1. Graphical representation of physiologic dead space fraction determined by volumetric capnography, using the approaches of Bohr and Enghoff, which shows how use of the Enghoff equation can overestimate alveolar dead space (VD-alv) (shaded areas) by substitution of the partial pressure of arterial carbon dioxide (PaCO2) for the partial pressure of mixed alveolar carbon dioxide (PACO2), determined by identifying the mid-point of phase III of the expired volumetric capnogram.39,40 Also shown are the airway or anatomical dead space (VD-aw, determined by the Fowler method identified at the mid-point of phase II of the expired volumetric capnogram,41), the partial pressure of end-tidal carbon dioxide (PETCO2), and the partial pressure of mean expired carbon dioxide (PĒCO2) in relation to the volumetric capnogram.
Graphical representation of physiologic dead space fraction determined by volumetric capnography, using the approaches of Bohr and Enghoff, which shows how use of the Enghoff equation can overestimate alveolar dead space (VD-alv) (shaded areas) by substitution of the partial pressure of arterial carbon dioxide (PaCO2) for the partial pressure of mixed alveolar carbon dioxide (PACO2), determined by identifying the mid-point of phase III of the expired volumetric capnogram.39,40 Also shown are the airway or anatomical dead space (VD-aw, determined by the Fowler method identified at the mid-point of phase II of the expired volumetric capnogram,41), the partial pressure of end-tidal carbon dioxide (PETCO2), and the partial pressure of mean expired carbon dioxide (PĒCO2) in relation to the volumetric capnogram. (From reference 35, with permission.)‏
Mark S Siobal et al. Respir Care 2013;58:
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