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Basics of Mechanical Ventilation PDF

136 Pages·2018·6.21 MB·English
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Hooman Poor Basics of Mechanical Ventilation 123 Basics of Mechanical Ventilation Hooman Poor Basics of Mechanical Ventilation Hooman Poor Mount Sinai – National Jewish Health Respiratory Institute Icahn School of Medicine New York, NY USA ISBN 978-3-319-89980-0 ISBN 978-3-319-89981-7 (eBook) https://doi.org/10.1007/978-3-319-89981-7 Library of Congress Control Number: 2018944605 © Springer International Publishing AG, part of Springer Nature 2018 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of transla- tion, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimi- lar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of pub- lication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Printed on acid-free paper This Springer imprint is published by the registered company Springer International Publishing AG part of Springer Nature The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland Dedicated to Conner, Ellery, and Alden Preface Mechanical ventilators can be mysterious and intimidating. When using the ventilator, one is taking on the responsibility of breathing for another human being. Mechanical ventila- tion is one of the most complex and integral aspects of critical care medicine. As a pulmonary and critical care physician, I have taught mechanical ventilation to many medical students, residents, and fellows. During these teaching sessions, I have encoun- tered many shared misconceptions about how ventilators work. Much of this misunderstanding stems from the fact that the current nomenclature used in mechanical ventilation is inconsistent and confusing. My hope is that this book clarifies the fundamental concepts of mechanical ventilation. The ventilator does not function in isolation—it works in concert with the patient’s respiratory system. One cannot simply set the ventilator and walk away. Instead, it is impor- tant to monitor and adjust the ventilator settings based upon the complex interactions between the ventilator and the patient. Proper ventilator management is not merely a set of prescriptive steps; ventilator settings must be individually and continuously tailored to each patient and unique situation. Therefore, an in-depth understanding of how a ventilator operates is essential to achieving increased patient comfort and optimal patient outcomes. Learning how to manage patients on ventilators can be daunting. While there are many excellent, comprehensive vii viii Preface textbooks on mechanical ventilation, these tomes can be overwhelming to even the most dedicated students. The avail- able “shorter” books are insufficient as they often glance over crucial basic principles. As is the case with learning medicine in general, it is more effective to understand the foundational concepts than to simply memorize algorithms. This book delves into those foundational concepts, and does so clearly and succinctly. This book is written for anyone who cares for patients requiring mechanical ventilation—physicians, nurses, respira- tory therapists—and is intended for providers at all levels of training. It provides the nuts and bolts of how to properly manage the ventilator and serves as a practical resource in the intensive care unit in order to better care for critically ill patients. New York, NY, USA Hooman Poor Contents 1 Respiratory Mechanics ........................ 1 Lung Volume ................................ 1 Transpulmonary Pressure ...................... 2 Spontaneous Breathing........................ 3 Modeling the Respiratory System ............... 7 Suggested Readings........................... 10 2 Phase Variables .............................. 11 Anatomy of a Breath.......................... 11 Trigger...................................... 12 Target....................................... 18 Cycle ....................................... 25 Baseline..................................... 26 Suggested Readings........................... 27 3 Basic Modes of Ventilation..................... 29 Volume-Controlled Ventilation ................. 29 Pressure-Controlled Ventilation................. 30 Pressure Support Ventilation ................... 33 Volume-Controlled Ventilation Vs. Pressure- Controlled Ventilation................. 35 Pressure-Controlled Ventilation Vs. Pressure Support Ventilation ........................... 37 Suggested Readings........................... 38 4 Monitoring Respiratory Mechanics.............. 39 Two-Component Model ....................... 39 Airway Pressures ............................. 42 ix x Contents Diagnostic Algorithm ......................... 44 Suggested Readings........................... 48 5 Acute Respiratory Distress Syndrome ........... 49 Volutrauma.................................. 50 Barotrauma.................................. 51 Atelectrauma ................................ 52 Permissive Hypercapnia ....................... 55 Suggested Readings........................... 60 6 Obstructive Lung Diseases..................... 61 Breath Stacking and Auto-PEEP................ 61 Ventilator Management Strategies .............. 68 Suggested Readings........................... 73 7 Patient-Ventilator Dyssynchrony................ 75 Trigger-Related Dyssynchrony.................. 75 Target-Related Dyssynchrony .................. 88 Cycle-Related Dyssynchrony................... 89 Suggested Readings........................... 93 8 Indications for Mechanical Ventilation........... 95 Increased Work of Breathing................... 95 Increased Demand............................ 98 Neuromuscular Weakness...................... 100 Alveolar Hypoventilation...................... 100 Hypoxemia .................................. 101 Airway Protection ............................ 102 Suggested Readings........................... 103 9 Weaning from the Ventilator ................... 105 Assessing Readiness to Wean................... 105 Spontaneous Breathing Trial ................... 106 Cuff Leak Test ............................... 112 Suggested Readings........................... 114 10 Hemodynamic Effects of Mechanical Ventilation.. 115 Cardiopulmonary System ...................... 115 Intrathoracic Pressure . . . . . . . . . . . . . . . . . . . . . . . . . 117 Preload ..................................... 118 Afterload.................................... 119 Specific Hemodynamic Conditions . . . . . . . . . . . . . . 123 Suggested Readings........................... 127 Index .......................................... 129 Chapter 1 Respiratory Mechanics Understanding mechanical ventilation must start with a review of the physiology and mechanics of normal spontane- ous breathing. Spontaneous breathing is defined as move- ment of air into and out of the lungs as a result of work done by an individual’s respiratory muscles. Positive pressure ventilation, on the other hand, is defined as movement of air into the lungs by the application of positive pressure to the airway through an endotracheal tube, tracheostomy tube, or noninvasive mask. Lung Volume The lungs sit inside a chest cavity surrounded by the chest wall. The potential space between the lungs and the chest wall is known as the pleural space. The lungs, composed of elastic tissue, have a tendency to recoil inward, and the chest wall has a tendency to spring outward. If the lungs were removed from the chest cavity and were no longer being influenced by the chest wall or the pleural space, they would collapse like a deflated balloon. Similarly, removing the lungs from the chest cavity would cause the chest wall, no longer being influenced by the lungs or the pleural space, to spring outward. The equi- librium achieved between the lungs’ inward recoil and the © Springer International Publishing AG, 1 part of Springer Nature 2018 H. Poor, Basics of Mechanical Ventilation, https://doi.org/10.1007/978-3-319-89981-7_1

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This book is a practical and easily understandable guide for mechanical ventilation. With a focus on the basics, this text begins with a detailed account of the mechanisms of spontaneous breathing as a reference point to then describe how a ventilator actually works and how to effectively use it in
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