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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 ]
D LCO or T LCO (diffusing capacity or transfer factor of the lung for carbon monoxide (CO), [1]) is the extent to which oxygen passes from the air sacs of the lungs into the blood. Commonly, it refers to the test used to determine this parameter.
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]
Spirometry (meaning the measuring of breath) is the most common of the pulmonary function tests (PFTs). It measures lung function, specifically the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled.
The amount of He in the spirometer is known at the beginning of the test (concentration × volume = amount). The patient is then asked to breathe (normal breaths) in the mixture starting from FRC (functional residual capacity), which is the gas volume in the lung after a normal breath out. The spirometer measures helium concentration.
Spirometry classically reveals a reduction in the vital capacity (VC) with either a proportionate reduction in airflows, or increased airflows for the observed vital capacity. The latter finding reflects the increased lung stiffness (reduced lung compliance) associated with pulmonary fibrosis, which leads to increased lung elastic recoil. [35]
There are a number of non-equivalent scales used in the interpretation of peak expiratory flow. [4] Some examples of Reference Values are given below. There is a wide natural variation in results from healthy test subjects. Wright scale [5] [6] EN 13826 or EU scale [7] NHANESIII [8] reference values provided by the US Centers for Disease ...