- Bohr equation
The Bohr equation describes the amount of Physiological Dead Space in a person's lungs. This is given as a
ratioof dead spaceto tidal volume. It differs from Anatomical Dead Space as measured by Fowler's methodas it includes alveolardead space.
The bohr equation is used to quantify the ratio of physiological dead space to the total tidal volume, and gives an indication of the extent of wasted ventilation.
: [Respiratory Physiology: The Essentials, J. West, 2005, 7th ed, Page 169]
Its derivation is based on the fact that only the ventilated gases involved in gas exchange (Va) will produce CO2. Because the Total tidal volume (Vt) is made up of , we can substitute Va for .
: Where Fe = Fraction expired CO2, and Fa = Alveolar fraction of CO2.
: Substituted as above.
: Multiply out of the brackets.
: Divide by Vt and by Fa.
Fa is analogous to PaCO2, and Fe is analogous to partial pressure of expired CO2, therefore:
Wikimedia Foundation. 2010.