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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

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



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 Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


The measurement, by a form of gas meter (spirometer), of volumes of air that can be moved in or out of the lungs.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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Incentive spirometry for preventing pulmonary complications after coronary artery bypass graft.
AARC clinical practice guideline: Incentive spirometry: 2011.
Conclusion: Pre-operative incentive spirometry helps to reduce and prevent postoperative atelectasis in patients undergoing coronary artery bypass grafting.
Key Words: Incentive Spirometry, Coronary artery bypass grafting, Atelectasis
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.
The Incentive spirometry has been widely used in clinical practice, especially in the management of patients in the pre and post-operative stay of major surgeries, because of its low cost, easy availability and good compliance of patients to the method9,10.
Overend TJ, Anderson CM, Lucy SD, Bhatia C, Jonsson BI, Timmermans C (2001) The Effect of Incentive Spirometry on Postoperative Pulmonary Complications.
Incentive spirometry to prevent acute pulmonary complications in sickle cell diseases.
Each patient's nurse provided a 20-minute training in the use of incentive spirometry. The nurses encouraged the patients to increase their expiratory volumes and trained the caregivers to reinforce and, when needed, help patients perform incentive spirometry four times a day.
Bellet, Kalinyak, Shukla, Gelfand, and Rucknagel (1995) established the importance of incentive spirometry in their research, which demonstrated a statistically significant decrease in the development of acute chest syndrome in patients receiving incentive spirometry every 2 hours while awake, as compared to those patients who did not receive incentive spirometry.
The incentive spirometry requires work on the respiratory muscles, generating greater motor unit recruitment and thus muscle strengthening [36].
No other studies to date have assessed incentive spirometry use among hospitalized general medical patients, with most reports targeting specific surgical populations to evaluate the efficacy of incentive spirometry in preventing pulmonary complications.