which of the following values are needed to determine a patient's physiologic dead space?

which of the following values are needed to determine a patient

Currently, dead space is measured at the bedside by volumetric capnography, which reports expired CO 2 elimination as a function of expired VT, and VD/VTphys is calculated using the Enghoff’s modification of Bohr’s original equation: VD/VTphys = (PaCO 2 – PECO 2)/PaCO 2, where PaCO 2 is the arterial partial pressure of CO 2 obtained by arterial blood sampling and PECO 2 is an estimate of mixed expired partial pressure of CO 2 obtained from the mid-portion of phase III of the volumetric capnogram. The physiologic ventilatory dead space fraction (VD/VTphys) is usually defined as the fraction of tidal volume (VT) that does not participate in gas exchange.

Dead space comprises two separate components: airway dead space (the volume of areas that do not contribute to gas exchange) and alveolar dead space (the volume of well-ventilated alveoli that receive minimal blood flow). Similarly, despite the established usefulness of measuring physiologic variables such as dead space in mechanically ventilated ARDS patients, this practice is not widely employed.ĭead space refers to lung areas that are ventilated but not perfused. Nevertheless, a recent observational study in intensive care units in 50 countries found that prone positioning was used in only 16.3 % of patients with severe ARDS, whereas recruitment maneuvers were used in 32.7 %. For instance, prone positioning significantly improves mortality in patients with severe acute respiratory distress syndrome (ARDS), but the usefulness of recruitment measures in this population is still under debate. Why clinicians are slow to implement advances in diagnosis and treatment from well-designed clinical trials is a continuously debated question in critical care.

Which of the following values are needed to determine a patient's physiologic dead space?