Pulmonary compliance

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. 

The answer is A. Lung surfactant reduces surface tension of the fluid lining the alveoli to increase pulmonary compliance and facilitate exchange of gases dissolved in that fluid from inspired air into the airway epithelial cells and eventually by diffusion into the blood. Although all the other options represent properties of water or solutions, they have nothing to do with the properties of surfactant. 

Mitsuhata et al. (1994) induced systemic anaphylaxis in dogs sensitized to Ascaris suum by intravenous injection of the antigen and measured pulmonary resistance and dynamic pulmonary compliance. 

Valkila EH, Nieminen MM, Moilanen AK, et al. 1995. Asbestos-induced visceral pleural fibrosis reduces pulmonary compliance. Am J Ind Med 28 363-372. 

Activated neutrophils and platelets adhere to the pulmonary capillary endothelium, initiating multiple inflammatory cascades with a release a variety of toxic substances. There is diffuse pulmonary endothelial cell injury, increased capillary permeability, and alveolar epithelial cell injury. Consequently, interstitial pulmonary edema occurs and gradually progresses to alveolar flooding and collapse. The end result is loss of functional alveolar volume, impaired pulmonary compliance, and profound hypoxemia. ... 

In elderly subjects the elastic fibres showed a notable decrease along the alveolar walls while type III collagen increased when compared with that of non-elderly controls (D Errico et al. 1989). No variations of these components were detectable in the alveolar ducts or in the respiratory bronchi-oli. An increase in the thickness of the alveolar basement membranes were detected in some of the subjects when antibodies against type IV collagen and laminin were used, while antibodies to fibro-nectin and type V collagen did not reveal any modifications compared with the controls. The modifications revealed in the lungs of the elderly can be related to the alterations of the elastic recoil and pulmonary compliance observed in these subjects. 

Assisted ventilation may be of some benefit because pulmonary compliance Is usually compromised. Oxygen is contraindicated because it may exacerbate oxidative damage to the lung. 

The goals of management are to maintain pulmonary compliance and promote chest wall and lung growth (in pediatric patients), to maintain normal alveolar ventilation, and to maximize CPF. 

Air stacking increases voice volume, maximizes CPF, improves pulmonary compliance, prevents atelectasis, and indicates effective use of NIPPV. Anyone who can air stack can be extubated to NIPPV. Such patients can be extubated without being ventilator... 

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