Capnography
Capnography is the monitoring of the concentration or partial pressure of carbon dioxide (CO
2) in the respiratory gases. Its main development has been as a monitoring tool for use during anesthesia and intensive care. It is usually presented as a graph of expiratory CO
2 (measured in millimeters of mercury, "mmHg") plotted against time, or, less commonly, but more usefully, expired volume. The plot may also show the inspired CO
2, which is of interest when rebreathing systems are being used.