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The measurement, by a form of gas meter, of volumes of gas that can be moved in or out of the lungs. The classical spirometer is a hollow cylinder (bell) closed at its top. With its open end immersed in a larger cylinder filled with water, it is suspended by a chain running over a pulley and attached to a counterweight. The magnitude of a gas volume entering or leaving is proportional to the vertical excursion of the bell. Volume changes can also be determined from measurements of flow, or rate of volume change, that can be sensed and recorded continuously by a transducer that generates an electrical signal. The flow signal can be continuously integrated to yield a volume trace.

The volume of gas moved in or out with each breath is the tidal volume; the maximal possible value is the vital capacity. Even after the most complete expiration, a volume of gas that cannot be measured by the above methods, that is, the residual volume, remains in the lungs. It is usually measured by a gas dilution method or by an instrument that measures blood flow in the lungs. Lung volumes can also be estimated by radiological or optical methods.

At the end of an expiration during normal resting breathing, the muscles of breathing are minimally active. Passive (elastic and gravitational) forces of the lungs balance those of the chest wall. In this state the volume of gas in the lungs is the functional residual capacity or relaxation volume. Displacement from this volume requires energy from natural (breathing muscles) or artificial (mechanical) sources. See Respiration



the measurement of the breathing capacity of the lungs. Spirometry was introduced in 1846 by the English scientist J. Hutchison.

Breathing capacity comprises the resting tidal volume of air that moves in and out of the lungs with each breath (approximately 500 cc), the inspiratory reserve volume of air that enters the lungs with maximal inhalation (approximately 1,500 cc), and the expiratory reserve volume of air that emerges from the lungs with maximal exhalation after normal exhalation (approximately 1,600 cc).

The breathing capacity of the lungs is usually measured with a spirometer (see Figure 1), which consists of a water-filled cylindrical tank that contains a floating cylindrical bell (1). The bell is

Figure 1

open at the bottom end and balanced by two counterweights. A rubber connecting tube (2) passes beneath the bottom of the bell. When a person forcefully exhales into the tube after taking a deep breath, the exhaled air forces the interior cylinder to rise. The volume of exhaled air is measured in cm3 according to a calibrated scale (3). Air is released from the spirometer by turning a valve (4).

The spirometer is used in examining healthy persons and in diagnosing and treating diseases of the lungs and cardiovascular system. In recent years spirographs have also been used to measure breathing capacity. Respiratory movements are recorded on spirograms, and breathing capacity is calculated according to special tables.



The measurement, by a form of gas meter (spirometer), of volumes of air that can be moved in or out of the lungs.
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Joseph Carter, head of British Lung Foundation (BLF) Wales, said: "This is why we would like all health boards to invest more in diagnostic equipment - such as spirometry.
Spirometry variables were measured for a series of at least 3 acceptable forced expiratory readings.
To study whether Six-minute walk test and CAT Score can be used as an alternative to spirometry in resource-poor settings to predict the severity of COPD.
GOLD had been moving toward symptoms and exacerbations to guide treatment for several years before formalizing the break from spirometry in its Nov.
So we found that pre-operative incentive spirometry results in considerable reduction in incidence of post-operative atelectasis and it also can reduce ventilation time as well.
Although postbronchodilator spirometry is required to make a definitive diagnosis, "prescreening questionnaires can elicit current symptoms and previous exposures to harmful particles or gases," Dr.
Techniques such as deep inspiration (DI), incentive spirometry (IS) and positive airway pressure exercises result in the generation of a persistent increase in the transpulmonary pressure, with consequent expansion of collapsed alveolar units to prevent and/or to treat the post-operative complications8.
Spirometry was performed on a group of 40 mill workers (subjects) and 40 controls.
STAMPEDE II is a recently completed prospective study using pre- and postdeployment spirometry and impulse oscillometry (IOS) to determine if there is an objective decrease in pulmonary function following deployment.
For example, a lifelong smoker with an abnormal spirometry reading may have a forced expiratory volume in 1 second (FEV1) of less than 80 percent of predicted.
The value of periodic spirometry for early recognition of long-term excessive lung function decline in individuals.
Spirometry can also be used to monitor the effectiveness of certain treatments for lung disorders.