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24 Cards in this Set
- Front
- Back
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ventilation
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the flow of gas in and out of the lungs
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perfusion
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the filling of the capillaries with blood
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what may alters perfusion
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pulmunary artery pressure
alveolar pressure gravity |
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what may alter ventilation
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airway blockages,
local changes in compliance, gravity |
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what causes a ventilation-perfusion(V/Q) imbalance
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inadequate ventilation
inadequate perfusion or both |
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four possible V/Q states in the lungs
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normal V/Q ratio
low V/Q ratio(shunt) high V/Q ratio(dead space) absence of V/Q(silent unit) |
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normal V/Q ratio (1:1)
ventilation matches perfusion |
in a healthy lung, a given amount of blood passes an alveolus and is matched with an equal amount of gas
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low V/Q ratio (shunts)
perfusion exceeds ventilation |
blood bypasses the alveoli w/out gas exchange occurring;
this is seen with obstruction of distal airways, such as: pneumonia atelectasis tumor mucus plug |
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high V/Q ratio (dead space)
ventilation exceeds perfusion |
the alveoli do not have adequate blood supply for gas exchange to occur;
this is characteristic of a variety of disorders, including pulmonary emboli pulmonary infarction cardiogenic shock |
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absence of V/Q (silent unit)
absence or limited ventilation and perfusion |
this is seen with
pneumothorax & severe acute respiratory distress syndrome |
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average normal PaO2=
average normal PaCO2= *partial pressure varies in different lung areas |
100mmHg
40mmHg ` ` |
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under normal conditions and in upright positions,
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ventilation is greater than perfusion in the lung apices
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under normal conditions and in upright positions,
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perfusion and ventilation are greater in the lung bases
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where is the nervous system control of breathing initiated
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w/in the medulla oblongata and pons of the brain stem
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medulla oblongata
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controls inspiration, expiration, and breathing pattern
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pons
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controls rate and depth of respiration
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sensory input to brainstem
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impulses that influences breathing and respiration are transmitted to the brainstem from:
chemoreceptors, stretch receptors, proprioceptors, baroceptors, and the external environment. |
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central chemoreceptors in medulla
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> PCO2 and/or
< blood pH causes: > alveolar ventilation as a compensatory mechanism to maintain PCO2 and pH at normal levels |
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Peripheral chemorecptors in the aortic arch and carotid bodies
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< pH, and/or
> PCO2 and/or < PaO2 causes: > alveolar ventilation |
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what prevents overdistention of the lungswhen they are inflated
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-stretch receptors in the alveolar septa
-bronchi -bronchioles |
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proprioceptors in muscles and tendons of moveable joints
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stimulate ventilation w/exercise to increase O2 supply during increased O2 demand
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Baroreceptors alter respiration relative to changes in artial B/P
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elevated artial B/P lowers respiration
B/P below 80 mmHg increases respiration |
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external environment factors that ALTER respiration
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cold
physical stress air pollution smoking pain |
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external environment factors that INCREASE O2 demand
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infection
fever |
