Clinical Significance of Anatomical Dead Space
Estimating the dead space can be of significant value in clinical
situations for diagnostic, prognostic, and therapeutic value. Dead space
is an integral part of volume capnography, which measures expired CO2
and dead space (VDphys/VT) on a breath-by-breath basis for
efficient monitoring of patient ventilation. Despite that the VDphys/VT
ratio measured by Enghoff's equation is adversely affected by
pulmonary shunting in ARDS, VDphys/VT has been shown to be a
significant predictor of mortality during early-phase acute respiratory
distress syndrome (ARDS), and increases in the VDphys/VT ratio
correlated with poorer patient outcomes. Measurement of this dead
space provides a quantifiable indicator of overall lung function for
physicians to assess throughout the course of ARDS patients' hospital
course. PEEP, an integral part of ARDS ventilation management, can be
titrated to a patient's specific need based on capnography and dead space
monitoring, but this finding has not been consistently shown in multiple
studies.