Concordance between side-stream end-tidal carbon dioxide and arterial carbon dioxide partial pressure in respiratory service setting

Non-invasive monitoring of arterial oxygen using percutaneous pulse oximetry is well established. Although some studies show a good correlation of transcutaneous end-tidal carbon dioxide partial pressure (PetCO2) with arterial carbon dioxide partial pressure (PaCO2), they were performed in research settings and involved restricted populations such as paediatric, accident and emergency, or intensive care patients.1-5 The validity of non-invasive carbon dioxide (CO2) monitoring has never been as well accepted as transcutaneous oxygen saturation (SaO2). Nevertheless, the qualitative application of PetCO2 on validating endo-tracheal tube placement, dislodgement of tubing, efficacy of cardiopulmonary resuscitation is well established.5 There are also case reports of pulmonary embolism being detected based on PetCO2. 6 This study attempted to correlate PetCO2 with PaCO2 in respiratory patients with near-normal lung function, and those with mild respiratory failure, with a view to assessing the reliability of end-tidal capnometry in service settings. Objective To explore the correlation and concordance between end-tidal carbon dioxide and arterial carbon dioxide partial pressure, and confirm the experience of the general consensus among service environments.