12/14/2023 0 Comments Dead space vs shuntWhen alveolar PCO 2 is increased by any mechanism, PA CO2 calculated by Koulouris' method does not agree well with average alveolar PCO 2. Bohr-Enghoff but not Koulouris or Fowler dead-space increases with increasing severity of V̇/Q̇ maldistribution. Shunt increases the calculated Bohr-Enghoff dead-space, but does not affect Fowler, Bohr or Koulouris dead-spaces, or VD phys estimated by the shunt-corrected equation if pulmonary artery catheterization is available. When VD alv is increased, VD phys can be recovered by the Bohr and Bohr-Enghoff equations, but not by the Koulouris method. PA co2 was calculated by the method of Koulouris. Respiratory data generated by the model were analysed to calculate dead-spaces by the Fowler, Bohr, Bohr-Enghoff and Koulouris methods. Pulmonary shunt, V̇/Q̇ distribution and VD alv were varied in a tidally breathing cardiorespiratory model. This study evaluates the effects of increased alveolar dead-space (VD alv), pulmonary shunt, and abnormal ventilation perfusion ratio (V̇/Q̇) distributions on dead-space and alveolar partial pressure of carbon dioxide (PA co2) calculated by various methods, assesses a recently published non-invasive method (Koulouris method) for the measurement of Bohr dead-space, and evaluates an equation for calculating physiological dead-space (VD phys) in the presence of pulmonary shunt. Respiratory dead-space is often increased in lung disease.
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