Techniques for the measurement and monitoring of carbon dioxide in the blood

The relationship between an elevated partial pressure of carbon dioxide (Pco2) and reduced alveolar ventilation resulting from respiratory failure primarily affecting the respiratory pump was first reported during the 1952 Copenhagen polio epidemic. Several methods for Pco2 estimation, such as blood gas analyses, capnography, and transcutaneous Pco2 measurements, have since been developed to assess alveolar ventilation. The clinical setting in which CO2 measurement is valuable includes acute and chronic respiratory failure, transport, cardiopulmonary resuscitation, patient-controlled analgesia, and procedural sedation. The techniques that are currently available differ considerably regarding their accuracy, capacity to facilitate continuous assessment, side effects, availability, and their ability to assess additional information. Importantly, each technique has its own spectrum of indications and applications. Therefore, the different techniques are not competitive but, rather, complementary. As a consequence, it is reasonable to combine different techniques depending on specific clinical scenarios. This review summarizes the physiological background, historical development, instrument-specific technical aspects, and current recommendations for the clinical application of Pco2 assessment.