Diffusion capacity

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In biology, diffusion capacity is a measurement of the lung's ability to absorb and excrete gases, notably, oxygen and carbon dioxide. It is part of a comprehensive test series of lung function called pulmonary function testing.

The rate of flow is directly proportional to the oxygen gradient (per Fick's law of diffusion), and the diffusion capacity (DL) can be calculated as the ratio of oxygen flow over the oxygen gradient between the alveoli ("A") and the veins ("v"):

$D_L = \frac {V^*_{O2}}{P_{AO2} - P_{vO2}}$

(The asterisk should be read as a dot over the letter, which is used to denote rate in respiratory physiology.)

QUESTION: What do the above variables represent, specifically?

Because it can be difficult to measure these quantities, in Dlco, a small quantity of carbon monoxide is sometimes used, under the assummption that all the CO will bind, thus simplifying the equation:

$D_L = \frac {V^*_{O2}}{P_{ACO2}}$

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v • d • e

Respiratory system, physiology: respiratory physiology

Volumes:

lung volumes - vital capacity - functional residual capacity - respiratory minute volume - dead space - spirometry - body plethysmography - peak flow meter

ventilation (V) (positive pressure) breath (inhalation, exhalation) - respiratory rate - respirometer - pulmonary surfactant - compliance - hysteresivity - airway resistance

pulmonary circulation - perfusion (Q) - hypoxic pulmonary vasoconstriction - pulmonary shunt

ventilation/perfusion ratio (V/Q) and scan - zones of the lung - gas exchange - pulmonary gas pressures - alveolar gas equation - hemoglobin - oxygen-haemoglobin dissociation curve (2,3-DPG, Bohr effect, Haldane effect) - carbonic anhydrase (chloride shift) - oxyhemoglobin - respiratory quotient - arterial blood gas - diffusion capacity - Dlco

control of respiration: pons (pneumotaxic center, apneustic center) - medulla (dorsal respiratory group, ventral respiratory group) - chemoreceptors (central, peripheral) - pulmonary stretch receptors - Hering-Breuer reflex

high altitude - oxygen toxicity - hypoxia

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Categories: Pulmonology | Physiology | Medicine stubs

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