User Name-Shalini Varadhan
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Lung Compliance is defined as the change in lung volume produced by a unit change in transpulmonary pressure. It is represented by the gradient of the pressure–volume curve.1
Normal Range: The total compliance of both lungs together in normal adult human being average is about 200 milliliters of air per centimeter of water trans-pulmonary pressure. when trans pulmonary pressure increases one centimeter of water the lung volume after 10 to 20 seconds will expand 200 milliliteres.4
The diagram relates the lung volume differs to changes in the trans pulmonary pressure. It differs for inspiration and expiration.
The two compliance curves are:
- Inspiratory Compliance curve
- Expiratory Compliance curve
Types of Compliance
Dynamic Compliance :is defined as the change in lung volume per unit change in pressure in the presence of flow.
Static Compliance : is defined as the change in lung volume per unit change in pressure in the absence of flow.
The two important factors of Lung compliance :
Elastic Fibers : More fibers in the tissue lead to ease in expand-ability and there for compliance.
Surface tension : It is decrease due to the production of surfactant to prevent collapse.4
Hysteresis is the term used to describe the difference between inspiratory and expiratory compliance. Lung volume at any given pressure during inhalation is less than the lung volume at any given pressure during exhalation.3
Hysteresis is present in both static and dynamic lung compliance curves
Hysteresis develops due to:
- The effect of surfactant
- Relaxation of lung tissue
- Recruitment and derecruitment of alveoli
- Gas absrption during measurement
- Differences in expiratory and inspiratory air flow (for dynamic compliance)
|Lung compliance||Chest wall compliance|
|Increased lung compliance
||Increased chest wall compliance
|Decreased static lung compliance
Decreased dynamic lung compliance
|Decreased chest wall compliance
- Iotti, G., & Braschi, A. (1999). Measurements of respiratory mechanics during mechanical ventilation. Rhäzüns, Switzerland: Hamilton Medical Scientific Library.
- Harris, R. Scott. "Pressure-volume curves of the respiratory system." Respiratory care 50.1 (2005): 78-99.
- Rahn, Hermann, et al. "The pressure-volume diagram of the thorax and lung." American Journal of Physiology-Legacy Content 146.2 (1946): 161-178.