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Measurement of PEFR requires training to correctly use a meter and the normal expected value depends on the patient's sex, age, and height. It is classically reduced in obstructive lung disorders such as asthma. Due to the wide range of 'normal' values and the high degree of variability, peak flow is not the recommended test to identify asthma.
The most common parameters measured in spirometry are vital capacity (VC), forced vital capacity (FVC), forced expiratory volume (FEV) at timed intervals of 0.5, 1.0 (FEV1), 2.0, and 3.0 seconds, forced expiratory flow 25–75% (FEF 25–75) and maximal voluntary ventilation (MVV), [10] also known as Maximum breathing capacity. [11]
Lung volumes and lung capacities are measures of the volume of air in the lungs at different phases of the respiratory cycle. The average total lung capacity of an adult human male is about 6 litres of air. [1] Tidal breathing is normal, resting breathing; the tidal volume is the volume of air that is inhaled or exhaled in only a single such ...
This type of spirometer is used especially for measuring forced vital capacity without using water; it has broad measurements ranging from 1000 ml to 7000 ml. It is more portable and lighter than traditional water-tank type spirometers. This spirometer should be held horizontally while taking measurements because of the presence of a rotating disc.
The plethysmography technique applies Boyle's law and uses measurements of volume and pressure changes to determine total lung volume, assuming temperature is constant. [8] There are four lung volumes and four lung capacities. A lung's capacity consists of two or more lung volumes.
COPD is defined as a forced expiratory volume in 1 second divided by the forced vital capacity (FEV1/FVC) that is less than 0.7 (or 70%). [8] The residual volume, the volume of air left in the lungs following full expiration, is often increased in COPD, as is the total lung capacity, while the vital capacity remains relatively normal.
The helium dilution technique is the way of measuring the functional residual capacity of the lungs (the volume left in the lungs after normal expiration). This technique is a closed-circuit system where a spirometer is filled with a mixture of helium (He) and oxygen. The amount of He in the spirometer is known at the beginning of the test ...
A normal adult has a vital capacity between 3 and 5 litres. [3] A human's vital capacity depends on age, sex, height, mass, and possibly ethnicity. [ 4 ] However, the dependence on ethnicity is poorly understood or defined, as it was first established by studying black slaves in the 19th century [ 5 ] and may be the result of conflation with ...