Elastic recoil pressure

Compliance is defined as the change in volume produced by a unit change in lung elastic recoil pressure and is the most commonly measured index of the elastic properties of the lung. Elastic recoil pressure is the difference between the pressure in the alveolus and the pressure in the pleural space (intrapleural pressure). 

Lung volume increases approximately 10-fold between 1 month and 7 years (Table 1), but it then slows down until the age of 18 years (Fig. 9). The associated increase in elastic recoil pressure combined with a progressive decrease in closing volume will affect patterns of aerosol distribution and may... 

Changes in Lung Volume and Elastic Recoil Pressure... 

Pulmonary surfactant decreases surface tension of alveolar fluid. Reduced surface tension leads to a decrease in the collapsing pressure of the alveoli, an increase in pulmonary compliance (less elastic recoil), and a decrease in the work required to inflate the lungs with each breath. Also, pulmonary surfactant promotes the stability of the alveoli. Because the surface tension is reduced, the tendency for small alveoli to empty into larger ones is decreased (see Figure 17.2, panel b). Finally, surfactant inhibits the transudation cf fluid out of the pulmonary capillaries into the alveoli. Excessive surface tension would tend to reduce the hydrostatic pressure in the tissue outside the capillaries. As a result, capillary filtration would be promoted. The movement of water out of the capillaries may result in interstitial edema formation and excess fluid in the alveoli. 

Sweeney R. J., Prozesky V. M., and Springhorn K. A. (1997) Use of the elastic recoil detection analysis (ERDA) microbeam technique for the quantitative determination of hydrogen in materials and hydrogen partitioning between olivine and melt at high pressures. Geochim. Cosmochim. Acte 61, 101-113. 

As a part of the sustainable pressure must be used to overcome normal airway flow resistance and elastic recoil of lung and chest, the amount of pressure (Pa) allowed to be used to overcome abnormal airway blockage, such as plastic film blockage, is smaller and can be found by... 

Pressure for flow resistance + Pressure for elastic recoil)... 

Normal expiration is a passive process, and when the inspiratory muscles end their contraction, the elastic recoil of the lung pulls the lung back to its original size and shape. This process makes the alveolar pressure positive relative to the pressure at the mouth, and air flows out of the lung. During inspiration, the respiratory muscles must overcome the elastic properties of the lung (elastic recoil) and the resistance to airflow by the airways. During expiration, the flow of air is determined primarily by the elastic recoil and airway resistance. 

To account for the observed (slight) motion of tissue during isovolumic relaxation, we have modeled isovolumic relaxation kinematically. In accordance with Newton s law, inertial, recoil, and resistive terms are required. By changing variables from displacement (x) to pressure (P) in accordance with LaPlace s law, the expression for damped, harmonic motion applies. Lumped parameters account for elastic recoil (Ei) and viscosity (1/lt), and we include inertia as well [9] ... 

Another noteworthy anatomical feature of the arteries is the presence of elastic connective tissue. When the heart contracts and ejects the blood, a portion of the stroke volume flows toward the capillaries. However, much of the stroke volume ejected during systole is retained in the distensible arteries. When the heart relaxes, the arteries recoil and exert pressure on the blood within them, forcing this "stored" blood to flow forward. In this way, a steady flow of blood toward the capillaries is maintained throughout the entire cardiac cycle. 

Due to the significant amount of elastic connective tissue and smooth muscle in their walls, arteries tend to recoil rather powerfully, which keeps the pressure within them high. In contrast, veins contain less elastic connective tissue and smooth muscle so the tendency to recoil is significantly less and the pressure remains low. 

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