bohr's method for measuring physiologic dead space

Volumetric capnography is a promising technique to calculate true Bohr dead space. VD/VT Bohr-VCap = 45 ± 7 % P < 0.05).ĭifferent techniques to measure PACO2 and PeCO2 result in clinically relevant mean and individual differences in calculated VD/VT, particularly in patients with ARDS. For example, in patients with ARDS, VD/VTcalculated with Enghoff-InCal was much higher than Bohr-VCap (VD/VT Enghoff-InCal = 66 ± 10 % vs.

These differences strongly affected calculated VD/VT. InCal (post-cardiac surgery bias = -1.17 ± 0.50 kPa ARDS mean bias = -0.15 ± 0.53 kPa). VCap (post-cardiac surgery bias = 0.04 ± 0.19 kPa ARDS bias = 0.03 ± 0.27 kPa) and relatively low agreement with DBag vs. There was good agreement in PeCO2 calculated with DBag vs. PaCO2 was higher than PACO2, particularly in patients with ARDS (post-cardiac surgery PACO2 = 4.3 ± 0.6 kPa vs. Subsequently, VD/VT was calculated using four methods: Enghoff-DBag, Enghoff-InCal, Enghoff-VCap, and Bohr-VCap. PeCO2 was measured in expired air using three techniques: Douglas bag (DBag), indirect calorimetry (InCal), and VCap. PACO2 was measured using VCap to calculate Bohr dead space or substituted with partial pressure of carbon dioxide in arterial blood (PaCO2) to calculate the Enghoff modification. In a prospective, observational study, 15 post-cardiac surgery patients and 15 patients with ARDS were included. The purpose of the present study was to evaluate how VCap and other available techniques to measure PACO2 and partial pressure of carbon dioxide in mixed expired air (PeCO2) affect calculated VD/VT. Recently, a novel technique to calculate partial pressure of carbon dioxide in alveolar air (PACO2) using volumetric capnography (VCap) was validated. However, VD/VT is rarely calculated in clinical practice, because its measurement is perceived as challenging. In patients with acute respiratory distress syndrome (ARDS), VD/VT has prognostic value and can be used to guide ventilator settings. Physiological dead space (VD/VT) represents the fraction of ventilation not participating in gas exchange.

Bohr's method for measuring physiologic dead space