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The purpose of the present study was to evaluate how VCap and other available techniques to measure PACO 2 and partial pressure of carbon dioxide in mixed expired air (PeCO 2) affect calculated V D/V T. Recently, a novel technique to calculate partial pressure of carbon dioxide in alveolar air (PACO 2) using volumetric capnography (VCap) was validated. However, V D/V T is rarely calculated in clinical practice, because its measurement is perceived as challenging. In patients with acute respiratory distress syndrome (ARDS), V D/V T has prognostic value and can be used to guide ventilator settings. Physiological dead space (V D/V T) represents the fraction of ventilation not participating in gas exchange.
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