Prehospital end-tidal carbon dioxide measurement

Abstract

The prehospital environment presents numerous challenges regarding the diagnosis and subsequent management of critically ill patients—diagnostic aids are limited; point-of-care testing is almost universally unavailable and senior medical advice can be beyond timely reach. Pulse oximetry provides real-time assessment of peripheral tissue oxygen saturation, but not of ventilation adequacy. The past decade has seen the gradual introduction of end-tidal carbon dioxide monitoring or capnography into routine resuscitation practice following successive national audit reports, coronial reports and subsequent guidance regarding safe airway management. However, capnography alone does not prevent adverse outcomes, particularly if it is not properly interpreted. Capnography is now regarded as essential monitoring whenever airway management or ventilation is required. The increasing availability of capnography in the prehospital setting can provide dynamic, real-time information that can aid assessment and treatment of pathology at the first point of contact and direct onward management. This article reviews the pathophysiology associated with the production, transport and excretion of carbon dioxide and suggests a number of ways in which accurate measurement and interpretation can potentially be a useful diagnostic tool and inform management choices in the prehospital setting.