Respiration lecture 2 Flashcards
How can we determine subdivisions of the lung volumes?
With a spirometer
What is the function of a spirometer?
to measure the volumes of INHALED or EXHALED gas (not total lung volume)
What can spirometers measure?
Tidal volume
Vital capacity
Inspiratory capacity
Expiratory reserve volume
Inspiratory reserve volume
What are spirometers not used to measure?
Functional residual capacity
Total lung capacity
Residual volume
What is tidal volume?
The amount of air inhaled or exhaled in one breath during quiet breathing
What is inspiratory reserve volume (IRV)?
The additional volume of air that can be inhaled with maximum effort after a notmal tidal inspiration
What is expiratory reserve volume?
The additional air that can be exhaled with maximum effort after a normal tidal expiration
What is residual volume?
The amount of air remaining in the lungs after maximum expiration (will never be exhaled)
What is vital capacity?
The amount of air that can be exhaled with maximum effort after maximum inspiration (Deep breaths in and out)
How can you calculate vital capacity?
TV+ERV+IRV
What is inspiratory capacity?
Maximum amount of air that can be inhaled after a normal tidal expiration
How can you calculate inspiratory capacity?
TV+IRV
What is function residual capacity?
The amount of air remaining in the lungs after a normal tidal expiration
How can you calculate functional residual capacity?
RV+ERV
What is total lung capacity?
The maximum amount of air the lungs can contain
How can you calculate total lung capacity?
RV+VC
How can you directly measure FRC ?
By helium dilution
What is the formula for calculating the of FRC using helium dilution?
FRC = (C1 + V1/C2) - V1
What is the concentration of helium after equilibration? Why?
It is less concentrated because it’s diluted in the lungs
What is minute ventilation?
The amount of air inspired (or expired) into the lungs over a minutes
What is the formula for minute ventilation?
Ve=Vt x f
Vt: Tidal volume
f: number of breaths per minute
For a normal adult male, what is the normal value for minute ventilation not including anatomical dead space?
6000 mL/min
What is the normal values for tidal volume and # of breaths per minute in a normal adult male?
Vt = 500 mL
f = 12 breaths/min
What is anatomical dead space?
A place where air remained in the conducting airways and cannot do any gas exchanges
For a normal adult male, what is the normal value for minute ventilation including anatomical dead space? How is this calculated?
4200 mL/min
Ve=Vt x f
= (500-150) x 12
What is the volume of the anatomical dead space in an adult subject?
150 mL
What can we use to approximate anatomical dead space since it is difficult to measure?
Weight in pounds
When does alveolar dead space happen?
under pathological conditions
What happens to alveoli in alveolar dead space?
They get a decreased blood supply or no blood at all
What happens to inspired air when the alveoli do not receive enough blood?
It can’t make any gas exchanges even if the ventilation is the same
What is the sum of alveolar and anatomical dead space called?
Physiological dead space
What is the difference between minute and alveolar ventilation?
Minute ventilaton doesn’t take into account dead space whereas it’s in the calculations for alveolar ventilation
What are the 3 types of alveolar ventilation?
Normal
Hypoventilation
Hyperventilation
What is the pressure of O2 and CO2 in the air?
PO2 = 160 mmHg
PCO2 = 0.3 mmHg
What is the pressure of O2 and CO2 in the alveoli?
PO2 = 105 mmHg
PCO2 = 40 mmHg
What is the pressure of O2 and CO2 in the pulmonary veins (towards left heart) and systemic arteries moving towards the cells?
PO2 = 100 mmHg
PCO2 = 40 mmHg
What is the pressure of O2 and CO2 in the pulmonary arteries and systemic veins moving away from the cells into the right heart?
PO2 = 40 mmHg
PCO2 = 46 mmHg
What keeps PaCO2 at a constant level?
The alveolar ventilation
When does alveolar hyperventilation occur?
when more O2 is supplied and more CO2 is removed then the metabolic rate requires
What does ventilation need to be considered with?
metabolism
What happens to the Pa and PAO2 and the Pa and PACO2 during alveolar hyperventilation?
PA and Pa O2: rises
PA and Pa CO2: decreases
Why do people faint during hyperventilation?
arterial CO2 decreases → blood vessels constrict → Cerebral vasoconstriction reduces brain blood flow → less O₂ delivery → fainting.
What happens to the Pa and PAO2 and the Pa and PACO2 during alveolar hypoventilation?
PAO2: decreases
PACO2: rises
Why do we give people a paper bag to breathe into when they are hyperventilating?
because blowing into the bag builds int he CO2 inside of it, and breathing in the CO2 builds the pulmonary CO2 they don’t have enough of
Why does PAO2 fall below normal values during alveolar hypoventilation?
because the blood in the pulmonary capillary is less oxygenated
When does alveolar hypoventilation occur?
when there is damage to the respiratory muscles, chronic obstructive lung disease, when the chest cage is injured and when the CNS is depressed
How does oxygen from the alveolar gas transfer across the alveolar-capillary membrane?
by passive diffusion
What is diffusion governed by?
Fick’s Law
What is diffusion rate proportional to?
surface area (5-100 m^2)
partial pressure gradient
1/thickness (0.2 mm)
What is the pressure of O2 and CO2 in the blood when it reaches the alveolar capillaries?
PO2: low
PCO2: high
Where does O2 and CO2 diffuse?
O2: from the alveolar gas to the blood
CO2: from the blood to the alveolar gas
In order for a gas to diffuse through a liquid…
it must be soluble in the liquid
How much faster does CO2 diffuse as compared to O2 in the same liquid?
20x faster
What is the time required to reach equilibrium between alveolar air and capillary blood for O2 and CO2?
diffusion rate of both gases
the same for the two gases
The different pressure gradient (mmHg and 60 mmHg) does not make a difference in the rate of diffusion because of the solubility difference
What is the transit time of blood through pulmonary capillaries?
0.75 seconds at rest
In a normal lung, within what fraction of the red blood cell transit time is diffusion of both O2 and CO2 accomplished?
within 1/3 of the transit time
What happens to the diffusion time in someone who has edema? Why?
it decreases because the alveolar capillary membrane will be thicker due to built up liquid
What happens if the alveolar ventilation is increased but the metabolism needs stay the same
PO2 = increases
PCO2 = decreses
What happens if the alveolar ventilation is decreased but the metabolism needs stay the same
PO2 = decreases
PCO2 = increases
What happens if the metabolic needs go up but alveolar ventilation stays unchanged?
PO2 = decreases
PCO2 = increases
What happens if the metabolic needs go down but alveolar ventilation stays unchanged?
PO2 = increases
PCO2 = decreases
What happens if the alveolar ventilation increases proportionally to the metabolic needs
PO2 = no change
PCO2 = no change
