[Intensiva] Essentials of Mechanical Ventilation 3rd Ed. (2014)

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Essentials of Mechanical Ventilation

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Third Edition ��PhD,RRT Associate Professor of Anaesthesia Harvard Medical School

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Assistant Director of Respiratory Care Services Massachusetts General Hospital Boston, Massachusetts

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Professor of Anaesthesia

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Harvard Medical School

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Director of Respiratory Care Services Massachusetts General Hospital Boston, Massachusetts

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Dedication

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For Susan, Terri, Rob, Max, Abby, Lauren, and Matt-who make every day enjoyable. D.R.H.

For my children Robert, Julia, Katie, and Callie, who make it all worthwhile.

R.M.K.

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ix

Preface

xi

Abbreviations

Chapter 1 Chapter 2 Chapter 3

Chapter 4 Chapter 5

Chapter 6 Chapter 7

Chapter 8 Chapter 9

Chapter10

Chapter11 Chapter12

Chapter13

Chapter14

Chapter15 Chapter16

Chapter17 Chapter18

Chapter19

Chapter20

Chapter21

Chapter22

Physiologic Effects of Mechanical Ventilation Physiologic Goals of Mechanical Ventilation Ventilator-Induced Lung Injury Ventilator-Associated Pneumonia Ventilator Mode Classification Traditional Modes of Mechanical Ventilation Pressure and Volume Ventilation Advanced Modes of Mechanical Ventilation Flow Waveforms and I:E Ratios High Frequency Ventilation Noninvasive Ventilation Humidification and the Ventilator Circuit F102, Positive End-Expiratory Pressure, and Mean Airway Pressure Initial Settings for Mechanical Ventilation Patient-Ventilator Asynchrony Ventilator Liberation

Acute Respiratory Distress Syndrome Obstructive Lung Disease Chest Trauma Head Injury Postoperative Mechanical Ventilation Neuromuscular Disease

1

12

20 29

40

50 60

72

88

102

110

121

132 143 151

164

177 189

202

210 220

227

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viii

Contents

Chapter23

Chapter24

Chapter25 Chapter26

Chapter27

Chapter28 Chapter29

Chapter30

Chapter31

Chapter32

Chapter33 Chapter34

Chapter35 Chapter36

Chapter37 Chapter38

Index

Cardiac Failure Burns and Inhalation Injury Bronchopleural Fistula Drug Overdose

237

Blood Gases Pulse Oximetry, Capnography, and Transcutaneous Monitoring Hemodynamic Monitoring Basic Pulmonary Mechanics During Mechanical Ventilation Advanced Pulmonary Mechanics During Mechanical Ventilation Nutritional Assessment

267

Airway Management Airway Clearance Inhaled Drug Delivery Emergency Ventilation and Ventilation in a Disaster Mobilization and Portable Ventilation Extracorporeal Life Support

244

254 262

281 291

300

308 325

335 344 353

360 370

376

385

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Mechanical ventilation is an integral part of the care of many critically ill patients. It is also provided at sites outside the ICU and outside the hospital, including long-term acute c are hospitals and the home. A thorough understanding of the essentials of mechanical ventila­ tion is requisite for respiratory therapists and critical care physicians. A general knowledge of the principles of mechanical ventilation is also required of critical care nurses and pri­ mary care physicians whose patients occasionally require ventilatory support. This book is intended to be a practical guide to adult mechanical ventilation. We have written this book from our perspective of over 75 years of experience as clinicians, educa­ tors, researchers, and authors. We have made every attempt to keep the topics current and with a distinctly clinical focus. As in the previous editions, we have kept the chapters short, focused, and practical. There have been many advances in t he practice of mechanical ventilation over the past 10 years. Hence, much of the book is rewritten. Like previous editions, the book is divided into four parts. Part 1, Principles of Mechanical Ventilation, describes basic principles of mechanical ventilation and then continues with issues such as indications for mechanical ventilation, appropriate physiologic goals, and weaning from mechanical ventilation. Part 2, Ventilator Management, gives practical advice for ventilating patients with a variety of diseases. Part 3, Monitoring During Mechanical Ventilation, discusses blood gases, hemo ­ dynamics, mechanics, and waveforms. In the final part, Topics Related to Mechanical Ven­ tilation, we discuss issues such as airway management, aerosol delivery, extracorporeal life support, and miscellaneous ventilatory techniques. This is a book about mechanical ventilation and not mechanical ventilators. We do not describe the operation of any specific ventilator (although we do discuss s ome modes specific to some ventilator types) . We have tried to keep the material covered in this book generic and it is, by and large, applicable to any adult mechanical ventilator. We do not cover issues related to pediatric and neonatal mechanical ventilation. Because these topics are adequately covered in pediatric and neonatal respiratory care books, we decided to limit the focus of this book to adult mechanical ventilation. Although we provide a short bibliog­ raphy at the end of each chapter, we have specifically tried to make this a practical b ook and not an extensive reference book. This book is written for all clinicians caring for mechanically ventilated patients. We believe that it is unique and hope you will enjoy reading it as much as we have enjoyed writing it. Dean R. Hess, PhD, RRT Robert M. Kacmarek, PhD, RRT

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A/C AG APRV ARDS ARDSnet AVAPS BAL BE BEE BSA CCI Cao2 Cc 'o2 CDC CI CL

c1-

CMV co

Co2 COPD CPAP

Assist/ control Anion gap Airway pressure release ventilation Acute respiratory distress syndrome ARDS network Average volume assured pressure support Bronchoalveolar lavage Base excess Basal energy expenditure Body surface area Chronic critical illness Oxygen content of arterial blood Pulmonary capillary oxygen content Centers for Disease Control and Prevention Cardiac index Lung compliance Chloride ion Continuous mandatory ventilation Carbon monoxide Oxygen content of the blood Chronic obstructive pulmonary disease Continuous positive airway pressure

CPP CPR csv

CT Cvo2 CVP cw

Do 2 EAdi ECLS ECMO EELV EPAP fb fc

FI0 2 FRC Hb HbCO H co3 HFJV HFOV -

HFPPV

Cerebral perfusion pressure Cardiopulmonary resuscitation Continuous spontaneous ventilation Computed tomography Mixed venous oxygen content Central venous pressure Chest wall compliance Oxygen delivery Electrical activity of the diaphragm Extracorporeal life support Extracorporeal membrane oxygenation End-expiratory lung volume Expiratory positive airway pressure Frequency of breathing; respiratory rate Heart rate Fraction of inspired oxygen Functional residual capacity Hemoglobin Carboxyhemoglobin Bicarbonate concentration High frequency jet ventilation High frequency oscillatory ventilation High frequency positive pressure ventilation xi

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HFV HME Hz I:E IBW ICP ICU IMV iNO IPAP ISB IVAC

LV LVSWI MAP MDI MIC MIE MMV MODS MPAP NO Na+ NAVA NIV NPE or

�Paw

Abbreviations

High frequency ventilation Heat and moisture exchanger Hertz Inspiratory time to expiratory time ratio Ideal body weight (sometimes called predicted body weight) Intracranial pressure Intensive care unit Intermittent mandatory ventilation Inhaled nitric oxide Inspiratory positive airway pressure Isothermal saturation boundary Infection related ventilator associated condition Joules Left ventricle Left ventricular stroke work index Mean arterial pressure Metered-dose inhaler Maximum insufflation capacity Mechanical insufflationexsufflator Mandatory minute ventilation Multiple organ dysfunction syndrome Mean pulmonary artery pressure Nitric oxide Sodium Neurally adjusted ventilatory assist Noninvasive ventilation Neurogenic pulmonary edema Oxygenation index Change in airway pressure

�pL �POP �Ppl P(a-et)C02 Pao/ PAo2 Pao/ F102 P(A-a)o2 Paco2 Palv Palv Pao2 PA02 PAP PAV Paw Pb Pbo2 PC-CMV PC-IMV PCIRV Pco2 PCV PCWP Pdi P'Eco2 PHp PEEP

Transpulmonary pressure Plethysmographic waveform amplitude Change in pleural pressure Difference between arterial and end-tidal Pco2 Ratio of arterial PO 2 to alveolar Po2 Ratio of arterial Po2 to F102 Difference between alveolar Po2 and arterial Po2 Partial pressure of carbon dioxide in arterial blood Mean alveolar pressure Alveolar pressure Partial pressure of oxygen in arterial blood Alveolar Po2 Pulmonary artery pressure Proportional-assist ventilation Mean airway pressure Barometric pressure Brain Po 2 Continuous mandatory ventilation with pressure control Pressure-controlled intermittent mandatory ventilation Pressure-controlled inverse ration ventilation Partial pressure of carbon dioxide Pressure-controlled ventilation Pulmonary capillary wedge pressure Transdiaphragmatic pressure Mixed exhaled Pco2 Water vapor pressure Positive end -expiratory pressure

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Abbreviations

PEG Peso Petco 2 Pexhco 2 pH PI PImax PI mm. PIP Pmus PMV Po 2 Pplat PPV PRVC PSV Ptcco 2 Ptco2 Pvco 2 Pvent PVI Pvo 2 PVR Qc

Q/QT

R

Percutaneous endoscopic gastrostomy Esophageal pressure End-tidal Pco 2 Measured mixed exhaled PC0 2 including gas compressed in the ventilator circuit Negative log of the hydrogen ion concentration Plethysmographic perfusion index Maximum inspiratory pressure Minimal value of the plethysmographic perfusion index Peak inspiratory pressure Pressure generated by the respiratory muscles Prolonged mechanical ventilation Partial pressure of oxygen Plateau pressure Arterial pulse pressure variation Pressure-regulated volume control Pressure support ventilation Transcutaneous Pco 2 Transcutaneous Po 2 Mixed venous Pco 2 Pressure-generated by the ventilator Plethysmographic variability index Mixed venous Po 2 Pulmonary vascular resistance Cardiac output Pulmonary shunt Respiratory quotient

RE REE REM R, RSBI RVSWI Sao 2 SBT Scvo 2 SID SIMV Sjvo 2 Spco SpHb Sp Met Spo 2 svi

Svo2 SVR SVRI TE T, TT UUN v

VA V/Q

Expiratory resistance Resting energy expenditure Rapid eye movement Inspiratory resistance Rapid shallow breathing index Right ventricular stroke work index Hemoglobin oxygen saturation of arterial blood Spontaneous breathing trial Central venous oxygen saturation Strong ion difference Synchronized intermittent mandatory ventilation Jugular venous oxygen saturation Carbon monoxide measured by pulse oximetry Hemoglobin measured by pulse oximetry Methemoglobin measured by pulse oximetry Hemoglobin oxygen saturation measured by pulse oximetry Stroke volume index Mixed venous oxygen saturation Systemic vascular resistance Systemic vascular resistance index Expiratory time Inspiratory time Total cycle time Urine urea nitrogen Flow Alveolar ventilation Ratio of ventilation to blood flow

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VAC VAE VAP vc

Vco 2 VD VE

v,

vcv

VC-CMV

Abbreviations

Ventilator-associated condition Ventilator-associated event Ventilator-associated pneumonia Vital capacity Carbon dioxide production Dead space ventilation Minute ventilation Inspiratory flow Volume-controlled ventilation Continuous mandatory ventilation with volume control

VC-IMV VD/VT VILI Vo2 vs

VT w l

volume-controlled intermittent mandatory ventilation Dead space to tidal volume ratio Ventilator-induced lung injury Oxygen consumption Volume support Tidal volume Work Time constant

Part 1

Principles of Mechanical Ventilation

Chapter 1 Physiologic Effects of Mechanical Ventilation

•

•

•

Introduction Mean Airway Pressure Pulmonary Effects

Shunt Ventilation Atelectasis Barotrauma Ventilator-Induced Lung Injury Pneumonia Hyperventilation and Hypoventilation Oxygen Toxicity

•

Cardiac Effects

•

Renal Effects

•

Nutritional Effects

• •

Gastric Effects Neurologic Effects

•

Neuromuscular Effects

•

Airway Effects

•

Patient-Ventilator Asynchrony

•

Points to Remember

• • •

•

Hepatosplanchnic Effects Sleep Effects Mechanical Malfunctions Additional Reading

1

2

Port 1 : Principles of Mechanical Ven tilation

1. List the factors affecti n g mean ai rway pressu re d u ri n g positive pressu re

venti lation.

2. Descri be the effects of positive pressure venti lation on s h u nt a n d dead space. 3. Discuss the roles of a lveolar overd istention and ope n i n g/closing on venti lator­

ind uced l u n g i nj u ry.

4. Discuss the physiologic effects of positive pressu re venti lation on the p u l monary,

card iac, renal, hepatic, gastric, and neuro m u scu l a r fu nction.

5. Discuss the effects of positive pressu re venti lation on n utrition, the ai rway, and

sleep.

6. Descri be methods that can be used to m i n i m ize the ha rmfu l effects of positive

pressu re venti lation.

Introduction

Ventilators used in adult acute care use positive pressure applied to the airway opening to inflate the lungs. Although positive pressure i s responsible for the beneficial effects of mechanical ventilation, it is also responsible for many potentially deleterious side effects. Application of mechanical ventilation requires an understanding of both its beneficial and adverse effects. In the care of an individual patient, this demands appli­ cation of strategies that maximize the potential benefit of mechanical ventilation while minimizing the potential for harm. Due to the homeostatic interactions between the lungs and other body systems, mechanical ventilation can affect nearly every organ system of the body. This chapter provides an overview of the beneficial and adverse physiologic effects of mechanical ventilation. Mean Airway Pressure

-------

During normal spontaneous breathing, intrathoracic pressure i s negative throughout the ventilatory cycle. Intrapleural pressure varies from about -5 em H 2 0 during exha­ lation to -8 em H2 0 during inhalation. Alveolar pressure fluctuates from + 1 em H 2 0 during exhalation to -1 em H2 0 during inhalation. The decrease in intrapleural pres ­ sure during inhalation facilitates 1 ung inflation and venous return. Transpulmonary pressure is the difference between proximal airway pressure and intrapleural pressure. The greatest static transpulmonary pressure that can be generated normally during spontaneous inspiration is less than 35 em H 2 0. Intrathoracic pressure fluctuations during positive pressure ventilation a re oppo­ site to those that occur during spontaneous breathing. During positive pressure ven ­ tilation, the mean intrathoracic pressure is usually positive. Intrathoracic pressure increases during inhalation and decreases during exhalation. Thus, venous r eturn is greatest during exhalation and it may be decreased if expiratory t ime is too short or mean alveolar pressure is too high.

Chapter 1: Physiologic Effects of Mechanical Ventilation

3

Many of the beneficial and adverse effects associated with mechanical ventila ­ tion are related to mean airway pressure. Mean airway pressure is the average pressure applied to the airway during the ventilatory cycle. It is related to both the amount and duration of pressure applied during the inspiratory phase (peak inspiratory pressure, inspiratory pressure waveform, a nd inspiratory time) and the expiratory phase (positive end-expiratory pressure [PEEP] and respiratory rate). Pulmonary Effects

------

Shunt

Figure 1 - 1 Sche­ matic illustration of anatomic shunt and capillary shunt.

Shunt is perfusion (blood flow) without ventilation (Figure 1 - 1 ) . Pulmonary shunt occurs when blood flows from the right heart to the left heart without participating in gas exchange. The result of shunt is hypoxemia. Shunt can be either c apillary shunt or anatomic shunt. Capillary shunt results when blood flows past unventilated alveoli. Examples of capillary shunt are atelectasis, pneumonia, pulmonary edema, and acute respiratory distress syndrome (ARDS). Anatomic s hunt occurs when blood flows from the right heart to the left heart and completely bypasses the lungs. Normal anatomi ­ cal shunt occurs due to the Thebesian veins and the bronchial circulation. Abnormal anatomic shunt occurs with congenital cardiac defects. Total s hunt is the sum of the capillary and anatomic shunt. Positive pressure ventilation usually decreases shunt and improves arterial oxygenation. An inspiratory pressure that exceeds the alveolar opening pressure expands a collapsed alveolus, and an expiratory pressure greater than alveolar closing pressure prevents its collapse. By maintaining alveolar recruitment with an adequate expiratory pressure setting, arterial oxygenation is improved. However, if positive pres­ sure ventilation produces overdistention of s orne lung units, this may result in redis­ tribution of pulmonary blood flow to unventilated regions (Figure 1 -2). In this case, positive pressure ventilation paradoxically results in hypoxemia. Although positive pressure ventilation may improve capillary s hunt, it may worsen anatomic shunt. An increase in alveolar pressure may increase pulmonary vascular r esis­ tance, which could result in increased flow through the anatomic shunt, decreased flow through the lungs, and worsening hypoxemia. Thus, mean airway pressure should be kept as low as possible if an anatomic right-to­ left shunt is present. A relative shunt effect can occur with poor distribution of ventilation, such as might result from airway disease. With poor From distribution of ventilation, some rig ht alveoli are underventilated rela­ heart tive to perfusion (shunt-like effect and low ventilation-perfusion ratio), whereas other alveoli are

4

Port 1 : Principles of Mechanical Ven tilation

I n c reased s h u nt I n c reased dead space

Figure 1 -2 Alveolar overd istention, resulting in redistribution of pul­ monary blood flow to u nventilated units and an increased shunt.

overventilated (dead space effect and high ventilation-perfusion ratio). Positive pressure ventilation may improve the distribution of ventilation, particularly by improving t he ventilation of previously underventilated areas of the lungs. Ventilation

Ventilation is the movement of gas into and out of the lungs. Tidal volume (� T) is the amount of gas inhaled or exhaled with a single breath and minute ventilation (V ) is the E volume of gas breathed in 1 minute. Minute ventilation i s the product of tidal volume (VT) and respiratory frequency (fb) :

V =V T x f E

b

Ventilation can be either dead space ventilation (V ) or alveolar ventilation ( V). D alveolar ventilation: Minute ventilation is the sum of dead space ventilation and

V =V +VA E D

Figure 1 -3 Sche­ matic illustration of mechanica l dead space, ana­ tomic dead space, and alveolar dead space.

Alveolar ventilation participates in gas exchange (Figure 1 -3), whereas dead space ventilation does not. In other words, dead space is ventilation without perfusion. Ana ­ tomic dead space is the volume of the conducting airways of the lungs, and is about 1 50 mL in normal adults. Alveolar dead space refers to alveoli that are ventilated but not perfused, and is increased by any condition that decreases pulmo­ nary blood flow. Total physiologic dead space fraction (V /VT) is n