Physiological Responses To Intermittent Hypoxia In Humans

Recently, endurance athletes and high altitude climbers have gained access to commercially available, portable normobaric hypoxic chambers. Intermittent exposures to hypoxia in these chambers may elicit adaptations similar to those observed during acclimatization to altitude. Manufactures of these systems purport that intermittent exposures may elicit adaptations similar to those observed in response to the hypoxia of high altitude, however there have been no reports in the scientific literature that ventilatory acclimatization or alterations in cerebrovascular dynamics occur following repeated episodes in the portable chambers. The main conclusions are that an intermittent normobaric hypoxic intervention, consisting of five consecutive overnight exposures to a simulated altitude of 4300m, elicits perturbations in the acute cerebrovascular and ventilatory responses to both hypoxia and hypercapnia, which are similar to changes following chronic altitude exposure. Individual variability to intermittent hypoxia may have an impact on the rate at which the process of acclimatization proceeds. The extent of physiological and symptomatic responses to intermittent hypoxia are likely to be associated with the severity of hypoxia as well as the length and number of recurrent episodes of hypoxia.

Intermittent hypoxia can cause significant structural and functional impact on the systemic, organic, cellular and molecular processes of human physiology and pathophysiology. This book focuses on the most updated scientific understanding of the adaptive (beneficial) and maladaptive (detrimental) responses to intermittent hypoxia and their potential pathogenetic or prophylactic roles in the development and progression of major human diseases. This is a comprehensive monograph for clinicians, research scientists, academic faculty, postgraduate and medical students, and allied health professionals who are interested in enhancing their up-to-date knowledge of intermittent hypoxia research and its translational applications in preventing and treating major human diseases.

In consolidation of the most updated experimental results and perspectives from diverse research fields on a main theme - Intermittent Hypoxia, this book encompasses the structural, physiological, pathophysiological, biochemical, genetic, metabolic, and therapeutic aspects of intermittent hypoxia and provides an open forum to promote the bench-to-bed translational implications of both adaptive (beneficial) and maladaptive (detrimental) responses to intermittent hypoxia in animals and humans. Authored by 74 leading scientists from 17 countries in Asia, Europe, North America, and Oceana, the 30 chapters are grouped under 7 different sections covering the profound effects of intermittent hypoxia particularly on cardiovascular, respiratory, nervous, and skeletal muscular systems. Special attentions are paid to the protective or injurious roles played by intermittent hypoxia and their underlying cellular and molecular mechanisms in several major human diseases such as acute myocardial infarction, stroke, sleep apnea, and Parkinsons disease. Several chapters have also reviewed the use of intermittent hypoxia training for enhancing exercise performance in elite athletes. Overall, as endorsed by Professor John B. West (Member, Institute of Medicine, National Academy of Sciences of U.S.A.; Editor-in-Chief, High Altitude Medicine and Biology) through his Foreword for the book, this is the most comprehensive monograph to date on the topic of intermittent hypoxia, which can cause significant structural and functional impact on the systemic, organic, cellular and molecular processes of human physiology and pathophysiology. Hence, this book could serve as a thorough reference for research scientists, physicians, academic faculty, graduate and medical students, athletic coaches and trainers, who are interested in enhancing their knowledge about the past, present, and future of intermittent hypoxia research and its translational applications for prevention and treatment of major diseases and improving exercise performance.

The appearance of photosynthetic organisms about 3 billion years ago increased the partial pressure of oxygen (PO2) in the atmosphere and enabled the evolution of organisms that use glucose and oxygen to produce ATP by oxidative phosphorylation. Hypoxia is commonly defined as the reduced availability of oxygen in the tissues produced by different causes, which include reduction of atmospheric PO2 as in high altitude, and secondary to pathological conditions such as sleep breathing and pulmonary disorders, anemia, and cardiovascular alterations leading to inadequate transport, delivery, and exchange of oxygen between capillaries and cells. Nowadays, it has been shown that hypoxia plays an important role in the genesis of several human pathologies including cardiovascular, renal, myocardial and cerebral diseases in fetal, young and adult life. Several mechanisms have evolved to maintain oxygen homeostasis. Certainly, all cells respond and adapt to hypoxia, but only a few of them can detect hypoxia and initiate a cascade of signals intended to produce a functional systemic response. In mammals, oxygen detection mechanisms have been extensively studied in erythropoietin-producing cells, chromaffin cells, bulbar and cortical neurons, pulmonary neuroepithelial cells, smooth muscle cells of pulmonary arteries, and chemoreceptor cells. While the precise mechanism underpinning oxygen, sensing is not completely known several molecular entities have been proposed as possible oxygen sensors (i.e. Hem proteins, ion channels, NADPH oxidase, mitochondrial cytochrome oxidase). Remarkably, cellular adaptation to hypoxia is mediated by the master oxygen-sensitive transcription factor, hypoxia-inducible factor-1, which can induce up-regulation of different genes to cope the cellular effects related to a decrease in oxygen levels. Short-term responses to hypoxia included mainly chemoreceptor-mediated reflex ventilatory and hemodynamic adaptations to manage the low oxygen concentration while more prolonged exposures to hypoxia can elicit more sustained physiological responses including switch from aerobic to anaerobic metabolism, vascularization, and enhancement of blood O2 carrying capacity. The focus of this research topic is to provide an up-to-date vision on the current knowledge on oxygen sensing mechanism, physiological responses to acute or chronic hypoxia and cellular/tissue/organ adaptations to hypoxic environment.

Hypoxia remains a constant threat throughout life. It is for this reason that the International Hypoxia Society strives to maintain a near quarter century tradition of presenting a stimulating blend of clinical and basic science discussions. International experts from many fields have focused on the state-of-the-art discoveries in normal and pathophysiological responses to hypoxia. Topics in this volume include gene-environment interactions, a theme developed in both a clinical context regarding exercise and hypoxia, as well as in native populations living in high altitudes. Furthermore, experts in the field have combined topics such as skeletal muscle angiogenesis and hypoxia, high altitude pulmonary edema, new insights into the biology of the erythropoietin receptor, and the latest advances in cardiorespiratory control in hypoxia. This volume explores the fields of anatomy, cardiology, biological transport, and biomedical engineering among many others.

The latest in a series of books from the International Hypoxia Symposia, this volume spans reviews on key topics in hypoxia, and abstracts from poster and oral presentations. The biannual International Hypoxia Symposia are dedicated to hosting the best basic scientific and clinical minds to focus on the integrative and translational biology of hypoxia. Long before ‘translational medicine’ was a catchphrase, the founders of the International Hypoxia Symposia brought together basic scientists, clinicians and physiologists to live, eat, ski, innovate and collaborate in the Canadian Rockies. This collection of reviews and abstracts is divided into six sections, each covering new and important work relevant to a broad range of researchers interested in how humans adjust to hypoxia, whether on the top of Mt. Everest or in the pulmonary or cardiology clinic at low altitude. The sections include: Epigenetic Variations in Hypoxia High Altitude Adaptation Hypoxia and Sleep Hypoxia and the Brain Molecular Oxygen Sensing Physiological Responses to Hypoxia

Respiratory Muscle Training: theory and practice is the world’s first book to provide an "everything-you-need-to-know" guide to respiratory muscle training (RMT). Authored by an internationally-acclaimed expert, it is an evidence-based resource, built upon current scientific knowledge, as well as experience at the cutting-edge of respiratory training in a wide range of settings. The aim of the book is to give readers: 1) an introduction to respiratory physiology and exercise physiology, as well as training theory; 2) an understanding of how disease affects the respiratory muscles and the mechanics of breathing; 3) an insight into the disease-specific, evidence-based benefits of RMT; 4) advice on the application of RMT as a standalone treatment, and as part of a rehabilitation programme; and finally, 5) guidance on the application of functional training techniques to RMT. The book is divided into two parts – theory and practice. Part I provides readers with access to the theoretical building blocks that support practice. It explores the evidence base for RMT as well as the different methods of training respiratory muscles and their respective efficacy. Part II guides the reader through the practical implementation of the most widely validated form of RMT, namely inspiratory muscle resistance training. Finally, over 150 "Functional" RMT exercises are described, which incorporate a stability and/or postural challenge – and address specific movements that provoke dyspnoea. Respiratory Muscle Training: theory and practice is supported by a dedicated website (www.physiobreathe.com), which provides access to the latest information on RMT, as well as video clips of all exercises described in the book. Purchasers will also receive a three-month free trial of the Physiotec software platform (via www.physiotec.ca), which allows clinicians to create bespoke training programmes (including video clips) that can be printed or emailed to patients. Introductory overviews of respiratory and exercise physiology, as well as training theory Comprehensive, up-to-date review of respiratory muscle function, breathing mechanics and RMT Analysis of the interaction between disease and respiratory mechanics, as well as their independent and combined influence upon exercise tolerance Analysis of the rationale and application of RMT to over 20 clinical conditions, e.g., COPD, heart failure, obesity, mechanical ventilation Evidence-based guidance on the implementation of inspiratory muscle resistance training Over 150 functional exercises that incorporate a breathing challenge www.physiobreathe.com - access up-to-date information, video clips of exercises and a three-month free trial of Physiotec’s RMT exercise module (via www.physiotec.ca)