Capnometry in Exotic Animal Species

Key Points

  • Capnometry describes the maximum value of carbon dioxide measured at the end of expiration or end-tidal carbon dioxide (ETCO2).
  • Ventilation status, in the form of ETCO2, should ideally be monitored during general anesthesia.
  • End-tidal carbon dioxide levels correlate fairly well with arterial carbon dioxide (PaCO2) in birds and mammals.
  • Capnography should only be used to measure trends in reptiles as ETCO2 levels can be quite different from PaCO2 due to cardiac shunting of blood past the lungs.
  • Both side-stream and mainstream capnographs can be used in exotic animal patients. Although side-stream units have a reduced effect on mechanical dead space, they are not reliable with small respiratory volumes.
  • Normocapnia in mammals is associated with an ETCO2 of 35-45 mm Hg.
  • Research suggests that an ETCO2 of 30-45 mm Hg is considered appropriate for the anesthetized grey parrot.
  • Hypoventilation and hypercapnia are a potential problem in every species under general anesthesia, however the negative physiologic effects of hypoventilation develop much more rapidly in anesthetized birds. Therefore, assisted ventilation should begin immediately after anesthetic induction in birds to prevent hypercapnia and hypoxemia.
  • This article is part of a RACE-approved Anesthetic Monitoring teaching module. Visit the articles on monitoring the degree of central nervous system depression (anesthetic depth), vital signsblood pressure, pulse oximetry, and electrocardiography in exotic animal patients for additional information.

Capnometry measures the maximum value of carbon dioxide (CO2) obtained at the end of expiration or end-tidal carbon dioxide (ETCO2). There is good correlation between ETCO2 and arterial CO2 in birds and mammals and capnography can be used as a reliable tool to evaluate the adequacy of ventilation in these species. Capnography can only be used to identify trends in reptiles because of cardiac shunting of blood past the reptilian lungs . . .


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References


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FURTHER READING

Becker DE, Casabianca AB. Respiratory monitoring: physiological and technical considerations. Anesth Prog 56(1):14-22, 2009.

Burton JH, Harrah JD. Germann CA, Dillon DC. Does end-tidal carbon dioxide monitoring detect respiratory events prior to current sedation monitoring practices? Acad Emerg Med 13(5):500-504, 2006.

Fox LK, Flegal MC, Kuhlman SM. Principles of anesthesia monitoring – capnography. J Invest Surg 22(6):452-454, 2009.

Heard D. Galliformes and columbiformes. In: West G, Heard D, Caulkett N (eds). Zoo Animal and Wildlife Immobilization and Anesthesia, 2nd ed. Ames, IA: Wiley Blackwell; 2015:871.

Kodali BS. Capnography outside the operating rooms. Anesthesiology 118(1):192-201, 2013. Available at http://anesthesiology.pubs.asahq.org/article.aspx?articleid=2034665&resultClick=3.
Longley L. Anaesthesia of Exotic Pets. London: Elsevier; 2008.

Nevarez JG. Monitoring during avian and exotic pet anesthesia, Semin Avian Exot Pet Med 14(4):277-283, 2005.

Storz JF, Natarajan C, Moriyama H, et al. Oxygenation properties and isoform diversity of snake hemoglobins. Am J Physiol Regul Integr Comp Physiol 309(9):R1178-R1191, 2015.

Taylor, EW , Leite, CAC, Mckenzie, DJ, Wang, T. Control of respiration in fish, amphibians and reptiles
Braz J Med Biol Res 43(5):409-424, 2010.

Thawley V, Waddel LS. Pulse oximetry and capnometry. Topics in Companion Animal Medicine 28(3):124-128, 2013.

Torsoni MA, Stoppa GR, Turra A, Ogo SH. Functional behavior of tortoise hemoglobin Geochelone denticulata. Braz J Biol 62(4A): 725-733, 2002.

To cite this page:

Lafferty K, Pollock CG. Capnometry in exotic animal species. May 17, 2018. LafeberVet Web site. Available at https://lafeber.com/vet/capnometry/