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Diffusing capacity of the lung (D L) (also known as transfer factor) measures the transfer of gas from air in the lung, to the red blood cells in lung blood vessels. It is part of a comprehensive series of pulmonary function tests to determine the overall ability of the lung to transport gas into and out of the blood.
Pulmonary function testing (PFT) is a complete evaluation of the respiratory system including patient history, physical examinations, and tests of pulmonary function. The primary purpose of pulmonary function testing is to identify the severity of pulmonary impairment. [ 1 ]
There is no universally recognized reference value range for DLCO as of 2017, [10] but values in the 80%-120% of predicted range based on instrument manufacturer standards are generally considered normal. [11] A D LCO of less than 60% predicted portends a poor prognosis for lung cancer resection.
Diffusing capacity (or DLCO) is the carbon monoxide uptake from a single inspiration in a standard time (usually 10 seconds). During the test the person inhales a test gas mixture that consisting of regular air that includes an inert tracer gas and CO, less than one percent.
In obstructive lung disease, the FEV1 is reduced due to an obstruction of air escaping from the lungs. Thus, the FEV1/FVC ratio will be reduced. [4] More specifically, according to the National Institute for Clinical Excellence, the diagnosis of COPD is made when the FEV 1 /FVC ratio is less than 0.7 or [8] the FEV 1 is less than 75% of predicted; [9] however, other authoritative bodies have ...
In obstructive lung disease however, the FEV1/FVC is less than 0.7, indicating that FEV1 is significantly reduced when compared to the total expired volume. This indicates that the FVC is also reduced, but not by the same ratio as FEV1. [8] One definition requires a total lung capacity which is 80% or less of the expected value. [9]
Pulmonary compliance is calculated using the following equation, where ΔV is the change in volume, and ΔP is the change in pleural pressure: = For example, if a patient inhales 500 mL of air from a spirometer with an intrapleural pressure before inspiration of −5 cm H 2 O and −10 cm H 2 O at the end of inspiration.
Impaired diffusion, a reduced capacity for gas molecules to move between the air in the alveoli and the blood, which occurs when alveolar–capillary membranes thicken. This can happen in interstitial lung diseases such as pulmonary fibrosis , sarcoidosis , hypersensitivity pneumonitis , and connective tissue disorders.