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Biology Apr 2022The use of normobaric hypoxia can bring benefits to sports performance because it improves haematological parameters and/or physical activity tests. Our objective was to... (Review)
Review
BACKGROUND
The use of normobaric hypoxia can bring benefits to sports performance because it improves haematological parameters and/or physical activity tests. Our objective was to conduct a systematic review so as to analyse the methods used in hypoxia and to detect its effects on middle- and/or long-distance runners.
METHODS
Research was conducted using five electronic databases (PubMed, SportDiscus, Cochrane Library, Scopus and PEDro) until December 2021. The methodological quality of the included studies was assessed using the PEDro scale.
RESULTS
Having analysed 158 studies, 12 were chosen for the qualitative and quantitative synthesis. A significant improvement on time until exhaustion was detected, and oxygen saturation decreased after the intervention. There were no significant changes in the 3000-metre time trial or in the haematocrit percentage. The changes in percentage of reticulocytes, heart rate, maximal heart rate, lactate concentration and erythropoietin were heterogeneous between the different research studies.
CONCLUSION
short exposure (less than 3 h to normobaric hypoxia significantly increases the time to exhaustion). However, longer exposure times are necessary to increase haemoglobin. Altitude and exposure time are highly heterogeneous in the included studies.
PubMed: 35625417
DOI: 10.3390/biology11050689 -
Early Human Development Sep 2023To investigate whether immediate response to inhaled nitric oxide (iNO) therapy is associated with reduced mortality in preterm infants with hypoxemic respiratory... (Meta-Analysis)
Meta-Analysis
Association between immediate oxygenation response and survival in preterm infants receiving rescue inhaled nitric oxide therapy for hypoxemia from pulmonary hypertension: A systematic review and meta-analysis.
PURPOSE
To investigate whether immediate response to inhaled nitric oxide (iNO) therapy is associated with reduced mortality in preterm infants with hypoxemic respiratory failure (HRF) and pulmonary hypertension (PH).
METHODS
A systematic review and meta-analysis of observational studies was conducted to examine the association between immediate response (improved oxygenation ≤6 h) compared to non-response, and all-cause mortality among preterm infants <34 weeks gestational age without congenital anomalies or genetic disorders who received iNO treatment. Adjusted and unadjusted odds ratio, were pooled using a random effects meta-analysis Hartung-Knapp-Sidik-Jonkman approach. Subgroup analyses were planned for infants with preterm premature rupture of membranes (PPROM) and those treated within 72 h after birth.
RESULTS
The primary analysis included 5 eligible studies, a total of 400 infants (196 responders; 204 non-responders). The studies were rated as low to moderate risk of bias based on the Quality in Prognostic Studies tool. Immediate iNO responsiveness was associated with reduced odds of mortality [odds ratio (OR) 0.22, 95 % confidence interval (95 % CI) (0.10-0.49)]. Although there was insufficient data for a subgroup analysis of infants with PPROM, infants treated with iNO within 72 h demonstrated consistent findings of reduced mortality [OR 0.21 95 % CI (0.13-0.36)]. Based on the GRADE approach, considering the risk of bias of included studies, the overall strength of evidence was rated as moderate.
CONCLUSION
There is evidence to suggest that immediate improvement in oxygenation following iNO therapy is associated with reduced odds of mortality before discharge in preterm infants with HRF and clinically suspected or confirmed PH.
Topics: Infant; Female; Infant, Newborn; Humans; Infant, Premature; Nitric Oxide; Hypertension, Pulmonary; Hypoxia; Respiratory Insufficiency; Administration, Inhalation
PubMed: 37542786
DOI: 10.1016/j.earlhumdev.2023.105841 -
Diving and Hyperbaric Medicine Sep 2023Hypoxia can cause central nervous system dysfunction and injury. Hypoxia is a particular risk during rebreather diving. Given its subtle symptom profile and its... (Review)
Review
INTRODUCTION
Hypoxia can cause central nervous system dysfunction and injury. Hypoxia is a particular risk during rebreather diving. Given its subtle symptom profile and its catastrophic consequences there is a need for reliable hypoxia monitoring. Electroencephalography (EEG) is being investigated as a real time monitor for multiple diving problems related to inspired gas, including hypoxia.
METHODS
A systematic literature search identified articles investigating the relationship between EEG changes and acute cerebral hypoxia in healthy adults. Quality of clinical evidence was assessed using the Newcastle-Ottawa scale.
RESULTS
Eighty-one studies were included for analysis. Only one study investigated divers. Twelve studies described quantitative EEG spectral power differences. Moderate hypoxia tended to result in increased alpha activity. With severe hypoxia, alpha activity decreased whilst delta and theta activities increased. However, since studies that utilised cognitive testing during the hypoxic exposure more frequently reported opposite results it appears cognitive processing might mask hypoxic EEG changes. Other analysis techniques (evoked potentials and electrical equivalents of dipole signals), demonstrated sustained regulation of autonomic responses despite worsening hypoxia. Other studies utilised quantitative EEG analysis techniques, (Bispectral index [BISTM], approximate entropy and Lempel-Ziv complexity). No change was reported in BISTM value, whilst an increase in approximate entropy and Lempel-Ziv complexity occurred with worsening hypoxia.
CONCLUSIONS
Electroencephalographic frequency patterns change in response to acute cerebral hypoxia. There is paucity of literature on the relationship between quantitative EEG analysis techniques and cerebral hypoxia. Because of the conflicting results in EEG power frequency analysis, future research needs to quantitatively define a hypoxia-EEG response curve, and how it is altered by concurrent cognitive task loading.
Topics: Adult; Humans; Diving; Hypoxia; Electroencephalography; Central Nervous System; Hypoxia, Brain
PubMed: 37718302
DOI: 10.28920/dhm53.3.268-280 -
Intubation using apnoeic oxygenation to prevent desaturation: A systematic review and meta-analysis.Journal of Critical Care Oct 2017To determine whether or not apnoeic oxygenation reduces the incidence of hypoxaemia during endotracheal intubation. (Meta-Analysis)
Meta-Analysis Review
PURPOSE
To determine whether or not apnoeic oxygenation reduces the incidence of hypoxaemia during endotracheal intubation.
MATERIALS AND METHODS
A systematic search of six databases for all relevant studies until November 2016 was performed. All study designs using apnoeic oxygenation during intubation were eligible for inclusion. All studies were assessed for level of evidence and risk of bias. A meta-analysis was performed on all data using Revman 5.3.
RESULTS
Seventeen studies including 2422 patients were retrieved. Overall there was a significant reduction in the incidence of desaturation (RR=0.65; p<0.00001), critical desaturation (RR=0.61, p=0.002) and safe apnoea time (WMD=1.73min, p<0.00001). There was no significant difference in mortality (RR=0.77, p=0.08).
CONCLUSIONS
In patients whom are being intubated for any indication other than respiratory failure, apnoeic oxygenation at any flow rate 15L or greater is likely to reduce their incidence of desaturation (<90%) and critical desaturation (<80%). However, further high quality RCTs are required given the high degree of heterogeneity in many of the outcomes and subgroup analyses.
Topics: Apnea; Humans; Hypoxia; Intensive Care Units; Intubation, Intratracheal; Oxygen Inhalation Therapy; Practice Guidelines as Topic; Respiration, Artificial; Respiratory Insufficiency
PubMed: 28477509
DOI: 10.1016/j.jcrc.2017.04.043 -
High Altitude Medicine & Biology Dec 2023Guo, Hai, Linjie Cheng, Dilihumaier Duolikun, and Qiaoling Yao. Aerobic exercise training under normobaric hypoxic conditions to improve glucose and lipid metabolism in... (Meta-Analysis)
Meta-Analysis
Aerobic Exercise Training Under Normobaric Hypoxic Conditions to Improve Glucose and Lipid Metabolism in Overweight and Obese Individuals: A Systematic Review and Meta-Analysis.
Guo, Hai, Linjie Cheng, Dilihumaier Duolikun, and Qiaoling Yao. Aerobic exercise training under normobaric hypoxic conditions to improve glucose and lipid metabolism in overweight and obese individuals: a systematic review and meta-analysis. 24:312-320, 2023. Obesity is a critical public health issue around the world, reaching epidemic proportions in some countries. However, only a few studies have examined the effects of hypoxic training on metabolic parameters in an obese population. This systematic review and meta-analysis aimed to determine the effects of aerobic exercise training under normobaric hypoxic conditions versus normoxic training in improving glucose and lipid metabolism in obese individuals. A systematic search of PubMed, EMBASE, Web of Science, and Wan Fang databases (up to August 2021) was performed to identify randomized controlled trials (RCTs) of overweight or obese human subjects eligible for inclusion. Main study endpoints were changes in body mass index (BMI), waist/hip (W/H) ratio, leptin, blood glucose and insulin levels, as well as blood lipids between hypoxic and normoxic conditioning. Fourteen RCTs with a total of 413 subjects qualified for inclusion. Pooled analyses revealed that BMI ( = 0.38), W/H ratio ( = 0), blood glucose ( = 0.01), and triglyceride ( = -2.27) were not significantly different between aerobic exercise training under hypoxic and normoxic conditions. However, significant differences were found in heart rate at rest ( = -4.50) between aerobic exercise training under hypoxic versus normoxic conditions. In conclusion, no significant benefits were noted in aerobic exercise training under hypoxic conditions over normoxic conditions in overweight or obese individuals. However, the maximum training heart rate mm was significantly higher under hypoxic conditions than under normoxic conditions. Future studies with larger samples controlling for exercise-related parameters, and addressing the potential modifying effects of level of hypoxia, sex, or age on the role of hypoxic exercise training are warranted. PROSPERO registration number: CRD42020221680.
Topics: Humans; Overweight; Glucose; Blood Glucose; Obesity; Exercise; Hypoxia; Lipid Metabolism
PubMed: 38127802
DOI: 10.1089/ham.2022.0099 -
The Lancet. Global Health Mar 2022Pneumonia accounts for around 15% of all deaths of children younger than 5 years globally. Most happen in resource-constrained settings and are potentially preventable.... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Pneumonia accounts for around 15% of all deaths of children younger than 5 years globally. Most happen in resource-constrained settings and are potentially preventable. Hypoxaemia is one of the strongest predictors of these deaths. We present an updated estimate of hypoxaemia prevalence among children with pneumonia in low-income and middle-income countries.
METHODS
We conducted a systematic review using the following key concepts "children under five years of age" AND "pneumonia" AND "hypoxaemia" AND "low- and middle-income countries" by searching in 11 bibliographic databases and citation indices. We included all articles published between Nov 1, 2008, and Oct 8, 2021, based on observational studies and control arms of randomised and non-randomised controlled trials. We excluded protocol papers, articles reporting hypoxaemia prevalence based on less than 100 pneumonia cases, and articles published before 2008 from the review. Quality appraisal was done with the Joanna Briggs Institute tools. We reported pooled prevalence of hypoxaemia (SpO <90%) by classification of clinical severity and by clinical settings by use of the random-effects meta-analysis models. We combined our estimate of the pooled prevalence of pneumonia with a previously published estimate of the number of children admitted to hospital due to pneumonia annually to calculate the total annual number of children admitted to hospital with hypoxaemic pneumonia.
FINDINGS
We identified 2825 unique records from the databases, of which 57 studies met the eligibility criteria: 26 from Africa, 23 from Asia, five from South America, and four from multiple continents. The prevalence of hypoxaemia was 31% (95% CI 26-36; 101 775 children) among all children with WHO-classified pneumonia, 41% (33-49; 30 483 children) among those with very severe or severe pneumonia, and 8% (3-16; 2395 children) among those with non-severe pneumonia. The prevalence was much higher in studies conducted in emergency and inpatient settings than in studies conducted in outpatient settings. In 2019, we estimated that over 7 million children (95% CI 5-8 million) were admitted to hospital with hypoxaemic pneumonia. The studies included in this systematic review had high τ (ie, 0·17), indicating a high level of heterogeneity between studies, and a high I value (ie, 99·6%), indicating that the heterogeneity was not due to chance. This study is registered with PROSPERO, CRD42019126207.
INTERPRETATION
The high prevalence of hypoxaemia among children with severe pneumonia, particularly among children who have been admitted to hospital, emphasises the importance of overall oxygen security within the health systems of low-income and middle-income countries, particularly in the context of the COVID-19 pandemic. Even among children with non-severe pneumonia that is managed in outpatient and community settings, the high prevalence emphasises the importance of rapid identification of hypoxaemia at the first point of contact and referral for appropriate oxygen therapy.
FUNDING
UK National Institute for Health Research (Global Health Research Unit on Respiratory Health [RESPIRE]; 16/136/109).
Topics: Child, Preschool; Comorbidity; Developing Countries; Humans; Hypoxia; Infant; Internationality; Pneumonia; Poverty; Prevalence
PubMed: 35180418
DOI: 10.1016/S2214-109X(21)00586-6 -
Cellular Physiology and Biochemistry :... 2018Patients with myocardial infarction and hypoxemia require supplemental oxygen. However, the current therapeutic paradigm is contradicted by several recent studies in... (Meta-Analysis)
Meta-Analysis
BACKGROUND/AIMS
Patients with myocardial infarction and hypoxemia require supplemental oxygen. However, the current therapeutic paradigm is contradicted by several recent studies in which the post-infarcted heart appears to benefit from systemic hypoxia. With this systematic review and meta-analysis, we aimed to discover whether systemic hypoxia is beneficial or detrimental to the infarcted myocardium.
METHODS
We conducted an electronic search of the PubMed, EMBASE, and Web of Science databases and extracted the outcomes of cardiac function, geometry, and hemodynamics. A random-effect model was applied when the I2 value of greater than 50%. The sensitivity analysis was performed by omitting one study at a time, and publication bias was assessed using Egger's test. In addition, the quality of studies was evaluated using the risk of bias tool devised by the Systematic Review Centre for Laboratory Animal Experimentation.
RESULTS
Six reports comprising 14 experiments were ultimately screened from among 10,323 initially identified preclinical studies. Few studies reported the method of randomization and none described allocation concealment, random outcome assessment or blinding. Overall, chronic hypoxia was found to have a beneficial effect on the ejection fraction (standard mean difference [SMD] = 5.39; 95% confidence interval [CI], 3.83 to 6.95; P < 0.001) of the infarcted heart, whereas acute hypoxia significantly improved hemodynamics, as indicated by an increase in the maximal rate of rise of left ventricular pressure (SMD = 1.27; 95% CI, 0.27 to 2.28; P = 0.013) and cardiac output (SMD = 1.26; 95% CI, 0.34 to 2.18; P = 0.007) and a decrease in total systematic vascular resistance (SMD = -0.89; 95% CI, -1.24 to -0.53; P < 0.001). Furthermore, a reduced oxygen content increased the stroke volume (P = 0.010). However, hypoxia reduced the end-systolic (SMD = -2.67; 95% CI, -4.09 to -1.26; P < 0.001) and end-diastolic (SMD = -3.61; 95% CI, -4.65 to -2.57; P < 0.001) left ventricular diameters and increased the total pulmonary resistance (SMD = 0.76; 95% CI, 0.20 to 1.33; P = 0.008), pulmonary arterial mean pressure (SMD = 2.02; 95% CI, 0.23 to 3.81; P = 0.027), and left atrial pressure (SMD = 1.20; 95% CI, 0.57 to 1.82; P < 0.001).
CONCLUSION
Hypoxia significantly improved heart function after infarction, with particular beneficial effects on systolic function and hemodynamics. However, it had slightly adverse effects on pulmonary circulation and left ventricular geometry. A lower inspired oxygen concentration may improve cardiac function, although further research is needed to determine the optimum level of hypoxia. Finally, more studies of hypoxia and myocardial infarction in larger species are required before these findings can be incorporated into therapeutic guidelines.
Topics: Animals; Blood Gas Analysis; Databases, Factual; Heart Ventricles; Hemodynamics; Hypoxia; Myocardial Infarction; Myocardium
PubMed: 30466079
DOI: 10.1159/000495397 -
Seizure Dec 2018To estimate the incidence of ictal hypoxemia (IH) and to identify clinical and study-related factors modulating the estimate. (Meta-Analysis)
Meta-Analysis
PURPOSE
To estimate the incidence of ictal hypoxemia (IH) and to identify clinical and study-related factors modulating the estimate.
METHODS
We searched articles recording concurrent peri-ictal and ictal EEG and Sp02 in adults and children with epilepsy. Studies reporting the total number of seizures recorded and the number of seizures with IH were included in a random-effects meta-analysis. A random-effects meta-regression was used to identify variables affecting study heterogeneity.
RESULTS
Twenty-one studies, including 917 participants and 1840 with SpO2 data available were included. The meta-analysis showed a pooled incidence of IH of 35/100 seizures (95% CI 27-44). Sp02 desaturation threshold was associated with the incidence of IH, with less severe desaturations resulting in higher IH frequencies. The incidence of IH was 41/100 seizures (95% CI 29-54) for adults and 47/100 seizures (95% CI 15-78) for tonic-clonic seizures. The meta-regression showed that SpO2 desaturation severity was the sole variable significantly correlated with the incidence of ictal hypoxemia (p = 0.00).
CONCLUSION
In a population with refractory epilepsy IH is a frequent phenomenon, especially in adults and in patients presenting with tonic-clonic seizures. The severity of IH appeared independent from the age group and from seizure type and is probably the major clinical concern for its correlation with potentially life-threatening cardiorespiratory alterations and sudden unexpected death in epilepsy (SUDEP).
Topics: Epilepsy; Humans; Hypoxia; Incidence; Seizures
PubMed: 30391664
DOI: 10.1016/j.seizure.2018.10.011 -
Respiratory Investigation Jul 2023Supplemental oxygen is widely used for dyspnea relief; however, its efficacy is yet to be verified. This study aimed to determine the efficacy of supplemental oxygen for... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Supplemental oxygen is widely used for dyspnea relief; however, its efficacy is yet to be verified. This study aimed to determine the efficacy of supplemental oxygen for dyspnea relief in patients with advanced progressive illness.
METHODS
In this systematic review, several databases, including MEDLINE and EMBASE, were searched to identify eligible randomized controlled trials (RCTs) on the topic published up to September 23, 2019. The search criteria included RCTs investigating patients with advanced progressive illness (advanced cancer, chronic obstructive pulmonary disease, and chronic heart failure). The study protocol was registered with PROSPERO (No. CRD42020161838). Separate analyses were pre-planned regarding the presence or absence of resting hypoxemia.
RESULTS
RCTs investigating supplemental oxygen for dyspnea relief in participants with and without resting hypoxemia (39 and five, respectively) were included in the study. Heterogeneity of supplemental oxygen for dyspnea in RCTs, including participants without resting hypoxemia was evident; hence, post-hoc analyses in four subgroups (supplemental oxygen during exercise or daily activities, short-burst oxygen, continuous supplemental oxygen, and supplemental oxygen during rehabilitation intervention) were conducted. In the meta-analysis, supplemental oxygen during exercise was found to improve dyspnea in patients without resting hypoxemia compared with that in the control (standardized mean difference = -0.57, 95% confidence interval = -0.77 to -0.38). However, supplemental oxygen for the other subgroups failed to improve patients' dyspnea.
CONCLUSION
The results of this systematic review do not support supplemental oxygen therapy for dyspnea relief in patients with advanced progressive illness, except during exercise.
Topics: Humans; Oxygen Inhalation Therapy; Pulmonary Disease, Chronic Obstructive; Oxygen; Dyspnea; Hypoxia
PubMed: 37105126
DOI: 10.1016/j.resinv.2023.03.005 -
Critical Reviews in Oncology/hematology Mar 2021This review aimed to systematize and quantify the existing evidence about the effect of tumor vascularization on its growth, in preclinical studies. (Meta-Analysis)
Meta-Analysis Review
PURPOSE
This review aimed to systematize and quantify the existing evidence about the effect of tumor vascularization on its growth, in preclinical studies.
METHODOLOGY
A computerized research on databases PubMed, Scopus and EBSCO was performed to identify studies that evaluate both the vascularization parameters and the development of the tumors in animal models and the mean differences were calculated through a random effects model.
RESULTS
Thirteen studies met the inclusion criteria and were included in the systematic review, of which, 6 studies were included in the meta-analysis. Besides tumor vascular density that all studies evaluated, 3 studies analysed the tumor perfusion, 2 studies the tumor hypoxia and 3 studies assessed the grade of vessel maturation. Most of the studies (11) related decreased tumor vascularization and a concomitant inhibition of tumor growth or metastasis development. Quantitatively, the decrease in tumor vascularization contributed to a significant decrease in the tumor growing rate of 5.23 (-9.20, -1.26).
CONCLUSION
A reduced level of tumor vascularization seems to be able to inhibit tumor growth and progression.
Topics: Animals; Humans; Neoplasms; Neovascularization, Pathologic; Tumor Hypoxia
PubMed: 33508446
DOI: 10.1016/j.critrevonc.2021.103245