![]() 2 Physiologic dead-space fraction (dead space divided by tidal volume ), as defined by Bohr and Enghoff, is the sum of anatomic or airway dead space (V D-anat) and alveolar dead space (V D-alv) divided by the V T. Different capnographic indices can be useful to evaluate therapeutic interventions or setting mechanical ventilation.ĭead space acute respiratory distress syndrome (ARDS) lung recruitment volumetric capnography.Dead-space ventilation, the portion of a tidal volume that does not contribute to gas exchange, was first described and calculated by the Bohr equation in 1891, 1 and later by the Enghoff modification of the Bohr equation in 1938. Dead space measurement is a reliable method that provides important clinical and prognostic information. Different patterns of ventilation affect also CO 2 elimination in fact, end-inspiratory pause prolongation reduces dead space, increasing respiratory system compliance plateau pressure and consequently driving pressure increase accordingly. ![]() Dead space guided recruitment allows avoiding regional overdistension or reduction in cardiac output in critical care patients with ALI or ARDS. Lung recruitment is a dynamic process that combines recruitment manoeuvres (RMs) with positive end expiratory pressure (PEEP) and low Vt to recruit collapsed alveoli. ![]() Different dead space indices can provide useful information in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) patients, where changes in microvasculature are the main determinants for the increase in dead space and consequently a worsening of the outcome. Dead space is not routinely measured in critical care practice, because the difficulties in in interpreting capnograms and the different methods of calculations. Dead space is the portion of each tidal volume that does not take part in gas exchange and represents a good global index of the efficiency of the lung function.
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