35 ventilation Flashcards
what is partial pressure?
the pressure exerted by an individual gas in a mixture of known gases. expressed in dry gas concentrations
if there is water vapor that must be removed
what is fractional concentration?
percentage of a gas in a mixture of gasses
what is the fractional concentration of oxygen?
21
what is the partial pressure of nitrogen?
160
what is the partial pressure of nitrogen?
600
what is the barometric pressure?
760 mmhg
how to calculate partial pressure of oxygen in the atmosphere?
Po2= Pb X Fo2
Fo2 fractional concentration of oxygen= 21%
Pb= barometric pressure= 760mmhg
Po2= partial pressure
given barometric pressure of 286
what is the Po2?
60
because
286*0.21= 60
How do you calculate partial pressure of inspired oxygen in trachea?
water vapor is included now…
Pio2= (Pb-PH20) * Fio2
760-47*0.21= PiO2= 149.7
pb= 760 atmospheric
Ph20=partial pressure of water=47
FiO2= fractional oxygen= 0.21
pio2= inspired/humidified/count water vapor
what is the partial pressure oxygen and CO2 at ambient dry air?
oxygen= 160, 21%
CO2=0 0
what is the partial pressure of oxygen and CO2 at moist trachael air?
oxygen= 150mmhg, 20% CO2= 0,0
what is the partial pressure at alveolar air of oxygen and CO2?
oxygen= 102 mmgh, 14% CO2= 40 mmhg 5%
what is the partial pressure of oxygen and CO2 at arterial blood ?
oxygen= 95
CO2=40
what is the partial pressure of oxygen and CO2 at venous blood ?
oxygen= 40
CO2=46
what is minute ventilation?
volume of air entering the lungs per minute
what is the equation of minute ventilation/total ventilation?
Ve=VTxf
Vt= tidal volume f= fréquence/ rate of breathing
example tidal volume= 500ml
breathing frequency= 12 breaths per minute
0.5L*12= 6 l/min
what is dead space?
place in respiratory system where gas exchange does not occur, conducting zone is a dead space= anatomic dead space
for example take in 500ml but 150 ml go to dead space and 350 get to alveoli and goes to alveoli and does gas exchange
what is the normal ratio of Vd/Vt?
dead space/tidal volume
0.25-0.35 in healthy people
what is alveolar dead space?
air going to alveoli but doesn’t go through gas exchange
what is the equation for physiological deadspace?
physiological deadspace= anatomical Vd + alveolar Vd
in healthy people physiological dead space = anatomical dead pace
what is case where alveolar deadspace is large?
pulmonary embolism
How do you calculate alveolar ventilation?
Va= (Vt f)- (Vdf)
air
Va= volume of air added to alveoli Vd= volume of air in deadspace
29/min respirations
tidal volume= 400 ml
deadspace volume=150
what is minute ventilation?
29*400= 11600
tidal volume * respirations 29
how do you calculate alveolar ventilation?
Va= (Vt-Vd) * breaths/min
Vt= tidal volume Va= alveolar ventilation Vd= dead space
volume of air delivered to respiratory zone per minute
29/min respirations
tidal volume= 400 ml
deadspace volume=150
what is alveolar ventilation?
7250
Va= (Vt-Vd) * breaths/min
(400-150)*29= 7250
how is dead space measured at anatomical dead space?
Fowler’s method
how is physiological dead space measured?
Bohr’s method
How is alveolar dead space measured?
need to subtract anatomical and physiological dead space
how do you calculate a healthy deadspace?
1 ml per pound..
ex= 150 lbs
so 150 ml*12= 1800ml/min
How is fowler’s method done?
inspire 100% after tidal expiration
exhale to RV (residual volume)
plotted Nitrogen released and monitored
what is the equation for Bohr method?
Vd/Vt= 1 - PeCO2/PaCO2
Vd= dead space
Vt=tidal volume
PeCO2= expired partial pressure of CO2
PaCO2= alveolar partial pressure
clinically it is assumed that alveolar CO2 and arterial are the same PaCO2 ( arterial) and PACO2 ( alveolar)
If PaCO2= 40 mm hg and PeCO2 =28 mmhg
If Vt= 500 what is Vd?
1-28/40= 0.3
0.3*500
Vd= 150
what is a normal body PH
7.35-7.45
what is a normal HCO3?
23-28
what is an equation for alveolar ventilation?
VA= (VeCO2 *0.863)/ PaC02 VA= alveolar ventilation VeCO2= expired volume of CO2 in one minute
PaCO2= partial pressure of alveolar CO2
as alveolar ventilation increases carbon dioxide _______
decreases
With hyperventilation you have what?
respiratory alkalosis
with hyperventilation you have ?
respiratory acidosis
what is the A-a O2 gradient?
the difference between the alveolar oxygen gas tension (PAO2) and arterial oxygen tension (Pa02)
A-aO2 gradient= PAO2-PaO2
A-a O2 gradient=(PiO2-[(PaCO2/R]-PaO2
A normal or elevated A-a gradient of more than 15 can be a sign of?
hypoxemia
elevated A-a means a high respiratory effort to achieve oxygenation; pulmonary problem
Low oxygenation due to hypoventilation; extra- pulmonary source of hypoxemia would not affect A-a gradient
what is hypoventilation?
decreased alveolar ventilation with increased PaCO2
ventilation refers to alveoli, it is inversely proportional to pressure of CO2
what is hyperventilation?
increased alveolar ventilation with decreased PaCO2
what is hypercapnia?
increased CO2 in blood PaCO2 above 48 mmhg
what is hypopnea?
decreased ventilation in response to lowered metabolic CO2 production
breath slower
what is hyperpnea?
increased ventilation in response to increased metabolic CO2 production ( ex is exercise) which should purge CO2
breath faster
what is eupnea?
normal breathing
what is tachypnea?
increased frequency of breathing
swift breathing. ventilation may or may not be changed dependent on tidal volume
what is dyspnea?
shortness of breath/labored breathing/ ill breathing
what is apnea?
temporary cessation of breathing
A 23 year old pre- med students comes to the clinic because she is anxious about her physiology exam. physical examination and laboratory investigations shows that the patient is hyperventilating. which of the following changes would be likely?
Hyperventilation looks at the alveoli..
this means that there is hyperventilated alveoli and decreased PaCO2 because they are inverse to each other.
ALSO hyperventilation increased the partial pressure of O2
