On-line expiratory CO2 monitoring

  • Roger Fletcher


The single breath test for carbon dioxide (SBT-CO2) is the plot of expired FCO2 or CO2% against expired volume. It can be monitored during anaesthesia and in the intensive care unit with modest additions to generally available equipment. This paper describes some aspects of a computer program for presenting SBT-CO2 during controlled ventilation, in particular, the corrections to the primary data necessary for scientific accuracy. Examples are given of how the use of SBT-CO2 has increased our understanding of factors which influence the arterial-endtidal PCO2 difference (PaCO2-PE, CO2). PaCO2-PE, CO2 is, in a given individual, usually dependent on tidal volume and frequency. Changes in lung volume and manoeuvres such as opening the pleura also affect gas exchange. Monitoring CO2 elimination gives a measure of metabolic rate if ventilation and pulmonary perfusion are maintained. This facilitates ventilatory therapy in situations where CO2 production is greatly increased, e.g. sepsis and tetanus. On the other hand, if metabolism and ventilation are unchanged, a reduction in CO2 elimination implies reduced pulmonary perfusion. This can be seen during increased right-left shunting, such as in surgery in patients with congenital heart disease.


expiratory CO2 end-tidal CO2 metabolism ventilation perfusion 


  1. 1.
    Fletcher R, Jonson B, Cumming G, Brew J: The concept of deadspace with special references to the single breath test for carbon dioxide. Br J Anaesth 53: 77–88, 1981.PubMedCrossRefGoogle Scholar
  2. 2.
    Fletcher R, Jonson B: Deadspace and the single breath test for carbon dioxide during anaesthesia and artificial ventilation. Br J Anaesth 56: 109–119, 1984.PubMedCrossRefGoogle Scholar
  3. 3.
    Olsson SG, Fletcher R, Jonson B, Nordström L, Prakash O: Clinical studies of gas exchange during ventilatory support — a method using the Siemens-Elema CO2 Analyzer. Br J Anaesth 52: 491–499, 1980.PubMedCrossRefGoogle Scholar
  4. 4.
    Fletcher R, Malmkvist G, Jonson B, Jansson L: On-line deadspace measurement during cardiac surgery. Acta Anaesth Scand 30: 259–299, 1986.Google Scholar
  5. 5.
    Fletcher R, Niklason L, Drefeldt B: Gas exchange during controlled ventilation in children with normal and abnormal pulmonary circulation. Anesth Analg 65: 645–652, 1986. mal pulmonary circulation. Anesth Analg, in press.PubMedGoogle Scholar
  6. 6.
    Fletcher R, Werner O, Nordström L, Jonson B: Sources of error and corrections in measurement of carbon dioxide elimination with the Siemens-Elema CO2 Analyzer. Br J Anaesth 55: 177–185, 1983.PubMedCrossRefGoogle Scholar
  7. 7.
    Fletcher R: The single breath test for carbon dioxide. (1980) Thesis, University of Lund, Sweden (can be obtained from the author).Google Scholar
  8. 8.
    Aitken RS, Clarke-Kennedy AE: On the fluctuation in the composition of the alveolar air during the respiratory cycle in muscular exercise. J Physiol 65: 389–411, 1928.PubMedGoogle Scholar
  9. 9.
    Fowler WS: Lung function studies. II. The respiratory deadspace. Am J Physiol 154: 405–416, 1948.PubMedGoogle Scholar
  10. 10.
    Langley F, Even P, Duroux P, Nicolas RL, Cumming G: Ventilatory consequences of unilateral pulmonary artery occlusion. Les Colloques de l'Institut National de la Santé et de la Recherche Médicale 51: 209–212, 1975.Google Scholar
  11. 11.
    Wolff G, Brunner JX: Series deadspace volume assessed as the mean value of a distribution function. Int J Clin Monitoring Computing 1: 177–181, 1985.CrossRefGoogle Scholar
  12. 12.
    Fletcher R, Ranklev E, Olsson A-K, Leander S: Malignant hypothermia syndrome in an anxious patient. Br J Anaesth 53: 993–995, 1981.PubMedCrossRefGoogle Scholar
  13. 13.
    Fletcher R, Blennow G, Olsson A-K, Ranklev E, Törnebrandt K: Malignant hyperthermia in a myopathic child. Prolonged postoperative course requiring dantrolene. Acta Anaesth Scand 26: 435–438, 1982.PubMedCrossRefGoogle Scholar
  14. 14.
    Tydén HE, Joachimsson PO, Nyström SO: Ventilatory and metabolic effects of external heat supply after aortocoronary bypass surgery. Acta Anaesth Scand 29: (suppl 80) 80, 1985.Google Scholar
  15. 15.
    Schuller JL, Bovill JG, Nijveld A: End-tidal carbon dioxide concentration as an indicator of pulmonary blood flow during closed heart surgery in children. Br J Anaesth 57: 1257–1259, 1985.PubMedCrossRefGoogle Scholar
  16. 16.
    Fletcher R, Jögi P: Gas exchange during thoractomy in children. Br J Anaesth 58: 807 p, 1986.Google Scholar
  17. 17.
    Eckenhoff JE, Enderby GEH, Larsson A, Endridge A, Judevine DE: Pulmonary gas exchange during deliberate hypotension. Br J Anaesth 35: 750–758, 1963.PubMedCrossRefGoogle Scholar
  18. 18.
    Werner O, Malmkvist G, Beckman A, Stahle S, Nordström L: Carbon dioxide elimination from each lung during endobronchial anaesthesia. Br J Anaesth 56: 995–1001, 1984.PubMedCrossRefGoogle Scholar
  19. 19.
    Fletcher R, Jögi P: The effect of septal defect closure on gas exchange. Clinical Physiology, in press.Google Scholar
  20. 20.
    Raemer DB, Francis D, Philip IH, Gabel RA: Variation in PCO2 between arterial blood and peak expired gas during anesthesia. Anesth Analg 62: 1065 ff., 1983.Google Scholar
  21. 21.
    Jonmarker C, Nordström L, Werner O: Changes in functional residual capacity during cardiac surgery. Br J Anaesth 58: 428–432, 1986.PubMedCrossRefGoogle Scholar
  22. 22.
    Fletcher R: Deadspace, invasive and non-invasive. Br J Anaesth 57: 245–249, 1985.PubMedCrossRefGoogle Scholar

Copyright information

© Martinus Nijhoff Publishers 1986

Authors and Affiliations

  • Roger Fletcher
    • 1
  1. 1.Department of AnaesthesiaUniversity HospitalLundSweden

Personalised recommendations