3/12/2024 0 Comments Alveolar dead space paco2![]() J Physiol 47:431–445įowler WS (1948) Lung function studies II. Krogh A, Lindhard J (1913) On the average composition of the alveolar air and its variations during the respiratory cycle. Haldane JS, Priestley JG (1905) The regulation of the lung-ventilation. Keywordsīohr C (1891) Über die Lungeatmung. Conclusions: VDBohr can be calculated with accuracy using volumetric capnography. Mean VDBohr from VC was close to the value obtained by MIGET with a mean bias of 0.010 ml and limits of agreement between -0.044 and 0.064 ml. Mean PACO2 from VC was very similar to the one obtained by MIGET with a mean bias of -0.10 mmHg and limits of agreement between -2.18 and 1.98 mmHg. Results: We found close linear correlations between the two methods for calculating both PACO2 (r = 0.99) and VDBohr (r = 0.96), respectively (both p\0.0001). Then, PACO2 was obtained applying the alveolar air formula (PACO2 = VCO2/alveolar ventilation). MIGET estimated expired CO2 output (VCO2) and PeCO2 by its V/Q algorithms. PACO2 was determined by VC as the midpoint of the slope of phase III of the capnogram, while mean expired partial pressure of CO2 (PeCO2) was calculated as the mean expired fraction of CO2 times the barometric minus the water vapor pressure. Methods: Expired gases of seven lung-lavaged pigs were analyzed at different lung conditions using mainstream VC and multiple inert gas elimination technique (MIGET). The aim of this work was to validate VDBohr using PACO2 derived from volumetric capnography (VC) against VDBohr with PACO2 values obtained from the standard alveolar air formula. Purpose: Bohr’s dead space (VDBohr) is commonly calculated using end-tidal CO2 instead of the true alveolar partial pressure of CO2 (PACO2).
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