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American Journal of Obstetrics and... Jun 2023The onset of regular, strong, and progressive uterine contractions may result in both mechanical (compression of the fetal head and/or umbilical cord) and hypoxic... (Review)
Review
The onset of regular, strong, and progressive uterine contractions may result in both mechanical (compression of the fetal head and/or umbilical cord) and hypoxic (repetitive and sustained compression of the umbilical cord or reduction in uteroplacental oxygenation) stresses to a human fetus. Most fetuses are able to mount effective compensatory responses to avoid hypoxic-ischemic encephalopathy and perinatal death secondary to the onset of anaerobic metabolism within the myocardium, culminating in myocardial lactic acidosis. In addition, the presence of fetal hemoglobin, which has a higher affinity for oxygen even at low partial pressures of oxygen than the adult hemoglobin, especially increased amounts of fetal hemoglobin (ie, 180-220 g/L in fetuses vs 110-140 g/L in adults), helps the fetus to withstand hypoxic stresses during labor. Different national and international guidelines are currently being used for intrapartum fetal heart rate interpretation. These traditional classification systems for fetal heart rate interpretation during labor are based on grouping certain features of fetal heart rate (ie, baseline fetal heart rate, baseline variability, accelerations, and decelerations) into different categories (eg, category I, II, and III tracings, "normal, suspicious, and pathologic" or "normal, intermediary, and abnormal"). These guidelines differ from each other because of the features included within different categories and because of their arbitrary time limits stipulated for each feature to warrant an obstetrical intervention. This approach fails to individualize care because the "ranges of normality" for stipulated parameters apply to the population of human fetuses and not to the individual fetus in question. Moreover, different fetuses have different reserves and compensatory responses and different intrauterine environments (presence of meconium staining of amniotic fluid, intrauterine inflammation, and the nature of uterine activity). Pathophysiological interpretation of fetal heart rate tracing is based on the application of the knowledge of fetal responses to intrapartum mechanical and/or hypoxic stress in clinical practice. Both experimental animal studies and observational human studies suggest that, just like adults undertaking a treadmill exercise, human fetuses show predictable compensatory responses to a progressively evolving intrapartum hypoxic stress. These responses include the onset of decelerations to reduce myocardial workload and preserve aerobic metabolism, loss of accelerations to abolish nonessential somatic body movements, and catecholamine-mediated increases in the baseline fetal heart rate and effective redistribution and centralization to protect the fetal central organs (ie, the heart, brain, and adrenal glands), which are essential for intrauterine survival. Moreover, it is essential to incorporate the clinical context (progress of labor, fetal size and reserves, presence of meconium staining of amniotic fluid and intrauterine inflammation, and fetal anemia) and understand the features suggestive of fetal compromise in nonhypoxic pathways (eg, chorioamnionitis and fetomaternal hemorrhage). It is important to appreciate that the timely recognition of the speed of onset of intrapartum hypoxia (ie, acute, subacute, and gradually evolving) and preexisting uteroplacental insufficiency (ie, chronic hypoxia) on fetal heart rate tracing is crucial to improve perinatal outcomes.
Topics: Adult; Animals; Female; Humans; Pregnancy; Cardiotocography; Fetal Hemoglobin; Heart Rate, Fetal; Hypoxia; Infant, Newborn, Diseases; Inflammation; Oxygen
PubMed: 37270259
DOI: 10.1016/j.ajog.2022.05.023 -
Journal of Clinical Nursing Apr 2016The research was conducted to evaluate oxygen saturation values measured in healthy individuals in different body positions.
AIMS AND OBJECTIVES
The research was conducted to evaluate oxygen saturation values measured in healthy individuals in different body positions.
BACKGROUND
Changes in position affect ventilation-perfusion rates, oxygen transport and lung volume in normal lungs. There have been few studies and not enough information about which positioning of a healthy individual can increase oxygenation.
DESIGN
A descriptive study.
METHODS
A sample of 103 healthy individuals with no chronic disease, anaemia or pain was included in the research. Individuals were positioned in five different positions: sitting upright, supine position, prone position, lying on the left side and lying on the right side. Oxygen saturation and pulse rates were then measured and recorded after the individuals held each position for ten minutes.
RESULTS
It was found that the average oxygen saturation value when measured while sitting in an upright position in a chair was significantly higher than that measured when the individual was lying on the right or left side of the body. Oxygen saturation values measured in the five different body positions were significantly higher in women, in individuals below the age of 35, in those with Body Mass Indexes of below 25 kg/m(2), and in nonsmokers.
CONCLUSION
All of the oxygen saturation values measured in the five different body positions were in the normal range. Although oxygen saturation values were within the normal range in the five different body positions, post hoc analysis showed that the best oxygenation was in the 'sitting upright' position while the lowest oxygenation was in the supine position.
RELEVANCE TO CLINICAL PRACTICE
Based on the results of this research, it can be concluded that the differences among oxygen saturation values according to the different body positions were statistically significant.
Topics: Adult; Body Mass Index; Female; Heart Rate; Humans; Male; Middle Aged; Oximetry; Oxygen; Patient Positioning; Posture; Reference Values; Respiration; Respiratory Rate
PubMed: 26879626
DOI: 10.1111/jocn.13189 -
Journal of Applied Physiology... Apr 2017The maximum rate of O uptake (i.e., V̇o), as measured during large muscle mass exercise such as cycling or running, is widely considered to be the gold standard... (Review)
Review
The maximum rate of O uptake (i.e., V̇o), as measured during large muscle mass exercise such as cycling or running, is widely considered to be the gold standard measurement of integrated cardiopulmonary-muscle oxidative function. The development of rapid-response gas analyzers, enabling measurement of breath-by-breath pulmonary gas exchange, has facilitated replacement of the discontinuous progressive maximal exercise test (that produced an unambiguous V̇o-work rate plateau definitive for V̇o) with the rapidly incremented or ramp testing protocol. Although this is more suitable for clinical and experimental investigations and enables measurement of the gas exchange threshold, exercise efficiency, and V̇o kinetics, a V̇o-work rate plateau is not an obligatory outcome. This shortcoming has led to investigators resorting to so-called secondary criteria such as respiratory exchange ratio, maximal heart rate, and/or maximal blood lactate concentration, the acceptable values of which may be selected arbitrarily and result in grossly inaccurate V̇o estimation. Whereas this may not be an overriding concern in young, healthy subjects with experience of performing exercise to volitional exhaustion, exercise test naïve subjects, patient populations, and less motivated subjects may stop exercising before their V̇o is reached. When V̇o is a or the criterion outcome of the investigation, this represents a major experimental design issue. This CORP presents the rationale for incorporation of a second, constant work rate test performed at ~110% of the work rate achieved on the initial ramp test to resolve the classic V̇o-work rate plateau that is the unambiguous validation of V̇o The broad utility of this procedure has been established for children, adults of varying fitness, obese individuals, and patient populations.
Topics: Exercise; Exercise Test; Heart Rate; Humans; Kinetics; Muscle, Skeletal; Oxygen; Oxygen Consumption; Pulmonary Gas Exchange
PubMed: 28153947
DOI: 10.1152/japplphysiol.01063.2016 -
Nigerian Journal of Clinical Practice Nov 2023The physical examination is a key part of a continuum that extends from the history of the present illness to the therapeutic outcome. An understanding of the... (Review)
Review
The physical examination is a key part of a continuum that extends from the history of the present illness to the therapeutic outcome. An understanding of the pathophysiological mechanism behind a physical sign is essential for arriving at the correct diagnosis. Early detection of deteriorating physical/vital signs and their appropriate interpretation is thus the key to achieve correct and timely management. By definition, vital signs are "the signs of life that may be monitored or measured, namely pulse rate, respiratory rate, body temperature, and blood pressure." Vital signs are the simplest, cheapest and probably the most inexpensive information gathered bedside in outpatient or hospitalized patients. The pulse oximeter was introduced in the 1980s. It is an accurate and non-invasive method for the measurement of arterial hemoglobin oxygen saturation (SaO2). Pulse oximetry-based arterial oxygen saturation can be effectively used bedside in in-hospital and ambulatory patients with diagnosed or suspected lung disease. The present pandemic of COVID-19 should be considered as a wake-up call. Articles related to arterial oxygen saturation and its importance as a vital sign in patient care were searched online especially in PubMed. Available studies were studied in full length and data was extracted. Discussion: A. Clinical Utility of Oxygen Saturation Monitoring: There are many studies reporting the clinical applicability and usefulness of pulse oximetry in the early detection of hypoxemic events during intraoperative and postoperative periods. B. Role of clinical expertise accompanied by knowledge of physiology: A diagnostic sign is useful only if it is interpreted accurately and applied appropriately while evaluating a patient. The World Health Organisation also appreciates these facts and published "The WHO Pulse Oximetry Training Manual." Understanding the physiology behind and overcoming limitations of the diagnostic sign by clinical expertise is important. While using pulse oximetry, a clinician needs to keep in mind the sigmoidal nature of the oxygen-Hb dissociation curve. Considering these benefits of SaO2 measurement, there have been several references in the past to consider oxygen saturation as the fifth vital sign. In the present pandemic oxygen saturation i.e., SpO2 (arterial oxygen saturation) measured by pulse oxymeter, has been the single most important warning and prognostic sign be it for households, offices, street vendors, hospitals or governments. Measurement of trends of SaO2 added with respiratory rate will provide clinicians with a holistic overview of respiratory functions and multidimensional conditions associated with hypoxemia.
Topics: Humans; Heart Rate; Hypoxia; Oximetry; Oxygen; Oxygen Saturation
PubMed: 38044759
DOI: 10.4103/njcp.njcp_2026_21 -
International Journal of Radiation... Mar 2019It has been known for over 100 years that tumor hypoxia, a near-universal characteristic of solid tumors, decreases the curative effectiveness of radiation therapy....
PURPOSE
It has been known for over 100 years that tumor hypoxia, a near-universal characteristic of solid tumors, decreases the curative effectiveness of radiation therapy. However, to date, there are no reports that demonstrate an improvement in radiation effectiveness in a mammalian tumor on the basis of tumor hypoxia localization and local hypoxia treatment.
METHODS AND MATERIALS
For radiation targeting of hypoxic subregions in mouse fibrosarcoma, we used oxygen images obtained using pulse electron paramagnetic resonance pO imaging combined with 3D-printed radiation blocks. This achieved conformal radiation delivery to all hypoxic areas in FSa fibrosarcomas in mice.
RESULTS
We demonstrate that treatment delivering a radiation boost to hypoxic volumes has a significant (P = .04) doubling of tumor control relative to boosts to well-oxygenated volumes. Additional dose to well-oxygenated tumor regions minimally increases tumor control beyond the 15% control dose to the entire tumor. If we can identify portions of the tumor that are more resistant to radiation, it might be possible to reduce the dose to more sensitive tumor volumes without significant compromise in tumor control.
CONCLUSIONS
This work demonstrates in a single, intact mammalian tumor type that tumor hypoxia is a local tumor phenomenon whose treatment can be enhanced by local radiation. Despite enormous clinical effort to overcome hypoxic radiation resistance, to our knowledge this is the first such demonstration, even in preclinical models, of targeting additional radiation to hypoxic tumor to improve the therapeutic ratio.
Topics: Animals; Cell Line, Tumor; Electron Spin Resonance Spectroscopy; Kaplan-Meier Estimate; Mice; Oxygen; Radiotherapy, Image-Guided; Tumor Hypoxia
PubMed: 30414912
DOI: 10.1016/j.ijrobp.2018.10.041 -
American Journal of Perinatology Jul 2019The objective of this study is to revise novel evidence and forthcoming clinical trials that focused on the gap of knowledge raised during the 2015 guidelines for... (Review)
Review
The objective of this study is to revise novel evidence and forthcoming clinical trials that focused on the gap of knowledge raised during the 2015 guidelines for neonatal resuscitation. Literature search on main topics on neonatal resuscitation published after 2015 edition of the consensus on science and guidelines was performed. Only relevant articles (mainly randomized controlled trials [RCTs] and meta-analyses) were included and presented as descriptive review. In the past years, new RCTs and/or meta-analyses have become available on umbilical cord clamping and umbilical cord milking, oxygen concentrations to start resuscitation in term and preterm infants, use of laryngeal mask, sustained lung inflation, less invasive surfactant administration, and heart rate assessment. Despite the increasing available literature on neonatal resuscitation in the past years, many interventions are still performed without robust scientific evidence. Adequately powered and well-designed RCTs are needed to optimize management of neonates at birth.
Topics: Clinical Trials as Topic; Constriction; Heart Rate; Humans; Infant, Newborn; Infant, Premature; Oxygen; Practice Guidelines as Topic; Respiration, Artificial; Resuscitation; Umbilical Cord
PubMed: 31238355
DOI: 10.1055/s-0039-1691797 -
American Journal of Obstetrics &... Jul 2021This study aimed to determine if maternal intrapartum administration of oxygen altered the rate of cesarean delivery compared with room air. (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
This study aimed to determine if maternal intrapartum administration of oxygen altered the rate of cesarean delivery compared with room air.
DATA SOURCES
This study was a systematic review and meta-analysis of randomized controlled trials. Searches were performed in MEDLINE, OVID, Scopus, ClinicalTrials.gov, and the Cochrane Central Register of Controlled Trials using a combination of key words related to "pregnant patients," "labor," "oxygen," "fetus," "newborn," and pregnancy outcomes from database inception until April 2020. The study was registered in PROSPERO (registration number CRD42020162110).
STUDY ELIGIBILITY CRITERIA
The inclusion criteria were randomized controlled trials of maternal administration of oxygen compared with room air in labor. The exclusion criteria were quasi-randomized trials and oxygen administered for planned cesarean deliveries. The primary outcome was the rate of cesarean delivery. Secondary maternal and neonatal outcomes, including cord gas values, were analyzed.
METHODS
The Cochrane Handbook guidelines were used to assess bias in trials. To calculate the relative risk or mean differences with confidence intervals, a random-effects model was employed. Subgroup analyses were performed for women who received oxygen for nonreassuring fetal heart rate monitoring or prophylactically.
RESULTS
Five randomized controlled trials, including 768 women, were included in the meta-analysis, 3 using prophylactic oxygen and 2 using oxygen for nonreassuring fetal heart rate monitoring. The risk of bias was generally considered low. There was no statistically significant difference in the rate of cesarean delivery between patients administered oxygen and patients provided room air (16 of 365 [4.4%] vs 11 of 379 [2.9%]; risk ratio 1.5; 95% confidence interval, 0.7-3.3). In addition, there were no statistically significant differencs in the rates of cesarean delivery for nonreassuring fetal heart rate monitoring, operative vaginal deliveries, Apgar scores of <7, neonatal intensive care unit admissions, or cord blood gas values. There were no statistically significant difference when analyzing oxygen for nonreassuring fetal heart rate monitoring alone or prophylactic oxygen alone. Data regarding FHT is mixed, with one study suggesting an improvement and three suggesting no change.
CONCLUSION
Maternal intrapartum oxygen administration was not associated with any differences in the rate of cesarean delivery or any secondary outcomes compared with room air overall and in the subgroups of therapeutic (for nonreassuring fetal heart rate monitoring) or prophylactic administration in this meta-analysis. Large randomized controlled trials are necessary to further examine any possible benefits or harms of oxygen administration in labor, particularly for nonreassuring fetal heart rate monitoring.
Topics: Cesarean Section; Delivery, Obstetric; Female; Heart Rate, Fetal; Humans; Infant, Newborn; Labor, Obstetric; Oxygen; Pregnancy
PubMed: 33836306
DOI: 10.1016/j.ajogmf.2021.100374 -
Respiratory Care Oct 2020Oxygen titration is recommended to avoid hyperoxemia and hypoxemia. Automated titration, as well as the [Formula: see text] target, may have an impact on oxygen...
BACKGROUND
Oxygen titration is recommended to avoid hyperoxemia and hypoxemia. Automated titration, as well as the [Formula: see text] target, may have an impact on oxygen utilization, with potential logistical effects in emergency and military transportation. We sought to assess the oxygen flow required for different [Formula: see text] targets in spontaneously breathing subjects, and to evaluate individualized automated oxygen titration to maintain stable oxygenation in subjects with COPD and healthy subjects with induced hypoxemia.
METHODS
In the first part of the study, oxygen flow was evaluated in hospitalized subjects for different [Formula: see text] targets from 90% to 98%. Oxygen requirements to reach these targets were determined using a device that automatically adjusts oxygen flow every second on the basis of the [Formula: see text] target. In the second part of the study, the same automated oxygen titration method was used to correct hypoxemia in subjects with COPD and in healthy subjects with induced hypoxemia while the subjects wore a gas mask. Oxygen flow, [Formula: see text], and heart rate were continuously recorded.
RESULTS
Thirty-six spontaneously breathing hospitalized subjects were included in the first part of the study. Oxygen flow was reduced more than 6-fold when the [Formula: see text] target was decreased from 98% to 90%. The second part of the study included 15 healthy and 9 subjects with stable COPD. In healthy subjects, heterogeneous oxygen flows were required to correct induced hypoxemia (0.2-2.5 L/min). In subjects with COPD, oxygen flow varied from 0 L/min (in 9 of 18 tested conditions) to 2.9 L/min.
CONCLUSIONS
Significant reductions in the amount of oxygen delivered could be obtained with optimized [Formula: see text] targets. Oxygen delivery through a gas mask to correct hypoxemia is feasible, and automated oxygen titration may help individualize oxygen administration and reduce oxygen utilization. (ClinicalTrials.gov registration: NCT02782936, NCT02809807.).
Topics: Automation; Heart Rate; Humans; Hypoxia; Lung; Oxygen; Oxygen Consumption; Respiration
PubMed: 32071135
DOI: 10.4187/respcare.07240 -
Clinical and Experimental Hypertension... Dec 2023Hypoxia is a physiological state characterized by reduced oxygen levels in organs and tissues. It is a common clinicopathological process and a major cause of health... (Review)
Review
OBJECTIVES
Hypoxia is a physiological state characterized by reduced oxygen levels in organs and tissues. It is a common clinicopathological process and a major cause of health problems in highland areas. Heart rate variability (HRV) is a measure of the balance in autonomic innervation to the heart. It provides valuable information on the regulation of the cardiovascular system by neurohumoral factors, and changes in HRV reflect the complex interactions between multiple systems. In this review, we provide a comprehensive overview of the relationship between high-altitude hypoxia and HRV. We summarize the different mechanisms of diseases caused by hypoxia and explore the changes in HRV across various systems. Additionally, we discuss relevant pharmaceutical interventions. Overall, this review aims to provide research ideas and assistance for in-depth studies on HRV. By understanding the intricate relationship between high-altitude hypoxia and HRV, we can gain insights into the underlying mechanisms and potential therapeutic approaches to mitigate the effects of hypoxia on cardiovascular and other systems.
METHODS
The relevant literature was collected systematically from scientific database, including PubMed, Web of Science, China National Knowledge Infrastructure (CNKI), Baidu Scholar, as well as other literature sources, such as classic books of hypoxia.
RESULTS
There is a close relationship between heart rate variability and high-altitude hypoxia. Heart rate variability is an indicator that evaluates the impact of hypoxia on the cardiovascular system and other related systems. By improving the observation of HRV, we can estimate the progress of cardiovascular diseases and predict the impact on other systems related to cardiovascular health. At the same time, changes in heart rate variability can be used to observe the efficacy of preventive drugs for altitude related diseases.
CONCLUSIONS
HRV can be used to assess autonomic nervous function under various systemic conditions, and can be used to predict and monitor diseases caused by hypoxia at high altitude. Investigating the correlation between high altitude hypoxia and heart rate variability can help make HRV more rapid, accurate, and effective for the diagnosis of plateau-related diseases.
Topics: Humans; Altitude Sickness; Altitude; Heart Rate; Hypoxia; Oxygen
PubMed: 37552638
DOI: 10.1080/10641963.2023.2238923 -
Critical Reviews in Biomedical... 2019Heart rate and through-body blood perfusion are vital measurements in all stages of patient care, be it predictive, in the clinical setting, or outpatient monitoring....
Heart rate and through-body blood perfusion are vital measurements in all stages of patient care, be it predictive, in the clinical setting, or outpatient monitoring. Irregular, underachieving, or overperforming heart rate is the main precursor of most cardiovascular diseases that have severe long-term complications. In addition to heart rate, the shape of the pulse waveforms can indicate the heart's valve health and electrophysiology health. The goal of the study was to design a noninvasive device for continuously measuring a patient's heart rate with clinical-grade accuracy along with the ability to indicate pulse waveforms for the patient and physician. An accurate, easy-to-use heart-rate measuring device prototype was developed that did not require the sensor to have direct skin contact to obtain measurements. The statistical analysis of the data gathered by the prototype compared to the data collected from the industry standard device indicated significant correlation. The two-sample T-test for the data recorded from the prototype and the data collected from the industry commercially available pulse oximeter showed a P-value of 0.521, which indicates that there was no significant difference between the prototype and the commercially available pulse oximeter when measuring heart rate.
Topics: Alkenes; Calibration; Electrocardiography; Electrophysiological Phenomena; Equipment Design; Ethylenes; Heart Rate; Humans; Linear Models; Materials Testing; Microcomputers; Movement; Oximetry; Oxygen; Perfusion; Reproducibility of Results; Styrene
PubMed: 31679242
DOI: 10.1615/CritRevBiomedEng.2019026539