Canadian Journal of Anaesthesia

, Volume 39, Issue 6, pp 617–632 | Cite as

Capnometry and anaesthesia

  • K. Bhavani-Shankar
  • H. Moseley
  • A. Y. Kumar
  • Y. Delph
Review Article


In the last decade, capnography has developed from a research instrument into a monitoring device considered to be essential during anaesthesia to ensure patient safety. Hence, a comprehensive understanding of capnography has become mandatory for the anaesthetist in charge of patients in the operating room and in the intensive care unit. This review of capnography includes the methods available to determine carbon dioxide in expired air, and an analysis of the physiology of capnograms, which are followed by a description of the applications of capnography in clinical practice. The theoretical backgrounds of the effect of barometric pressure, water vapour, nitrous oxide and other factors introducing errors in the accuracy of CO2 determination by the infra-red technique, currently the most popular method in use, are detailed. Physiological factors leading to changes in end-tidal carbon dioxide are discussed together with the clinical uses of this measurement to assess pulmonary blood flow indirectly, carbon dioxide production and adequacy of alveolar ventilation. The importance of understanding the shape of the capnogram as well as end-tidal carbon dioxide measurements is emphasized and its use in the early diagnosis of adverse events such as circuit disconnections, oesophageal intubation, defective breathing systems and hypoventilation is highlighted. Finally, the precautions required in the use and interpretation of capnography are presented with the caveat that although no instrument will replace the continuous presence of the attentive physician, end-tidal carbon dioxide monitoring can be effective in the early detection of anaesthesia-related intraoperative accidents.

Key words

carbon dioxide: end-tidal, measurement, monitoring measurement techniques: capnometry monitoring: carbon dioxide 


La capnographie est maintenant un élément essentiel du monitorage des patients pendant l’anesthésie générate et tout anesthésiste doit comprendre les principes de fonctionnement de cette technique. La présente révision décrit les méthodes disponibles de mesure de gaz carbonique (CO2) expiré, ainsi qu ’une analyse de la physiologie associée aux différents capnogrammes. Une description des applications cliniques de la capnographie fait suite à ces énoncés théoriques. Les effets de la pression barométrique, de la vapeur d’eau, du protoxide d’azote et de plusieurs autres facteurs affectant la mesure du CO2 a l’aide d’infra-rouge sont décrits. La capnographie permet une mesure indirecte de la circulation pulmonaire, de la production de CO2 et de la ventilation alveolaire. Ces mesures sont influencees par de nombreux facteurs physiologiques qu ’il importe de bien connaître afin de déterminer les limites de ce monitorage. Une bonne interprétation de la forme des cburbes de capnographie est nécessaire afin de permettre la détection précoce d’incidents dangereux tels un défaut ou débranchement du circuit anesthésique, une intubation oesophagienne ou une hypoventilation. Le présent travail permet à l’anesthésiste de revoir toutes ces notions et rappelle que même si la capnographie ne remplace pas la vigilance du clinicien, elle peut permettre la détection rapide d’événements qui pourraient mener à des complications anesthésiques.


  1. 1.
    Kalenda Z. Mastering Infrared Capnography. The Netherlands: Kerckebosch-Zeist, 1989.Google Scholar
  2. 2.
    Leigh MD, Jones JC, Motley HL. The expired carbon dioxide as a continuous guide of the pulmonary and circulatory systems during anesthesia and surgery. J Thorac Cardiovasc Surg 1961; 41: 597–610.Google Scholar
  3. 3.
    Luft KF. Uber eine neue methode der registrierenden gasanalyse mit hiffe der absorption ultraroter strahlen ohne spektrale zerlegung. Zeitschrift Fur Technische Physik 1943; 24: 97–104Google Scholar
  4. 4.
    Caplan RA, Posner KL, Ward RJ, Cheney FW. Adverse respiratory events in anesthesia: a closed claims analysis. Anesthesiology 1990; 72: 828–33.PubMedCrossRefGoogle Scholar
  5. 5.
    Cooper JB, Newbower RS, Kitz RJ. An analysis of major errors and equipment failures in anesthesia management: considerations for prevention and detection. Anesthesiology 1984; 60: 34–42.PubMedCrossRefGoogle Scholar
  6. 6.
    Eichhorn JH. Prevention of intraoperative anesthesia accidents and related severe injury through safety monitoring. Anesthesiology 1989; 70: 572–7.PubMedCrossRefGoogle Scholar
  7. 7.
    Tinker JH, Dull DL, Caplan RA, Ward RJ, Cheney FW. Monitoring devices in prevention of anesthetic mishaps: a closed claims analysis. Anesthesiology 1989; 71: 541–6.PubMedCrossRefGoogle Scholar
  8. 8.
    Weingarten M. Anesthetic and ventilator mishaps: prevention and detection. Crit Care Med 1986; 14: 1084–6.PubMedCrossRefGoogle Scholar
  9. 9.
    Coti CJ, Liu LMP, Szyfelbein SK, et al. Intraoperative events diagnosed by expired carbon dioxide monitoring in children. Can Anaesth Soc J 1986; 33: 315–20.Google Scholar
  10. 10.
    Birmingham PK, Cheney FW, Ward RJ. Esophageal intubation: a review of detection techniques. Anesth Analg 1986; 65: 886–91.PubMedCrossRefGoogle Scholar
  11. 11.
    O’Flaherty D, Adams AP. The end-tidal carbon dioxide detector. Assessment of new method to distinguish oesophageal from tracheal intubation. Anaesthesia 1990; 45: 653–5.PubMedCrossRefGoogle Scholar
  12. 12.
    Linko K, Paloheimo M, Tammisto T. Capnography for detection of accidental oesophageal intubation. Acta Anaesthesiol Scand 1983; 27: 199–202.PubMedGoogle Scholar
  13. 13.
    Murray IP, Modell JH. Early detection of endotracheal tube accidents by monitoring carbon dioxide concentration in respiratory gas. Anesthesiology 1983; 59: 344–6.PubMedCrossRefGoogle Scholar
  14. 14.
    Lillie PE, Roberts JG. Carbon dioxide monitoring. Anaesth Intensive Care 1988; 16: 41–4.PubMedGoogle Scholar
  15. 15.
    Guidelines to the practice of anaesthesia as recommended by the Canadian Anaesthetist’s Society. Toronto, 1989.Google Scholar
  16. 16.
    Raemer DB, Philip JH. Monitoring anesthetic and respiratory gases.In: Blitt CD (Ed.). Monitoring in Anesthesia and Critical Care Medicine. 2nd edition. New York: Churchill Livingstone, 1990: 373–86.Google Scholar
  17. 17.
    Tremper KK, Barker SJ. Fundamental principles of monitoring instrumentation.In: Miller RD (Ed.). Anesthesia Vol I. 3rd ed. New York: Churchill Livingstone, 1990: 957–99.Google Scholar
  18. 18.
    Carbon dioxide monitors. Health Devices 1986; 15: 255–85.Google Scholar
  19. 19.
    Møllgaard K. Acoustic gas measurement. Biomedical Instrumentation and Technology 1989; 23: 495–7.PubMedGoogle Scholar
  20. 20.
    Raemer DB, Calalang I. Accuracy of end-tidal carbon dioxide tension analyzers. J Clin Monit 1991; 7: 195–208.PubMedCrossRefGoogle Scholar
  21. 21.
    Olsson SG, Fletcher R, Jonson B, Nordstrom L, Prakash O. Clinical studies of a gas exchange during ventilatory support — a method of using the Siemens-Elema CO2 analyzer. Br J Anaesth 1980; 52: 491–9.PubMedCrossRefGoogle Scholar
  22. 22.
    Paloheimo M, Valli M, Ahjopalo H. A guide to CO2 monitoring. Finland: Datex Instrumentarium, 1988.Google Scholar
  23. 23.
    Kennell EM, Andrews RW, Wollman H. Correction factors for nitrous oxide in the infrared analysis of carbon dioxide. Anesthesiology 1973; 39: 441–3.PubMedCrossRefGoogle Scholar
  24. 24.
    Fletcher R, Werner O, Nordstrom L, Jonson B. Sources of error and their correction in the measurement of carbon dioxide elimination using the Siemens-Elema CO2 analyzer. Br J Anaesth 1983; 55: 177–85.PubMedCrossRefGoogle Scholar
  25. 25.
    Parbrook GD, Davis PD, Parbrook EO. Gas chromatography and mass spectrometry.In: Basic Physics and Measurement in Anaesthesia. 3rd ed. London: Butter-worth-Heinemann, 1990: 257–64.Google Scholar
  26. 26.
    From RP, Scamman FL. Ventilatory frequency influences accuracy of end-tidal CO2 measurements: analysis of seven capnometers. Anesth Analg 1988; 67: 884–6.PubMedCrossRefGoogle Scholar
  27. 27.
    Pasucci RC, Schena JA, Thompson JE. Comparison of a sidestream and mainstream capnometer in infants. Crit Care Med 1989; 17: 560–2.CrossRefGoogle Scholar
  28. 28.
    Brunner JX, Westenskow DR. How the rise time of carbon dioxide analysers influences the accuracy of carbon dioxide measurements. Br J Anaesth 1988; 61: 628–38.PubMedCrossRefGoogle Scholar
  29. 29.
    Schena J, Thompson J, Crone RK. Mechanical influences on the capnogram. Crit Care Med 1984; 12: 672–4.PubMedCrossRefGoogle Scholar
  30. 30.
    Nunn JF. Applied Respiratory Physiology. 3rd edition. London: Butterworths, 1987: 221–3.Google Scholar
  31. 31.
    Fletcher R. The single breath test for carbon dioxide. Thesis, Lund, 1980.Google Scholar
  32. 32.
    Fletcher R, Jonson B, Cumming G, Brew J. The concept of deadspace with special reference to the single breath test for carbon dioxide. Br J Anaesth 1981; 53: 77–88.PubMedCrossRefGoogle Scholar
  33. 33.
    West JB, Fowler KT, Hugh-Jones P, O’Donell TV. The measurement of the inequality of ventilation and of perfusion in the lung by the analysis of single expirate. Clin Sci 1957; 16: 549–65.PubMedGoogle Scholar
  34. 34.
    Nunn JF, Hill DW. Respiratory dead space and arterial to end-tidal CO2 tension difference in anesthetized man. J Appl Physiol 1960; 15: 383–9.PubMedGoogle Scholar
  35. 35.
    Fletcher R, Jonson B. Deadspace and the single breath test for carbon dioxide during anaesthesia and artificial ventilation. Br J Anaesth 1984; 56: 109–19.PubMedCrossRefGoogle Scholar
  36. 36.
    Shankar KB, Moseley H, Kumar Y, Vemula V. Arterial to end-tidal carbon dioxide tension difference during Caesarean section anaesthesia. Anaesthesia 1986; 41: 698–702.PubMedCrossRefGoogle Scholar
  37. 37.
    Askrog V. Changes in (a-A)CO2 difference and pulmonary artery pressure in anesthetized man. J Appl Physiol 1966; 21: 1299–305.PubMedGoogle Scholar
  38. 38.
    Fletcher R, Malmkvist G, Niklasson L, Jonson B. On linemeasurement of gas-exchange during cardiac surgery. Acta Anaesthesiol Scand 1986; 30: 295–9.PubMedCrossRefGoogle Scholar
  39. 39.
    Shankar KB, Moseley H, Kumar Y. Negative arterial to end-tidal gradients. Can J Anaesth 1991; 38: 260–1.PubMedGoogle Scholar
  40. 40.
    Russell GB, Graybeal JM, Strout JC. Stability of arterial to end-tidal carbon dioxide gradients during postoperative cardiorespiratory support. Can J Anaesth 1990; 37: 560–6.PubMedGoogle Scholar
  41. 41.
    Rich GF, Sconzo JM. Continuous end-tidal CO2 sampling within the proximal endotracheal tube estimates arterial CO2 tension in infants. Can J Anaesth 1991; 38: 201–3.PubMedGoogle Scholar
  42. 42.
    Shankar KB, Moseley H, Kumar Y, Vemula V, Krishnan A. The arterial to end-tidal carbon dioxide tension difference during anaesthesia for tubal ligations. Anaesthesia 1987; 42: 482–6.PubMedCrossRefGoogle Scholar
  43. 43.
    Jones NL, Robertson DG, Kane JW. Differences between end-tidal and arterial PCO2 in exercise. J Appl Physiol 1979; 47: 954–60.PubMedGoogle Scholar
  44. 44.
    Fletcher R. Arterial to end-tidal CO2 tension differences. Anaesthesia 1987; 42: 210–1.PubMedCrossRefGoogle Scholar
  45. 45.
    Weil MH, Bisera J, Trevino RP, Rackow EC. Cardiac output and end-tidal carbon dioxide. Crit Care Med 1985; 13: 907–9.PubMedGoogle Scholar
  46. 46.
    Pyles ST, Berman LS, Modell JH. Expiratory valve dysfunction in a semiclosed circle anesthesia circuits — verification by analysis of carbon dioxide waveform. Anesth Analg 1984; 63: 536–7.PubMedCrossRefGoogle Scholar
  47. 47.
    Berman LS, Pyles ST. Capnographic detection of anaesthesia circle valve malfunctions. Can J Anaesth 1988; 35: 473–5.PubMedGoogle Scholar
  48. 48.
    Van Genderingen HR, Gravenstein N, Van der Aa JJ, Gravenstein JS. Computer-assisted capnogram analysis. J Clin Monit 1987; 3: 194–200.PubMedCrossRefGoogle Scholar
  49. 49.
    Weingarten M. Respiratory monitoring of carbon dioxide and oxygen: a ten-year perspective. J Clin Monit 1990; 6: 217–25.PubMedCrossRefGoogle Scholar
  50. 50.
    Good ML. Capnography: a comprehensive review. American Society of Anesthesiologists Refresher Course Lectures: San Francisco, 1991: 431.Google Scholar
  51. 51.
    Adams AP. Capnography and pulse oximetry.In: Atkins RS, Adams AP (Eds.). Recent Advances in Anaesthesia and Analgesia. London: Churchill Livingstone, 1989: 155–75.Google Scholar
  52. 52.
    Smalhout B, Kalenda Z. An Atlas of Capnography. 2nd ed. Utrecht: Kerckebosch-Zeist, 1981.Google Scholar
  53. 53.
    Hoffbrand BI. The expiratory capnogram: a measure of ventilation-perfusion inequalities. Thorax 1966; 21: 518–23.PubMedCrossRefGoogle Scholar
  54. 54.
    Tulou PP, Walsh PM. Measurement of alveolar carbon dioxide tension at maximal expiration as an estimate of arterial carbon dioxide tension in patients with airway obstruction. Am Rev Respir Dis 1970; 102: 921–6.PubMedGoogle Scholar
  55. 55.
    Swedlow DB, Irving SM. Monitoring and patient safety.In: Blitt CD (Ed.). Monitoring in Anesthesia and Critical Care Medicine. 2nd ed., New York: Churchill Livingstone, 1990: 33–64.Google Scholar
  56. 56.
    Lent G, Heipertz W, Epple E. Capnometry for continuous postoperative monitoring of nonintubated, spontaneously breathing patients. J Clin Monit 1991; 7: 245–8.CrossRefGoogle Scholar
  57. 57.
    Roy J, McNulty SE, Torjman MC. An improved nasal prong apparatus for end-tidal carbon dioxide monitoring in awake, sedated patients. J Clin Monit 1991; 7: 249–52.PubMedCrossRefGoogle Scholar
  58. 58.
    Brampton WJ, Watson RJ. Arterial to end-tidal carbon dioxide tension difference during laparoscopy. Anaesthesia 1990; 45: 210–4.PubMedCrossRefGoogle Scholar
  59. 59.
    Bowe EA, Boyson PG, Broome JA, Klein JrEF. Accurate determination of end-tidal carbon dioxide during administration of oxygen by nasal cannulae. J Clin Monit 1989; 5: 105–10.PubMedCrossRefGoogle Scholar
  60. 60.
    Martin DG. Leak detection with a capnograph. Anaesthesia 1987; 42: 1025.PubMedCrossRefGoogle Scholar
  61. 61.
    Sum Ping ST, Mehta MP, Symreng T. Reliability of capnography in identifying esophageal intubation with carbonated beverage or antacid in the stomach. Anesth Analg 1991; 73: 333–7.PubMedCrossRefGoogle Scholar
  62. 62.
    Linko K, Paloheimo M. Capnography facilitates blind nasotracheal intubation. Acta Anaesthesiol Belg 1983; 34: 117–22.PubMedGoogle Scholar
  63. 63.
    Omoigui S, Glass P, Martel DLJ, et al. Blind nasal intubation with audio-capnometry. Anesth Analg 1991; 72: 392–3.PubMedCrossRefGoogle Scholar
  64. 64.
    Shafieha MJ, Sit J, Kartha R, et al. End-tidal CO2 analyzers in proper positioning of the double-lumen tubes. Anesthesiology 1986; 64: 844–5.PubMedCrossRefGoogle Scholar
  65. 65.
    Shankar KB, Moseley H, Kumar AY. Dual end-tidal CO2 monitoring and double-lumen tubes. Can J Anaesth 1992; 39: 100–1.PubMedGoogle Scholar
  66. 66.
    Baudendistel L, Goudsouzian N, Coti C, Strafford M. End-tidal CO2 monitoring: its use in the diagnosis and management of malignant hyperpyrexia. Anaesthesia 1984; 39: 1000–3.PubMedCrossRefGoogle Scholar
  67. 67.
    Smelt WLH, De Lange JJ, Booij LHDJ. Capnography and air embolism. Can Anaesth Soc J 1986; 33: 113–5.PubMedGoogle Scholar
  68. 68.
    Shulman D, Aronson HB. Capnography in the early diagnosis of carbon dioxide embolism during laparoscopy. Can Anaesth Soc J 1984; 31: 455–9.PubMedGoogle Scholar
  69. 69.
    Falk JL, Rackow EC, Weil MH. End-tidal carbon dioxide concentration during cardiopulmonary resuscitation. N Engl J Med 1988; 318: 607–11.PubMedGoogle Scholar
  70. 70.
    Sanders AB, Kern KB, Otto CW, Milander MM, Ewy GA. End-tidal carbon dioxide monitoring during cardiopulmonary resuscitation. A prognostic indicator for survival. JAMA 1989; 262: 1347–51.PubMedCrossRefGoogle Scholar
  71. 71.
    Mason CJ. Single breath end-tidal PCO2 measurements during high frequency jet ventilation in critical care patients. Anaesthesia 1986; 41: 1251–4.PubMedCrossRefGoogle Scholar
  72. 72.
    Blanch L, Fernandez R, Benito S, Mancebo J, Net A. Effects of PEEP on the arterial minus end-tidal carbon dioxide gradient. Chest 1987; 92: 451–4.PubMedCrossRefGoogle Scholar
  73. 73.
    Mogue LR, Rantala B. Capnometers. J Clin Monit 1988; 7: 245–8.Google Scholar
  74. 74.
    McEvedy BAB, Mcleod ME, Kirpalani H, Volgyesi GA, Lerman J. End-tidal carbon dioxide measurements in critically ill neonates: a comparison of sidestream and mainstream capnometers. Can J Anaesth 1990; 37: 322–6.PubMedGoogle Scholar
  75. 75.
    Hillier SC, Badgwell JM, Mcleod ME, Creighton RE, Lerman J. Accuracy of end-tidal PCO2 measurements using a sidestream capnometer in infants and children ventilated with the Sechrist infant ventilator. Can J Anaesth 1990; 37: 318–21.PubMedGoogle Scholar
  76. 76.
    Gravenstein N, Lampotang S, Beneken JEW. Factors influencing capnography in the Bain circuit. J Clin Monit 1985; 1:6–10.PubMedCrossRefGoogle Scholar
  77. 77.
    Eichhorn JH. Did monitoring standards influence outcome? Anesthesiology 1989; 71: 808–10.Google Scholar
  78. 78.
    Brown FN, McIntyre RW. Is the tide turning? Can J Anaesth 1990; 37: 4–6.PubMedGoogle Scholar
  79. 79.
    Duncan PG, Cohen MM. Pulse oximetry and capnography in anaesthetic practice: an epidemiological appraisal. Can J Anaesth 1991; 38: 619–25.PubMedCrossRefGoogle Scholar
  80. 80.
    Chopin C, Fesard P, Mangalaboyi J, et al. Use of capnography in diagnosis of pulmonary embolism during acute respiratory failure of chronic obstructive pulmonary disease. Crit Care Med 1990; 18: 353–7.PubMedCrossRefGoogle Scholar
  81. 81.
    Chambers JB, Kiff PJ, Gardner WN, Jackson G, Bass C. Value of measuring end-tidal partial pressure of carbon dioxide as an adjunct to treadmill excercise testing. BMJ 1988; 296: 1281–5.PubMedGoogle Scholar

Copyright information

© Canadian Anesthesiologists 1992

Authors and Affiliations

  • K. Bhavani-Shankar
    • 1
  • H. Moseley
    • 1
  • A. Y. Kumar
    • 1
  • Y. Delph
    • 1
  1. 1.Department of AnaesthesiaQueen Elizabeth Hospital, University of West IndiesBarbadosWest Indies

Personalised recommendations