Alveolar dead space is calculated as the difference between anatomical dead space estimated by the Fowler equal area method and physiologic dead space. By quantifying this dilution it is possible to measure anatomical and alveolar dead space, employing the concept of mass balance, as expressed by Bohr equation.Physiologic dead space is usually estimated by the Bohr-Enghoff equation or the Fletcher method. Just as dead space wastes a fraction of the inhaled breath, dead space dilutes alveolar air during exhalation. Mammals breathe in and out of their lungs, wasting that part of the inspiration which remains in the conducting airways where no gas exchange can occur. In other words, not all the air in each breath is available for the exchange of oxygen and carbon dioxide. In physiology, dead space is the volume of air which is inhaled that does not take part in the gas exchange, either because it (1) remains in the conducting airways, or (2) reaches alveoli that are not perfused or poorly perfused. PeCO2 is the partial pressure of carbon dioxide in exhaled air.PaCO2 is the partial pressure of carbon dioxide in arterial blood.
The Bohr Method formula for the Physiologic Dead Space is:
However, this can be automatically converted to compatible units via the pull-down menu. Volume of Dead Space (V D): The calculator returns the volume in milliliters (ml).
The Physiologic Dead Space (Bohr Method) calculator computes the volume of dead space (V D) based on the tidal volume (V T) and the partial pressures of carbon dioxide in arterial blood, exhaled air and ambient air.
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