Fig. 3
From: Volumetric capnography: lessons from the past and current clinical applications
Fletcher approach for evaluating expired gases. The shaded area is the total dead space for the breath. Area z (area to the left of the solid line) is the airway dead space (VDaw), area y (area above the slope of phase III) is the alveolar dead space (VDalv, in this case as per Enghoff). As per the Fowler approach [2], area q is equal to area p. Area x (area under capnogram curve) is the volume of CO2 expired per breath (VTCO2,br)