Hyperbaric Oxygen Treatment In Research And Clinical Practice Mechanisms Of Action In Focus

Hyperbaric oxygen treatment (HBO2) is a widely accepted adjuvant therapy in various health conditions that exhibit impaired tissue blood flow. At high pressures, the delivery of the dissolved oxygen in plasma is enhanced, which contributes to better tissue oxygenation, cellular metabolism and ultimately, healing. However, this is not the only beneficial outcome of HBO2 treatment since oxygen is a highly reactive molecule and can induce upregulation of many enzymatic systems in the cell at the cellular, genetic and molecular level. Particularly, vascular/endothelial function is affected by the HBO2. Our understanding of these mechanisms is still emerging. There have been many controversies related to the HBO2 protocols and indications. As well as exhibiting beneficiary effects on the tissue perfusion, it is known that HBO2 demonstrates high toxicity at higher pressures, due to increased oxidative stress and barotrauma. On the other hand, there is a lack of translation of the knowledge on the mechanisms of action of HBO2 obtained from the experimental research to the clinical practice. Thus, this book presents the reader with an overview of the current knowledge on the mechanisms of HBO2 effects in various experimental models and clinical treatment protocols, in an attempt to provide a better understanding of how and when HBO2 should be used as an effective therapy without unwanted side effects.

Hyperbaric oxygen treatment (HBO2) is a widely accepted adjuvant therapy in various health conditions that exhibit impaired tissue blood flow. At high pressures, the delivery of the dissolved oxygen in plasma is enhanced, which contributes to better tissue oxygenation, cellular metabolism and ultimately, healing. However, this is not the only beneficial outcome of HBO2 treatment since oxygen is a highly reactive molecule and can induce upregulation of many enzymatic systems in the cell at the cellular, genetic and molecular level. Particularly, vascular/endothelial function is affected by the HBO2. Our understanding of these mechanisms is still emerging. There have been many controversies related to the HBO2 protocols and indications. As well as exhibiting beneficiary effects on the tissue perfusion, it is known that HBO2 demonstrates high toxicity at higher pressures, due to increased oxidative stress and barotrauma. On the other hand, there is a lack of translation of the knowledge on the mechanisms of action of HBO2 obtained from the experimental research to the clinical practice. Thus, this book presents the reader with an overview of the current knowledge on the mechanisms of HBO2 effects in various experimental models and clinical treatment protocols, in an attempt to provide a better understanding of how and when HBO2 should be used as an effective therapy without unwanted side effects.

The decade since the first Handbook on Hyperbaric Medicine has seen major advances: studies have clarified the actions of hyperbaric oxygenation; clinical practice is becoming more scientific; various organisational and operational guidelines are now widely accepted. This new Handbook arises from the EU Co-operation in Science and Technology (COST) programme for hyperbaric medicine, COST B14, in combination with the results of a number of recent experimental and clinical studies.

This comprehensive volume captures the latest scientific evidence, technological advances, treatments and impact of biotechnology in hyperbaric oxygen therapy. Divided into three distinct sections, the book begins with basic aspects that include history, equipment, safety and diagnostic approaches; this is followed by clinical applications for hyperbaric oxygen therapy in various modalities; the last section provides an overview of hyperbaric medicine as a specialty with best practices from around the world. Integration of multidisciplinary approaches to complex disorders are also covered. Updated and significantly expanded from previous editions, Textbook of Hyperbaric Medicine, 6th Edition will continue to be the definitive guide to this burgeoning field for students, trainees, physicians and specialists.

Background: Assessment of the critically ill is traditionally based on vital signs (blood pressure, pulse, respiratory rate, temperature and level of consciousness). Altered vital signs are, however, late indicators of deranged hemodynamics pointing to a need for additional, more sensitive markers of circulatory compromise. In the beginning of the 20th century, the capillary refill (CR) time evolved as a possible, non-invasive adjunct to early prediction of the outcome in the critically ill. The manoeuvre entails application of blanching pressure on the skin of the finger pulp or sternum for 5 seconds. After release of the pressure, the observer estimates time in seconds for the skin to return to original colour. This time is hypothesized to reflect the dynamics of the microcirculation and its possible connection with hemodynamics. In the 1980s the “normal capillary refill time” was set to < 2 seconds and later extended to 3 seconds, without a clear scientific foundation. Naked-eye estimations of CR time met increasing scepticism in the 1990s due to subjectivity and poor prognostic value for shock or death. Several basic traits, such as age and sex, as well as ambient temperature, were also shown to independently influence the CR time. Various methods have evolved with the capability to measure CR time quantitatively, one of which is Polarisation Spectroscopy Imaging (PSI). PSI measures the Red Blood Cell (RBC) concentration in tissue (e.g. the skin) and can be used to measure CR time. Objectives: The purpose of this study was to establish basic characteristics for quantified CR (qCR), identify possible influencing factors in healthy subjects and to investigate how this relates to current practice. We also sought to identify technical demands for transfer of the technique into clinical studies. In paper I we analysed the (qCR) time characteristics at 5 different skin sites (forehead, sternum, volar forearm, finger pulp and dorsum finger). The objective of paper II was to investigate the inter- and intra-observer variability of naked eye CR assessments of different professions, nurses, doctors and secretaries (representing laymen). In paper III we observed the effect of low ambient temperature on the qCR time in different skin sites. In paper IV, we transferred the equipment from a laboratory to a clinical setting in the Emergency Department (ED) for application on potentially critically ill patients. In this study we evaluated the most important factors determining a reliable data collection and influencing the amount of data possible to analyse. Methods: qCR time was measured in a total of 38 volunteers and 10 patients in different skin sites (2-5 skin sites) at different ambient temperatures. PSI (TiVi 600 and 700, WheelsBridge AB, Linköping, Sweden) was used to determine the rapid temporal changes in RBC concentration in skin during the CR manoeuvre. Films using a range of the first measurements from paper I were shown for assessment to 48 observers working in the ED. Results: In paper I we could delineate qCR curves and suggest 2 possible equivalents to the naked-eye observed CR time which we named Time to Return to Baseline 1 (tRtB1) and Time to Peak (tpk). We demonstrated differences in qCR-curves depending on skin site and possibly due to skin temperature. In paper II we showed a poor inter- and intra-observer reproducibility in visually estimating the CR time regardless of profession (clinicians or laymen). Paper III demonstrated a rapid effect of ambient temperature on qCR time in peripheral skin sites such as finger pulp. The forehead, regarded as a more central skin site was the most temperature stable site and showed least variability in qCR time as determined using tRtB1. Paper IV, a study on patients in an ED setting, yielded assayable data in 80% of the measurements. We identified critical performance parameters to address in the further development of a more robust, easy-to-use device for future validation of the possible relevance of qCR in patient triage and monitoring. Conclusions: CR time can be quantified using PSI. Quantified CR time demonstrated a large variability between different skin sites, specifically, skin temperature was shown to be an important factor influencing qCR time, particularly at the fingertip. Naked-eye estimates of CR time were highly variable, both within and between observers. Agreement between quantified CR time and naked-eye estimates was poor. The prototypic PSI technique was feasible in a clinical setting and, with further improvements, clinical evaluation of qCR in relation to relevant patient outcomes will be possible.

The Undersea and Hyperbaric Medical Society (UHMS) is an international, non-profit organization serving over 2,400 members from more than 50 countries. The UHMS is the primary source of scientific information for diving and hyperbaric medicine physiology worldwide, the breadth of which is illustrated in the triennial report, Hyperbaric Oxygen Therapy Indications. With leading experts authoring chapters in their respective fields, this publication continues to provide the most current and up to date guidance and support for scientists and practitioners of hyperbaric oxygen therapy. Hyperbaric Oxygen Therapy Indications, currently in its thirteenth edition, has grown in size and depth to reflect the evolution of the literature on the approved use of hyperbarics from both a clinical practice standpoint and insurance coverage perspective. To date, the committee recognizes fourteen indications, including the new indication, idiopathic sudden sensorineural hearing loss. Additionally, this book continues to be used by the Centers for Medicare and Medicaid Services and other third party insurance carriers in determining payment for HBO2 services.