History and Social Implications of the Pulse Oximeter.

The pulse oximeter is a portable, bedside tool that allows for the measurement of oxygen saturation in a patient's red blood cells. The technology is based on oxygenated and deoxygenated hemoglobin absorbing light at different wavelengths. The device calculates the ratio of oxygenated to deoxygenated hemoglobin in the blood, and an algorithm produces a percentage oxygen saturation value. Due to its portability and ease of use, it is a ubiquitous medical tool that is commonly used in medical practice. This paper reviews the history and evolution of this tool, and the scientific laws behind oximetry. It also introduces the importance of the pulse oximeter and its basic functions. In addition, the limitations of pulse oximetry are discussed, especially as they pertain to pigmented skin.

Pulse oximetry in pediatric care: Balancing advantages and limitations.

BACKGROUND: Pulse oximetry has become a cornerstone technology in healthcare, providing non-invasive monitoring of oxygen saturation levels and pulse rate. Despite its widespread use, the technology has inherent limitations and challenges that must be addressed to ensure accurate and reliable patient care. AIM: To comprehensively evaluate the advantages, limitations, and challenges of pulse oximetry in clinical practice, as well as to propose recommendations for optimizing its use. METHODS: A systematic literature review was conducted to identify studies related to pulse oximetry and its applications in various clinical settings. Relevant articles were selected based on predefined inclusion and exclusion criteria, and data were synthesized to provide a comprehensive overview of the topic. RESULTS: Pulse oximetry offers numerous advantages, including non-invasiveness, real-time feedback, portability, and cost-effectiveness. However, several limitations and challenges were identified, including motion artifacts, poor peripheral perfusion, ambient light interference, and patient-specific factors such as skin pigmentation and hemoglobin variants. Recommendations for optimizing pulse oximetry use include technological advancements, education and training initiatives, quality assurance protocols, and interdisciplinary collaboration. CONCLUSION: Pulse oximetry is crucial in modern healthcare, offering invaluable insights into patients' oxygenation status. Despite its limitations, pulse oximetry remains an indispensable tool for monitoring patients in diverse clinical settings. By implementing the recommendations outlined in this review, healthcare providers can enhance the effectiveness, accessibility, and safety of pulse oximetry monitoring, ultimately improving patient outcomes and quality of care.

Clinical evaluation of a smart wristband for monitoring oxygen saturation, pulse rate, and respiratory rate.

Recently, photoplethysmography-based vital parameter measurements have increased in popularity. However, clinical evaluation of these measurements is lacking. The objective of this study was to rigorously evaluate the clinical accuracy and reliability of a novel photoplethysmography-based wristband for measuring key vital parameters-oxygen saturation (SpO2), respiratory rate (RR), and pulse rate (PR)-during heart catheterisations. Vital parameters obtained during heart catheterisations by means of a photoplethysmography-based wristband (CardioWatch 287-2, Corsano Health) were compared to reference measurements performed by a Nellcor fingerclip (SpO2, PR) as well as a 5-lead ECG (RR) (QMAPP Haemodynamic Monitoring module, Fysicon B.V.) by means of correlation coefficients and root means squared error (RMSE). Effects of skin colour and arm hair density were additionally evaluated. In total, 945 samples from a total of 100 patients were included in the analysis. The correlation coefficients and RSME obtained for the difference between reference and photoplethysmography-based wristband measurements were r = 0.815 and 1.6% for SpO2, r = 0.976 and 0.9 brpm for RR, and r = 0.995 and 1.3 bpm for PR. Similar results were obtained across all skin colour and arm hair density subcategories. This study shows that photoplethysmography-based SpO2, RR, and PR measurements can be accurate during heart catheterisations. Future investigations are required to evaluate the wristband's performance under dynamic circumstances as well as over an extended time period. Trial registration: www.clinicaltrials.gov, NCT05566886.

Optimizing RBC Transfusion Strategies in Traumatic Brain Injury: Insights on Early Resuscitation and Cerebral Oxygenation.

Effective early resuscitation and maintenance of brain oxygenation are critical for improving the outcomes of patients with severe traumatic brain injury (TBI). Red blood cell (RBC) transfusion plays a vital role in this process. Although RBC transfusion can enhance cerebral oxygenation and stabilize hemodynamics, it also poses significant risks including transfusion-related lung injury and transfusion-associated circulatory overload, highlighting the importance of meticulous transfusion management. This review explores transfusion strategies during the early resuscitation phase and the management of anemia in patients with severe TBI, focusing on appropriate treatment targets, utilizing monitoring-based personalized approaches, and summarizing recent research and current insights.

Spiral volumetric optoacoustic tomography of reduced oxygen saturation in the spinal cord of M83 mouse model of Parkinson's disease.

PURPOSE: Metabolism and bioenergetics in the central nervous system play important roles in the pathophysiology of Parkinson's disease (PD). Here, we employed a multimodal imaging approach to assess oxygenation changes in the spinal cord of the transgenic M83 murine model of PD overexpressing the mutated A53T alpha-synuclein form in comparison with non-transgenic littermates. METHODS: In vivo spiral volumetric optoacoustic tomography (SVOT) was performed to assess oxygen saturation (sO2) in the spinal cords of M83 mice and non-transgenic littermates. Ex vivo high-field T1-weighted (T1w) magnetic resonance imaging (MRI) at 9.4T was used to assess volumetric alterations in the spinal cord. 3D SVOT analysis and deep learning-based automatic segmentation of T1w MRI data for the mouse spinal cord were developed for quantification. Immunostaining for phosphorylated alpha-synuclein (pS129 α-syn), as well as vascular organization (CD31 and GLUT1), was performed after MRI scan. RESULTS: In vivo SVOT imaging revealed a lower sO2SVOT in the spinal cord of M83 mice compared to non-transgenic littermates at sub-100 µm spatial resolution. Ex vivo MRI-assisted by in-house developed deep learning-based automatic segmentation (validated by manual analysis) revealed no volumetric atrophy in the spinal cord of M83 mice compared to non-transgenic littermates at 50 µm spatial resolution. The vascular network was not impaired in the spinal cord of M83 mice in the presence of pS129 α-syn accumulation. CONCLUSION: We developed tools for deep-learning-based analysis for the segmentation of mouse spinal cord structural MRI data, and volumetric analysis of sO2SVOT data. We demonstrated non-invasive high-resolution imaging of reduced sO2SVOT in the absence of volumetric structural changes in the spinal cord of PD M83 mouse model.

Utilization of NIRS Monitor to Compare the Regional Cerebral Oxygen Saturation Between Dexmedetomidine and Propofol Sedation in Mechanically Ventilated Critically ill Patients with Sepsis- A Prospective Randomized Control Trial.

AIM & BACKGROUND: Delirium frequently occurs in the acute phase of sepsis and is associated with increased ICU and hospital length of stay, duration of mechanical ventilation, and higher mortality rates. We utilized the Near-Infrared Spectroscopy monitor to measure and compare the regional cerebral oxygen saturation in mechanically ventilated patients of sepsis receiving either dexmedetomidine or propofol sedation and assessed the association between delirium and regional cerebral oxygen saturation. METHODS: A single center prospective randomized control trial conducted over a period of two years, 54 patients were included, equally divided between propofol and dexmedetomidine groups. Patients received a blinded study drug, propofol (10 mg/mL) or dexmedetomidine (5 mcg/mL) via infusion pump according to randomization. Infusion rates were adjusted every 10 min based on weight-based titration tables, aiming for target sedation (RASS -2 to 0). Management components included pain monitoring using the CPOT score and delirium assessment using CAM-ICU score. RESULTS: Dexmedetomidine group showed higher mean regional cerebral oxygen saturation as compared to propofol group (P = .036). No significant differences were found in mechanical ventilation or ICU stay durations, delirium-free days, or sedation cessation reasons. Delirium occurred in 36 patients, with lower mean regional cerebral oxygen saturation as compared to non-delirious patients. CONCLUSION: The dexmedetomidine group had higher regional cerebral oxygen saturation compared to the propofol group. Delirious patients showed lower cerebral oxygen saturation than non-delirious patients, suggesting a link between sedation type, cerebral oxygenation, and delirium.CTRI registration: REF/2021/11/048655 N.

Deep learning approaches for assessing pediatric sleep apnea severity through SpO2 signals.

Pediatric Sleep Apnea-Hypopnea (SAH) presents a significant health challenge, particularly in diagnostic contexts, where conventional Polysomnography (PSG) testing, although effective, can be distressing for children. Addressing this, our research proposes a less invasive method to assess pediatric SAH severity by analyzing blood oxygen saturation (SpO2) signals. We adopted two advanced deep learning architectures, namely ResNet-based and attention-augmented hybrid CNN-BiGRU models, to process SpO2 signals in a one-dimensional (1D) format for Apnea-Hypopnea Index (AHI) estimation in pediatric subjects. Employing the CHAT dataset, which includes 844 SpO2 signals, the data was partitioned into training (60%), testing (30%), and validation (10%) sets. A predefined validation subset was randomly selected to ensure the models' robustness via a threefold cross-validation approach. Comparative analysis revealed that while the ResNet model attained an average accuracy of 72.9% across four SAH severity categories with a kappa score of 0.57, the CNN-BiGRU-Attention model demonstrated superior performance, achieving an average accuracy of 75.95% and a kappa score of 0.63. This distinction underscores our method's efficacy in both estimating AHI and categorizing SAH severity levels with notable precision. Further, to evaluate diagnostic capabilities, the models were benchmarked against common AHI thresholds (1, 5, and 10 events/hour) in each test fold, affirming their effectiveness in identifying pediatric SAH. This study marks a significant advance in the field, offering a non-invasive, child-friendly alternative for pediatric SAH diagnosis. Although challenges persist in accurately estimating AHI, particularly in severe cases, our findings represent a critical stride towards improving diagnostic processes in pediatric SAH.

Smartwatch measurement of blood oxygen saturation for predicting acute mountain sickness: Diagnostic accuracy and reliability.

Objective: This study aims to assess the accuracy and stability of smartwatches in predicting acute mountain sickness (AMS). Methods: In locations exceeding an altitude of 2500 m, a cohort of 42 subjects had their Lake Louise AMS self-assessment score, blood oxygen saturation (SpO2), heart rate, and perfusion index measured using smartwatches, with the data seamlessly conveyed to the Huawei Cloud. Results: A significant decrease in SpO2 was observed in individuals positive for AMS compared to those negative (p < 0.05), with the mild AMS group exhibiting significantly lower SpO2 levels than the non-AMS group (p < 0.05). Furthermore, SpO2 emerged as a significant, independent predictor of AMS [ß=-0.086, p < 0.01, OR (95% CI) = 0.92 (0.87-0.97)], indicating that each unit increase in SpO2 decreases the probability of AMS occurrence by 8.6%. Conclusion: The Huawei smartwatches have demonstrated efficacy in diagnosing and foretelling AMS at elevations exceeding 4000 m, showcasing significant reliability and high precision in SpO2 measurement.

Effectiveness and safety of adjunctive non-drug measures in improving respiratory symptoms among patients with severe COVID-19: A multicenter randomized controlled trial.

BACKGROUND: The outbreak of coronavirus disease 2019 (COVID-19) infection posed a huge threat and burden to public healthcare in late 2022. Non-drug measures of traditional Chinese medicine (TCM), such as acupuncture, cupping and moxibustion, are commonly used as adjuncts in China to help in severe cases, but their effects remain unclear. OBJECTIVES: To observe the clinical effect of TCM non-drug measures in improving respiratory function and symptoms among patients with severe COVID-19. DESIGN, SETTING, PARTICIPANTS AND INTERVENTIONS: This study was designed as a multicenter, assessor-blind, randomized controlled trial. Hospitalized patients with COVID-19 were randomly assigned to the treatment or control group. The treatment group received individualized TCM non-drug measures in combination with prone position ventilation, while the control group received prone position ventilation only for 5 consecutive days. MAIN OUTCOME MEASURES: The primary outcome measures were the percentage of patients with improved oxygen saturation (SpO2) at the end of the 5-day intervention, as well as changes of patients' respiratory rates. The secondary outcome measures included changes in SpO2 and total score on the self-made respiratory symptom scale. The improvement rate, defined as a 3-day consecutive increase in SpO2, the duration of prone positioning, and adverse events were recorded as well. RESULTS: Among the 198 patients included in the intention-to-treat analysis, 159 (80.3%) completed all assessments on day 5, and 39 (19.7%) patients withdrew from the study. At the end of the intervention, 71 (91%) patients in the treatment group had SpO2 above 93%, while 61 (75.3%) in the control group reached this level. The proportion of participant with improved SpO2 was significantly greater in the intervention group (mean difference [MD] = 15.7; 95% confidence interval [CI]: 4.4, 27.1; P = 0.008). Compared to the baseline, with daily treatment there were significant daily decreases in respiratory rates in both groups, but no statistical differences between groups were found (all P ≥ 0.05). Compared to the control group, the respiratory-related symptoms score was lower among patients in the treatment group (MD = -1.7; 95%CI: -2.8, -0.5; P = 0.008) after day 3 of treatment. A gradual decrease in the total scores of both groups was also observed. Thirty-one adverse events occurred during the intervention, and 2 patients were transferred to the intensive care unit due to deterioration of their illness. CONCLUSION: TCM non-drug measures combined with prone positioning can effectively treat patients with severe COVID-19. The combined therapy significantly increased SpO2 and improved symptom scores compared to prone positioning alone, thus improving the patients' respiratory function to help them recover. However, the improvement rate did not differ between the two groups. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR2300068319). Please cite this article as: Yin X, Jin Z, Li F, Huang L, Hu YM, Zhu BC, Wang ZQ, Li XY, Li JP, Lao LX, Mi YQ, Xu SF. Effectiveness and safety of adjunctive non-drug measures in improving respiratory symptoms among patients with severe COVID-19: A multicenter randomized controlled trial. J Integr Med. 2024; Epub ahead of print.

The novel and slowest arterial pressure waves: clinical implications in children with congenital heart disease following cardiovascular surgery.

OBJECTIVES: Certain rhythmic arterial pressure waves in humans and animals have been noticed for over one century. We found the novel and slowest arterial pressure waves in children following surgical repair for CHD, and examined their characteristics and clinical implications. METHODS: We enrolled 212 children with 22 types of CHD within postoperative 48 h. We monitored haemodynamics (blood pressure, cardiac cycle efficiency, dP/dTmax), cerebral (ScO2), and renal (SrO2) oxygen saturation every 6 s. Electroencephalogram was continuously monitored. Mean blood flow velocity (Vm) of the middle cerebral artery was measured at 24 h. RESULTS: We found the waves with a frequency of ∼ 90 s immediately following surgical repair in 46 patients in 12 types of CHD (21.7%), being most prevalent in patients with aortic arch abnormalities (Aorta Group, n = 24, 42.3%) or ventricular septal defect (Ventricular Septal Defect Group, n = 12, 23.5%). In Aorta and Ventricular Septal Defect Groups, the occurrence of the waves was associated with lower blood pressures, dP/dTmax, cardiac cycle efficiency, ScO2, SrO2, Vm, worse electroencephalogram background abnormalities, higher number of electroencephalogram sharp waves, and serum lactate (Ps <0.0001-0.07), and were accompanied with fluctuations of ScO2 and SrO2 in 80.6% and 69.6% of patients, respectively. CONCLUSIONS: The waves observed in children following cardiovascular surgery are the slowest ever reported, occurring most frequently in patients with aortic arch abnormalities or ventricular septal defect. While the occurrence of the waves was associated with statistically worse and fluctuated ScO2 and SrO2, worse systemic haemodynamics, and electroencephalogram abnormalities, at present these waves have no known clinical relevance.

Assessment of accuracy of two pulse oximeters in infants with cyanotic and acyanotic congenital heart diseases.

BACKGROUND: Peripherally measured oxygen saturation (SpO2) may often differ from arterial oxygen saturation (SaO2), measured by co-oximetry, especially within the lower range of oxygen saturations. This can potentially impact clinical decisions and therapy in children with congenital heart disease, as critical hypoxemia might remain unnoticed. AIMS: Our aim was to investigate the accuracy of two different pulse oximeters compared to SaO2 in infants with congenital heart diseases. METHODS: Simultaneous recordings of SpO2, measured by two different pulse oximeters (Philips IntelliVue X3 Monitor and Nellcor™ OxiMax™), were compared to SaO2 obtained by arterial blood gas analysis. RESULTS: A total of 153 measurements were performed in 44 infants with arterial oxygen saturation between 70 and 100%. We divided the measurements into 3 subgroups: group 1-SaO2 70.0%-85.0%, group 2-SaO2 85.1%-94.0%, group 3-SaO2 >94.1%. For Philipps, the median bias was 5.3 (IQR: 2.6-8.7) %, 2.3 (IQR: 0.9-6.0) % and 1.1 (IQR: -0.8-2.4) % in group 1, 2 and 3, respectively. For OxiMax™, the median bias was 2.7 (IQR: 0.5-5.1) %, 0.2 (IQR: -0.9-2.6) % and -0.5 (IQR: -1.3-0.6) % in group 1, 2 and 3, respectively. Regarding the accuracy of these oximeters, as evaluated with the Accuracy root mean squared index (Arms), it was 9.8 versus 4.5% in group 1, 4.5 versus 2.9% in group 2 and 2.4 versus 1.9% in group 3 for Philipps and OxiMax™, respectively. CONCLUSIONS: In lower range saturations between 70% and 85% the accuracy of both pulse oximeters exceeded the threshold of ≤3% recommended by the Food and Drug Administration (FDA). Therefore, peripheral pulse oximetry within the lower range of oxygen saturations should be interpreted with caution in infants with congenital heart diseases, taking into consideration its limitations. Direct co-oximetry should be the preferred method to support clinical decisions in children with cyanotic congenital heart diseases.

Effect of APOE gene on cerebral oxygen saturation, cerebral electrical activity and prognosis after intracerebral hemorrhage.

Cerebral hemorrhage represents a severe neurological disorder with significant implications for patient health. Numerous factors play a crucial role in determining the prognosis of this condition. In recent years, research has highlighted the polymorphism of the apolipoprotein E (APOE) gene as being closely associated with cerebrovascular diseases and the recovery of neurological functions. This study aims to explore the influence of APOE gene polymorphism on cerebral oxygen saturation, cerebral electrical activity, and the clinical prognosis of patients experiencing cerebral hemorrhage. The goal is to identify potential new biomarkers that could enhance the management and treatment of individuals who have suffered from this type of bleed in the brain.To investigate this relationship, the study analyzed the ε2, ε3, and ε4 alleles of the APOE gene through gene sequencing techniques. Measurements of cerebral oxygen saturation and electrical brain activity were conducted using specialized equipment including brain oxygen monitors and electroencephalography (EEG) devices. Additionally, detailed clinical data were gathered, encompassing neurological function assessments and the duration of recovery for each patient.A comparative analysis was performed to assess the cerebral oxygen saturation levels, EEG characteristics, and overall prognosis associated with the different APOE genotypes. The findings indicated that patients carrying the APOE ε4 allele exhibited significantly impaired cerebral oxygen metabolism and diminished electrical activity in the initial stages of intracerebral hemorrhage. This impairment potentially results in a worse prognostic outlook when compared to individuals who are non-carriers of the APOE ε4 allele. Furthermore, the relationship between the pulsatility index (PR) and regional cerebral oxygen saturation (rScO2) was found to be negatively correlated. Specifically, patients with intracerebral hemorrhage who exhibited elevated PR levels alongside reduced rScO2 demonstrated poorer clinical outcomes.

Effect of optimizing cerebral oxygen saturation on postoperative delirium in older patients undergoing one-lung ventilation for thoracoscopic surgery.

OBJECTIVES: This randomized controlled trial investigated whether the regional cerebral oxygenation saturation (rScO2)-guided lung-protective ventilation strategy could improve brain oxygen and reduce the incidence of postoperative delirium (POD) in patients older than 65 years. METHODS: This randomized controlled trial enrolled 120 patients undergoing thoracic surgery who received one-lung ventilation (OLV). Patients were randomly assigned to the lung-protective ventilation group (PV group) or rScO2-oriented lung-protective ventilation group (TPV group). rScO2 was recorded during the surgery, and the occurrence of POD was assessed. RESULTS: The incidence of POD 3 days after surgery-the primary outcome-was significantly lower in the TPV group (23.3% versus 8.5%). Meanwhile, the levels of POD-related biological indicators (S100ß, neuron-specific enolase, tumor necrosis factor-α) were lower in the TPV group. Considering the secondary outcomes, both groups exhibited a lower oxygenation index after OLV, whereas partial pressure of carbon dioxide and mean arterial pressure were significantly increased in the TPV group. In addition, minimum rScO2 during surgery and mean rScO2 were higher in the TPV group than in the PV group. CONCLUSION: Continuous intraoperative monitoring of brain tissue oxygenation and active intervention measures guided by cerebral oxygen saturation are critical for improving brain metabolism and reducing the risk of POD.

Effect of Weighted Vest at 0%, 5% and 10% of Body Mass on Gasometry Biomarkers and Performance during a Rectangular Test in Trained Trail Runners.

Trail runners (TRs) must carry an extra load of equipment, food (bars and gels) and liquids, to delay the anticipation of fatigue and dehydration during their competitions. Therefore, we aimed to evaluate how an extra load can influence the metabolic level. Thirteen well-trained trail runners performed a randomized crossover study (total n = 39), completing three treadmill running sessions with a weighted vest of 0%, 5% and 10% of their body mass during a combined test (rectangular test + ramp test). In addition, biomarkers of oxygen metabolism, acid-base and electrolyte status pre-, during and post-test, as well as the rectangular from capillary blood of the finger and time to exhaustion, were analyzed. Repeated-measures ANOVA showed no significant difference between conditions for any of the analyzed biomarkers of blood gas. However, one-way ANOVA showed a significant difference in trial duration between conditions (p ≤ 0.001). Tukey's post hoc analysis observed a significant decrease in time to exhaustion in the weighted vest of 10% compared to 0% (p ≤ 0.001) and 5% (p ≤ 0.01) and 5% compared to 0% (p = 0.030). In addition, repeated-measures ANOVA detected a significant difference in pH in the group x time interaction (p = 0.035). Our results show that increasing the weighted vest (5% and 10%) anticipates fatigue in runners trained in TR. In addition, increasing the load decreased pH by a smaller magnitude at 10% compared to 0% and 5% at the end of the exercise protocol.

Exploratory Study of Relationship Between Obstructive Sleep Apnea Syndrome and Growth Hormones and Inflammatory Factors in Children.

Purpose: In children, obstructive sleep apnea (OSA) is associated with growth hormone level abnormalities and chronic systemic inflammation. This study was performed to investigate the relationship of the degree of OSA with insulin-like growth factor 1 (IGF-1) and inflammatory cytokines in pediatric OSA and the inter-relationship between inflammatory cytokines and growth hormones. Methods: Children with OSA and controls without OSA participated in the study. Information included polysomnography followed by measurement of IGF-1 and inflammatory marker levels. In total, 226 patients aged 2 to 12 years were divided into 4 groups: non-OSA, n = 57 (25.2%); mild OSA, n = 116 (51.3%); moderate OSA, n = 23 (10.2%); and severe OSA, n = 30 (13.3%). Results: Body height was not significantly different among the 4 groups. However, the minimum oxygen saturation and IGF-1 significantly differed among the different OSA groups (P = .0001 and P = .036, respectively). IGF-1 was significantly higher in the non-OSA group (P < .05) and mild OSA group (P < .01) than in the severe OSA group. As the severity of OSA increased, the interleukin-5 level significantly increased, which caused a difference between mild OSA and moderate OSA (P < .05) and between mild OSA and severe OSA (P < .001). In the univariate quantile regression analysis of IGF-1, there was a negative relationship between IGF-1 and IL-5 (P < .001). IGF-1 was positively correlated with age, height, and minimum oxygen saturation. Furthermore, there was a negative correlation between the IGF-1 level and the severity of OSA. Quantile regression analysis on the multivariable analysis of the IGF-1 association showed that height, sex, and severity of OSA played important roles in affecting IGF-1 levels. Conclusion: High IL-5 levels may lead to the low secretion of growth hormone level (IGF-1) in children, thus affecting growth and development.

Exogenous ketosis attenuates acute mountain sickness and mitigates normobaric high-altitude hypoxemia.

BACKGROUND: Acute mountain sickness (AMS) represents a considerable issue for individuals sojourning to high altitudes with systemic hypoxemia known to be intimately involved in its development. Based on recent evidence that ketone ester (KE) intake attenuates hypoxemia, we investigated whether exogenous ketosis might mitigate AMS development and to identify underlying physiological mechanisms. METHODS: Fourteen healthy, male participants were enrolled in two 29h protocols (simulated altitude of 4,000-4,500m) receiving either KE or a placebo (CON) at regular timepoints throughout the protocol in a randomized, crossover manner. Physiological responses were characterized after 15min and 4h in hypoxia, and the protocol was terminated prematurely upon development of severe AMS (Lake Louise Score ≥ 10). RESULTS: KE ingestion induced a consistent diurnal ketosis ([ßHB] of ~3 mM), whereas blood [ßHB] remained low (<0.6 mM) in CON. Each participant tolerated the protocol equally long or longer (n=6 or n=8, resp.) in KE. Protocol duration increased by 32% on average with KE, and doubled upon KE for severe AMS-developing participants (n=9). Relative to CON, KE induced a mild metabolic acidosis, hyperventilation, and relative sympathetic dominance. KE also inhibited the progressive hypoxemia that was observed between 15min and 4h in hypoxia in CON, while concomitantly increasing cerebral oxygenation and capillary pO2 within this timeframe despite a KE-induced reduction in cerebral oxygen supply. CONCLUSIONS: These data indicate that exogenous ketosis attenuates AMS development. The key underlying mechanisms include improved arterial and cerebral oxygenation, in combination with lowered cerebral blood flow and oxygen delivery, and increased sympathetic dominance.

Exploring the impact and influence of melanin on frequency-domain near-infrared spectroscopy measurements.

Significance: Near-infrared spectroscopy (NIRS) is a non-invasive optical method that measures changes in hemoglobin concentration and oxygenation. The measured light intensity is susceptible to reduced signal quality due to the presence of melanin. Aim: We quantify the influence of melanin concentration on NIRS measurements taken with a frequency-domain near-infrared spectroscopy system using 690 and 830 nm. Approach: Using a forehead NIRS probe, we measured 35 healthy participants and investigated the correlation between melanin concentration indices, which were determined using a colorimeter, and several key metrics from the NIRS signal. These metrics include signal-to-noise ratio (SNR), two measurements of oxygen saturation (arterial oxygen saturation, SpO 2 , and tissue oxygen saturation, StO 2 ), and optical properties represented by the absorption coefficient ( µ a ) and the reduced scattering coefficient ( µ s ' ). Results: We found a significant negative correlation between the melanin index and the SNR estimated in oxy-hemoglobin signals ( r s = - 0.489 , p = 0.006 ) and SpO 2 levels ( r s = - 0.413 , p = 0.023 ). However, no significant changes were observed in the optical properties and StO 2 ( r s = - 0.146 , p = 0.44 ). Conclusions: We found that estimated SNR and SpO 2 values show a significant decline and dependence on the melanin index, whereas StO 2 and optical properties do not show any correlation with the melanin index.

The effects of low vs. high rating of perceived exertion clamp exercise on performance, neuromuscular, and muscle oxygen saturation responses in females.

PURPOSE: This study examined the time course of changes in force, relative to critical force (CF), electromyographic amplitude (EMG AMP), neuromuscular efficiency (NE), and muscle oxygen saturation (SmO2), as well as time to task failure (TTF) and performance fatigability (PF) during isometric handgrip holds to failure (HTF) anchored to the rating of perceived exertion (RPE) at 3 and 7. METHODS: Ten females completed pre-test maximal voluntary isometric contractions (MVICs), submaximal HTF at four percentages of MVIC, an HTF at RPE = 3 and 7, and post-test MVICs. Analyses included paired samples t-tests, repeated measures ANOVAs and planned comparisons. RESULTS: TTF was not different between RPE 3 (540.4 ± 262.1 s) and 7 (592.2 ± 299.6 s), but PF for RPE 7 (42.1 ± 19.1%) was greater than RPE 3 (33.5 ± 15.4%) (p < 0.05). There were RPE-dependent decreases in force, EMG AMP, and NE across three discernable phases during the HTF (p < 0.01), but there were no significant changes in SmO2 across time. CONCLUSION: Although there were overall similar patterns across time for force, neuromuscular, and muscle metabolic responses between the RPE holds, the greater PF at RPE 7 than RPE 3 may be explained by the longer sustained time above CF at RPE 7, resulting in greater accumulation of intramuscular metabolites and afferent feedback. Throughout each trial, it is possible that force was adjusted to avoid the sensory tolerance limit, and the task was ended when force could no longer be reduced to maintain the assigned RPE, resulting in a similar TTF for RPE 7 and RPE 3.

Application value of dexmedetomidine in anesthesia for elderly patients undergoing radical colon cancer surgery.

BACKGROUND: Colon cancer presents a substantial risk to the well-being of elderly people worldwide. With advancements in medical technology, surgical treatment has become the primary approach for managing colon cancer patients. However, due to age-related physiological changes, especially a decline in cognitive function, older patients are more susceptible to the effects of surgery and anesthesia, increasing the relative risk of postoperative cognitive dysfunction (POCD). Therefore, in the surgical treatment of elderly patients with colon cancer, it is of paramount importance to select an appropriate anesthetic approach to reduce the occurrence of POCD, protect brain function, and improve surgical success rates. AIM: To explore the value of dexmedetomidine (Dex) in anesthesia for elderly patients undergoing radical colon cancer surgery. METHODS: One hundred and seventeen patients with colon cancer who underwent elective surgery under general anesthesia were selected and divided into two groups: A and B. Group A received Dex before anesthesia induction, and B group received an equivalent amount of normal saline. Changes in the mini-mental state examination, regional cerebral oxygen saturation (rSO2), bispectral index, glucose uptake rate (GluER), lactate production rate (LacPR), serum S100ß and neuron-specific enolase (NSE), POCD, and adverse anesthesia reactions were compared between the two groups. RESULTS: Surgical duration, duration of anesthesia, and intraoperative blood loss were comparable between the two groups (P > 0.05). The overall dosage of anesthetic drugs used in group A, including propofol and remifentanil, was significantly lower than that used in group B (P < 0.05). Group A exhibited higher rSO2 values at the time of endotracheal intubation, 30 min after the start of surgery, and immediately after extubation, higher GluER values and lower LacPR values at the time of endotracheal intubation, 30 min after the start of surgery, immediately after extubation, and 5 min after extubation (P < 0.05). Group A exhibited lower levels of serum S100ß and NSE 24 h postoperatively and a lower incidence of cognitive dysfunction on the 1st and 5th postoperative days (P < 0.05). CONCLUSION: The use of Dex in elderly patients undergoing radical colon cancer surgery helps maintain rSO2 Levels and reduce cerebral metabolic levels and the incidence of anesthesia- and surgery-induced cognitive dysfunction.

Usefulness of bilateral cerebral regional oxygen saturation measurements in determining selective cerebral perfusion flow rate in a pediatric patient with aortic arch stenosis: a case report.

BACKGROUND: We report a pediatric case where bilateral regional oxygen saturation (rSO2) measurements were useful in determining the selective cerebral perfusion (SCP) flow rate. CASE PRESENTATION: A 9-year-old Japanese boy, 128 cm tall and weighing 25.6 kg, was scheduled for aortic arch reconstruction due to a 90-100 mmHg pressure gradient. Pediatric-sized oximetry sensors were attached to the bilateral forehead area. The rSO2 levels were 70-80% on the right and 80-90% on the left during cardiopulmonary bypass. Immediately following deep hypothermic circulatory arrest with the body temperature cooled to 25 °C, SCP was initiated from the right brachiocephalic artery at 10 mL/kg/min. As the rSO2 decreased steeply to 43-45% on the right and to 32-38% on the left, the SCP flow was increased to 15 mL/kg/min. The right rSO2 increased promptly to 50-60%, but the left rSO2 remained at 30-40%. After the SCP flow was increased to 20 mL/kg/min, bilateral rSO2 levels of 50-60% were obtained, and the SCP flow rate was maintained. The patient was transferred to the ICU postoperatively and extubated on the second postoperative day with no neurological abnormalities. CONCLUSIONS: Bilateral rSO2 measurements are essential even for a pediatric patient undergoing SCP, despite the limited forehead area.