Volume capnography: A narrative review

Abstract

Volume capnography is the graph of expired carbon dioxide concentration against the expired volume. It often requires special and bulky equipment to be recorded. It can be used to estimate the dead space with fair amount of precision. Various formulae and equations have been described to estimate the dead space. While the Bohr formula is likely the most accurate for measurement of dead space, the Enghoff's equation is likely the most popular and convenient to use. Volume capnography has found uses in both the operating room (OR) and the Intensive Care Unit setting. It can be used to identify the optimal level of positive end-expiratory pressure in patients suffering from the acute respiratory distress syndrome as well as to identify its effect on the ventilation. In the OR, it can be invaluable to monitor ventilation and alveolar recruitment in the obese population. It is also a useful diagnostic adjunct in medical emergencies like pulmonary embolism. In the pediatric population, it finds uses in the monitoring of infants suffering from bronchiolitis. In spite of its multiple and diverse uses, it remains an underutilized technology; the main reasons for this being lack of experience of the providers with volume capnography and the expensive and bulky equipment that is often required. However, volume capnography has a great deal of potential and with further advances in technology, is likely to gain popularity.