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Functional components of the tidal volume obtained with volumetric capnography in an anesthetized Western lowland gorilla (Gorilla gorilla)

      Physiologic dead space (VD-Bohr) is the portion of the tidal volume (VT) not participating in gas exchange, composed of anatomical (VDaw) and alveolar (VDalv) dead spaces. The VD-Bohr is expressed as a ratio of the VT (VD-Bohr/VT), and the calculation requires measurement of the mixed expired (PeCO2) and mean alveolar (PaCO2) carbon dioxide, which cannot be obtained with traditional time-based capnography monitors. Volumetric capnography (Vcap) plots expired CO2 as a function of the expired volume and provides real-time reading of PeCO2, VDaw and alveolar volume (VTalv). Furthermore, identification of the midpoint of phase III of the Vcap waveform using mathematical models allows the determination of PaCO2 and calculation of the VD-Bohr (
      • Tusman G.
      • Sipmann F.S.
      • Borges J.B.
      • et al.
      Validation of Bohr dead space measured by volumetric capnography.
      ).
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