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Respiratory Care Oct 2014Oxygen is essential for normal aerobic metabolism in mammals. Hypoxia is the presence of lower than normal oxygen content and pressure in the cell. Causes of hypoxia... (Review)
Review
Oxygen is essential for normal aerobic metabolism in mammals. Hypoxia is the presence of lower than normal oxygen content and pressure in the cell. Causes of hypoxia include hypoxemia (low blood oxygen content and pressure), impaired oxygen delivery, and impaired cellular oxygen uptake/utilization. Many compensatory mechanisms exist at the global, regional, and cellular levels to allow cells to function in a hypoxic environment. Clinical management of tissue hypoxia usually focuses on global hypoxemia and oxygen delivery. As we move into the future, the clinical focus needs to change to assessing and managing mission-critical regional hypoxia to avoid unnecessary and potential toxic global strategies. We also need to focus on understanding and better harnessing the body's own adaptive mechanisms to hypoxia.
Topics: Adaptation, Physiological; Humans; Hypoxia; Oxygen; Oxygen Inhalation Therapy
PubMed: 25161296
DOI: 10.4187/respcare.03357 -
Respiratory Care Jul 2021Hypoxemia is common in postoperative patients and is associated with prolonged hospital stays, high costs, and increased mortality. This review discusses the... (Review)
Review
Hypoxemia is common in postoperative patients and is associated with prolonged hospital stays, high costs, and increased mortality. This review discusses the postoperative management of hypoxemia in regard to the use of conventional oxygen therapy, high-flow nasal cannula oxygen therapy, CPAP, and noninvasive ventilation. The recommendations made are based on the currently available evidence.
Topics: Cannula; Continuous Positive Airway Pressure; Humans; Hypoxia; Noninvasive Ventilation; Oxygen; Oxygen Inhalation Therapy
PubMed: 34006596
DOI: 10.4187/respcare.08929 -
American Journal of Physiology.... Nov 2014Intermittent hypoxia (IH) has been the subject of considerable research in recent years, and triggers a bewildering array of both detrimental and beneficial effects in... (Review)
Review
Intermittent hypoxia (IH) has been the subject of considerable research in recent years, and triggers a bewildering array of both detrimental and beneficial effects in multiple physiological systems. Here, we review the extensive literature concerning IH and its impact on the respiratory, cardiovascular, immune, metabolic, bone, and nervous systems. One major goal is to define relevant IH characteristics leading to safe, protective, and/or therapeutic effects vs. pathogenesis. To understand the impact of IH, it is essential to define critical characteristics of the IH protocol under investigation, including potentially the severity of hypoxia within episodes, the duration of hypoxic episodes, the number of hypoxic episodes per day, the pattern of presentation across time (e.g., within vs. consecutive vs. alternating days), and the cumulative time of exposure. Not surprisingly, severe/chronic IH protocols tend to be pathogenic, whereas any beneficial effects are more likely to arise from modest/acute IH exposures. Features of the IH protocol most highly associated with beneficial vs. pathogenic outcomes include the level of hypoxemia within episodes and the number of episodes per day. Modest hypoxia (9-16% inspired O2) and low cycle numbers (3-15 episodes per day) most often lead to beneficial effects without pathology, whereas severe hypoxia (2-8% inspired O2) and more episodes per day (48-2,400 episodes/day) elicit progressively greater pathology. Accumulating evidence suggests that "low dose" IH (modest hypoxia, few episodes) may be a simple, safe, and effective treatment with considerable therapeutic potential for multiple clinical disorders.
Topics: Animals; Bone and Bones; Cardiovascular System; Humans; Hypoxia; Inflammation; Nervous System; Oxygen; Respiratory System; Time Factors
PubMed: 25231353
DOI: 10.1152/ajpregu.00208.2014 -
Kardiologia Polska Jun 2019High altitude is a fascinating model of hypoxia effects on the human body but is also an extreme environment which directly influences millions of people who either... (Review)
Review
High altitude is a fascinating model of hypoxia effects on the human body but is also an extreme environment which directly influences millions of people who either travel to high altitude locations or live there permanently. A significant progress was made over the past decades in the understanding of physiological background of responses to altitude, and recently a number of studies regarding clinical aspects of high altitude exposure were published. In particular, more is known about the changes occurring in systemic blood pressure in individuals exposed to high altitude as well as on the effects of antihypertensive drugs in this setting. The present article provides an overview of principal physiological and clinical aspects related to systemic blood pressure control and its changes at high altitude, mainly during the acute exposure. The evidence on blood pressure changes at rest and during exercise is discussed, as well as the underlying mechanisms and possible clinical implications.
Topics: Altitude; Altitude Sickness; Antihypertensive Agents; Atmospheric Pressure; Blood Pressure; Humans; Hypertension; Hypoxia
PubMed: 31099758
DOI: 10.33963/KP.14832 -
Journal of Applied Physiology... May 2021The word "hypoxia" has recently come to the attention of the general public on two occasions, the Nobel Prize in Medicine or Physiology in 2019 and the recent COVID-19...
The word "hypoxia" has recently come to the attention of the general public on two occasions, the Nobel Prize in Medicine or Physiology in 2019 and the recent COVID-19 pandemic. In the academic environment, hypoxia is a current topic of research in biology, physiology, and medicine: in October 2020, there were more than 150,000 occurrences of "hypoxia" in the PubMed database. However, the first occurrence is dated to 1945, while the interest for the effects of oxygen lack on the living organisms started in the mid-19th century, when scientists explored high altitude regions and mainly used the terms "anoxia" or "anoxemia." I therefore researched online through multiple databases to look for the first appearance of "hypoxia" and related terms "hypoxemia" and "hypoxybiosis" in scientific literature published in English, German, French, Italian, and Spanish. Viault and Jolyet used "Hypohématose" in 1894, but this term has not been used since. Hypoxybiosis first appeared in 1909 in Germany, then hypoxemia in 1923 in Austria, and hypoxia in 1938 in Holland. It was then exported to the United States where it appeared in 1940 in cardiology and anesthesiology. The clinical distinction between anoxia and hypoxia was clearly defined by Carl Wiggers in 1941. Hypoxia (decrease in oxygen), by essence variable in time and in localization in the body, in contrast with anoxia (absence of oxygen), illustrates the concept of homeodynamics that defines a living organism as a complex system in permanent instability, exposed to environmental and internal perturbations.
Topics: COVID-19; Germany; History, 20th Century; Humans; Hypoxia; Inventions; Netherlands; Pandemics; SARS-CoV-2
PubMed: 33703942
DOI: 10.1152/japplphysiol.00936.2020 -
Ugeskrift For Laeger Nov 2022Oxygen is a standard treatment for patients with chronic lung diseases and hypoxemia. The two main groups of lung diseases leading to oxygen treatment is chronic... (Review)
Review
Oxygen is a standard treatment for patients with chronic lung diseases and hypoxemia. The two main groups of lung diseases leading to oxygen treatment is chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD). Several guidelines for home oxygen therapy for patients with ILD is, however, based on older observation and extrapolations from studies on COPD. This review focuses on the different oxygen treatment modalities for patients with ILD focusing on present evidence and upcoming trials that might change the oxygen therapy approach for patients with ILD.
Topics: Humans; Oxygen Inhalation Therapy; Lung Diseases, Interstitial; Pulmonary Disease, Chronic Obstructive; Oxygen; Hypoxia
PubMed: 36426814
DOI: No ID Found -
Experimental Neurology Jun 2021Therapeutic hypothermia (TH) is well established as a standard treatment for term and near-term infants. However, therapeutic effects of hypothermia following neonatal...
Therapeutic hypothermia (TH) is well established as a standard treatment for term and near-term infants. However, therapeutic effects of hypothermia following neonatal anoxia in very premature babies remains inconclusive. The present rodent model of preterm neonatal anoxia has been shown to alter developmental milestones and hippocampal neurogenesis, and to disrupt spatial learning and memory in adulthood. These effects seem to be reduced by post-insult hypothermia. Epigenetic-related mechanisms have been postulated as valuable tools for developing new therapies. Dentate gyrus neurogenesis is regulated by epigenetic factors. This study evaluated whether TH effects in a rodent model of preterm oxygen deprivation are based on epigenetic alterations. The effects of TH on both developmental features (somatic growth, maturation of physical characteristics and early neurological reflexes) and performance of behavioral tasks at adulthood (spatial reference and working memory, and fear conditioning) were investigated in association with the possible involvement of the epigenetic operator Enhancer of zeste homolog 2 (Ezh2), possibly related to long-lasting effects on hippocampal neurogenesis. Results showed that TH reduced both anoxia-induced hippocampal neurodegeneration and anoxia-induced impairments on risk assessment behavior, acquisition of spatial memory, and extinction of auditory and contextual fear conditioning. In contrast, TH did not prevent developmental alterations caused by neonatal anoxia and did not restore hippocampal neurogenesis or cause changes in EZH2 levels. In conclusion, despite the beneficial effects of TH in hippocampal neurodegeneration and in reversing disruption of performance of behavioral tasks following oxygen deprivation in prematurity, these effects seem not related to developmental alterations and hippocampal neurogenesis and, apparently, is not caused by Ezh2-mediated epigenetic alteration.
Topics: Animals; Animals, Newborn; Female; Hippocampus; Hypothermia, Induced; Hypoxia, Brain; Lactation; Male; Rats; Rats, Wistar; Spatial Memory; Treatment Outcome
PubMed: 33713657
DOI: 10.1016/j.expneurol.2021.113691 -
Experimental Physiology Dec 2019• What is the topic of this review? To explore the unique evolutionary origins of the human brain and critically appraise its energy budget, including limits of oxygen... (Review)
Review
NEW FINDINGS
• What is the topic of this review? To explore the unique evolutionary origins of the human brain and critically appraise its energy budget, including limits of oxygen and glucose deprivation during anoxia and ischaemia. • What advances does it highlight? The brain appears to be more resilient to substrate depletion than traditionally thought, highlighting greater resilience and an underappreciated capacity for functional recovery.
ABSTRACT
The human brain has evolved into an unusually large, complex and metabolically expensive organ that relies entirely on a continuous supply of O and glucose. It has traditionally been assumed that its exorbitant energy budget, combined with little to no energy reserves, renders it especially vulnerable to anoxia and ischaemia, with substrate depletion and progression towards cell death largely irreversible and rapid. However, new and exciting evidence suggests that neurons can survive for longer than previously thought, highlighting an unexpected resilience and underappreciated capacity for functional recovery that has changed the way we think about brain cell death. Nature has the potential to unlock some of the mysteries underlying ischaemic survival, with select vertebrates having solved the problem of anoxia-hypoxia tolerance over millions of years of evolution. Better understanding of their survival strategies, including remarkable adaptations in brain physiology and redox homeostasis, might help to identify new therapeutic targets for human diseases characterized by O deprivation, ischaemia-reperfusion injury and ageing.
Topics: Adaptation, Physiological; Animals; Brain Death; Energy Metabolism; Glucose; Humans; Hypoxia; Oxygen
PubMed: 31605408
DOI: 10.1113/EP088005 -
Annual Review of Pathology Jan 2024Oxygen (O) is essential for cellular metabolism and biochemical reactions. When the demand for O exceeds the supply, hypoxia occurs. Hypoxia-inducible factors (HIFs) are... (Review)
Review
Oxygen (O) is essential for cellular metabolism and biochemical reactions. When the demand for O exceeds the supply, hypoxia occurs. Hypoxia-inducible factors (HIFs) are essential to activate adaptive and survival responses following hypoxic stress. In the gut (intestines) and liver, the presence of oxygen gradients or physiologic hypoxia is necessary to maintain normal homeostasis. While physiologic hypoxia is beneficial and aids in normal functions, pathological hypoxia is harmful as it exacerbates inflammatory responses and tissue dysfunction and is a hallmark of many cancers. In this review, we discuss the role of gut and liver hypoxia-induced signaling, primarily focusing on HIFs, in the physiology and pathobiology of gut and liver diseases. Additionally, we examine the function of HIFs in various cell types during gut and liver diseases, beyond intestinal epithelial and hepatocyte HIFs. This review highlights the importance of understanding hypoxia-induced signaling in the pathogenesis of gut and liver diseases and emphasizes the potential of HIFs as therapeutic targets.
Topics: Humans; Hypoxia; Oxygen; Signal Transduction; Liver Diseases
PubMed: 37832943
DOI: 10.1146/annurev-pathmechdis-051122-094743 -
Comparative Biochemistry and... Jun 2007The freshwater turtle Trachemys scripta is among the most anoxia-tolerant of vertebrates, a true facultative anaerobe able to survive without oxygen for days at room... (Review)
Review
The freshwater turtle Trachemys scripta is among the most anoxia-tolerant of vertebrates, a true facultative anaerobe able to survive without oxygen for days at room temperature to weeks or months during winter hibernation. Our good friend and colleague Peter Lutz devoted nearly 25 years to the study of the physiology of anoxia tolerance in these and other model organisms, promoting not just the basic science but also the idea that understanding the physiology and molecular mechanisms behind anoxia tolerance provides insights into critical survival pathways that may be applicable to the hypoxic/ischemic mammalian brain. Work by Peter and his colleagues focused on the factors which enable the turtle to enter a deep hypometabolic state, including decreases in ion flux ("channel arrest"), increases in inhibitory neuromodulators like adenosine and GABA, and the maintenance of low extracellular levels of excitatory compounds such as dopamine and glutamate. Our attention has recently turned to molecular mechanisms of anoxia tolerance, including the upregulation of such protective factors as heat shock proteins (Hsp72, Hsc73), the reversible downregulation of voltage gated potassium channels, and the modulation of MAP kinase pathways. In this review we discuss three phases of anoxia tolerance, including the initial metabolic downregulation over the first several hours, the long-term maintenance of neuronal function over days to weeks of anoxia, and finally recovery upon reoxygenation, with necessary defenses against reactive oxygen stress.
Topics: Adaptation, Physiological; Animals; Hypoxia; Ion Channels; Oxygen; Signal Transduction; Turtles
PubMed: 17049896
DOI: 10.1016/j.cbpa.2006.08.041