Calculating the Effect of Altered Respiratory Parameters on Capnographic Indices

Capnography, the monitoring of exhaled CO2, has been clinically utilized as a noninvasive measure of alveolar ventilation. The shape of the capnogram is significantly altered in patients with lung disease or hemodynamic instability. Shape indices obtained from the capnogram provide an indication of dead space ventilation, ventilation/perfusion status, and the extent of rebreathing. In this study, the quantitative relationship between physical respiratory parameters and capnographic shape indices was determined using a mathematical model of CO2 exchange in a tidally ventilated lung. This relationship may provide clinicians with guidance for physiological interpretation of capnograms.

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