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  1. Home
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  3. Capnography
  • Cited by 29
Publisher:
Cambridge University Press
Online publication date:
August 2011
Print publication year:
2011
Online ISBN:
9780511933837
DOI:
https://doi.org/10.1017/CBO9780511933837
Subjects:
Anesthesia, Intensive Care, Pain Management, Emergency Medicine, Medicine
Information

Book description

In recent years capnography has gained a foothold in the medical field and is fast becoming a standard of care in anaesthesiology and critical care medicine. In addition, newer applications have emerged which have expanded the utility of capnographs in a number of medical disciplines. This new edition of the definitive text on capnography reviews every aspect of this valuable diagnostic technique. An introductory section summarises the basic physiology of carbon dioxide generation and transport in the body. A technical section describes how the instruments work, and a comprehensive clinical section reviews the use of capnography to diagnose a wide range of clinical disorders. Edited by the world experts in the technique, and with over 40 specialist contributors, Capnography, second edition, is the most comprehensive review available on the application of capnography in health care.

Reviews

Review of the first edition: ‘… addresses the physiologic and technological considerations that need to be understood to make capnography a clinically useful tool and should be standard reading for those who depend on it as an anesthetic monitor.'

Source: Anesthesiology Journal

Review of the first edition: ‘… a good addition to the reference library of departments of anesthesiology, critical care and emergency medicine.'

Source: Canadian Journal of Anesthesiology

'The inclusion of informative chapters on neonatal monitoring, sleep medicine, sedation, and veterinary medicine usefully widens the appeal of the book … [It] should be seen as an essential specialist reference book for the departmental library that those interested and/or needing to gain knowledge in capnography … can dip in and out of when required.'

Source: British Journal of Anaesthesia

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Contents

Page 2 of 2

Contents
  • 23 - PaCO2, PetCO2, and gradient
    pp 225-230
  • View abstract

    Summary

    Mankind lives, works, and plays within an extensive range of high- and low-pressure environments. It is important to understand how altitude affects atmospheric pressure and subsequent alveolar oxygen availability. In addition to pressure-related changes, there are multiple environmental stresses that occur during high-altitude exposures that amplify potential dangers. The most serious complications of altitude exposure are associated with a syndrome known as acute mountain sickness (AMS). Typical symptoms include headache, nausea, anorexia, insomnia, and, occasionally, vomiting. A variety of medications may impact the course of these conditions. The sulfa-based, carbonic anhydrase inhibitor diuretic, acetazolamide, induces metabolic acidosis, stimulating ventilation and thereby mimicking the natural respiratory response to altitude, which may assist in hastening acclimatization. Hyperbaric chambers, commonly used for treatment of diving injuries, carbon monoxide poisonings, or wound care, are examples of the therapeutic benefits of elevated pressures. Capnometers measure either partial pressures or percent volumes of gases.
  • 24 - The physiologic basis for capnometric monitoring in shock
    pp 231-238
  • View abstract

    Summary

    This chapter describes several conditions that have been associated with hypocapnia and in which capnography biofeedback may present a viable biobehavioral treatment option. Given the assumed central role of hypocapnia in panic development and maintenance, capnometry-assisted respiratory training (CART) was developed as a novel, non-pharmacological treatment to counteract the respiratory abnormalities observed in panic disorder (PD). To overcome the deficiencies of earlier hypoventilation training studies in asthma, CART has successfully been adapted to asthma patients. Panic and asthma patients in the studies described here showed clear clinical benefits from using a portable capnometer as a behavioral therapy tool. Portable capnometry devices facilitate the patient's home training efficiency, self-modification efforts, and treatment compliance by immediate, objective feedback of respiratory parameters. Ambulatory capnometry devices with electronic data storage allow the therapist to track a patient's progress without having to rely exclusively on retrospective self-reporting.
  • 25 - Carbon dioxide production, metabolism, and anesthesia
    pp 239-249
  • View abstract

    Summary

    This chapter reviews the current status of combining the new evolving technologies of CO2 monitoring and non-invasive positive pressure ventilation (NPPV). It explores the advantages as well as the challenges that prompt further research. The non-invasive character of both NPPV and capnography make the combination attractive for the clinical management of acute and chronic respiratory failure. Several different types of patient interfaces are available for the delivery of non-invasive ventilation, including full face masks, complete face masks, nasal masks, sealed helmets, nasal pillows, mouthpieces and custom-fabricated masks. Sidestream gas measurement offers a number of sampling locations, including: inside the mask, at the mask outlet, or with the nasal cannula at or near the patient's nostrils. It is plausible that the synergies between NPPV and time/volumetric capnography will help the clinician to more rapidly identify therapeutic pressure levels that optimize CO2 elimination and patient work of breathing-key objectives for non-invasive ventilation.
  • 26 - Tissue- and organ-specific effects of carbon dioxide
    pp 250-258
  • View abstract

    Summary

    Monitoring PETCO2 serves as a useful adjunct in weaning postoperative patients from mechanical ventilation. Several laboratory techniques are commonly used as adjuncts to clinical assessment of the adequacy of ventilation. This chapter focuses on the procedures that are utilized for weaning patients from the ventilator. Successful weaning during the postoperative period requires the assurance that the patient is clinically stable and without clinically significant residual effects of the anesthetic agents utilized during surgery. Some clinicians utilize PETCO2 as a marker of the metabolic rate and, therefore, as a way of determining optimal ventilator settings during the weaning process. A variety of different devices are available to the practitioner caring for these patients. Data from PETCO2 monitoring should be used in conjunction with information derived from a clinical evaluation of the patient.
  • 27 - Atmospheric monitoring outside the healthcare environment and within enclosed environments: a historical perspective
    pp 261-271
  • View abstract

    Summary

    This chapter focuses on the use of capnography to optimize and minimize the length of mechanical ventilation. Mechanical ventilation can be divided into three phases: acute stabilization, pre-weaning, and weaning/ extubation readiness testing. Alveolar minute ventilation is determined from the volumetric capnogram. Liberation from mechanical ventilation implies the use of an extubation readiness test to withdraw mechanical ventilation as soon as the patient meets extubation criteria regardless of the level of ventilatory support. A myriad of adversities make weaning and liberation from mechanical ventilation an extremely important clinical issue. With the majority of intensive care unit (ICU) patients requiring mechanical ventilation, minimizing the duration of mechanical ventilation while optimizing the potential for successful extubation is crucial in the management of critically ill patients. Capnography, both time-based and volumetric, allows mechanical ventilatory strategies to be designed with clear, precise, objective criteria.
  • 28 - Capnography in veterinary medicine
    pp 272-280
  • View abstract

    Summary

    Volumetric capnography (VC) provides valuable insights into lung collapse-recruitment physiology in a noninvasive and real-time manner, and thus lends itself to monitoring cyclic recruitment maneuvers at the bedside. Lung recruitment is a pressure-dependent phenomenon. Positive end-expiratory pressure (PEEP) needed to prevent the lung from recollapse after the recruitment maneuver is higher in patients with pulmonary diseases. Lung recruitment improves CO2 elimination by increasing the area of the alveolar-capillary membrane available for gas exchange. Lung recruitment affects the last two processes, mainly as a consequence of opening previously collapsed pulmonary capillaries and alveoli. Data from VC during lung recruitment can be grouped and analyzed in four principal ways according to CO2 kinetics: lung perfusion; gas exchange; lung ventilation; and gas transport within the airways. The sensitivity and specificity of non-invasive VC can be enhanced by supplemental invasive measurements of gas exchange.
  • 29 - Carbon dioxide pathophysiology
    pp 283-294
  • View abstract

    Summary

    This chapter highlights the role of capnography as a monitoring tool with the different adjuncts to mechanical ventilation that are currently used in critically ill patients. The application of positive end-expiratory pressure (PEEP) is used to increase lung volume and improve oxygenation in patients with acute lung injury (ALI). Studies of unilateral lung injury demonstrate that the consolidated lung regions do not expand to total lung capacity during inflation. Tracheal gas insufflation (TGI) is an adjunct to mechanical ventilation that allows ventilation with small tidal volumes while CO2 is satisfactorily eliminated. High-frequency ventilation (HFV) techniques have three essential elements in common: a high-pressure flow generator, a valve for flow interruption, and a circuit for connection to the patient. Measurement of deadspace fraction early in the course of acute respiratory failure may provide clinicians important physiologic and prognostic information.
  • 31 - Ventilation/perfusion abnormalities and capnography
    pp 313-328
  • View abstract

    Summary

    This chapter discusses two roles for capnography in the assessment and treatment of patients in cardiac arrest. It evaluates the efficacy of cardiopulmonary resuscitation (CPR), and cessation of resuscitation. A number of animal studies have shown an excellent correlation between end-tidal carbon dioxide (PETCO2) and cardiac output during states of low flow and during CPR. An animal model with ultrasound flow probes and radioactive microspheres was used to examine the relationships between PETCO2 and cardiac output, cerebral perfusion, and renal perfusion. A number of studies have found that PETCO2 values may change transiently after the administration of intravenous epinephrine or sodium bicarbonate. One of several studies that examined the active compression/decompression CPR (active compression/decompression (ACD)/CPR) technique used PETCO2 as a marker for cardiac output to compare the hemodynamics generated by the ACD/CPR method to standard CPR in the out-of-hospital setting.
  • 32 - Capnographic measures
    pp 329-339
  • View abstract

    Summary

    This chapter describes the pathophysiologic basis and use of capnography in the detection of pulmonary embolism (PE) from a variety of causes. Pulmonary embolism results in an increase in respiratory deadspace, specifically alveolar deadspace, which can be determined with parameters obtained with capnography. Pulmonary embolism results in an occlusion or limitation of flow in the pulmonary vasculature to respiratory units. Pulmonary embolism effects an increase in the physiologic deadspace by increasing alveolar deadspace, a component of the physiologic deadspace. FDlate is determined from fitting the phase III slope portion of the volumetric capnogram. The ability of volumetric capnography to track the resolution of pulmonary emboli with thrombolytic therapy has also been investigated. Evaluation of patients with various parameters derived from capnography holds promise for early bedside non-invasive detection of embolism, thereby allowing prompt and effective therapy.
  • 33 - Improving the analysis of volumetric capnograms
    pp 340-346
  • View abstract

    Summary

    This chapter reviews the background and theory of complete and partial CO2 rebreathing Fick cardiac output (QT) measurement, the literature on clinical testing, and presents examples that demonstrate its utility during acute hemodynamic challenges. The classic Fick principle was designed to measure pulmonary capillary blood flow (QC), which comprises 98% of QT in subjects with little or no intrapulmonary or cardiac shunting. Clinical experience has repeatedly demonstrated that severe acute reduction in pulmonary blood flow during constant ventilation, e.g. due to ventricular fibrillation, is accompanied by a major PETCO2 reduction. The most critical need for continuous QT measurements is seen in patients with hemodynamic instability. Clinical experience with non-invasive cardiac output monitoring has also provided readily recognizable hemodynamic profiles of vasodilation, hypovolemia, sepsis, and acute heart failure. Continuous non-invasive QT monitoring can provide critical cardiovascular information during everyday clinical practice.
  • 34 - Capnography and the single-path model applied to cardiac output recovery and airway structure and function
    pp 347-359
  • View abstract

    Summary

    Quantitative and/or qualitative analysis of exhaled carbon dioxide (CO2) has become standard practice in many clinical situations. The rationale for measuring the partial pressure of CO2 (PCO2) in exhaled gas is the assumption that end-tidal PCO2 (PETCO2) is a reflection of alveolar PCO2 (PaCO2). Hemoglobin plays an essential role in CO2 transport and elimination. Elimination of CO2 from the lung occurs as a function of gas exchange between the atmosphere and alveoli. In order to gain a greater understanding of the gradient between PaCO2 and PETCO2, an analysis of the interaction of pulmonary ventilation and perfusion is necessary. The alveolar gas equation (AGE) is used to analyze the effect of ventilation on oxygenation of arterial blood. An understanding of the interrelationship between pulmonary perfusion, ventilation, tidal volume, and regional VA/Q will enhance the utility of capnography as a monitor.
  • 35 - Carbon dioxide and the control of breathing: a quantitative approach
    pp 360-370
  • View abstract

    Summary

    Common clinical situations that lead to shock include hemorrhage, myocardial infarction, heart failure, trauma, sepsis, and cardiac arrest. Regardless of the cause, clinicians are better able to treat shock if they understand the underlying mechanisms, shared mechanisms, and physiologic events. It is the relationship between VO2 and carbon dioxide (CO2) production (VOCO2) that forms the general foundation for the utility of VOCO2 and end-tidal PCO2 (PETCO2) monitoring in shock states. The ability of the measurement of the partial pressure of expired carbon dioxide (PETCO2) monitoring to reflect tissue perfusion lies in its ability to closely reflect alveolar CO2. Several options to monitor tissue CO2 in various shock states have been studied, and include transcutaneous CO2(PtcCO2) skin monitoring, interstitial fiberoptic PCO2, gastric mucosal CO2 via gastric tonometry (PgCO2), and sublingual tonometry (PslCO2). These measurements detect changes in tissue CO2 as a reflection of changes in DO2.
  • 36 - Technical specifications and standards
    pp 373-380
  • View abstract

    Summary

    The amounts of O2 consumed and CO2 produced reflect the rate of body metabolism and the types of nutrients metabolized. The tasks of the respiratory and cardiovascular systems are to ensure that the cells of the body receive sufficient O2 and adequate amounts of CO2 are removed. Human lungs excrete almost all the CO2 produced, with only a miniscule amount excreted through the skin. When measuring CO2 production, gas leaks around endotracheal tubes render measurements inaccurate due to loss of expiratory minute ventilation. Anesthesia and surgery greatly affect body homeostasis and, consequently, alter the performance of the respiratory, cardiovascular, and metabolic systems, which influences the elimination of CO2 from the human body. The CO2 insufflated into the peritoneal cavity diffuses into the abdominal organs and abdominal wall. The use of hypothermic cardiopulmonary bypass (CPB) during open-heart surgery causes many changes in body homeostasis.
  • 37 - Carbon dioxide measurement
    pp 381-396
  • View abstract

    Summary

    This chapter focuses on the effects of hypo- and hypercapnia at the organ and tissue level. Carbon dioxide's role in determining acid-base status and tissue oxygenation is described, followed by its effects on major organ systems. The higher lipid solubility of CO2 compared to hydrogen ions allows acid-base changes caused by respiratory acidosis and alkalosis to equilibrate between extra- and intracellular fluids much faster than changes caused by metabolic acidosis or alkalosis. The primary determinants of tissue oxygen availability are arterial O2 tension, cardiac output, and local perfusion. Hypocapnia induced by hyperventilation is clinically used for treatment of increased intracranial pressure (ICP), but the compromise in tissue perfusion, and thus the resulting secondary ischemia, should be factored into the risk-benefit equation. The active management of CO2 is a promising strategy to consider for improving tissue perfusion, providing anti-inflammatory effects, and preventing apoptotic injury.
  • 39 - Combining flow and carbon dioxide
    pp 407-412
  • View abstract

    Summary

    Enclosed and semi-enclosed environments, particularly those in extremely isolated and hostile environments, such as outer space and the deep oceans, present unique challenges in terms of maintaining safe working conditions for the individuals exposed to them. The best approach to view the current concern about greenhouse gases is to revisit the past, particularly through ice core analysis, which can yield a record of thousands of years. Many hazardous gases are present in mines, including sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and methane (CH4). The study of completely self-contained and renewable environments was attempted with several closed ecosystem experiments in order to better understand the closed environment of the planet we live on. Monitoring and control systems for these environments are highly complex and specialized to meet unique challenges.
  • 40 - Brief history of time and volumetric capnography
    pp 415-429
  • View abstract

    Summary

    Veterinarians familiar with capnography have frequently encountered technical difficulties associated with the use of older or less expensive capnometers, especially when sampling respiratory gas from relatively small, spontaneously breathing, anesthetized animals that frequently demonstrate altered patterns of breathing. Volumetric capnography simultaneously measures expired CO2 and tidal volume, facilitating the identification of CO2 from three sequential compartments: apparatus (anesthetic equipment), anatomic deadspace, and progressively emptying alveoli (alveolar gas). Although mammalian respiratory anatomy and function are remarkably similar among species, there are obvious allometric differences. Capnography in animals such as rodents and birds, nevertheless, remains challenging. A wide range of respiratory volumes exists among animal species. There is remarkable similarity in arterial blood pH and gas values. Capnometry is more commonly used to monitor ventilation in anesthetized horses. Capnography has also been used to evaluate pulmonary function in awake dolphins.
  • 42 - The early days of volumetric capnography
    pp 457-460
  • View abstract

    Summary

    This chapter discusses the reduced and increased CO2 pressures and outlines some of the pathophysiology of CO2 production and transport, with special reference to capnography. Capnography has a special use in the assessment of patients for brain death with regard to the apnea test, wherein measurement of CO2 tensions are a component of assessing the viability of the brainstem. Any disruption in normal mitochondrial function manifests as diminished energy reserves and CO2 production, and is most rapidly evident in organs with high-energy requirements such as the brain, heart, kidney, and, especially, the eye. Carbonic anhydrase comprises a family name for a group of zinc-dependent enzymes that catalyze the reaction of bicarbonate and a proton to form water and CO2. Sodium bicarbonate is sometimes intravenously injected to treat acidemia in patients suffering from metabolic acidosis.
  • Appendix: Patterns of time-based capnograms
    pp 461-465
  • View abstract

    Summary

    Capnography can provide important clues concerning the acid-base status of patients. Arterial blood gas analysis is essential to properly evaluate the acid-base status, and diagnose and treat underlying disorders. Acids and bases are constantly formed in the body as by-products of metabolism, and are carefully regulated. Buffering mechanisms include intracellular and extracellular chemical buffers, regulation of CO2 by the respiratory and central nervous systems (CNS), and control of bicarbonate by the kidney. Capillary blood samples can be used, particularly in children, to measure arterial blood gases (ABGs). Loop and thiazide diuretics can incite a metabolic alkalosis, while carbonic anhydrase inhibitors can cause a metabolic acidosis. Overdoses of drugs can produce mixed acid-base disorders, such as the combined metabolic acidosis and respiratory alkalosis from a salicylate overdose. Simple acid-base disorders involve a primary abnormality in either metabolism or respiration that produces a secondary change, or compensatory response, in the other component.

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