Ebook Clinical application of mechanical ventillation (4/E): Part 1

(BQ) Part 1 book Clinical application of mechanical ventillation has contents: Principles of mechanical ventilation, effects of positive pressure ventilation, classification of mechanical ventilators, special airways for ventilation,... and other contents.

Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it David W Chang Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it This is an electronic version of the print textbook Due to electronic rights restrictions, some third party content may be suppressed Editorial review has deemed that any suppressed content does not materially affect the overall learning experience The publisher reserves the right to remove content from this title at any time if subsequent rights restrictions require it For valuable information on pricing, previous editions, changes to current editions, and alternate formats, please visit www.cengage.com/highered to search by ISBN#, author, title, or keyword for materials in your areas of interest Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it David W Chang, Ed.D., RRT–NPS Professor Department of Cardiorespiratory Care University of South Alabama Mobile, Alabama Australia • Brazil • Japan • Korea • Mexico • Singapore • Spain • United Kingdom • United States Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it Clinical Application of Mechanical Ventilation, Fourth Edition David W Chang Vice President, Careers & Computing: Dave Garza Publisher, Health Care: Stephen Helba Associate Acquisitions Editor: Christina Gifford Director, Development–Careers & Computing: Marah Bellegarde Product Development Manager, Careers: Juliet Steiner Associate Product Manager: Meghan E Orvis Editorial Assistant: Cassie Cloutier © 2014, 2006, 2001, 1997 Delmar, Cengage Learning ALL RIGHTS RESERVED No part of this work covered by the copyright herein may be reproduced, transmitted, stored, or used in any form or by any means graphic, electronic, or mechanical, including but not limited to photocopying, recording, scanning, digitizing, taping, Web distribution, information networks, or information storage and retrieval systems, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without the prior written permission of the publisher For product information and technology assistance, contact us at Cengage Learning Customer & Sales Support, 1-800-354-9706 For permission to use material from this text or product, submit all requests online at www.cengage.com/permissions Further permissions questions can be e-mailed to permissionrequest@cengage.com Executive Brand Manager: Wendy Mapstone Market Development Manager: Jonathan Sheehan Senior Production Director: Wendy Troeger Production Manager: Andrew Crouth Senior Content Project Manager: Kara A DiCaterino Senior Art Director: David Arsenault Cover Image: © Icons Jewelry/www.shutterstock.com © Sebastian Kaulitzki/www.shutterstock.com Library of Congress Control Number: 2012953799 ISBN-13: 978-1-1115-3958-0 ISBN-10: 1-1115-3958-8 Delmar Maxwell Drive Clifton Park, NY 12065-2919 USA Cengage Learning is a leading provider of customized learning solutions with office locations around the globe, including Singapore, the United Kingdom, Australia, Mexico, Brazil, and Japan Locate your local office at: international.cengage.com/region Cengage Learning products are represented in Canada by Nelson Education, Ltd To learn more about Delmar, visit www.cengage.com/delmar Purchase any of our products at your local college store or at our preferred online store www.cengagebrain.com Notice to the Reader Publisher does not warrant or guarantee any of the products described herein or perform any independent analysis in connection with any of the product information contained herein Publisher does not assume, and expressly disclaims, any obligation to obtain and include information other than that provided to it by the manufacturer The reader is expressly warned to consider and adopt all safety precautions that might be indicated by the activities described herein and to avoid all potential hazards By following the instructions contained herein, the reader willingly assumes all risks in connection with such instructions The publisher makes no representations or warranties of any kind, including but not limited to, the warranties of fitness for particular purpose or merchantability, nor are any such representations implied with respect to the material set forth herein, and the publisher takes no responsibility with respect to such material The publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or part, from the readers’ use of, or reliance upon, this material Printed in the United States of America 17 16 15 14 13 Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it Dedicated with love to my wife, Bonnie and our children, Michelle, Jennifer, and Michael for their support in my professional endeavors and personal leisure activities Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it Contents Preface Acknowledgments xxvi xxx Chapter 1: Principles of Mechanical Ventilation Introduction Airway Resistance Factors Affecting Airway Resistance Airway Resistance and the Work of Breathing (∆P) Effects on Ventilation and Oxygenation Airflow Resistance Lung Compliance Compliance Measurement Static and Dynamic Compliance Compliance and the Work of Breathing Effects on Ventilation and Oxygenation Deadspace Ventilation Anatomic Deadspace Alveolar Deadspace Physiologic Deadspace Ventilatory Failure Hypoventilation Ventilation/Perfusion (V/Q) Mismatch Intrapulmonary Shunting Diffusion Defect Oxygenation Failure Hypoxemia and Hypoxia Clinical Conditions Leading to Mechancial Ventilation Depressed Respiratory Drive Excessive Ventilatory Workload Failure of Ventilatory Pump 3 5 6 10 10 10 11 11 11 12 12 13 14 15 16 17 18 18 18 19 VII­ Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it VIII Contents Summary Self-Assessment Questions Answers to Self-Assessment Questions References Additional Resources 21 21 24 24 25 Chapter 2: Effects of Positive Pressure Ventilation Introduction Pulmonary Considerations Spontaneous Breathing Positive Pressure Ventilation Airway Pressures Compliance Cardiovascular Considerations Mean Airway Pressure and Cardiac Output Decrease in Cardiac Output and O2 Delivery Blood Pressure Changes Pulmonary Blood Flow and Thoracic Pump Mechanism Hemodynamic Considerations Positive Pressure Ventilation Positive End-Expiratory Pressure Renal Considerations Renal Perfusion Indicators of Renal Failure Effects of Renal Failure on Drug Clearance Hepatic Considerations PEEP and Hepatic Perfusion Indicators of Liver Dysfunction Effects of Decreased Hepatic Perfusion on Drug Clearance Abdominal Considerations Effects of PEEP and Increased Intra-Abdominal Pressure Gastrointestinal Considerations Nutritional Considerations Muscle Fatigue Diaphragmatic Dysfunction Nutritional Support Nutrition and the Work of Breathing Neurologic Considerations Hyperventilation Ventilatory and Oxygenation Failure Indicators of Neurologic Impairment Summary Self-Assessment Questions Answers to Self-Assessment Questions References 27 28 28 28 29 30 30 30 31 31 32 34 34 34 35 35 36 36 38 38 38 38 39 39 40 40 41 41 41 42 43 43 44 44 45 45 48 48 Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it Monitoring in Mechanical Ventilation 259 Accuracy and Clinical Use of Pulse Oximetry SpO2 above 92% correlates with a PaO2 above 60 mm Hg Pulse oximetry has been used as a reliable noninvasive means of monitoring oxygenation in mechanically ventilated patient SpO2 of 95% has a strong correlation with PaO2 of 70 mm Hg with a sensitivity of 100% (Niehoff et al., 1988) SpO2 can be used to facilitate FIO2 weaning The FIO2 may be reduced to an appropriate level by use of a single arterial blood gas measurement followed by multiple pulse oximetry measurements (Rotello et al., 1992) Oxygenation of the ventilator-dependent patient can be assured when the SpO2 is kept above 92% as this level correlates with a PaO2 above 60 mm Hg (Jubran et al., 1990) Table 9-9 outlines other clinical application of pulse oximetry Limitations of Pulse Oximetry SpO2 has good correlation with arterial oxygen saturation (SaO2) when the SaO2 is 95% or greater dyshemoglobins: Hemoglobins that not carry oxygen (e.g., carboxyhemoglobin, methemoglobin) In the presence of dyshemoglobins, pulse oximeter reads higher than actual SaO2 Low perfusion and presence of dyshemoglobins may lead to SpO2 that are higher than the actual SaO2 SpO2 has good correlation with arterial oxygen saturation (SaO2) when the SaO2 is 95% or greater (Niehoff et al., 1988) SpO2 becomes less accurate as SaO2 decreases, and over estimation of a patient’s oxygenation status may result The accuracy of pulse oximetry can be affected by factors such as artifact and underlying patient conditions Artifact due to motion remains a cause of inaccurate measurement despite corrective efforts (Pologe, 1987) Sunlight has been reported to give a falsely low SpO2 measurement (Abbott, 1986) Nail polish (primarily blue, green, and black), and intravascular dyes can also give a falsely low SpO2 reading (Welch, DeCesare & Hess, 1990) Improper placement of the oximeter probe can give a faulty SpO2 reading as well If a patient is wearing nail polish, the probe may be placed sideways (White et al., 1989) Pathologic factors such as low perfusion states and presence of dyshemoglobins may lead to SpO2 measurements that are higher than the actual SaO2 (Schnapp & Cohen, 1990) Table 9-10 shows the factors that affect the accuracy of pulse oximetry Integrated Pulse CO-Oximetry In addition to the SpO2 and PR (pulse rate), an integrated pulse CO-oximetry (Masimo Rainbow SET®) uses signal extraction technology to measure a patient’s hemoglobin TABLE 9-9 Clinical Application of Pulse Oximetry Clinical Application Examples Monitor oxygenation status Mechanical ventilation Intubation Surgery Titrate FIO2 Increase FIO2 in hypoxemia Decrease FIO2 in weaning Verify ABG accuracy Compare O2 saturation readings to rule out venous sample © Cengage Learning 2014 Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it 260 Chapter TABLE 9-10 Factors That Affect the Accuracy of Pulse Oximetry Factors Type of Inaccuracy Sunlight SpO2 measures lower than actual SaO2 Nail polish Fluorescent light Intravenous dyes Dyshemoglobins (methemoglobin, sulfahemoglobin, SpO2 measures higher than actual SaO2 carboxyhemoglobin) Low perfusion states © Cengage Learning 2014 Integrated pulse CO-oximetry is capable of measuring the hemoglobin (SpHb™), oxygen content (SpOC™),carboxyhemoglobin (SpCO®), methemoglobin (SpMet®), pleth variability index (PVI®), and perfusion index (PI) (SpHb™), oxygen content (SpOC™), carboxyhemoglobin (SpCO®), methemoglobin (SpMet®), pleth variability index (PVI®), and perfusion index (PI) Pleth variability index (PVI®)(Masimo Corp., Irvine, CA, USA) is an algorithm allowing for automated and continuous calculation of the respiratory variations in the pulse oximeter plethysmographic (∆POP) waveform amplitude PVI has been used to predict fluid responsiveness in mechanically ventilated patients during general anesthesia (Cannesson et al., 2008) Perfusion index (PI) is a relative assessment of the pulse strength at the monitoring site The PI display ranges from 0.02% (very weak pulse strength) to 20% (very strong pulse strength) During sensor placement, use a site with the highest PI number (strongest pulse amplitude) The PI is influenced primarily by the amount of blood at the monitoring site, not by the level of oxygenation in the blood Preliminary data from one study show that low PI values correspond with illness on neonates (DeFelice et al., 2002) Other applications of PI include assessment of pain in the anesthetized state (Hagar et al., 2004) and as an early indicator of successful epidural block in laboring women (Kakazu et al., 2005) END-TIDAL CARBON DIOXIDE MONITORING end-tidal carbon dioxide monitoring: The CO2 level measured at the end of exhalation; measured in mm Hg End-tidal carbon dioxide monitoring is done to monitor a patient’s ventilatory status Once a good correlation is established between PaCO2 and end-tidal PCO2 (PetCO2), the number of routine blood gases may be reduced In addition, changes of the PetCO2 values and waveforms may also be obtained and interpreted for additional information about the patient/ventilator system Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it Monitoring in Mechanical Ventilation 261 Capnography Capnography is a measurement of the partial pressure of carbon dioxide in a gas sample When the sample is collected at the end of expiration, it is called end-tidal partial pressure of carbon dioxide (PetCO2) PetCO2 monitoring provides real-time, noninvasive analysis of a patient’s expired CO2 trend during mechanical ventilation Ventilators have built-in end-tidal CO2 monitoring capabilities The exhaled CO2 from the patient ventilator circuit is collected and measured by the infrared absorption technique (Hess, 1990) A mainstream sensor is placed directly onto the ventilator circuit, usually attached to an adaptor on the endotracheal tube A sidestream sensor aspirates a sample of gas via a small tube connected to the endotracheal tube adaptor Figure 9-12 illustrates the mainstream and sidestream capnography sensors The major advantage of mainstream analysis is the fast response time between actual CO2 sampling and the display update The disadvantage of the mainstream adaptor is its excessive weight on the endotracheal tube as well as the additional deadspace in the ventilator/patient circuit With mainstream sampling, water condensation does not affect analysis; however, secretion buildup on the cell windows can affect the accuracy A mainstream analyzer also tends to be more frequently handled than the sidestream sensor because the clinician must disconnect it manually to suction the patient (Shelley, 1989) A sidestream analyzer (aspirating analyzer) places the analyzing mechanism safely within the monitor and draws a sample via a tube connected at the patient’s airway (e.g., endotracheal tube) The major advantage with sidestream analysis is the ease of handling, and the analyzer can be attached to other patient devices (e.g., cannula, mask) The major disadvantage is that with periodic aspiration of air samples, secretions and water can be drawn into the sampling tube and cause an occlusion Lag time for CO2 display is slightly longer (a few tenths of a second) than the mainstream analyzer but it is negligible Equipment contamination may be a problem with the sidestream analyzer (Shelley, 1989) Capnography Waveforms and Clinical Application The PetCO2 may be used to estimate the PaCO2 A capnogram (Figure 9-13) shows the changes in PECO2 during a complete respiratory cycle The PECO2 is at zero before exhalation At the beginning of exhalation, the PECO2 remains at zero as anatomic deadspace volume exits the airways (phase I) The PECO2 then increases dramatically as alveolar gas begins mixing with deadspace gas (phase II) Then the curve plateaus, reflecting the exhalation of alveolar gas (phase III) The end of the “alveolar plateau” is called the end-tidal PCO2 (PetCO2) Since the PetCO2 approximates the alveolar PCO2, this value may be used to estimate the PaCO2 Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it 262 Chapter A Sensor Unit Cell ET Tube Ventilator Used with permission from Criticare Systems, Inc B Figure 9-12  (A) Mainstream capnography sensor; (B) Sidestream capnography sensor Transitory events can be examined by review of the capnographic tracing The capnogram can be useful in determining accidental esophageal intubations, endotracheal tube cuff leaks, and airway obstructions It can also be used to determine the synchronization of respiratory frequencies between the patient and ventilator Some other clinical applications for capnography include use during weaning, cardiopulmonary resuscitation, intubation, bronchoscopy, and hypocapnic management of patients with head trauma (Carlon et al., 1988; Hess, 1990) The capnographs not provide absolute measurements but they can be used to follow the PCO2 changes in hemodynamically stable trauma patients (Hess, 1990) Figure 9-14 shows the representative capnograms that correlate with some clinical conditions Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it Monitoring in Mechanical Ventilation 263 50 40 C B End Exhalation 30 Normal Bronchospasm 20 © Cengage Learning 2014 10 A Time Beginning Exhalation A B C D Used with permission from Criticare Systems, Inc Figure 9-13  The normal capnogram (solid line) (A, phase I) PCO2 is near zero and it represents gas in anatomic deadspace; (A to B, phase II) PCO2 rises rapidly as alveolar gas mixes with deadspace gas; (B to C, phase III) alveolar plateau shows arrival of gas flow from alveoli; Point (C) is the end-tidal PCO2 (PetCO2) Dotted line represents tracing in bronchospasm (Reference: Hess, 1990.) Figure 9-14  Abnormal capnograms monitored via real time or trend screen (A) Cardiac arrest (real time) The PetCO2 values drop suddenly and proportionally This condition indicates lung perfusion is inadequate due to a decreased cardiac output (B) Effectiveness of external compressions can be monitored by the resultant rise in PetCO2 as shown in the trend screen (C) Kinked ET tube (trend screen) As the ET tube is obstructed (partially or completely), the PetCO2 values reflect the degree of obstruction With complete obstruction, zero PetCO2 is seen (D) Disconnection Immediate disappearance of the PetCO2 values and wave form are observed Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it 264 Chapter P(a-et)CO2 Gradient Under ideal conditions, the PaCO2 is about mm Hg higher than the PetCO2 resulting a P(a-et)CO2 of mm Hg The correlation between PaCO2 and PetCO2 is excellent and the P(a-et)CO2 gradient (difference) between these two measurements is about mm Hg in normal individuals For critical patients, a gradient of mm Hg is considered acceptable (Niehoff et al., 1988) The P(a-et)CO2 gradient is primarily affected by alveolar deadspace ventilation (Perel & Stock, 1992), old age, presence of pulmonary disease, and changes in mechanical volume and modality Table 9-11 lists some specific conditions that increase the P(a-et)CO2 gradient Disposable ETCO2 Detector Capnography can also be estimated via a low-cost, dis- posable, plastic, CO2 (pH)-sensitive device With this device attached to the endotracheal tube, one can quickly differentiate tracheal from esophageal intubation (Hess, 1990) This occurs when the pH-sensitive device on the material senses the changes in CO2 concentration Limitations of Capnography Monitoring Capnography readings reflect only the changes in a patient’s ventilatory status, rather than the improvement or deterioration of the patient Decreased PetCO2 may not be indicative of improvement in gas exchange Capnography readings reflect only the changes in a patient’s ventilatory status, rather than the improvement or deterioration of the patient (Whitaker, 2001) An example of this is deadspace ventilation as seen in pulmonary embolism (Figure 9-15) A decrease in PetCO2 due to physiologic deadspace ventilation does not mean that the patient’s ventilatory status has improved Lowering the ventilator frequency in this situation could lead to grave consequences Other conditions leading to an increase in deadspace ventilation (thus a decrease in PetCO2) are hypotension and high intrathoracic pressure secondary to mechanical ventilation (Whitaker, 2001) This could cause the practitioner to incorrectly assume that the decreased PetCO2 indicates an improvement in gas exchange TABLE 9-11 Factors That Increase the P(a-et)CO2 Gradient Clinical Condition Factors Ventilation Increased deadspace ventilation Positive pressure ventilation Perfusion Decreased cardiac output Decreased pulmonary perfusion Cardiac arrest Pulmonary embolic disease Temperature Hyperthermia Hypothermia © Cengage Learning 2014 Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it 265 Monitoring in Mechanical Ventilation End-tidal PCO2 = 30 mm Hg Obstruction PACO2 40 mm Hg mm Hg Arterial PCO2 40 mm Hg 46 mm Hg Mixed Venous PCO2 © Cengage Learning 2014 PACO2 mm Hg Figure 9-15  Deadspace ventilation induced by blockage of a portion of the pulmonary blood flow (e.g., pulmonary embolism) This condition leads to a reduced PetCO2 reading TRANSCUTANEOUS BLOOD GAS MONITORING Transcutaneous blood gas monitoring involves placement of a miniature Clark (PO2) or a Severinghaus (PCO2) electrode on the skin via a double-sided adhesive disk A heating coil in the electrode increases the permeability of the epidermis, thus facilitating diffusion of gas from the underlying capillaries to the electrode Transcutaneous blood gas monitoring has been used more often in neonates than in adults (Eberhard et al., 1981) Transcutaneous PO2 (PtcO2) transcutaneous PO2 (PtcO2): Measurement of PO2 through the skin by means of a miniature Clark (PO2) electrode For an adequate blood flow to the skin, a heating element is used to provide a constant temperature (e.g., 44ºC) to the skin The clinical optimal range of PtcO2 for most infants is 50 mm Hg to 70 mm Hg The transcutaneous PO2 (PtcO2) provides a noninvasive measurement of arterial oxygen tension The PtcO2 monitor uses a combined platinum and silver electrode covered by an oxygen-permeable hydrophobic (water-repelling) membrane, with a built-in reservoir of phosphate buffer and potassium chloride Since the PtcO2 sensor requires an adequate blood flow to the skin, a small heating element is placed in the silver anode to provide a constant temperature (e.g., 44ºC) to the skin Following the initial setup or site change, the PtcO2 should be correlated with an arterial or capillary sample The value from the PtcO2 monitor should be recorded immediately after obtaining the arterial or capillary sample (Klein, 2008) In neonates, the transcutaneous PO2 (PtcO2) closely approximates the PaO2 But in adults, the PtcO2 measures lower than the actual PO2 due to thicker skin in adults For this reason, pulse oximetry (SpO2) is the preferred method to monitor the oxygenation status of adult patients PtcO2 also approximates the central organ PO2 (Tremper et al., 1979) It has a good correlation with the cardiac output changes in a mechanically ventilated patient (Shapiro et al., 1989) Since PtcO2 values correlate well with arterial values within the whole PO2 range (particularly in the PO2 range below 100 mm Hg), Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it 266 Chapter the PtcO2 can be used as an indicator of hypoxemia (Huch et al., 1974) The clinical optimal range of PtcO2 for most infants is 50 mm Hg to 70 mm Hg (Klein, 2008) Accuracy of the PtcO2 electrode is affected by skin edema, hypothermia, and capillary perfusion status Limitations Accuracy of the PtcO2 electrode is affected by skin edema, hypothermia, and capillary perfusion status PtcO2 becomes less accurate when the measuring range is greater than 80 mm Hg (Palmisano et al., 1990) When cardiac output decreases, as with the patient in shock, a disproportionate fall in PtcO2 occurs Two other disadvantages of transcutaneous monitors are the need for frequent site changes (every hours) to avoid erythemia and burns to the infant’s skin, and a long equilibration time after each site change Transcutaneous PCO2 (PtcCO2) transcutaneous PCO2 (PtcCO2): Measurement of PCO2 through the skin by means of a miniature Severinghaus (PCO2) electrode Transcutaneous PCO2 (PtCO2) monitoring is done to provide a means of continuous ventilatory assessment The PtcCO2 is measured by heating the underlying skin to 44°C (40°C to 42°C in neonates, maximum 45°C), which facilitates CO2 diffusion across the skin to the CO2 electrode The correlation between PtcCO2 and PaCO2 is good in neonates as long as perfusion is normal This correlation in adults shows mixed results, but in general the PtcCO2 may be useful as a monitoring tool once the trend has been established Limitations It should be noted that PtcCO2 values are usually higher than PaCO2 values This is due to increased CO2 production as underlying tissues are heated (Marini, 1988) In addition, during shock or low perfusion states, the PtcCO2 measures higher than the actual PaCO2 due to increased accumulation of tissue CO2 (Tremper et al., 1981) CEREBRAL PERFUSION PRESSURE Maintenance of adequate CPP reduces mortality cerebral perfusion pressure (CPP): Pressure required to provide blood flow, oxygen, and metabolite to the brain CPP MAP ICP Normal range 70 to 80 mm Hg CPP should range between 70 and 80 mm Hg Cerebral perfusion pressure (CPP) is the pressure required to provide blood flow, oxygen, and metabolites to the brain Under normal conditions, the brain regulates its own blood flow regardless of the systemic blood pressure and cerebral vascular resistance This autoregulation may be lost following head trauma, where the cerebral vascular resistance is often greatly elevated The brain also becomes vulnerable to changing blood pressures Depending on the degree of decrease in cerebral perfusion, effects on the brain may range from cerebral ischemia to brain death (Bouma et al., 1990; Marion et al., 1991) The optimum level of CPP is not defined, but the critical threshold is believed to be from 70 to 80 mm Hg Mortality increases about 20% for each 10 mm Hg drop in CPP In studies involving severe head injuries, 35% reduction in mortality was achieved when the CPP was maintained above 70 mm Hg (Bouma et al., 1992; Rosner et al., 1990) Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it Monitoring in Mechanical Ventilation A higher CPP may be maintained by raising the MAP or by lowering the ICP The normal ICP is to 12 mm Hg; clinical practice , 20 mm Hg Systemic hypotension is associated with poor outcomes in patients with severe head injuries 267 CPP is the difference between the mean arterial pressure (MAP) and the intracranial pressure (ICP) The relationship is shown as follows: CPP MAP ICP Based on the relationship of MAP and ICP, a higher CPP may be maintained by raising the MAP or by lowering the ICP In clinical practice ICP is usually controlled within normal limits (i.e., ,20 mm Hg) However, it is unknown whether ICP control is necessary, providing that CPP is maintained above the critical threshold by raising the MAP (Changaris et al., 1987; Rosner et al., 1990) In the absence of hemorrhage, the MAP should be managed initially by maintaining an adequate fluid balance It may then be followed by using a vasopressor such as norepinephrine or dopamine Systemic hypotension (i.e., SBP ,90 mm Hg) should be avoided and controlled as soon as possible because adequate systemic perfusion is necessary to prevent cerebral ischemia (due to lack of cerebral blood flow) For patients with severe brain injury, systemic hypotension contributes to an increased morbidity and mortality (Chesnut et al., 1993; Marmarou et al., 1991) SUMMARY Monitoring in mechanical ventilation is done to provide information about the condition of the patient and the overall effectiveness of a treatment plan The results obtained from different monitoring techniques should be used and interpreted together and should not be treated as isolated measurements For example, a decrease in end-tidal CO2 may indicate the presence of deadspace ventilation But this assumption must be confirmed with other supporting evidence such as a concurrent decrease in perfusion (decrease in cardiac output or other hemodynamic values) Trending or interpreting a series of measurements is also more meaningful since the overall condition of a patient is a dynamic process, not a set of separated events Finally, the condition of the patient should be assessed in conjunction with the monitoring results This is because the patient may temporarily compensate for abnormal conditions under extremely stressful settings This erroneous “normal” measurement may not be apparent by reviewing the laboratory results alone Therefore, careful examination of the patient should always be a vital part of monitoring in mechanical ventilation Self-Assessment Questions A patient suddenly develops shortness of breath and the SpO2 drops to 87% The therapist should anticipate a moderate increase of all of the following measurements except: A heart rate B minute ventilation C respiratory frequency D temperature Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it 268 Chapter Prolonged suctioning of the lungs via the endotracheal tube is not advised because this can induce: A hypovolemia and shock B bradycardia and arrhythmia C hyperventilation D productive coughs One of the complications of positive pressure ventilation is that it can cause a(n) _ venous return and _ A increased, hypertension B increased, hypotension C decreased, hypertension D decreased, hypotension A blood gas sample was collected from a hypothermic patient whose core temperature was 24°C If the sample was analyzed at 37°C with a PO2 of 90 mm Hg, the temperature corrected PO2 (to patient’s 24°C) would be: A negligible or almost 90 mm Hg B much higher than 90 mm Hg C much lower than 90 mm Hg D dependent on the position of the oxyhemoglobin curve A physician asks the therapist to evaluate the breath sounds of a patient who has an admitting diagnosis of pneumonia By placing the stethoscope diaphragm next to the side of the spine below the scapula, the therapist is listening to the breath sounds of the _ segments of the _ lobes A posterior, upper B superior, middle C posterior, middle D superior, lower to Match the breath sounds with the conditions that may be the cause of these abnormalities Use each answer only once Breath Sound Condition 6.  Diminished or absent A.  Lung consolidation 7.  Wheezes B.  Airway obstruction 8.  Inspiratory crackles C.  Excessive secretions 9.  Coarse crackles D.  Airway narrowing 10 Excessive positive pressure or volume during mechanical ventilation may _ the intrathoracic pressure and _ the cardiac and urine outputs A increase, increase B increase, decrease C decrease, increase D decrease, decrease 11 Infiltrates appear to be _ shadows on the chest radiograph and they are caused by presence of _ A black, blood or fluid B black, secretions or atelectasis C white, blood or fluid D white, secretions or atelectasis Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it Monitoring in Mechanical Ventilation 269 12 Metabolic acidosis (low bicarbonate) with a(n) _ anion gap is called hyperchloremic metabolic acidosis because the excessive chloride (Cl–) ions _ the deficiency of bicarbonate (HCO3–) ions in the plasma A normal, offset B normal, aggravate C abnormal, offset D abnormal, aggravate 13 A patient who has been undergoing the weaning process from mechanical ventilation suddenly stops breathing spontaneously The therapist should expect to see the following changes on the next set of blood gas results except: A increase in PO2 B increase in PCO2 C decrease in pH D decrease in HCO32 14 In blood gas interpretation, the PaCO2 is primarily used to assess a patient’s _ status, and the PO2 is useful for the _ status A ventilatory, acid-base B ventilatory, oxygenation C acid-base, oxygenation D acid-base, ventilatory 15 to 17 Match the causes of hypoxemia with the characteristics that may be used to distinguish these abnormalities Use each answer only once Cause of Hypoxemia Characteristics 15.  Hypoventilation A.  Normal or low PaCO2; hypoxemia does not respond to high levels of oxygen 16.  V/Q mismatch or diffusion defects B.  High PaCO2; hypoxemia improves with ventilation and low levels of oxygen 17.  Intrapulmonary shunt C.  Normal or low PaCO2; hypoxemia responds very well to moderate levels of oxygen 18 A patient rescued from a house fire has an admitting diagnosis of severe smoke inhalation She is breathing spontaneously and receiving 100% oxygen via a non-rebreathing mask Due to her condition, pulse oximetry _ be done because _ A should, of cost savings B should, continuous monitoring is being done C should not, the SpO2 reading will be higher than actual SaO2 D should not, the SpO2 reading will be required lower than actual SaO2 19 In metabolic acidosis, patients with adequate lung function are capable of compensating for this condition by _ This would cause the end-tidal CO2 readings to be _ than normal A hyperventilation, higher B hyperventilation, lower C hypoventilation, higher D hypoventilation, lower Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it 270 Chapter 20 Which of the following statements is not true regarding transcutaneous oxygen and carbon dioxide monitors? A Site changes are required every to hours B Long equilibration time for calibration C Accurate PO2 and PCO2 measurements D More accurate in neonatal use 21 In order to ensure adequate blood flow to the brain, the cerebral perfusion pressure (CPP) should be maintained between: A and 20 mm Hg B 30 and 50 mm Hg C 70 and 80 mm Hg D 100 and 120 mm Hg Answers to Self-Assessment Questions D D 13 A 19 B B A 14 B 20 C D C 15 B 21 C C 10 B 16 C D 11 D 17 A B 12 A 18 C References Abbott, M A (1986) Monitoring oxygen saturation levels in the early recovery phase of general anesthesia In T P Payne & J W Severinghaus (Eds.), Pulse oximetry (pp 165–172) Dorchester, England: Springer-Verlag Adams, A P., & Hahn, C E W (1982) Principles and practice of blood gas analysis Edinburgh, Scotland: Churchill Livingstone Bouma, G J., & Muizelaar, J P (1990) Relationship between cardiac output and cerebral blood flow in patients with intact and with impaired autoregulation Journal of Neurosurgery, 73, 368–374 Bouma, G J., Muizelaar, J P., Bandoh, K & Marmarou, A (1992) Blood pressure and intracranial pressurevolume dynamics in severe head injury: Relationship with cerebral blood flow Journal of Neurosurgery, 77, 15–19 Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it Monitoring in Mechanical Ventilation 271 Burton, G G., Hodgkin, J E., & Ward, J J (1997) Respiratory care: A guide to clinical practice (4th ed.) Baltimore, MD: Lippincott Williams & Wilkins Cannesson, M., Besnard, C., Durand, P G., Bohé, J., & Jacques, D (2008) Pleth variability index to monitor the respiratory variations in the pulse oximeter plethysmographic wave form amplitude and predict fluid responsiveness in the operating theatre British Journal of Anaesthesia, 101, 200–206 Carlon, G., Ray, C., Mordownik, S., Kopec, I., & Groeger, J S (1988) Capnography in mechanically ventilated patients Critical Care Medicine,16, 550–556 Chang, D W (2012) Respiratory care calculations (3rd ed.) Clifton Park, NY: Delmar, Cengage Learning Changaris, D G., McGraw, C P., Richardson, J D., Garretson, H D., Arpin, E J., & Shields, C B (1987) Correlation of cerebral perfusion pressure and Glasgow Coma Scale to outcome Journal of Trauma, 27, 1007–1013 Chesnut, R M., Marshall, S B., Piek, J., Blunt, B A., Klauber, M R., & Marshall, L F (1993) Early and late systemic hypotension as a frequent and fundamental source of cerebral ischaemia following severe brain injury in the Traumatic Coma Data Bank Acta Neurochirurgica Supplement, 59, 121–125 DeFelice, C., Vecchio, A D., Criscuolo, M., Lozupone, A., Parrini, S., & Latini, G (2002) The pulse oximeter perfusion index as a predictor for high illness severity in neonates European Journal of Pediatrics, 161, 561–562 Eberhard, P., Mindt, W., & Schafer, R (1981) Cutaneous blood gas monitoring in the adult Critical Care Medicine, 9, 702–705 Girault, C., Defouilloy, C., Richard, J C., & Muir, J F (1994) Weaning criteria from mechanical ventilation Monaldi Archives for Chest Disease, 49(2), 118–124 Gravelyn, T R., & Weg, J R (1980) Respiratory rate as an indicator of acute respiratory dysfunction Journal of the American Medical Association, 244, 1123–1125 Hagar, H., Church, S., Mandadi, G., Pulley, D., & Kurz, A (2004) The perfusion index measured by a pulse oximeter indicates pain stimuli in anesthetized volunteers Anesthesiology, 101, A514 Hess, D (1990) Capnometry and capnography: Technical aspects, physiologic aspects, and clinical applications Respiratory Care, 35, 557–573 Huch, R., Lubbers, D W., & Huch, A (1974) Reliability of transcutaneous monitoring of arterial PO2 in newborn infants Archives of Disease in Childhood, 49(3), 213–218 Jubran, A., & Tobin, M J (1990) Reliability for pulse oximetry in titrating supplemental oxygen therapy in ventilator-dependent patients CHEST Journal, 97, 1420–1425 Kakazu, C Z., Chen, B J., & Kwan, W F (2005) Masimo set technology using perfusion index is a sensitive indicator for epidural onset Anesthesiology, 103, A576 Klein, J (2008) Transcutaneous oxygen (TcPO2) monitors http://www.uihealthcare.com/depts/med/pediatrics/ iowaneonatologyhandbook/pulmonary/transoxygen.html.Accessed August 8, 2011 Kraus, P A., Lipman, J., Lee, C C., Wilson, W E., Scribante, J., Barr, J., Brown, J M (1993) Acute lung injury at Baragwanath ICU—An eight-month audit and call for consensus for other organ failure in the adult respiratory distress syndrome CHEST Journal, 103(6), 1832–1836 Krieger, B P., & Ershowshy, P (1994) Noninvasive detection of respiratory failure in the intensive care unit CHEST Journal, 2, 254–261 Malley, W J (1990) Clinical blood gases—application & noninvasive alternatives Philadelphia, PA: W B Saunders Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it 272 Chapter Marini, J J (1988) Monitoring during mechanical ventilation Clinics in Chest Medicine, 9(1)73–100 Marion, D W., Darby, J., & Yonas, H (1991) Acute regional cerebral blood flow changes caused by severe head injuries Journal of Neurosurgery, 74, 407–414 Marmarou, A., Anderson, R L., Ward, J D., Choi, S C., & Young, H F (1991) Impact of ICP instability and hypotension on outcome in patients with severe head trauma Journal of Neurosurgery, 75, S59–S66 Niehoff, J., Delguercio, C., LaMorte, W., Hughes-Grasberger, S L., Heard, S., Dennis, R., & Yeston, N (1988) Efficacy of pulse oximetry andcapnometry in postoperative ventilatory weaning Critical Care Medicine, 16(7), 701–705 Novametrix Medical Systems, Inc (1991) Capnograph Monitor Model 1260 User’s Manual Wallingford, CT Palmisano, B W., & Severinghaus, J W (1990) Transcutaneous PCO2 and PO2: A multicenter study of accuracy Journal of Clinical Monitoring and Computing, 6, 189–195 Perel, A., & Stock, M C (1992) Handbook of mechanical ventilatory support Baltimore, MD: Lippincott Williams & Wilkins Pologe, J A (1987) Pulse oximetry: Technical aspects International Anesthesiology Clinics, 25, 137–154 Rooth, G (1974) Acid-base and electrolyte balance Chicago, IL: Year Book Medical Publishers Rosner, M J., & Daughton, S (1990) Cerebral perfusion pressure management in head injury Journal of Trauma, 30, 933–941 Rotello, L C., Warren, J., Jastremski, M S., & Milewski, A (1992) A nurse-directed protocol using pulse oximetry to wean mechanically ventilated patients from toxic oxygen concentrations CHEST Journal, 102, 1833–1835 Schnapp, L M., & Cohen, N H (1990) Pulse oximetry uses and abuses CHEST Journal, 98, 1244–1250 Shapiro, B A., & Cane, R D (1989) Blood gas monitoring: Yesterday, today, and tomorrow Critical Care Medicine, 17, 573–581 Shapiro, B A., Peruzzi, W T., & Kozlowski-Templin, R (1994) Clinical application of blood gases (5th ed.) St Louis, MO: Mosby Shelley, E J (1989) CSI capnography training manual Waukesha, WI: Criticare Systems Stoller, J K (1991) Establishing clinical unweanability Respiratory Care, 36, 186–198 Tobin, M J (1990) Respiratory monitoring during mechanical ventilation Critical Care Clinics, 6(3), 679–707 Tobin, M J., Perez, W., Guenther, S M., Semmes, B J., Mador, M J., Allen, S J., Dantzker, D R (1986) The pattern of breathing during successful and unsuccessful trails of weaning from mechanical ventilation American Review of Respiratory Disease, 134, 1111–1118 Tremper, K., & Shoemaker, W C (1981) Transcutaneous oxygen monitoring of critically ill adults with and without low flow shock Critical Care Medicine, 9, 706–709 Tremper, K., Waxman, K., & Shoemaker, W C (1979) Effects of hypoxia and shock on trans cutaneous PO2 values in dogs Critical Care Medicine, 7, 526 Welch, J P., DeCesare, R., & Hess, D (1990) Pulse oximetry: Instrumentation and clinical applications Respiratory Care, 35, 584–601 West, J B (2011) Respiratory physiology (9th ed) Philadelphia, PA: Lippincott Williams & Wilkins Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it Monitoring in Mechanical Ventilation 273 Whitaker, K B (2001) Comprehensive perinatal and pediatric respiratory care (3rd ed.).Clifton Park, NY: Delmar, Cengage Learning White, G C (2003) Basic clinical lab competencies for respiratory care: an integrated approach (4th ed.) Clifton Park, NY: Delmar, Cengage Learning White, P F., & Boyle, W A (1989) Nail polish and oximetry Anesthesia & Analgesia, 68, 546–547 Wilkins, R L., & Dexter, J R (1998) Respiratory disease—Principles of patient care (2nd ed.) Philadelphia, PA: F A Davis Copyright 2013 Cengage Learning All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Editorial review has deemed that any suppressed content does not materially affect the overall learning experience Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it ... Resources XI 10 5 10 6 10 7 10 8 10 8 10 8 10 9 10 9 10 9 11 1 11 2 11 2 11 3 11 3 11 4 11 4 11 5 11 5 11 5 11 6 11 6 11 9 11 9 12 3 Chapter 5: Special Airways For Ventilation Introduction Oropharyngeal Airway Types of Oropharyngeal... Contraindications Safety Requirements 15 1 15 2 15 3 15 4 15 4 15 5 15 5 15 6 15 6 15 7 16 1 16 2 16 2 16 3 16 3 16 3 16 5 16 7 16 8 16 8 16 8 17 1 17 1 17 1 17 2 17 3 17 5 17 7 17 7 17 7 Copyright 2 013 Cengage Learning All Rights... Hypoxia Clinical Conditions Leading to Mechancial Ventilation Depressed Respiratory Drive Excessive Ventilatory Workload Failure of Ventilatory Pump 3 5 6 10 10 10 11 11 11 12 12 13 14 15 16 17 18 18