Pulmonary compliance
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Assistant Editor-in-Chief: Soumya Sachdeva
Overview
Compliance is the ability of the lungs to stretch in a change in volume relative to an applied change in pressure. It is an important measurement in respiratory physiology.[1][2][3]
- fibrosis is associated with a decrease in pulmonary compliance.
- emphysema/COPD are associated with an increase in pulmonary compliance.
Pulmonary surfactant increases compliance.
Compliance is greatest at moderate lung volumes, and much lower at volumes which are very low or very high.
Calculation
Compliance is calculated using the following equation, where ΔV is the change in volume, and ΔP is the change in pressure:[4]
<math>C = \frac{ \Delta V}{ \Delta P} </math>
Factors affecting lung compliance
- Lung volume - A person with only one lung has half the change in lung volume for a given change in pressure
- Phase of respiratory cycle - It is slightly greater when measured during deflation than when measured during inflation
- Effect of gravity - It is less at apices of the lungs as there are more distended alveoli at the apex
- Surface tension - If surface tension is high as in deficiency of surfactant , more pressure is required to distend the lungs ,therefore,compliance is decreased
Specific Compliance
Compliance divided by'''FRC''' (in mLs)
Unit = /cmH2O
- Normal value = 0.05/cmH2O
- Similar values in both sexs and all ages including neonates
- Is a measurement of the intrinsic elastic property of the lung tissue
References
- ↑ http://oac.med.jhmi.edu/res_phys/Encyclopedia/Compliance/Compliance.HTML
- ↑ Nikischin W, Gerhardt T, Everett R, Bancalari E (1998). "A new method to analyze lung compliance when pressure-volume relationship is nonlinear". Am J Respir Crit Care Med. 158 (4): 1052–60. PMID 9769260. article
- ↑ Essentials of Human Physiology by Thomas M. Nosek. Section 4/4ch2/s4ch2_21.
- ↑ http://www.cvphysiology.com/Blood%20Pressure/BP004.htm