This is due to the fact that a highly compliant lung results in many Atelectasis which makes inflation difficult. High compliance indicates a pliable lung (one with low elastic recoil) and can be thought of as a grocery bag – this is the case often seen in emphysema. Compliance diminishes with age and menopause. Lung compliance, or pulmonary compliance, is a measure of the lung's ability to stretch and expand (distensibility of elastic tissue). during abdominal insufflation, ascites, intrinsic lung disease, obesity, pulmonary edema, tension pneumothorax). Since, the surface tension forces are eliminated in the liquid-filled lungs as there is no air-liquid interface, the elastance becomes much lower (approximately one-fourth) compared to a normal lung as the elastance is entirely due to the elastin fibers. Lung compliance, or pulmonary compliance, is a measure of the lung's ability to stretch and expand (distensibility of elastic tissue). Chest wall compliance is the opposite of elasticity, and elasticity is the tendency of lung tissue to return to its original (or relaxed) position after an applied force has been removed. Elastic Resistance to Breathing Elastic Recoil of the Lungs • The tendency of elastic lung tissue to recoil from the chest wall results in a sub-atmospheric intrapleural pressure. They must be elastic to recoil and push air out during expiration. The elastance of the whole respiratory system depends on the elastance of the chest wall and that of the lungs. Figure 1. It can be calculated using the following equation. Pulmonary compliance refers to the relationship between the volume of the lungs and the transmural pressure across the lungs. IPF results in profound reductions in lung compliance. The ability of the lungs to expand is expressed using a measure known as the lung compliance. Low compliance indicates a stiff lung (one with high elastic recoil) and can be thought of as a thick balloon – this is the case often seen in fibrosis. Reduction in the surface tension would lead to a reduction in the trasnpulmonary pressure that is required to keep the alveoli expanded. Elastance, also known as the elastic resistance is the reciprocal of compliance, i.e. It is defined as the change in lung volumes divided by the change in transpulmonary pressure. 4 In the figure, lung volume is expressed as a function of pressure. Lung compliance is the change in lung volume per unit change in pressure. As a result, the compliance of the lung is the least at high lung volumes and greatest as the residual volume (RV) is approached []. The elastance of the gas-filled lungs can be assumed to have the same elastance as that, which is attached to the thoracic wall. The two important factors of Lung compliance : Elastic Fibers : More fibers in the tissue lead to ease in expand-ability and there for compliance. Dynamic compliance is always lower than or equal to static lung compliance because PIP − PEEP is always greater than Pplat − PEEP. The observed age differences in lung compartment volumes can largely be accounted for by the decrease in chest wall compliance. These enzymes are secreted by leukocytes (white blood cells) in response to a variety of inhaled irritants, such as cigarette smoke. The surface tension in the lungs is reduced by a chemical agent, known as surfactant, secreted by the type II alveolar cells in the lungs. This accounts for approximately one fourth to one third of the elastic resistance of the lungs and holds the responsibility of generating the recoil forces necessary to increase the intra-alveolar pressure during expiration, which is a passive process. Compliance= change in volume / change in pressure ; Lung volume depends on body size. The surface of the alveolar cells is moist, and so the alveoli can be pictured as air filled sacs lined with water. Compliance is inversely related to the elastic recoil of the lungs, so thickening of lung tissue will decrease lung compliance. Elastance and Compliance express the same properties of the connective tissue from different points of view. Lung elastic recoil (affected by age and disease states, eg. Details regarding the secretion of surfactant and the functions of surfactant will be described in a separate hub. Dynamic compliance represents pulmonary compliance during periods of gas flow, such as during active inspiration. In clinical practice it is separated into two different measurements, static compliance and dynamic compliance. Because lung compliance is so dependent on lung volume (compliance can fall by 50% with resection of one lung, for example, even though the elastic properties of the remaining lung are unaltered), its variability can be somewhat reduced by correcting it for height, predicted TLC, or measured FRC.69 Elasticity is less for instance for arteries so they are less compliant. When interpreted according to Hooke’s Elastance = 1/Compliance = Pressure change / Volume change. These distorting forces are usually those of intrapleural pressure, which becomes more negative to bring about inspiration and then becomes less negative, and the elasticity of the lungs leads to quiet expiration. On the other hand, only peak inspiratory pressure increases (plateau pressure unchanged) when airway resistance increases (e.g. Thus, this decreases the power that needs to be generated by the muscles of inspiration and hence, the work of breathing. the pressure change that is required to elicit a unit volume change. elastance: [ e-las´tans ] the quality of recoiling on removal of pressure without disruption, or an expression of the measure of the ability to do so in terms of unit of volume change per unit of pressure change; it is the reciprocal of compliance. Pplat is never bigger than PIP and is typically <10 cm H2O lower than PIP when airway resistance is not elevated. The lungs must also be able to overcome the force of surface tension from water on lung tissue during inflation in order to be compliant, and greater surface tension causes lower lung compliance. When a whole lung is considered, the transmural pressure is the transpulmonary pressure (intra-alveolar pressure – intra-pleural pressure). During this maneuver, airflow is transiently (~0.5 sec) discontinued, which eliminates the effects of airway resistance. As lung volume increased pulmonary compliance decreased more in the young than in the old. is the maximum amount of air a person can expel from the lungs after a maximum inhalation. In clinical practice it is separated into two different measurements, static compliance and dynamic compliance. higher lung compliance indicates that the lungs stretch easily=easier to breath. This occurs as the lungs in this case become fibrotic, lose their distensibility and become stiffer. The dimensions of compliance in respiratory physiology are inconsistent with the dimensions of compliance in physics-based applications. Low compliance indicates a stiff lung and means extra work is required to bring in a normal volume of air. What is the mathematical formula for compliance? This reflects progressive stretching of elastin fibers to their physical limits as well as increasing surface tension as alveoli expand. Since the alveoli are globular structures, having a thin lining of fluid, which comes into contact with air, the net surface tension force acts inwards. ; Elastance: The arteries are more elastic.This property makes up the basis for “windcastle effect” in the aorta. Compliance:Dilation of the arteries, veins in response to mechanical load. Intrinsic restrictive lung disease . Elastance: Resistance, stiffness of the arteries, veins in response to mechanical load. As alveoli are inter-connected, any alveolus tending to collapse will be held open, because it will be supported by the walls of adjoining alveoli; this interaction between alveoli is termed interdependence. ELASTANCE Because of the presence of elastic and collagen fibers in its parenchyma, the lung has principles of elasticity. The ability of the lungs to expand is expressed using a measure known as the lung compliance. The lungs are both compliant and elastic. It can be calculated with the formula: Pplat is measured at the end of inhalation and prior to exhalation by using an inspiratory hold maneuver. In medicine, compliance and elasticity are different ways to describe how stretchy, springy or flexible something is. It is important to understand that the lung (or any other elastic structure) will not increase in size if the pressure within it and around it are increased equally at the same time. In this condition extra work is required to get air out of the lungs. There seems to some sort of relationship between compliance and elasticity. Arteries have … In physiology. The more compliant the lungs are, the more they are able to stretch in response to a force, and the lower the compliance, the less they stretch in response. The presence of surfactant in this fluid breaks up the surface tension of water, making it less likely that the alveolus can collapse inward. In addition, patients often have difficulties inhaling air as well. Dynamic lung compliance is the compliance of the lung at any given time during actual movement of air. By Jon Trister MD. The looped P-V curve practically means that as lung volume increases, the elastic elements approach their limits of distensibility and a given change in transpulmonary pressure produces smaller and smaller increases in lung volume. emphysema reduces it) Chest wall compliance (affected by chest injuries, burns, surgery, eg. Then: Static compliance represents pulmonary compliance during periods without gas flow, such as during an inspiratory pause. the pressure change that is required to elicit a unit volume change. At low lung volumes the pulmonary compliance is high; however, as the lungs expand their compliance progressively decreases. Compliance is highest at moderate lung volumes, and much lower at volumes which are very low or very high. [2][3], Pulmonary surfactant increases compliance by decreasing the surface tension of water. Both peak inspiratory and plateau pressure increase when elastic resistance increases or when pulmonary compliance decreases (e.g. Lung compliance is the volume change that could be achieved in the lungs per unit pressure change. Arterial compliance is measured by ultrasound as a pressure (carotid artery) and volume (outflow into aorta) relationship. Changes in the elastance (and therefore the compliance) of the chest wall are uncommon. Lung compliance is the volume change that could be achieved in the lungs per unit pressure change. Elastance is a measure of the work that has to be exerted by the muscles of inspiration to expand the lungs. Volume/Pressure= Compliance Pressure/Volume= Elastance. determinant of lung compliance is not the elasticity of the lung tissues, but the surface tension at the air-water interfaces within the alveoli. whereas in newtonian physics, compliance is defined as the inverse of the elastic stiffness constant k. Pulmonary compliance is analogous to Capacitance. Compliance: Arteries are less compliant and veins are more compliant. One of the most common clinical features of it is difficulty taking a deep breath. Fibrotic lung disease inadequate surfactant production. Patients with emphysema have a very high lung compliance due to the poor elastic recoil. Surface tension : It is decrease due to the production of surfactant to prevent collapse. Lung compliance is the ability of the lungs to stretch or expand to allow an increase in the volume of air during inspiration (taking a breath). Compliance ) of the lungs per unit pressure change the power that needs to be exerted by change. 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