12), mild-EID (n=15), and severe-EID (n=10). The ΔCAVI values was -0.53 (-0.95 to -0.31) in non-EID group, -0.20 (-1.45 to 0.50) in mild-EID group, 0.6 (0.08 to 0.73) in severe-EID group. Parametric tests indicated significant differences in ΔCAVI among EID groups (p = 0.005). Pairwise comparisons demonstrated significant distinctions between mild-EID and severe-EID groups, as well as between non-EID and severe-EID groups (p = 0.048 and p = 0.003, respectively). Multivariable analysis, adjusting for age, sex, GOLD stage, diffusion capacity, and blood pressure, identified severe-EID as an independent factor associated with ΔCAVI (B = 1.118, p = 0.038). Conclusion: Patients with COPD and severe-EID may experience worsening arterial stiffness even during short periods of exercise.

Acute physiological responses of blood flow restriction between high-intensity interval repetitions in trained cyclists.

Blood flow restriction (BFR) is increasingly being used to enhance aerobic performance in endurance athletes. This study examined physiological responses to BFR applied in recovery phases within a high-intensity interval training (HIIT) session in trained cyclists. Eleven competitive road cyclists (mean ± SD, age: 28 ± 7 years, body mass: 69 ± 6 kg, peak oxygen uptake: 65 ± 9 mL · kg-1 · min-1) completed two randomised crossover conditions: HIIT with (BFR) and without (CON) BFR applied during recovery phases. HIIT consisted of six 30-s cycling bouts at an intensity equivalent to 85% of maximal 30-s power (523 ± 93 W), interspersed with 4.5-min recovery. BFR (200 mmHg, 12 cm cuff width) was applied for 2-min in the early recovery phase between each interval. Pulmonary gas exchange (V̇O2, V̇CO2, and V̇E), tissue oxygen saturation index (TSI), heart rate (HR), and serum vascular endothelial growth factor concentration (VEGF) were measured. Compared to CON, BFR increased V̇CO2 and V̇E during work bouts (both p < 0.05, dz < 0.5), but there was no effect on V̇O2, TSI, or HR (p > 0.05). In early recovery, BFR decreased TSI, V̇O2, V̇CO2, and V̇E (all p < 0.05, dz > 0.8) versus CON, with no change in HR (p > 0.05). In late recovery, when BFR was released, V̇O2, V̇CO2, V̇E, and HR increased, but TSI decreased versus CON (all p < 0.05, dz > 0.8). There was a greater increase in VEGF at 3-h post-exercise in BFR compared to CON (p < 0.05, dz > 0.8). Incorporating BFR into HIIT recovery phases altered physiological responses compared to exercise alone.

Tactile breathing guidance increases oxygen saturation but not alertness or hypoxia symptoms.

We investigated the effect of tactile guided slow deep breathing compared with that of spontaneous breathing on blood oxygen saturation (SpO2), alertness, and hypoxia symptoms during acute hypobaric hypoxia. We also evaluated the usability of this tactile breathing guidance. Twelve male military pilots were exposed to a simulated altitude of 4,572 m (15,000 ft) in a repeated measures study while breathing spontaneously and during tactile guided slow deep breathing. Under both breathing conditions, measurements were performed at rest and during the performance of a cognitive task. The Stanford Sleepiness Scale was used to rate alertness, and hypoxia symptoms were reported using a list of general hypoxia symptoms. Usability was evaluated in a questionnaire. Tactile guidance of slow deep breathing significantly increased (p <.001) the SpO2 - 88% (95% confidence interval (CI) [84%, 91%]) at rest and 85% (95% CI [81%, 88%]) during the cognitive task - compared with spontaneous breathing - 78% (95% CI [75%, 81%]) at rest and 78% (95% CI [76%, 80%]) during the cognitive task. This increase in SpO2 had no effect on the level of alertness and number of hypoxia symptoms. Pilots were positive about the intensity and sensation of the vibration signal, but had difficulty following the vibration pattern during the cognitive task. Pre-training may improve slow deep breathing technique during performance of cognitive tasks.

Closed-loop oxygen control for critically ill patients--A systematic review and meta-analysis.

BACKGROUND: The impact of closed-loop control systems to titrate oxygen flow in critically ill patients, including their effectiveness, efficacy, workload and safety, remains unclear. This systematic review investigated the utilization of closed-loop oxygen systems for critically ill patients in comparison to manual oxygen titration systems focusing on these topics. METHODS AND FINDINGS: A search was conducted across several databases including MEDLINE, CENTRAL, EMBASE, LILACS, CINAHL, LOVE, ClinicalTrials.gov, and the World Health Organization on March 3, 2022, with subsequent updates made on June 27, 2023. Evidence databases were searched for randomized clinical parallel or crossover studies investigating closed-loop oxygen control systems for critically ill patients. This systematic review and meta-analysis was performed following the Preferred Reporting Items for Systematic Review and Meta-analysis guidelines. The analysis was conducted using Review Manager software, adopting the mean difference or standardized mean difference with a 95% confidence interval (95% CI) for continuous variables or risk ratio with 95% CI for dichotomous outcomes. The main outcome of interest was the percentage of time spent in the peripheral arterial oxygen saturation target. Secondary outcomes included time for supplemental oxygen weaning, length of stay, mortality, costs, adverse events, and workload of healthcare professional. A total of 37 records from 21 studies were included in this review with a total of 1,577 participants. Compared with manual oxygen titration, closed-loop oxygen control systems increased the percentage of time in the prescribed SpO2 target, mean difference (MD) 25.47; 95% CI 19.7, 30.0], with moderate certainty of evidence. Current evidence also shows that closed-loop oxygen control systems have the potential to reduce the percentage of time with hypoxemia (MD -0.98; 95% CI -1.68, -0.27) and healthcare workload (MD -4.94; 95% CI -7.28, -2.61) with low certainty of evidence. CONCLUSION: Closed-loop oxygen control systems increase the percentage of time in the preferred SpO2 targets and may reduce healthcare workload. TRIAL REGISTRATION: PROSPERO: CRD42022306033.

Addition of Mask to High-flow Nasal Oxygen: A Strategy to Improve Oxygenation in Hypoxemic Respiratory Failure Secondary to COVID-19.

PURPOSE: High-flow nasal cannula (HFNO) reduces the need for invasive mechanical ventilation in COVID-19 patients with hypoxemic-respiratory failure. During HFNO entrainment of room air dilutes the delivered fractional inspiratory oxygen (FiO2), thereby preventing improvement in oxygenation. The placement of a mask over HFNO to improve oxygenation has provided conflicting results. We aimed to determine and compare the effect of placing various mask types over HFNO on oxygen saturation (SPO2). MATERIALS AND METHODS: In this prospective physiological study 40 patients with COVID-19-associated hypoxemic respiratory failure on HFNO with O2 concentration <92% were included. The effect of placing different masks over HFNO on oxygenation, respiratory rate, heart rate, blood pressure, patient comfort, and partial pressure of carbon dioxide level (pCO2) was recorded after a prespecified time interval. RESULTS: We observed a significantly higher mean SPO2 and lower mean respiratory rate on using various study masks over HFNO compared to HFNO alone. On comparing various mask types, the use of N95 masks and nonrebreather (NRB) masks with O2 showed a significant increase in O2 concentration and reduction in respiratory rate compared to surgical mask (SM) and NRB without O2. The proportion of patients who achieved SPO2 of >92% was higher with the use of N95 masks (47.5%) or NRB with O2 (45%) over HFNO compared to SM (35%) and NRB without O2 (35%). No significant change was observed in heart rate, blood pressure, and CO2 level with the use of any mask over HFNO. CONCLUSION: This study demonstrates improvement in oxygenation and reduction in respiratory rate with the use of various masks over HFNO in patients of COVID-19-related hypoxemic-respiratory-failure. Significantly greater benefit was achieved with the use of N95 or NRB with O2 compared to SM or NRB without O2.

Chronic Obstructive Pulmonary Disease and Oxygen Therapy: A Double-edged Sword.

Oxygen, like all medicines, is a drug which needs moderation. Hypoxia, as well as excess oxygen supplementation, can be harmful in a patient with chronic obstructive pulmonary disease (COPD). Both the European and the British guidelines recommend a target oxygen saturation of 88-92% in patients with COPD. Hypoxia can result in symptoms, such as restlessness, anxiety, agitation, and headache, while excess oxygen can lead to altered sensorium due to the retention of carbon dioxide (CO2) in patients with COPD. We often come across patients who come with breathlessness and have hypoxia, and the knee-jerk reaction is to start the patient on oxygen support to maintain an oxygen saturation of >95%, and this may result in hypercapnia and type II respiratory failure. Here, we present a descriptive review of the proper application of oxygen therapy in a patient presenting with acute exacerbation of COPD, the rationale behind the target oxygen saturations, and the mechanisms of type II respiratory failure due to hyperoxygenation.

Effect of Skin Pigmentation and Finger Choice on Accuracy of Oxygen Saturation Measurement in an IoT-Based Pulse Oximeter.

Pulse oximeters are widely used in hospitals and homes for measurement of blood oxygen saturation level (SpO2) and heart rate (HR). Concern has been raised regarding a possible bias in obtaining pulse oximeter measurements from different fingertips and the potential effect of skin pigmentation (white, brown, and dark). In this study, we obtained 600 SpO2 measurements from 20 volunteers using three UK NHS-approved commercial pulse oximeters alongside our custom-developed sensor, and used the Munsell colour system (5YR and 7.5YR cards) to classify the participants' skin pigmentation into three distinct categories (white, brown, and dark). The statistical analysis using ANOVA post hoc tests (Bonferroni correction), a Bland-Altman plot, and a correlation test were then carried out to determine if there was clinical significance in measuring the SpO2 from different fingertips and to highlight if skin pigmentation affects the accuracy of SpO2 measurement. The results indicate that although the three commercial pulse oximeters had different means and standard deviations, these differences had no clinical significance.

The Association of Cerebral Oxygen Desaturation with Postoperative Cognitive Dysfunction in Older Patients: A Review.

Postoperative cognitive dysfunction (POCD) is a neurological complication associated with surgery and anesthesia that is commonly observed in older patients, and it can significantly affect patient prognosis and survival. Therefore, predicting and preventing POCD is important. Regional cerebral oxygen saturation (rSO2) reflects cerebral perfusion and oxygenation, and decreased intraoperative cerebral oxygen saturation has been reported to increase the risk of POCD. In this review, we elucidated the important relationship between the decline in rSO2 and risk of POCD in older patients. We also emphasized the importance of monitoring rSO2 during surgery to predict and prevent adverse perioperative cognitive outcomes. The findings reveal that incorporating intraoperative rSO2 monitoring into clinical practice has potential benefits, such as protecting cognitive function, reducing perioperative adverse outcomes, and ultimately improving the overall quality of life of older adults.

Multispectral Imaging-Based System for Detecting Tissue Oxygen Saturation With Wound Segmentation for Monitoring Wound Healing.

OBJECTIVE: Blood circulation is an important indicator of wound healing. In this study, a tissue oxygen saturation detecting (TOSD) system that is based on multispectral imaging (MSI) is proposed to quantify the degree of tissue oxygen saturation (StO2) in cutaneous tissues. METHODS: A wound segmentation algorithm is used to segment automatically wound and skin areas, eliminating the need for manual labeling and applying adaptive tissue optics. Animal experiments were conducted on six mice in which they were observed seven times, once every two days. The TOSD system illuminated cutaneous tissues with two wavelengths of light - red ([Formula: see text] nm) and near-infrared ([Formula: see text] nm), and StO2 levels were calculated using images that were captured using a monochrome camera. The wound segmentation algorithm using ResNet34-based U-Net was integrated with computer vision techniques to improve its performance. RESULTS: Animal experiments revealed that the wound segmentation algorithm achieved a Dice score of 93.49%. The StO2 levels that were determined using the TOSD system varied significantly among the phases of wound healing. Changes in StO2 levels were detected before laser speckle contrast imaging (LSCI) detected changes in blood flux. Moreover, statistical features that were extracted from the TOSD system and LSCI were utilized in principal component analysis (PCA) to visualize different wound healing phases. The average silhouette coefficients of the TOSD system with segmentation (ResNet34-based U-Net) and LSCI were 0.2890 and 0.0194, respectively. CONCLUSION: By detecting the StO2 levels of cutaneous tissues using the TOSD system with segmentation, the phases of wound healing were accurately distinguished. This method can support medical personnel in conducting precise wound assessments. Clinical and Translational Impact Statement-This study supports efforts in monitoring StO2 levels, wound segmentation, and wound healing phase classification to improve the efficiency and accuracy of preclinical research in the field.

Automated oxygen titration with non-invasive ventilation in hypoxaemic adults with cardiorespiratory disease: a randomised cross-over trial.

BACKGROUND: Closed-loop oxygen control systems automatically adjust the fraction of inspired oxygen (FiO2) to maintain oxygen saturation (SpO2) within a predetermined target range. Their performance with low and high-flow oxygen therapies, but not with non-invasive ventilation, has been established. We compared the effect of automated oxygen on achieving and maintaining a target SpO2 range with nasal high flow (NHF), bilevel positive airway pressure (bilevel) and continuous positive airway pressure (CPAP), in stable hypoxaemic patients with chronic cardiorespiratory disease. METHODS: In this open-label, three-way cross-over trial, participants with resting hypoxaemia (n=12) received each of NHF, bilevel and CPAP treatments, in random order, with automated oxygen titrated for 10 min, followed by 36 min of standardised manual oxygen adjustments. The primary outcome was the time taken to reach target SpO2 range (92%-96%). Secondary outcomes included time spent within target range and physiological responses to automated and manual oxygen adjustments. RESULTS: Two participants were randomised to each of six possible treatment orders. During automated oxygen control (n=12), the mean (±SD) time to reach target range was 114.8 (±87.9), 56.6 (±47.7) and 67.3 (±61) seconds for NHF, bilevel and CPAP, respectively, mean difference 58.3 (95% CI 25.0 to 91.5; p=0.002) and 47.5 (95% CI 14.3 to 80.7; p=0.007) seconds for bilevel and CPAP versus NHF, respectively. Proportions of time spent within target range were 68.5% (±16.3), 65.6% (±28.7) and 74.7% (±22.6) for NHF, bilevel and CPAP, respectively.Manually increasing, then decreasing, the FiO2 resulted in similar increases and then decreases in SpO2 and transcutaneous carbon dioxide (PtCO2) with NHF, bilevel and CPAP. CONCLUSION: The target SpO2 range was achieved more quickly when automated oxygen control was initiated with bilevel and CPAP compared with NHF while time spent within the range across the three therapies was similar. Manually changing the FiO2 had similar effects on SpO2 and PtCO2 across each of the three therapies. TRIAL REGISTRATION NUMBER: ACTRN12622000433707.

Noninvasive Ventilation for Preoxygenation during Emergency Intubation.

BACKGROUND: Among critically ill adults undergoing tracheal intubation, hypoxemia increases the risk of cardiac arrest and death. The effect of preoxygenation with noninvasive ventilation, as compared with preoxygenation with an oxygen mask, on the incidence of hypoxemia during tracheal intubation is uncertain. METHODS: In a multicenter, randomized trial conducted at 24 emergency departments and intensive care units in the United States, we randomly assigned critically ill adults (age, ≥18 years) undergoing tracheal intubation to receive preoxygenation with either noninvasive ventilation or an oxygen mask. The primary outcome was hypoxemia during intubation, defined by an oxygen saturation of less than 85% during the interval between induction of anesthesia and 2 minutes after tracheal intubation. RESULTS: Among the 1301 patients enrolled, hypoxemia occurred in 57 of 624 patients (9.1%) in the noninvasive-ventilation group and in 118 of 637 patients (18.5%) in the oxygen-mask group (difference, -9.4 percentage points; 95% confidence interval [CI], -13.2 to -5.6; P<0.001). Cardiac arrest occurred in 1 patient (0.2%) in the noninvasive-ventilation group and in 7 patients (1.1%) in the oxygen-mask group (difference, -0.9 percentage points; 95% CI, -1.8 to -0.1). Aspiration occurred in 6 patients (0.9%) in the noninvasive-ventilation group and in 9 patients (1.4%) in the oxygen-mask group (difference, -0.4 percentage points; 95% CI, -1.6 to 0.7). CONCLUSIONS: Among critically ill adults undergoing tracheal intubation, preoxygenation with noninvasive ventilation resulted in a lower incidence of hypoxemia during intubation than preoxygenation with an oxygen mask. (Funded by the U.S. Department of Defense; PREOXI ClinicalTrials.gov number, NCT05267652.).

Nocturnal hypoxemic burden and micro- and macrovascular disease in patients with type 2 diabetes.

BACKGROUND: Micro- and macrovascular diseases are common in patients with type 2 diabetes mellitus (T2D) and may be partly caused by nocturnal hypoxemia. The study aimed to characterize the composition of nocturnal hypoxemic burden and to assess its association with micro- and macrovascular disease in patients with T2D. METHODS: This cross-sectional analysis includes overnight oximetry from 1247 patients with T2D enrolled in the DIACORE (DIAbetes COhoRtE) study. Night-time spent below a peripheral oxygen saturation of 90% (T90) as well as T90 associated with non-specific drifts in oxygen saturation (T90non - specific), T90 associated with acute oxygen desaturation (T90desaturation) and desaturation depths were assessed. Binary logistic regression analyses adjusted for known risk factors (age, sex, smoking status, waist-hip ratio, duration of T2D, HbA1c, pulse pressure, low-density lipoprotein, use of statins, and use of renin-angiotensin-aldosterone system inhibitors) were used to assess the associations of such parameters of hypoxemic burden with chronic kidney disease (CKD) as a manifestation of microvascular disease and a composite of cardiovascular diseases (CVD) reflecting macrovascular disease. RESULTS: Patients with long T90 were significantly more often affected by CKD and CVD than patients with a lower hypoxemic burden (CKD 38% vs. 28%, p < 0.001; CVD 30% vs. 21%, p < 0.001). Continuous T90desaturation and desaturation depth were associated with CKD (adjusted OR 1.01 per unit, 95% CI [1.00; 1.01], p = 0.008 and OR 1.30, 95% CI [1.06; 1.61], p = 0.013, respectively) independently of other known risk factors for CKD. For CVD there was a thresholdeffect, and only severly and very severly increased T90non-specific was associated with CVD ([Q3;Q4] versus [Q1;Q2], adjusted OR 1.51, 95% CI [1.12; 2.05], p = 0.008) independently of other known risk factors for CVD. CONCLUSION: While hypoxemic burden due to oxygen desaturations and the magnitude of desaturation depth were significantly associated with CKD, only severe hypoxemic burden due to non-specific drifts was associated with CVD. Specific types of hypoxemic burden may be related to micro- and macrovascular disease.

[Evaluation of revascularization efficiency using near-infrared oximetry in patients with diabetic foot syndrome]. / Otsenka effektivnosti revaskulyarizatsii u patsientov s sindromom diabeticheskoi stopy metodom parainfrakrasnoi oksimetrii.

OBJECTIVE: To evaluate prognostic significance of tissue oximetry in healing of trophic defects in patients with diabetic foot syndrome (DFS) after endovascular revascularization. MATERIAL AND METHODS: In 42 patients with DFS, tissue oximetry was performed in angiosome projection with the FORE-SIGHT MC-2000 (CASMED) device before and the next day after revascularization of lower limb arteries. The 1st group included 30 patients with wound healing throughout 3 months, the 2nd group included 12 patients with amputation or no healing of trophic defects. RESULTS: Direct revascularization was more common in the 1st group (p=0.001). On the day after intervention, oxygen saturation (StO2) increased in all angiosomes in both groups (p<0.05). StO2 increment differed significantly between groups in all angiosomes except for point I (p<0.05). According to ROC analysis, StO2 increment by 4.5% in absolute values and 7.9% in percentage leads to trophic defect healing within 3 months (sensitivity and specificity were 76.7% and 66.7% for absolute values, 80% and 58.3% for percentage, respectively). CONCLUSION: Evaluation of StO2 in target angiosome may be valuable to predict trophic defect healing after endovascular surgery.

Distribution-informed and wavelength-flexible data-driven photoacoustic oximetry.

Significance: Photoacoustic imaging (PAI) promises to measure spatially resolved blood oxygen saturation but suffers from a lack of accurate and robust spectral unmixing methods to deliver on this promise. Accurate blood oxygenation estimation could have important clinical applications from cancer detection to quantifying inflammation. Aim: We address the inflexibility of existing data-driven methods for estimating blood oxygenation in PAI by introducing a recurrent neural network architecture. Approach: We created 25 simulated training dataset variations to assess neural network performance. We used a long short-term memory network to implement a wavelength-flexible network architecture and proposed the Jensen-Shannon divergence to predict the most suitable training dataset. Results: The network architecture can flexibly handle the input wavelengths and outperforms linear unmixing and the previously proposed learned spectral decoloring method. Small changes in the training data significantly affect the accuracy of our method, but we find that the Jensen-Shannon divergence correlates with the estimation error and is thus suitable for predicting the most appropriate training datasets for any given application. Conclusions: A flexible data-driven network architecture combined with the Jensen-Shannon divergence to predict the best training data set provides a promising direction that might enable robust data-driven photoacoustic oximetry for clinical use cases.

Machine learning-based prediction of cerebral oxygen saturation based on multi-modal cerebral oximetry data.

This study develops machine learning-based algorithms that facilitate accurate prediction of cerebral oxygen saturation using waveform data in the near-infrared range from a multi-modal oxygen saturation sensor. Data were obtained from 150,000 observations of a popular cerebral oximeter, Masimo O3™ regional oximetry (Co., United States) and a multi-modal cerebral oximeter, Votem (Inc., Korea). Among these observations, 112,500 (75%) and 37,500 (25%) were used for training and test sets, respectively. The dependent variable was the cerebral oxygen saturation value from the Masimo O3™ (0-100%). The independent variables were the time of measurement (0-300,000 ms) and the 16-bit decimal amplitudes values (infrared and red) from Votem (0-65,535). For the right part of the forehead, the root mean square error of the random forest (0.06) was much smaller than those of linear regression (1.22) and the artificial neural network with one, two or three hidden layers (2.58). The result was similar for the left part of forehead, that is, random forest (0.05) vs logistic regression (1.22) and the artificial neural network with one, two or three hidden layers (2.97). Machine learning aids in accurately predicting of cerebral oxygen saturation, employing the data from a multi-modal cerebral oximeter.

Machine Learning-Based Critical Congenital Heart Disease Screening Using Dual-Site Pulse Oximetry Measurements.

BACKGROUND: Oxygen saturation (Spo2) screening has not led to earlier detection of critical congenital heart disease (CCHD). Adding pulse oximetry features (ie, perfusion data and radiofemoral pulse delay) may improve CCHD detection, especially coarctation of the aorta (CoA). We developed and tested a machine learning (ML) pulse oximetry algorithm to enhance CCHD detection. METHODS AND RESULTS: Six sites prospectively enrolled newborns with and without CCHD and recorded simultaneous pre- and postductal pulse oximetry. We focused on models at 1 versus 2 time points and with/without pulse delay for our ML algorithms. The sensitivity, specificity, and area under the receiver operating characteristic curve were compared between the Spo2-alone and ML algorithms. A total of 523 newborns were enrolled (no CHD, 317; CHD, 74; CCHD, 132, of whom 21 had isolated CoA). When applying the Spo2-alone algorithm to all patients, 26.2% of CCHD would be missed. We narrowed the sample to patients with both 2 time point measurements and pulse-delay data (no CHD, 65; CCHD, 14) to compare ML performance. Among these patients, sensitivity for CCHD detection increased with both the addition of pulse delay and a second time point. All ML models had 100% specificity. With a 2-time-points+pulse-delay model, CCHD sensitivity increased to 92.86% (P=0.25) compared with Spo2 alone (71.43%), and CoA increased to 66.67% (P=0.5) from 0. The area under the receiver operating characteristic curve for CCHD and CoA detection significantly improved (0.96 versus 0.83 for CCHD, 0.83 versus 0.48 for CoA; both P=0.03) using the 2-time-points+pulse-delay model compared with Spo2 alone. CONCLUSIONS: ML pulse oximetry that combines oxygenation, perfusion data, and pulse delay at 2 time points may improve detection of CCHD and CoA within 48 hours after birth. REGISTRATION: URL: https://www.clinicaltrials.gov/study/NCT04056104?term=NCT04056104&rank=1; Unique identifier: NCT04056104.

Relative Severity of Human Performance Decrements Recorded in Rapid vs. Gradual Decompression.

INTRODUCTION: Cabin decompression presents a threat in high-altitude-capable aircraft. A chamber study was performed to compare effects of rapid (RD) vs. gradual decompression and gauge impairment at altitude with and without hypoxia, as well as to assess recovery.METHODS: There were 12 participants who completed RD (1 s) and Gradual (3 min 12 s) ascents from 2743-7620 m (9000-25000 ft) altitude pressures while breathing air or 100% O2. Physiological indices included oxygen saturation (SPo2), heart rate (HR), respiration, end tidal O2 and CO2 partial pressures, and electroencephalography (EEG). Cognition was evaluated using SYNWIN, which combines memory, arithmetic, visual, and auditory tasks. The study incorporated ascent rate (RD, gradual), breathing gas (air, 100% O2) and epoch (ground-level, pre-breathe, ascent-altitude, recovery) as factors.RESULTS: Physiological effects in hypoxic "air" ascents included decreased SPo2 and end tidal O2 and CO2 partial pressures (hypocapnia), with elevated HR and minute ventilation (V˙E); SPo2 and HR effects were greater after RD (-7.3% lower and +10.0 bpm higher, respectively). HR and V˙E decreased during recovery. SYNWIN performance declined during ascent in air, with key metrics, including composite score, falling further (-75% vs. -50%) after RD. Broad cognitive impairment was not recorded on 100% O2, nor in recovery. EEG signals showed increased slow-wave activity during hypoxia.DISCUSSION: In hypoxic exposures, RD impaired performance more than gradual ascent. Hypobaria did not comprehensively impair performance without hypoxia. Lingering impairment was not observed during recovery, but HR and V˙E metrics suggested compensatory slowing following altitude stress. Participants' cognitive strategy shifted as hypoxia progressed, with efficiency giving way to "satisficing," redistributing effort to easier tasks.Beer J, Mojica AJ, Blacker KJ, Dart TS, Morse BG, Sherman PM. Relative severity of human performance decrements recorded in rapid vs. gradual decompression. Aerosp Med Hum Perform. 2024; 95(7):353-366.

Quantitative evaluation of the impact of variation of optical parameters on the estimation of blood hematocrit and oxygen saturation for dual-wavelength photoacoustics.

Photoacoustic (PA) spectroscopy is considered to be one of the most effective ways to measure the levels of hematocrit (H) and oxygenation saturation (S O 2) of blood, which are essential for diagnosing blood-related illnesses. This simulation study aims to investigate the impact of individual optical parameters, i.e., optical absorption coefficient (µ a), scattering coefficient (µ s), and anisotropy factor (g), on the accuracy of this technique in estimating the blood properties. We first performed the Monte Carlo simulations, using realistic optical parameters, to obtain the fluence maps for various samples. The wavelengths of the incident light were chosen to be 532, 700, 1000, and 1064 nm. Thereafter, the k-Wave simulations were executed, incorporating those fluence maps to generate the PA signals. The blood properties were obtained using the PA signals. We introduced variations in µ a, µ s, and g ranging from -10% to +10%, -10% to +10%, and -5% to +1%, respectively, at 700 and 1000 nm wavelengths. One parameter, at both wavelengths, was changed at a time, keeping others fixed. Subsequently, we examined how accurately the blood parameters could be determined at physiological hematocrit levels. A 10% variation in µ a induces a 10% change in H estimation but no change in S O 2 determination. Almost no change has been seen for µ s variation. However, a 5% (-5% to 0%) variation in the g factor resulted in approximately 160% and 115% changes in the PA signal amplitudes at 700 and 1000 nm, respectively, leading to ≈125% error in hematocrit estimation and ≈14% deviation in S O 2 assessment when nominal S O 2=70%. It is clear from this study that the scattering anisotropy factor is a very sensitive parameter and a small change in its value can result in large errors in the PA estimation of blood properties. In the future, in vitro experiments with pathological blood (inducing variation in the g parameter) will be performed, and accordingly, the accuracy of the PA technique in quantifying blood H and S O 2 will be evaluated.