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31 Cards in this Set
- Front
- Back
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on inspiration what happens |
the dome shaped diaphragm contract, the abdominal contents are forced down and forward, and the rib cage is widened (opens outward and upward); both increase the volume of the thorax |
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on expiration what happens |
the abdominal muscles contract and push the diaphragm up |
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the internal intercostals are involved in forced |
exhalation |
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the external intercostals are involved in |
inhalation |
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when the external intercostal muscles contract |
the rubs are pulled upward and forward and they rotate on an axis joining the tubercle and the head of rib; as a result both the lateral and anteroposterior diameters of the thorax increase |
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when the internal intercostal muscles contract |
they have the opposite action |
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in standard exhalation |
no muscle contraction is needed; the muscles relax and exhalation is the result of elastic recoil |
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inspiration is |
active and involuntary |
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the most important muscle of inspiration |
the diaphragm |
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muscles that play a lesser role during tidal inspiration |
external intercostals |
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what muscles contract during tidal inspiration to prevent tracheal collapse |
muscles of the tongue and pharynx |
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during normal breathing what moves |
the chest wall moves out and up while the diaphragm descends during inspiration |
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in quadriplegia |
the diaphragm is preserved but the intercostals are lost; the abdomen moves out while the chest caves in during inspiration |
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in diaphragm fatigue |
there is also paradoxical motion but the chest wall expands while the diaphragm is pulled up during inspiration |
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the pressure volume curve |
the lung is held at each pressure for a few seconds while its volume is measured; the curve is nonlinear and becomes flatter at high expanding pressures; the inflation and deflation curves are not the same (this is called hysteresis) |
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compliance definition |
the partial derivative of volume with respect to pressure; C=deltaV/deltaP |
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compliance in the pressure volume curve |
compliance is equal to the slope of the tangent lines at each point along the P-V curve; compliance decreases with volume |
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hysteresis |
the pressure for inflation is greater than the pressure for deflation at any given lung volume; without hysteresis any multi unit lung would be unstable with all alveoli emptying into a single alveolus |
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gravity and pleural pressure |
because of the weight of the lung the intrapleural pressure is less negative at the base than at the apex; as a consequence the basal lung is relatively compressed; -10 cm H2O at the top and -2.5 cm H2O at the bottom; because of this there is more air at the top of the lung but the bottom has a greater change in air (the air moves here preferentially during inspiration); the less negative pleural pressure at the base means the basilar units are less inflated than the apical units; since the basilar units are at a lower point along the P-V curve their compliance is higher and incremental inflation will be greater than in the apical units |
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functional residual compacity |
this is when there is normal exhalation without the use of any muscles; the tendency of the lung to recoil to its deflated volume is balanced by the tendency of the chest cage to bow out; as a result the intrapleural pressure is substratospheric (it is negative); pneumothorax allows the lung to collapse and the thorax to spring out |
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chest wall versus lung |
FRC occurs whenever the outward recoil of the chest wall is equal to the inward recoil of the lung such that the pressure in the lung is 0 (the intrapleural space will have a negative pressure do to the pulling from both sides) |
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respiratory compliance |
C=deltaV/deltaP for the respiratory curve; note the sigmoid shape; FRC tends to be at the point of max compliance with the system becoming stiffer at both higher and lower volumes; a low compliance is stiff and resists expansion; a high compliance is floppy and exerts little pressure to deflate; normal respiratory compliance for adults is 100 ml/cm H2O |
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emphysema and hyperinflation |
emphysema is the loss of elastic recoil in the lung; as recoil goes to 0 the pressure of the respiratory system approaches the chest wall curve; note the intercept of the chest wall curve under these conditions= over 75% of TLC; get a barrel chest |
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restrictive lung diseases such as pulmonary fibrosis cause |
stiff lungs or low compliance; lung volumes ar elow |
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emphysema causes |
destruction of the elastic elements of the lung; the lung has abnormally high compliance; lung volumes are high |
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hyperinflation in emphysema will be limited by |
the chest wall; eventually the total system will be stiff due to limits of chest wall motion |
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FVC+ |
TLC-RV |
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FEV1= |
forced expiratory volume for 1 second; volume exhaled during first 1 second |
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a normal flow volume loop looks like |
a child's drawing of a sailboat; the inspiratory limb is the rounded hull under the water; the expiratory limb is a triangular sail; airflow obstruction produces a smaller boat with a sagging (scooped) sail; restriction produces a smaller boat with a normal sail shape |
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COPD |
airflow obstruction |
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central airway obstruction is obstruction where |
at the trachea or vocal cords or one of the mainstem bronchi; on the flow volume loop either the sail is clipped, the hull is clipped, or both are clipped; both clipped=fixed obstruction like tracheal stenosis after a trach; sail is clipped=intrathoracic obstruction; hull is clipped=extrathoracic obstruction |
