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Updated: Mar 23, 2026
Expired CO2 Measurement in Intubated or Spontaneously Breathing Patients from the Emergency Department
Published on: January 29, 2011
[Monitoring of pCO2 during ventilation]
F S Magnet1, W Windisch2, J H Storre2,3
1Fakultät für Gesundheit/Department für Humanmedizin, Lungenklinik Köln-Merheim, Kliniken der Stadt Köln gGmbH, Universität Witten/Herdecke, Ostmerheimer Str. 200, 51109, Köln, Deutschland. magnetf@kliniken-koeln.de.
Abstract:
Respiratory insufficiency type 2 (ventilatory failure) is characterized by hypercapnia due to alveolar hypoventilation. Therefore, the monitoring of pCO2 is essential for diagnostic and surveillance purposes. Various techniques which differ in the way of measurement (e.g., invasive/noninvasive, continuous/noncontinuous) and their indication are available. Arterial blood gas analysis (ABG) as an invasive procedure is the gold standard procedure and is mostly used in emergency medicine or intensive care units (ICUs). Another method to evaluate pCO2 is capillary blood gas analysis (CBG). Furthermore, endtidal pCO2-(PetCO2) and transcutaneous CO2-measurement (PtcCO2) are able to continuously and noninvasively monitor pCO2. PetCO2 is mostly used in the field of anesthesiology during general anesthesia and is integrated in many ventilators, also in ICUs. However, PetCO2 is limited in monitoring pCO2 in patients with lung disease and it is only reasonably usable in invasively ventilated patients. Transcutaneous pCO2 (PtcCO2) is available as an alternative, especially in chronic respiratory failure and to diagnose hypoventilation in sleep-related breathing disorders, and it has substantial advantages in these indications compared to discontinuous measurements, e.g., blood gas analysis. The various methods to monitor pCO2 are generally used synergistically in clinical practice.
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