![]() ![]() 1 Later, Enghoff proposed a simplification of Bohr's formulae to calculate the physiologic dead space ratio at the bedside using arterial P CO 2 (P aCO 2) instead of P ACO 2. Employing the law of mass conservation, Bohr proposed a formula using alveolar P CO 2 (P ACO 2) to estimate physiologic dead space, expressed as a ratio of dead space volume (V D) to tidal volume (V T). ![]() V d V t = P A C O 2 − P e C O 2 P A C O 2 Ī common step is to then presume that the partial pressure of carbon dioxide in the end-tidal exhaled air is in equilibrium with that gas' tension in the blood that leaves the alveolar capillaries of the lung.Lung physiologic dead space (V D) is defined as the wasted tidal volume during respiration (ie, the volume remaining in the conducting airways and in poorly perfused and non-perfused alveoli that are not participating in gas exchange). The original formulation by Bohr, required measurement of the alveolar partial pressure P A. 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. It differs from anatomical dead space as measured by Fowler's method as it includes alveolar dead space. This is given as a ratio of dead space to tidal volume. The Bohr equation, named after Danish physician Christian Bohr (1855–1911), describes the amount of physiological dead space in a person's lungs. ![]() Not to be confused with the Bohr model or the Bohr effect. ![]()
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