Decrease In SpO2 Research Articles

Gas exchange efficiency slopes to assess exercise tolerance in chronic obstructive pulmonary disease

BackgroundIn patients with chronic obstructive pulmonary disease (COPD), the clinical use of the minute ventilation-carbon dioxide production (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2) slope has been reported as a measure of exercise efficiency, but the oxygen uptake efficiency slope (OUES), i.e., the slope of oxygen uptake (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}O2) versus the logarithmically transformed \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E, has rarely been reported.MethodsWe hypothesized that the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope is more useful than OUES in clinical use for the pathophysiological evaluation of COPD. Then, we investigated the cardiopulmonary exercise testing parameters affecting each of these slopes in 122 patients with all Global Initiative for Chronic Obstructive Lung Disease (GOLD) COPD grades selected from our database.ResultsCompared with the GOLD I-II group (n = 51), peak \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}O2 (p < 0.0001), OUES (p = 0.0161), \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E at peak exercise (p < 0.0001), and percutaneous oxygen saturation (SpO2) at peak exercise (p = 0.0004) were significantly lower in the GOLD III-IV group (n = 71). The GOLD III-IV group was divided into two groups by the exertional decrease in SpO2 from rest to peak exercise: 3% or less (the non-desaturation group: n = 23), or greater than 3% (the desaturation group: n = 48). OUES correlated only weakly with peak \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}O2, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E at peak exercise, and the difference between inspired and expired mean O2 concentrations (ΔFO2) at peak exercise, i.e., an indicator of oxygen consumption ability throughout the body, in the GOLD III-IV group with exertional hypoxemia. In contrast, the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope was significantly correlated with ΔFO2 at peak exercise, regardless of the COPD grade and exertional desaturation. Across all COPD stages, there was no correlation between the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope and \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E at peak exercise, and stepwise analysis identified peak \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}O2 (p = 0.0345) and ΔFO2 (p < 0.0001) as variables with a greater effect on the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope.ConclusionsThe OUES may be less useful in advanced COPD with exertional hypoxemia. The \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope, which is independent of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E, focuses on oxygen consumption ability and exercise tolerance in COPD, regardless of the exertional hypoxemia level and COPD grade. Therefore, the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}E-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rm{\\dot V}$$\\end{document}CO2 slope might be useful in establishing or evaluating tailor-made therapies for individual patient’s pathologies in COPD as an indicator focusing on oxygen consumption ability.

Standardization of transthoracic impedance values for estimating heart failure and its utility

Abstract Background The use of intrathoracic impedance for examining pleural effusion in heart failure patients has been explored previously. However, due to concerns about its accuracy and complexity, transthoracic impedance values have had limitations in quantifying extravascular lung water. Our dual objectives were to clarify the relationship between intrathoracic conditions and percutaneous transthoracic impedance values, and to establish a basic model for a new machine learning-based estimation system for assessing intrathoracic conditions in patients with heart failure. Methods First, we developed a live porcine congested lung model that induced pleural effusion by substantial fluid loading, and then longitudinally evaluated its correlation with percutaneous transthoracic impedance values. Second, we conducted multi-frequency bioelectrical impedance analysis to simultaneously collect electrical, physical, and hematological data from 63 hospitalized heart failure patients and 82 healthy volunteers Results In the porcine model, pleural effusion correlated with a concurrent decrease in SpO2 and a gradual decrease in impedance. We indexed and generated features from the measured values and developed an intrathoracic estimation model based on electrical measurements and clinical findings using a decision tree-based machine learning approach. Among the 286 features collected per individual, the model used 16 features. Notably, the model demonstrated high accuracy in discriminating patients with pleural effusion, achieving an AUC of 0.905 (95% CI: 0.870-0.940) in cross-validation, significantly outperforming the conventional frequency-based method. Conclusions Transthoracic impedance values, when indexed, reflect intrathoracic conditions and improve estimation. Our results highlighted the potential of machine learning and thoracic impedance measurement for accurate estimation of pleural effusion. This approach provides an effective means of assessing intrathoracic conditions. Figure: The upper figure shows the relationship between impedance values and pleural effusion in the congested lung model. On these results, human data were collected to construct the estimation model. The lower illustrates the accuracy of the model and provides a comprehensive view of the system.

Justification of the possibility of using liquid artificial lung ventilation for the treatment of acute respiratory distress syndrome of toxic genesis

Introduction. Pulmonotoxicants are chemicals that cause bronchospasm and damage to the alveolar capillary membrane. Lesions of the respiratory system with pulmonotoxicants in industrial accidents are especially relevant at the present time. Existing methods of treatment for the defeat of pulmonotoxicants and the development of acute respiratory distress syndrome (ARDS) are becoming ineffective, therefore, one of the tasks of modern medicine is to develop new methods of treating ARDS. One of these methods may be the creation of a "therapeutic window" by using perfluorocarbon (PFC) liquids. This article will present an experimental assessment of the use of liquid artificial lung ventilation (LALV) PFC liquids on the ARDS lung model. The study aims to explore the possibility of using liquid artificial lung ventilation to create a therapeutic window in the treatment of acute respiratory distress syndrome of a chemical nature. Materials and methods. The authors conducted a study on male Wistar rats aged 4 months, weighing 180–190 g. Toxic pulmonary edema was caused by endotracheal administration of 0.1 m HCl solution. The anesthetized patients were intubated using a cannula, after which the researchers intratracheally injected 0.1 M HCl solution at a dose of 2 ml/kg, a decrease in saturation below 80 was expected. Then the experts randomized the animals by weight into groups of 6 individuals each. They connected the animals of the control group to a ventilator. The animals of the experimental group were treated with PFC liquids for an hour, then transferred to a ventilator. Perfluorodecalin was used as a PFC liquid. The scientists recorded heart rate, blood oxygen saturation, rectal temperature, life expectancy and overall survival by group. Results. In the control group, after instillation of 0.1 M HCl solution and connection to a ventilator during the first 25–30 minutes, there was a gradual decrease in SpO2 to 74.0±5.6% (background — 95.0±3.5%) and an increase in heart rate to 182.0±8.6 beats/min., (background — 278.0±14.8 beats/min.) after which there was decompensation of the animal condition. In animals of the experimental group, after connecting to the LALV device, a sharp decrease in heart rate was recorded during the first 5 minutes to 61.0±8.5 beats/min. In turn, saturation did not change significantly throughout the LALV and was in the range from 95 to 100%. As a result of the experiments, it was noted that the average survival time in the experimental group was 256.0±34.5 minutes, which was significantly (p&lt;0.001) more than 5 times higher than this indicator in the control animals — 45.3±4.3 minutes. There were no significant changes in the study of rectal temperature in the animals of the control group. In turn, the animals of the experimental group showed a sharp decrease in rectal temperature during the first 30 minutes from the beginning of LALV, on average by 5.8±1.60°С. As a result of the pathoanatomic autopsy, differences in lung mass coefficients were revealed in different groups. Thus, in the control group and the experimental groups, it was 1.67±0.06 and 2.4±0.045%, respectively. Conclusion. On the model of ARDS caused by endotracheal administration of 0.1M hydrochloric acid solution, it was shown that living with the use of PFC of low temperature liquids, unlike conventional mechanical ventilation, allows for a long time to maintain a stable condition of animals; evacuate a significant amount of edematous fluid from the lungs and thereby increase the duration of their survival. The data presented above indicate that the use of hypothermic LALV can be used to create a "therapeutic window" for ARDS, including its most severe form — the alveolar stage of toxic pulmonary edema. Ethics. Studies involving laboratory animals were conducted in compliance with the following regulations: the Helsinki Declaration of 2000 "On humane treatment of animals", Order No. 755 of the Ministry of Health of the USSR dated 08/12/1977 "Rules for carrying out work using experimental animals", Order No. 199n of the Ministry of Health of the Russian Federation dated 04/01/2016 "On approval of the rules of laboratory practice". The protocol of the study was approved by the Ethics Committee of the Izmerov Research Institute of Occupational Health. Protocol No. 4 dated May 25, 2022.

Pilot study of home-based monitoring for early prediction of acute exacerbations in patients with fibrosing interstitial lung diseases

This study aimed to assess the potential of home monitoring using a monitoring application for the early prediction of acute exacerbations (AEs) in patients with fibrosing interstitial lung diseases (F-ILDs) by tracking symptoms, peripheral blood oxygen saturation (SpO2), and heart rate (HR). Data on symptoms, SpO2, and HR before and after a 1-min sit-to-stand test (1STST) were collected using an online home monitoring application. Symptoms were recorded at least 3 times a week, including cough intensity and frequency (Cough Assessment Test scale (COAT) score), breathlessness grade (modified Medical Research Council (mMRC) score), and SpO2 and HR before and after 1STST. Eighty-five patients with stable F-ILDs were enrolled. We observed a significant increase in COAT and mMRC scores, alongside a significant decrease in SpO2 before and after 1STST, 2 weeks before the first recorded AE. Furthermore, a combination of variables-an increase in COAT (≥ 4) and mMRC(≥ 1) scores, a decrease in SpO2 at rest (≥ 5%), and a decrease in SpO2 after 1STST (≥ 4%)- proved the most effective in predicting AE onset in patients with F-ILDs at 2 weeks before the first recorded AE. Home telemonitoring of symptoms, SpO2 holds potential value for early AE detection in patients with F-ILDs.

Arterial Oxygen Desaturation Hinders Gamified Working Memory Performance.

Hypoxia presents a physiological challenge to the Warfighters during military aviation and subterranean warfare operations by decreasing the supply of oxygen to the brain, which results in a reduced cognitive function depending on the magnitude and duration of hypoxic exposure. Moderate hypoxic exposures, fractions of inspired oxygen (FiO2) of 0.11 to 0.14, show no effects on simple tasks, but complex tasks like working memory may be hindered. Unfortunately, people often cannot recognize their own symptoms of hypoxemia, which are individualistic at moderate hypoxic exposure. Thus, screening tools, like gamified cognitive assessments, during moderate hypoxia may provide personnel objective feedback to initiate safety protocols before a possible accident. However, whether gamified assessments of working memory are sensitive to moderate hypoxia is unknown. Therefore, we tested the hypothesis which moderate normobaric hypoxia decreases gamified working memory performance when accounting for the individualistic responses of arterial blood oxygen saturations. Following 3 consecutive days of 2 practice sessions per day, 30 healthy adults (25 ± 5 years, 10 women) completed three 1-min rounds of the tablet-based working memory game (Backtracker, Statespace Labs, Inc.) at baseline and 60 and 90 min after exposure to FiO2 (= 0.138 ± 0.002 [hypoxia] and 0.201± 0.004 [normoxia] oxygen). Both conditions were completed on the same day and administered in a single-blind, block randomized manner. Arterial oxyhemoglobin saturation was estimated via forehead pulse oximetry (SpO2). Data were analyzed using linear mixed effects modeling. Compared to normoxia (99 ± 1%), SpO2 was lower (P < .001) at 60 (90 ± 2%) and 90 (90 ± 2%) min of hypoxia. A decrease in SpO2 was associated with a statistically significant decrease in the proportion of both tiles with the correct location (P < .02; -0.016) and correct order of appearance recalled (P < .01; -0.016). A decrease in SpO2 was associated with a statistically significant decrease in median time to first tap (P < .01; -0.041s) and median time between taps (P<.01; -0.030s). A significant interaction effect between the SpO2 decrease and baseline performance was found for proportion of tiles with the correct location recalled (P < .05; -0.014), median time to first tap (P <.01; -0.070s), and median time between taps (P < .01; -0.037s). A significant interaction effect between the SpO2 decrease and the path length was found for the proportion of tiles with the correct location recalled (P < .01; +0.021), median time to first tap (P < .01; -0.036s), and median time between taps (P < .01; -0.043s). These findings indicate that greater decreases in SpO2 during moderate hypoxic exposure hinder performance on a gamified assessment of working memory as measured by the proportion of correctly identified order and location of tiles. Considering the statistically significant decrease in both median time to first tap and median time between taps associated with the decrease in SpO2, participants are taking less time to plan or execute movements, which may compound or independently contribute to spatial and temporal memory mistakes.

The degree of respiratory depression according to the effect-site concentration in remimazolam target-controlled infusion: A randomised controlled trial.

Remimazolam is not only associated with a lower incidence of respiratory depression than propofol but also in itself has the risk of respiratory depression. We investigated respiratory depression following remimazolam infusion, targeting different effect-site concentrations using target-controlled infusion. A prospective, double-blind, randomised controlled study. Tertiary hospital, Suwon, South Korea, from April 2022 to November 2022. One hundred and seven patients scheduled for general anaesthesia were randomised into three groups targeting remimazolam effect-site concentrations of 500 (RMZ-500) ( n = 36), 1000 (RMZ-1000) ( n = 35) and 1500 ng ml -1 (RMZ-1500) ( n = 36). Remimazolam was solely infused for 10 min according to target effect-site concentrations. According to the degree of SpO 2 decrease, oxygen desaturations were managed with the following respiratory supports: jaw-thrust for SpO 2 less than 97%, 100% oxygen delivery for SpO 2 less than 93% and assisted ventilation for SpO 2 less than 90%. The incidence of each respiratory support, along with respiratory variables (at baseline, 5 min and 10 min after remimazolam infusion) and loss of consciousness were observed for 10 min after remimazolam target-controlled infusion. Both RMZ-1000 and RMZ-1500 required more frequent respiratory support than RMZ-500 (both P < 0.001), with nearly identical frequencies between RMZ-1000 and RMZ-1500. In terms of respiratory support, the incidence of assisted ventilation was significantly lower in RMZ-500 (2.8%) than RMZ-1000 (48.6%) and RMZ-1500 (50%) ( P < 0.001). RMZ-1000 and RMZ-1500 achieved loss of consciousness in all patients; RMZ-500 only achieved loss of consciousness in 86.1% of patients ( P = 0.010). In patients who maintained spontaneous respiration, tidal volume decreased by 41 to 48% and respiratory rate increased by 118 to 158% at 5 and 10 min, significantly compared to baseline in all groups ( P < 0.001). Remimazolam infusion, like that of other benzodiazepines, led to respiratory depression, which was more prominent at higher target effect-site concentrations. Therefore, appropriate countermeasures should be developed to prevent oxygen desaturation. CRIS ( https://cris.nih.go.kr ), identifier: KCT0006952.

Effect of oxygen supplementation on cognitive performance among HEMS providers after acute exposure to altitude: the HEMS II randomized clinical trial

ImportanceEmergency medical services (EMS) providers transiently ascend to high altitude for primary missions and secondary transports in mountainous areas in helicopters that are unpressurised and do not have facilities for oxygen supplementation. The decrease in cerebral oxygen saturation can lead to impairment in attention and reaction time as well as in quality of care during acute exposure to altitude.ObjectiveThe primary aim of the current study was to investigate the effect of oxygen supplementation on cognitive performance in Helicopter EMS (HEMS) providers during acute exposure to altitude.Design, setting, and participantsThis interventional, randomized, controlled, double-blind, cross-over clinical trial was conducted in October 2021. Each trial used a simulated altitude scenario equivalent to 4000 m, in which volunteers were exposed to hypobaric hypoxia with a constant rate of ascent of 4 m/s in an environmental chamber under controlled, replicable, and safe conditions. Trials could be voluntarily terminated at any time. Inclusion criteria were being members of emergency medical services and search and rescue services with an age between 18 and 60 years and an American Society of Anesthesiologists physical status class I.ExposuresEach participant conducted 2 trials, one in which they were exposed to altitude with oxygen supplementation (intervention trial) and the other in which they were exposed to altitude with ambient air supplementation (control trial).Main outcomes and measuresMeasurements included peripheral oxygen saturation (SpO2), cerebral oxygenation (ScO2), breathing and heart rates, Psychomotor Vigilance Test (PVT), Digit-Symbol Substitution Test (DSST), n-Back test (2-BACK), the Grooved Pegboard test, and questionnaires on subjective performance, stress, workload, and positive and negative affect. Paired t-tests were used to compare conditions (intervention vs. control). Data were further analyzed using generalized estimating equations (GEE).ResultsA total of 36 volunteers (30 men; mean [SD] age, 36 [9] years; mean [SD] education, 17 [4] years) were exposed to the intervention and control trials. The intervention trials, compared with the control trials, had higher values of SpO2 (mean [SD], 97.9 [1.6] % vs. 86 [2.3] %, t-test, p = 0.004) and ScO2 (mean [SD], 69.9 [5.8] % vs. 62.1 [5.2] %, paired t-test, p = 0.004). The intervention trials compared with the control trials had a shorter reaction time (RT) on the PVT after 5 min (mean [SD], 277.8 [16.7] ms vs. 282.5 [15.3] ms, paired t-test, p = 0.006) and after 30 min (mean [SD], 276.9 [17.7] ms vs. 280.7 [15.0] ms, paired t-test, p = 0.054) at altitude. While controlling for other variables, there was a RT increase of 0.37 ms for each % of SpO2 decrease. The intervention trials showed significantly higher values for DSST number of correct responses (with a difference of mean [SD], 1.2 [3.2], paired t-test, p = 0.035). Variables in the intervention trials were otherwise similar to those in the control trials for DSST number of incorrect responses, 2-BACK, and the Grooved Pegboard test.Conclusions and relevanceThis randomized clinical trial found that oxygen supplementation improves cognitive performance among HEMS providers during acute exposure to 4000 m altitude. The use of oxygen supplementation may allow to maintain attention and timely reaction in HEMS providers. The impact of repeated altitude ascents on the same day, sleep-deprivation, and additional stressors should be investigated.Trial registration NCT05073406, ClinicalTrials.gov trial registration.

A dive into the physiological responses to maximal apneas, O2 and CO2 tables in apnea novices.

Apnea duration is dependent on three factors: oxygen storage, oxygen consumption, hypoxia and hypercapnia tolerance. While current literature focuses on maximal apneas to improve apnea duration, apnea trained individuals use timed-repeated submaximal apneas, called "O2 and CO2 tables". These tables claim to accommodate the body to cope with hypoxia and hypercapnia, respectively. The aim of this study was twofold. First, to investigate the determinants of maximal apnea duration in apnea novices. Second, to compare physiologic responses to maximal apneas, O2 and CO2 tables. After medical screening, lung function test and hemoglobin mass measurement, twenty-eight apnea novices performed three apnea protocols in random order: maximal apneas, O2 table and CO2 table. During apnea, peripheral oxygen saturation (SpO2), heart rate (HR), muscle (mTOI) and cerebral (cTOI) tissue oxygenation index were measured continuously. End-tidal carbon dioxide (EtCO2) was measured before and after apneas. Larger lung volumes, higher resting cTOI and lower resting EtCO2 levels correlated with longer apnea durations. Maximal apneas induced greater decreases in SpO2 (- 16%) and cTOI (- 13%) than O2 (- 8%; - 8%) and CO2 tables (- 6%; - 6%), whereas changes in EtCO2, HR and mTOI did not differ between protocols. These results suggest that, in apnea novices, O2 and CO2 tables did not induce a more profound hypoxia and hypercapnia, but a similar reduction in oxygen consumption than maximal apneas. Therefore, apnea novices should mainly focus on maximal apneas to improve hypoxia and hypercapnia tolerance. The use of specific lung training protocols can help to increase oxygen storage capacity.

Hypothermia induced by bronchoalveolar lavage with perfluorocarbon liquids as a method for the treatment of the alveolar stage of toxic pulmonary edema. Experimental assessment

Introduction. The rapid development of the chemical industry in the Russian Federation is accompanied by an increase in the production and storage of highly toxic substances belonging to the group of pulmonotoxicantsare able to induce lung injury, the most severe form of which is toxic pulmonary edema (TPE). The treatment of TPE includes medication and respiratory therapy, but such a combination turns out to be insufficient, and therefore the development of new methods of treatment of the alveolar stage is an important task of modern medicine. One such approach is the use of therapeutic hypothermia, which can reduce the severity of TPE in general and the alveolar stage in particular. Recently, the use of various options for liquid ventilation of the lungs with perfluorocarbon (PFC) liquids for the induction of therapeutic hypothermia has attracted increasing attention from specialists. This article will present the results of an experimental assessment of the effect of hypothermia induced by BAL with PFC fluids on the course of the alveolar stage of toxic pulmonary edema. The study aims to determine the effect of hypothermia induced by bronchoalveolar lavage with a pre-cooled PFC liquid on the course of the alveolar stage of toxic pulmonary edema. Materials and methods. The authors conducted a study on male Wistar rats aged 4 months, weighing 200–220 g. TPE was modeled by intratracheal administration of 0.1 m HCl solution at a dose of 2 ml/kg. Specialists pre-injected atropine into the animals, then anesthetized, intubated with cannulas, injected a model substance and connected to a ventilator. After that, the animals were randomized by weight into two groups of 6 individuals each. In animals of the experimental and control groups, with a decrease in oxygen saturation (SpO2) below 80%, the researchers performed 2 procedures of bronchoalveolar lavage (BAL) with PFC liquid in a single dose of 2.0 ml / kg, with different temperatures. Perfluorodecalin was used as a PFC liquid. In the experimental group, the temperature of the PFC liquid during BAL was 0.5°C, in the control group — 38.0°C. Specialists recorded heart rate (HR), oxygen saturation, rectal temperature (Trect) and duration of survival. Results. Immediately after instillation of 0.1 M HCl solution, all animals showed a sharp decrease in SpO2 (from 97±1.3 to 64±11.5) and heart rate (HR), (from 269±8.7 to 123±24.5). Recovery of indicators was observed after administration of atropine sulfate. Over the next 25–30 minutes, the following signs appeared and subsequently intensified: a decrease in SpO2 below 80%, an increase in heart rate (HR) to 302±11.4 beats/min, the presence of wet wheezing in the lungs and the release of exudate from the endotracheal catheter. In response to the BAL, all animals showed an increase in SpO2 and a decrease in heart rate. So, in the control, in response to the BAL, SpO2 increased by 8.0±2.5%, and heart rate decreased by 21.0±5.4 beats /min. While in the experimental group there was an increase in SpO2, which was 11.0±3.1%, and a decrease in heart rate by 57.0±10.2 beats/min. At the same time, during the experiment, the researchers observed an increase in temperature in the control group by 0.08±0.02°C, and in the experimental group — its decrease by 0.70±0.07°C. The average survival time of animals in the control and experimental groups was 64.8±2.2 minutes and 91.2±5.9 minutes, respectively. Conclusion. The use of BAL PFC liquids with a low temperature makes it possible to increase the survival time of small laboratory animals in the alveolar stage of TPE due to the development of local and general hypothermia. The development of local hypothermia during BAL of the lungs makes it possible to remove a significant amount of edematous fluid, which, in turn, manifests itself in less pronounced respiratory and systemic hemodynamic disorders. Ethics. Studies involving laboratory animals were conducted in compliance with the following regulations: Helsinki Declaration of 2000 "On humane treatment of animals", Order of the Ministry of Health of the USSR No. 755 dated 08/12/1977 "Rules for carrying out work using experimental animals", Order of the Ministry of Health and Social Development of Russia No. 199n dated 04/01/2016 "On approval of the rules of laboratory practice". The research protocol was approved by the Ethics Committee of the Izmerov Research Institute of Occupational Health (Protocol No. 4 dated May 25, 2022).

6-minute walk test in patients hospitalized with COVID-19

Introduction. The 6 Minute Walk Test (6MWT) plays a key role in assessing functional exercise tolerance and prognosis for a wide range of chronic respiratory and cardiovascular diseases. In acute bronchopulmonary diseases, in particular COVID-19, there is practically no data on the possibilities of using 6MWT.Aim. To compare the results of a 6-minute walk test with clinical and laboratory parameters of patients hospitalized with new coronovirus infection.Materials and methods. The prospective, non-randomized comparative study sequentially enrolled 117 patients hospitalized with a confirmed diagnosis of COVID-19. Upon admission to the hospital, all patients performed 6MWT in accordance with international recommendations.Results. During the 6-minute trial, patients walked an average of 390 m (340.0; 420.0). In 96.6% of patients, there was a marked limitation of physical activity. Desaturation during the 6-minute test was registered in 25 (21.4%) patients. When conducting a correlation analysis, it was found that the result of the test with physical activity (the number of meters traveled) is associated with both initial and final SpO2, the presence of desaturation and the severity of dyspnea according to Borg, with the age of patients, the severity of the course of new coronovirus infection, laboratory signs of the activity of the inflammatory process upon admission. Relationships between the results of 6MWT (the number of meters covered and the % decrease in SpO2) and the duration of hospitalization, the maximum volume of lung damage according to CT data, the maximum severity of laboratory signs of inflammation (CRP, ferritin) during hospitalization, the need for oxygen therapy, the volume of anti-inflammatory therapy (doses of systemic glucocorticoids, pulse therapy with methylprednisolone). Patients with desaturation during exercise had a more severe course of the disease with a large amount of lung tissue damage, as well as higher laboratory indicators of the activity of the inflammatory process. It was also found that patients who desaturate during the exercise test more often required oxygen therapy during hospitalization, more often pulse therapy with methylprednisolone was performed.Conclusion. Patients with COVID-19 develop a decrease in physical performance, which is multifactorial. These include respiratory failure due to lung tissue damage, muscle weakness, nervous system damage (anxiety, depression), and systemic inflammation, which characterizes the severity of the infection and the associated immune response. The results of 6MWT may have a certain prognostic value in terms of the severity of the course of the disease, the severity of systemic inflammation, the need for oxygen therapy, and pulse therapy with glucocorticoids.

Evaluation of novel indices of walking performance taking oxygen desaturation into account during six-minute walk test in cardiovascular disease patients.

In pulmonary disease patients since oxygen desaturation during 6-min walk test (6MWT) affects walk distance (6MWD), some novel indices such as desaturation/distance ratio [DDR, oxygen desaturation area (DAO2)/6MWD] and distance-saturation product [DSP, 6MWD × minimum peripheral oxygen saturation (SpO2)] are evaluated. However, there has been no study examining these indices that consider exercise-induced desaturation (EID) in patients with cardiovascular disease. In 94 cardiovascular disease patients without pulmonary complications, 6MWT and echocardiography were performed at the entry of cardiac rehabilitation. SpO2 was measured during 6MWT using a continuously monitorable pulse oximeter, and DSP and DDR were calculated using minimum SpO2 and DAO2 [sum of (100-SpO2) per second during 6MWT], respectively. EID was defined as SpO2 decrease of ≥ 4% or minimum SpO2 of < 90% during 6MWT. DSP was slightly lower and DDR was markedly higher in patients with EID than in those without. When examining correlations of DSP and DDR with their components, DSP was correlated with 6MWD much closely than minimum SpO2, while DDR was correlated as closely with DAO2 as 6MWD. Furthermore, DAO2, but not minimum SpO2, had a direct correlation with 6MWD. As for associations with cardiac function, DSP was correlated with several cardiac parameters, but DDR was not correlated with any of these parameters. Our findings suggest that oxygen desaturation during 6MWT affects walking distance in cardiovascular disease patients even without pulmonary complications and that DDR is more appropriate than DSP as an index of walking performance that takes EID into consideration, independently of cardiac function.

Comparative analysis of videofluoroscopy and pulse oximetry for aspiration identification in patients with dysphagia after stroke and non-dysphagics

PurposeDysphagia is a prevalent symptom observed in acute stroke. Several bedside screening tests are employed for the early detection of dysphagia. Pulse oximetry emerges as a practical and supportive method to augment the existing techniques utilized during bedside swallowing assessments. Desaturation levels, as measured by pulse oximetry, are acknowledged as indicative of aspiration by certain screening tests. However, the predictive capability of pulse oximetry in determining aspiration remains a subject of controversy. The objective of this study was to compare aspiration and oxygen desaturation levels by time and aspiration severity in dysphagic patients compared to healthy controls. It also aimed to evaluate the accuracy of pulse oximetry by comparing it with VFSS findings in detecting aspiration in both liquid (IDDSI-0) and semi-solid (IDDSI-4) consistencies.Materials and methodsEighty subjects (40 healthy and 40 acute stroke patients) participated. Patients suspected of dysphagia underwent videofluoroscopy as part of the stroke unit’s routine procedure. Baseline SpO2 was measured before VFSS, and stabilized values were recorded. Sequential IDDSI-0 and IDDSI-4 barium tests were conducted with 5 ml boluses. Stabilized SPO2 values were recorded during swallowing and 3-min post-feeding. Patients with non-dysphagia received equal bolus monitoring. Changes in SPO2 during, before, and after swallowing were analyzed for each consistency in both groups.ResultsThe study revealed a statistically significant difference in SPO2 between patients with dysphagia and controls for IDDSI-4 and IDSSI-0. In IDDSI-4, 20% of patients experienced SpO2 decrease compared to 2.5% in control group (p = 0.013). For IDDSI-0, 35% of patients showed SpO2 decrease, while none in the control group did (p = 0.0001). Aspiration rates were 2.5% in IDDSI-4 and 57.5% in IDDSI-0. In IDDSI-0, SpO2 decrease significantly correlated with aspiration (p = 0.0001). In IDDSI-4, 20.5% had SpO2 decrease without aspiration, and showing no significant difference (p = 0.613). Penetration-Aspiration Scale scores had no significant association with SpO2 decrease (p = 0.602). Pulse oximetry in IDDSI-4 had limited sensitivity (0%) and positive predictive value, (0%) while in IDDSI-0, it demonstrated acceptable sensitivity (60.9%) and specificity (100%) with good discrimination capability (AUC = 0.83).ConclusionsA decrease in SPO2 may indicate potential aspiration but is insufficient alone for detection. This study proposes pulse oximetry as a valuable complementary tool in assessing dysphagia but emphasizes that aspiration cannot be reliably predicted based solely on SpO2 decrease.

Clinical significance of echocardiographic signs of right heart dysfunction in patients with chronic heart failure with preserved left ventricular ejection fraction

Aim: To analyze the features of clinical signs, quality of life and psycho-emotional state in patients with heart failure with preserved left ventricular ejection fraction (HFpEF) and non-obstructive atherosclerosis of the coronary arteries, depending on the presence of echocardiographic criteria for dysfunction of the right heart.Material and Methods. Patients underwent an extended protocol of echocardiography with an assessment of the structure and function of the right heart; ultrasound examination of the lungs with the determination of the number of B-lines; a six-minute walk test, a test for the presence of a symptom of bendopnea with the determination of blood oxygen saturation (SpO2) before and during the test. In addition, quality of life was assessed using the Minnesota questionnaire and the SF-36 questionnaire (The Short Form-36); the psycho-emotional state of patients was analyzed according to the HADS (Hospital Anxiety and Depression Scale), the level of adherence to treatment was analyzed according to the Morisky – Green questionnaire. Patients were divided into two groups depending on signs of right heart dysfunction: Tei index more than 0.54, tricuspid annulus systolic excursion (TAPSE) less than 17 mm, tricuspid annulus systolic velocity (RV S’) less than 9,5 cm/sec.Results. Echocardiographic signs of right heart dysfunction in patients with HFpEF was associated with lower quality of life indicators according to the SF-36 questionnaire, in particular, general health status (p = 0.008) and role limitations due to emotional problems (p = 0.03). During the bendopnea test (p = 0.04), the majority of patients with signs of dysfunction of the right heart (66.7%) had a decrease in SpO2, while in the comparison group the proportion of such patients was 36.7% (p = 0.04). The psycho-emotional state according to the HADS scale and adherence to treatment did not differ in both groups (p &gt; 0.05). The frequency of detection of B-lines according to lung ultrasound was also comparable.

Substantiation of the possibility of using bronchoalveolar lavage with perfluorocarbon fluids for the treatment of the alveolar stage of toxic pulmonary edema

Introduction. Toxic pulmonary edema is an acute syndrome characterized by the accumulation of fluid in the extravascular spaces of the lungs, impaired gas exchange, the formation of tissue hypoxia and acidosis, which can occur in acute inhalation poisoning with pulmonary toxicants at work. Existing methods of drug and respiratory therapy are ineffective in the development of alveolar pulmonary edema (end-stage acute respiratory distress syndrome; ARDS). In this regard, the search for new approaches to the treatment of this condition, which is characterized by almost 100 % mortality, is of great practical importance. One of such approaches is the use of perfluorocarbon (PFC) fluids, which, due to their unique physical and chemical properties, are able not only to ensure the evacuation of edematous fluid from the alveoli and respiratory tract, but also to restore gas exchange in the parts of the lungs filled with them. This article will present an experimental evaluation of the use of PFC fluids in a model of the alveolar stage of toxic pulmonary edema.&#x0D; The goal of the study is to determine the effect of bronchoalveolar lavage (BAL) using perfluorocarbons on the indicators of acute respiratory failure and the outcome of the alveolar stage of toxic pulmonary edema.&#x0D; Materials and methods. The study was carried out on male Wistar rats aged 4 months, weighing 180–230 g. Toxic pulmonary edema was initiated by endotracheal injection of 0.1 M HCl solution. Anesthetized rats were intubated with a cannula, then intratracheally injected with 0.1 M HCl solution at a dose of 2 ml/kg and connected to a ventilator. After that, the animals were randomized by weight into groups of 6 individuals each. Animals of the experimental group with a decrease in saturation below 80%, 2–6 procedures of bronchoalveolar lavage (BAL) with PFC-oxygenated liquid in a single dose of 2.0 ml/kg were performed. Heart rate, oxygen saturation, duration of survival, and overall survival by group were recorded.&#x0D; The resalts. In all rats, there was a decrease in oxygen saturation (SpO2) and heart rate (HR) after HCl administration, which was restored to the lower limits of normal within 5 minutes. However, after 25 to 30 minutes, the animals experienced a rapid decrease in SpO2, an increase in heart rate, the appearance of wet wheezing in the lungs, and the discharge of foamy fluid from the catheter. Against this background, there was a rapid death of animals, At the same time, the average duration of survival was 30.6±3.3 min. In turn, in the animals of the experimental group, after each BAL procedure, an increase in saturation was noted, it was possible to evacuate a total of 9.1±0.8 ml/kg of edematous fluid from the lungs. It was also noted that the average duration of survival of rats in the experimental group was 1.69 times and amounted to 51.6±3.8 minutes.&#x0D; Conclusions. The use of BAL with PFC fluids in the alveolar stage of toxic pulmonary edema makes it possible to evacuate a significant amount of edematous fluid from the lower parts of the lungs due to its displacement by a perfluorocarbon with a higher density; to short-term reduce the severity of manifestations of acute respiratory failure after instillation of oxygenated PFC liquid; to increase the duration of survival of animals by ensuring gas exchange in previously uninvolved parts of the lungs.&#x0D; Ethics. The study was conducted in accordance with the ethical principles of the Declaration of Helsinki. The Clinical Study Protocol was reviewed at a meeting of the local Ethics Committee FSBSI IRIOH. Protocol No. 4 of May 25, 2022.

Arterial oxygen desaturation during moderate hypoxia hinders sensorimotor performance.

Moderate hypoxia may impact cognitive and sensorimotor performance prior to self-recognized impairments. Therefore, rapid and objective assessment tools to identify people at risk of impaired function during moderate hypoxia is needed. Test the hypothesis that reductions in arterial oxygen saturation during moderate normobaric hypoxia (FiO2 = 14%) decreases gamified sensorimotor performance as measured by alterations of motor acuity. Following three consecutive days of practice, thirty healthy adults (25 ± 5 y, 10 females) completed three bouts of the tablet-based gamified assessment (Statespace Labs, Inc.) of motor acuity at Baseline and 60 and 90 min after exposure to 13.8 ± 0.2% (hypoxia) and 20.1 ± 0.4% (normoxia) oxygen. The gamified assessment involved moving the tablet to aim and shoot at targets. Both conditions were completed on the same day and were administered in a single-blind, block randomized manner. Performance metrics included shot time and shot variability. Arterial oxyhemoglobin saturation estimated via forehead pulse oximetry (SpO2). Data were analyzed using linear mixed effects models. Compared to normoxia (99±1%), SpO2 was lower (p<0.001) at 60 (89±3%) and 90 (90±2%) min of hypoxia. Shot time was unaffected by decreases in SpO2 (0.012, p = 0.19). Nor was shot time affected by the interaction between SpO2 decrease and baseline performance (0.006, p = 0.46). Shot variability was greater (i.e., less precision, worse performance) with decreases in SpO2 (0.023, p = 0.02) and depended on the interaction between SpO2 decrease and baseline performance (0.029, p< 0.01). Decreases in SpO2 during moderate hypoxic exposure hinders sensorimotor performance via decreased motor acuity, i.e., greater variability (less precision) with no change in speed with differing decreases in SpO2. Thus, personnel who are exposed to moderate hypoxia and have greater decreases in SpO2 exhibit lower motor acuity, i.e., less precise movements even though decision time and movement speed are unaffected.

Methemoglobinemia in a child with congenital epidermolysis bullosa

Introduction . Methemoglobinemia is a rather rare cause of hypoxemia and hypoxia, however, with a severe course of the disease and an increase in the concentration of methemoglobin in the blood of more than 20 %, this can cause the development of multi-organ dysfunction and death.The objective was to descript the case of methemoglobinemia in a child with congenital epidermolysis bullosa with the use of a combined drug containing benzocaine.Materials and methods. Newborn premature baby boy, from the first pregnancy, gestation period 36 weeks, suffering from congenital epidermolysis. Birth weight 2850 g, height 47 cm. Apgar score in the first minute – seven, on the fifth – eight points. As a local treatment, an aerosol for external use «Olazol» was prescribed. At the age of 56 hours from the moment of birth, a sharp deterioration in the child’s condition was noted in the form of a decrease in SpO2 to 72–76 %, pronounced tachycardia, an increase in methemoglobin concentration in the blood (53.7 %).Results. A distinctive feature of this case was the presence of severe methemoglobinemia, which led to severe metabolic acidosis, venous hypoxemia and tissue hypoxia. Timely diagnosis and adequate therapy in the early stages of the pathological process contributed to the complete stabilization of the child’s condition and the normalization of the blood gas composition fifteen hours after the start of therapy.Conclusion. The use of drugs containing benzocaine in the early neonatal period is a risk factor for the development of methemoglobinemia, which requires a dynamic assessment of the level of methemoglobin in the blood in order to prevent tissue hypoxia.

Falls in oxygen saturations accompany electrographic seizures in term neonates: an observational study

BackgroundEffective seizure detection is important however, clinical signs of seizure activity may be subtle in neonates. This study aimed to systematically investigate SpO2 and respiratory pattern changes associated with EEG seizures in term-born neonates.MethodAn observational study in term neonates at risk of seizures admitted to a single tertiary level neonatal intensive care unit. Synchronised high-resolution physiological data (ECG, pulse oximetry, respiration) and EEG/amplitude-integrated EEG (aEEG) monitoring were recorded. Sections of traces with evidence of clear EEG seizure activity were compared with physiological data recorded at the same time.Results22/44 (50%) neonates who had aEEG monitoring were noted to have electrographic seizures. Physiologic download measurements were available for 11 of these neonates. In nine of these, an acute drop in oxygen saturation (SpO2) of at least 5% was noted in at least one seizure. Accompanying apnoeas were noted in three neonates.ConclusionAcute decreases in SpO2 were seen in term neonates associated with seizures and these were not always accompanied by an apnoeic episode. Physiologic download in association with EEG monitoring may assist in improving seizure detection. Unexplained drops in SpO2 could indicate further investigation for possible seizures in at-risk neonates.ImpactA decrease in blood oxygen saturation (SpO2) associated with EEG seizures can occur in term infants with HIE or perinatal stroke.Drops in SpO2 associated with EEG seizures in term infants with HIE or stroke may occur in the absence of apnoeas.Unexplained acute falls in SpO2 in sick neonates may suggest possible seizures.Drops in SpO2 associated with seizures in term infants can occur over less than 3 minutes.Physiological monitoring alongside EEG monitoring could help to improve seizure detection.

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

This study aims to assess the accuracy and stability of smartwatches in predicting acute mountain sickness (AMS). 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. 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 [β=-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%. 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.

Efficacy of pulse oximetry for early diagnosis of pulmonary embolism after total knee arthroplasty

IntroductionEarly diagnosis and aggressive treatment of pulmonary embolism (PE) are crucial for preventing severe complications after total knee arthroplasty (TKA). This study aimed to examine the efficacy of measuring oxygen saturation (SpO2) using a pulse oximeter for early diagnosis of PE after total knee arthroplasty (TKA).Materials and methodsWe consecutively examined 1645 patients who underwent TKA between January 2015 and November 2019. Postoperative SpO2 was measured with a pulse oximeter, which was stopped if SpO2 was maintained at ≥ 95% until postoperative day 2 (POD2). To diagnose PE, computed tomographic pulmonary angiography (CTPA) was performed for specific indications, including persistently low SpO2 < 95% (group 1), sudden decrease in SpO2 (group 2), and decrease in SpO2 after POD3 with presenting symptoms (group 3). Also, we divided the patients into unilateral, simultaneous and sequential TKA groups and compared the results with specific statistical techniques.ResultsOf the 1645 patients who underwent TKA, there were 20 patients with PE (1.2%), and symptomatic PE was observed in only 4 patients (0.24%). CTPA was performed in 58 (3.5%) patients, of whom 20 were diagnosed with PE. In groups 1 (n = 34), 2 (n = 21), and 3 (n = 3), CTPA was performed 2.4, 2.6, and 8.3 days after TKA, respectively, and 12, 8, and 0 patients were diagnosed with PE, respectively. Of the 782, 416, and 447 unilateral, simultaneous, and sequential (done in same admission with interval 1 or 2 weeks) patients with TKA, 38, 18, and 2 received CTPA, and 13, 6, and 1 were diagnosed with PE, respectively. All patients diagnosed with PE have persistently low SpO2 < 95% (group 1), or sudden decrease in SpO2 (group 2) until POD2. Of the patients diagnosed with PE, SpO2 decreased without the presentation of symptoms in 16 patients (11 and 5 from groups 1 and 2, respectively) and with the presentation of symptoms, such as mild dyspnea and chest discomfort, in 4 patients (1 and 3 from groups 1 and 2, respectively).ConclusionsMeasuring SpO2 using a pulse oximeter until POD2 was an effective method for early diagnosis of PE after TKA. No case of morbidity or mortality was observed after early diagnosis with early stage CTPA and management of PE. We recommend measuring SpO2 with a pulse oximeter for early diagnosing of PE in TKA.

Inter-individual variability in peripheral oxygen saturation and repeated sprint performance in hypoxia: an observational study of highly-trained subjects.

Individual variations in peripheral oxygen saturation (SpO2) during repeated sprints in hypoxia and their impact on exercise performance remain unclear despite fixed external hypoxic stimuli (inspired oxygen fraction: FiO2). This study examined SpO2 individual variations during repeated sprints in hypoxia and their impact on exercise performance. Thirteen highly-trained sprint runners performed 10 × 10-s cycle sprints with 30-s passive recoveries in normobaric hypoxia (FiO2: 0.150). Mean power output (MPO), post-sprint SpO2, and heart rate for each sprint were assessed. Sprint decrement score (Sdec), evaluating fatigue development, was calculated using MPO variables. Participants were categorized into a high saturation group (HiSat, n = 7) or a low saturation group (LowSat, n = 6) based on their mean post-sprint SpO2 (measured 10-15 s after each sprint). Individual mean post-sprint SpO2 ranged from 91.6% to 82.2%. Mean post-sprint SpO2 was significantly higher (P < 0.001, d = 1.54) in HiSat (89.1% ± 1.5%) than LowSat (84.7% ± 1.6%). A significantly larger decrease in Sdec (P = 0.008, d = 1.68) occurred in LowSat (-22.3% ± 2.3%) compared to HiSat (-17.9% ± 2.5%). MPO (P = 0.342 d = 0.55) and heart rate (P = 0.225 d = 0.67) did not differ between groups. There was a significant correlation (r = 0.61; P = 0.028) between SpO2 and Sdec. In highly-trained sprint runners, individual responses to hypoxia varied widely and significantly affected repeated sprint ability, with greater decreases in SpO2 associated with larger performance alterations (i.e., larger decrease in Sdec).