Capnography

From Wikipedia, the free encyclopedia

Capnography is the monitoring of the respiratory carbon dioxide (CO₂) concentration as a time-concentration curve. It is a direct monitor of the inhaled and exhaled concentration of CO₂, and an indirect monitor of the CO₂ concentration in a patient's blood. During anaesthesia, there is interplay between two components: the patient and the anaesthesia administration device (which is usually a breathing circuit and a ventilator or respirator). The critical connection between the two components is either an endotracheal tube or a mask, and CO₂ is typically monitored at this junction. Capnography directly reflects the elimination of CO₂ by the lungs to the anaesthesia device. Indirectly, it reflects the production of CO₂ by tissues and the circulatory transport of CO₂ to the lungs.

Capnography provides information about CO₂ production, pulmonary (lung) perfusion, alveolar ventilation, respiratory patterns, and elimination of CO₂ from the anaesthesia breathing circuit and ventilator.

Capnography has been shown to be more effective than clinical judgement alone in the early detection of adverse respiratory events such as hypoventilation, oesophageal intubation and circuit disconnection; thus allowing patient injury to be prevented.

Capnography provides a rapid and reliable method to detect life-threatening conditions (malposition of tracheal tubes, unsuspected ventilatory failure, circulatory failure and defective breathing circuits) and to circumvent potentially irreversible patient injury.

Capnography and pulse oximetry together could have helped in the prevention of 93% of avoidable anaesthesia mishaps according to an ASA (American Society of Anesthesiologists) closed claim study.