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respiratory pathophysiology


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dorsal respiratory group
dorsal portion of medulla oblongata
mainly inspiration
dorsal resp. group receives info. from?
1) chemoreceptors
2) baroreceptors
3) other receptors in the lungs
ventral respiratory group
ventrolateral portion of medulla
inspiration or expiration
involved in increased levels of ventilation
pneumotaxic center
dorsally located in the pons
rate and pattern of breathing
limits the duration of inspiration
increase the RR
strong signal from pneumotaxic center
reduces the time of inspiration
weak signal from pneumotaxic center
increase the time of inspiration
which resp. group is most important in controlling resp.
dorsal resp. group
ultimate goal of resp.
to maintain proper [H], [O2], and [CO2] in the tissue
what stimulate the resp. center directly
increased [H] and [CO2], not [O2]
no direct effect on the resp. center
acts through the peripheral chemoreceptors
where chemoreceptors located?
carotid and aortic bodies
net diffusion of a gas in one direction
is a direct effect of its [ ] gradient
total pressure of a gas
is directly proportional to the [ ] of the gas molecules
partial pressure
the pressure of a specific gas
pressure of a gas in solution is determined by?
[gas] and the solubility coefficient
Henry's Law
pressure=[dissolved gas]/solubility coefficient
the solubility coefficient at body temp.
net diffusion
is determined by the difference bet. the 2 partial pressure
PP of a gas in the alveoli (O2) > blood
go to the blood
PP of a gas in the blood(CO2) > alveoli
will escape to the alveoli
respiratory volumes
1) TV
2) IRV
3) ERV
4) RV
tidal volume
500 ml
amt. of air inhaled or exhaled with each breath under resting conditions
inspiratory reserve volume
3100 ml
amt. of air that can be forcefully inhaled after a normal TV inhalation
expiratory reserve volume
1200 ml
amt. of air that can be forcefully exhaled after a normal TV exhalation
residual volume
1200 ml
amt. of air remaining in the lungs after a forced exhalation
respiratory capacities
1) TLC
2) VC
3) IC
4) FRC
total lung capacity
6000 ml
max. amt. of air contained in lungs after a max. inspiratory effort
vital capacity
4800 ml
max. amt. of air that can be expired after a max. inspiratory effort
VC =
should be 80 % TLC
inspiratory capacity
3600 ml
max. amt. of air that can be inspired after a normal expiration
IC =
functional residual capacity
2400 ml
volume of air remaining in the lungs after a normal TV expiration
alveoli > blood > tissue
tissue > blood > alveoli
Va/Q = 0
Va is 0 and there's still perfusion
no gas exchange
no ventilation
Va/Q = 0
PCO2 and PO2 ?
same as venous blood
PCO2 = 45 mm Hg
PO2 = 40 mm Hg
Va/Q = infin.
Va is perfect but no perfusion
no gas exchange
Va/Q = infin.
PCO2 and PO2 ?
same as inspired air
PCO2 = 0 mm Hg
PO2 = 149 mm Hg
normal Va/Q
PO2 = 104 mm Hg
Pco2 = 40 mm Hg
physiological shunt
the amt. of non-oxigenated blood/min.
physiologic dead space
the sum of 2 types of wasted ventilation
1) if Va/Q = higer than normal
2) vent. of the anatomical dead space areas
O2-Hgb dissociation curve
show a progressive increase in the % of Hgb bound to O2 as the PO2 increase
shifts to right
decreased affinity
cause for shifts to right
acute acidosis (< Ph)
increased PCO2
increased temp.
increased levels of 2,3-DPG
abnormal Hgb
shifts to left
increased affinity
causes for shifts to left
acute alkalosis (> Ph)
decreased PCO2
decreased temp.
decreased levels of 2,3-DPG
abnormal Hgb

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