Respiration - Lecture 2 Flashcards
How can we determine subdivisions of the lung volumes?
through spirometry
What is the function of a spirometer?
it measures volumes of inhaled or exhaled gas
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 or residual volume
What is tidal volume?
amount of air inhaled or exhaled in one breath during quiet breathing
What is inspiratory reserve volume (IRV)?
amount of air in excess of tidal inspiration that can be inhaled with maximum effort
What is expiratory reserve volume?
amount of air in excess of tidal expiration that can be exhaled with maximum effort
What is residual volume?
amount of air remaining in the lungs after maximum expiration
What is vital capacity?
amount of air that can be exhaled with maximum effort after maximum inspiration
How can you calculate vital capacity?
ERV + TV + 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?
maximum amount of air the lungs can contain
How can you calculate total lung capacity?
RV + VC
How can you 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 its diluted in the lungs
What is minute ventilation?
the amount of air inspired into the lungs over one minute
What is the formula for minute ventilation?
Ve = Tidal volume x # of breaths/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?
tidal volume = 500 mL
# of breaths per minute = 12
What is anatomical dead space?
a place where air remained in conducting airwaves but does not perform gas exchange
For a normal adult male, what is the normal value for minute ventilation including anatomical dead space?
4200 mL/min
What is the volume of the anatomical dead space in an adult subject?
about 150 mL
What can we use to approximate anatomical dead space since it is difficult to measure?
a subject’s weight in pounds
When does alveolar dead space happen?
under some pathological conditions
What happens to alveoli in alveolar dead space?
they receive a decreased blood supply or no blood supply at all
What happens to inspired air when the alveoli do not receive enough blood?
it does not take part in gas exchange
What is the sum of alveolar and anatomical dead space called?
physiolocical dead space
What is the difference between minute and alveolar ventilation?
the dead space ventilation that is wasted from the gas exchange point of view
What are the 3 types of alveolar ventilation?
normal ventilation, hyperventilation, hypoventilation
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 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?
PO2 = 40 mmHg
PCO2 = 46 mmHg
What keeps PaCO2 at a constant level?
alveolar ventilation
When does alveolar hyperventilation occur?
when more O2 is supplied and more CO2 is removed than the metabolic rate requires
What happens to the PaO2 and the PaCO2 during alveolar hyperventilation?
PAO2: rises
PACO2: decreases
What does ventilation need to be considered with?
metabolism
Why do people faint during hyperventilation?
because the arteriole CO2 decreases which makes blood vessels constrict
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
What happens to the PaO2 and the PaCO2 during alveolar hypoventilation?
PAO2: decreases
PACO2: rises
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 transferred 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?
20x faster
What is the time required for equilibrium between alveolar air and capillary blood for O2 and CO2?
the same for the two gases
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
