Total lung capacity

Total lung capacity (TLC) refers to the maximum volume of air that the lungs can hold after a maximum inhalation. It is approximately 6 liters for adult human males and 4.2 liters for adult human females. TLC is the sum of vital capacity and residual volume. It is an important measure in pulmonology and can be affected by diseases such as emphysema and pulmonary fibrosis.

Measurement

TLC can be measured using a number of techniques including spirometry, body plethysmography, and gas dilution techniques. Spirometry is the most common method, but it cannot measure the residual volume, so it cannot provide a direct measurement of TLC. Body plethysmography and gas dilution techniques can measure residual volume and therefore provide a direct measurement of TLC.

Factors affecting TLC

TLC can be affected by a number of factors including age, sex, body size, and disease. Age and sex are the most significant factors, with TLC generally being higher in males and decreasing with age. Diseases such as emphysema and pulmonary fibrosis can significantly reduce TLC.

Clinical significance

TLC is an important measure in the diagnosis and monitoring of lung diseases. A reduced TLC can indicate restrictive lung disease, while an increased TLC can indicate obstructive lung disease. TLC is also used in the calculation of other lung volumes and capacities.

See also

• Lung volumes
• Spirometry
• Pulmonology

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