|VT tidal volume during normal, quiet breathing
ERV expiratory reserve volume
FRC functional residual capacity
EVC expiratory vital capacity
IVC inspiratory vital capacity
TLC total lung capacity
TLC - total lung capacity
The total lung capacity, i.e. the volume of gas contained in the lung after a full inhalation, is determined by a number of factors:
- Normal mental function, so that the subject is capable of performing a full inspiratory maneuver.
- Intact neuromuscular apparatus (think e.g. of poliomyelitis, amyotrophic lateral sclerosis), no inhibition due to pain.
- Normal shape, mobility and elasticity of the thorax (abnormalities due e.g. to Bechterew’s disease, kyphosis, kyphoscoliosis, osteoporosis with collapsed vertebrae, sclerodermia, exceptionally extreme overweight).
- Normal elastic properties of the lung (increased TLC in pulmonary emphysema, decreased TLC in interstitial fibrosis, pleural fibrosis) and normal airway patency (atelectasis e.g. due to an obstructing tumor may lower the TLC);
- Normal thoracic content (disturbances include e.g. pleural effusions, cardiomegaly, pulmonary edema, pneumonectomy or lobectomy).
A restrictive ventilatory defect is associated with a diminished TLC, a very compliant lung with an enlarged TLC. An increased TLC is also observed in children who had asthma from childhood on (ref. 1), or who were born and raised at altitude. In adults the TLC is unaffected by age (ref. 2).
Ref. 1 - Large lungs and childhood asthma
- Greaves IA, Coleman HJH. Large lungs after childhood asthma: a consequence of enlarged airspaces. Aus NZ J Med 1985; 15: 427-434.
- Kraemer R, Meister B, Schaad UB, Rossi E. Reversibility of lung function abnormalities in children with perennial asthma. J Pediatr 1983; 102: 347-350.
- Merkus PJFM, van Essen-Zandvliet EEM, Kouwenberg JM, Duiverman EJ, van Houwelingen JC, Kerrebijn KF, Quanjer PhH. Large lungs during childhood asthma: a case-control study. Am Rev Respir Dis 1993; 148: 1484-1489.
- Weiss ST, Tosteson TD, Segal MR, Tager IB, Redline S, Speizer FE. Effects of asthma on pulmonary function in children. A longitudinal population-based study. Am Rev Respir Dis 1992; 145: 58-64.
Ref. 2 - Longitudinal behavior of spirometric indices
- Borsboom GJ, van Pelt W, van Houwelingen HC, van Vianen BG, Schouten JP, Quanjer PhH. Diurnal variation in lung function in subgroups from two Dutch populations: consequences for longitudinal analysis. Am J Respir Crit Care Med 1999; 159: 1163-1171.
- Quanjer PhH, Tammeling GJ, Cotes JE, Pedersen OF, Peslin R, Yernault JC. Lung volumes and forced ventilatory flows. Official Statement of the European Respiratory Society. Eur Respir J 1993; 6 suppl. 16: 5-40. Erratum Eur Respir J 1995; 8: 1629.