Skip to main content Accessibility help
  • Print publication year: 2011
  • Online publication date: August 2011

Appendix: Patterns of time-based capnograms


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.