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Phys2 Mech of Breath

Are the lungs and chest wall elastic structures? YES. But not in the sense that they are structures that can easily be stretched. Instead, they are structures that resist stretch, requiring energy to be stretch and returning to original size after being stretched.
What are the muscles invovled in inspiration? Primary: DIAPHRAGM (flattens, pushes rib margins outward INC chest Vol). Secondary: Ext Intercostal M (raise up ribs, INC chest Vol). Accessory: Scalenes and SCM (resp distress) **Inspiration is an active process requiring energy.
At rest, is expiration an active (energy using) process? NO. B/c of the chest wall and lungs' elasticity (resistance to change), relaxing the contracted inspiratory muscles will cause the lungs & chest wall to return to normal size. **Decreasing chest Vol and causing expiration.
What muscles contribute to active expiration? 1.Abdominal muscles (help to increase intra-abdominal pressure, hastening the diaphragm's return to its relaxed dome shape). 2.Int intercostal M (pull the ribs downward, DEC chest Vol).
Why do the lungs expand with the chest wall despite the fact that they want to be deflaited? B/c of cohesion b/w the pleura. The intrapleural fluid creates this cohesion, allowing the two layers (visceral & parietal) to slide about eachother but not seperate.
What is the Functional Residual Capacity (FRC)? it is the resting position that the lungs and the chest wall return to. It is created by a NEGATIVE intrapleural pressure which causes the lungs to pull the chest wall in and the chest wall to pull the lungs out (inflated) **TUG O' WAR**
What is a Pneumothorax and what is it's effects on the chest wall and lungs? Occurs when air enters the intrapleural space. This equalizes the previously negative pressure which allows the lungs and chest wall to seperate. Lungs: Collapsed inward. Chest wall: Moves outward.
What is the resting intrapleural pressure? During inspiration? Rest: -5cm H2O. Inspiration: -8cm H2O Expiration: returns back to -5cm H2O
If the net distending pressure on the chest wall & Lungs increases, what happens to the volume? INCREASES. **At 0 distention, the lungs & Chest wall are at FRC
Pressure changes occuring that drive inspiration & expiration? Alveolar pressure changes. When the chest wall expands and increases the chest volume, it decreases pressure in the alveoli (Boyle's Law) which causes an increased driving force to move air from the atmosphere into the lungs.
Why are stretchy lungs (LARGE lung volumes) problematic? Although they are easily distended, they are much harder to deflate b/c there is less inward pull of the lungs with inflation. **Easy to inflate, hard to deflate
Why are stiff lungs (SMALL lung volumes) problematic? B/c they are very hard to inflate (change their volume), however there is a much stronger inward pull on the lungs when they are finally inflated, making deflation easy. **Hard to inflate, easy to deflate
What specific lung volumes can't be measured with SIMPLE spirometry? 1.Functional Residual Capacity (Vol in the lungs after normal exp). 2.Residual Volume (Vol in lungs after max exp). 3.Total lung capacity.
Tidal Volume that volume of air moved into or out of the lungs during quiet breathin
Inspiratory Capacity (IC) Tidal volume(TV) + inspiratory reserve capacity(IRC). Maximum inhalation volume of the lungs
Vital Capacity (VC) VC = TLC - RV. It is the volume of the total lung capacity minus the residual volume. **Vol range of max inhalation and max exhalation.
Functional Residual Capacity The volume in the lungs at the end of quiet/resting exhalation.
Residual Volume (RV) the volume of air remaining in the lungs after a maximal exhalation
Total Lung Capacity (TLC) Vital Capacity (VC) + Residual Volume (RV). **total volume capacity of the lung.
Expiratory Reserve Volume (ERV) the maximal volume of air that can be exhaled from the end-expiratory position. **Functional Residual Capacity - RV.
What would you see with increased lung compliance? 1.STRETCHY lungs. 2.LARGER volume. 3.Easy to inflate, hard to deflate (less elastic recoil). **EMPHYSEMA (this is why the are barrel chested).
What would you see with reduced lung compliance? 1.STIFF lungs. 2.SMALL volume. 3.Hard to inflate, easy to deflate (inc elastic recoil). **Fibrosis & Alveolar Edema.
Increased compliance, ______ volumes? LARGE. (emphysema)
Reduced compliance, ______ volumes? SMALL (fibrosis, alveolar edema)
3 things controlling Lung Compliance 1.Elastic tissue (Elastin & collagen). 2.Surface tensoin (decreases compliance). 3.Ease of Rib movement.
What does compliance represent? The slope of the pressure-volume curve. **Inc Comp: Shifts up & left. **Dec Comp: Shifts down & Right
How does the amount of elastic tissue change with Emphysema? LESS elastic tissue than normal (doesn't have elastic recoil)
How does the amount of elastic tissue change with Pulmonary Fibrosis? MORE elastic tissue than normal (doesn't want to be stretched at all)
Spirometry changes with Emphysema INCREASE in: 1.TLC. 2.FRC. 3.RV. **Wider Vital Capacity curve.
Spirometry changes with Fibrosis DECREASE in: 1.TLC. 2.FRC. 3.RV. **More narrow Vital capacity curve
How does surface tension affect the lungs? makes them harder to inflate due to DECREASED compliance (Increased tension will generate a larger pressure inside the alveoli which will counter expansion). **this is why we produce surfactant
Atelectasis A collapse of a smaller Alveoli b/c surface tension was too great, forcing air out of the smaller alveoli into a larger one.
What produces surfactant? Type II alveolar cells. This phospholipid helps to DEC surface tension. **Hydrophobic tails repel eachother thus keeping the surface tension from pulling water together.
When is repulsion of hydrophobic surfactant tails the greatest? LOW SURFACE AREA
Effects of srufactant? 1.Inc Compliance. 2.Inc Alveolar stability. 3.Prevents pulmonary edema (reduces surface tension's suction of liquid out of the capillaries).
How would a patient with Pulmonary fibrosis present? 1.Shallow, rapid breathing (hard for them to inflate stiff lungs). 2.Smaller than normal lung volumes (dec compliance). 3.Honeycomb lungs.
Created by: WeeG



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