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PHGY 355 (1)

phgy355: dynamic compression

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PHGY 355
John T Fisher

Dynamic Compression • COPD ⿞Airway dynamic Compression ‣ large component of obstructive diseases • Flow-Volume Curve ⿞you can not break free of your maximal output no matter what ⿞your respiratory system can easily handle increased demands • Dynamic compression model ⿞going from a static to dynamic model ⿞once the chest wall starts to compress the lung,as you move mouthward, an equal pressure is attained between outside of the tube and inside,causes the airway to close in ⿞flow limitation occurs when alveolar and pleural pressures become equal • Maximal Expiratory flow and volume (slide) ⿞once you have a positive intrapleural pressure,the stiffness of the airway is exceeded,causing compression of the airway to occur ⿞transpulmonary pressure won't change from pointsA-B-C-D ‣ volume in the system is static ‣ it's the compression caused by the muscles that add pressure to the system • At very high lung volumes,expiratory compression won't occur • as you move mouthward,pressure drops due to resistance to flow • if an airway narrows,the pressure drop will occur more quickly,the equal pressure point then moves closer towards the periphery of the lung,causing more dynamic compression along the pathway • equal pressure point in the pathway moves around the lung system as you exhale,the lower the lung volume the closer towards the periphery the compression occurs • changing airway structural stiffness causes a change in the volume that
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