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86 Cards in this Set

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Why aren't the lungs completely filled during inspiration and emptied during expiration under normal resting conditions?
It's inefficient
What is residual volume?
The volume that will always be left in the lungs no matter how hard you try to blow it out.
What is the approximate value of RV in most people?
1.1 liters, 20-25% TLC
What is Vital Capacity?
TLC minus RV
What is Tidal volume?
the amt of air you normally take in - about 500 mL
What is FRC - functional residual capacity?
The amt of air left in the lungs at the end of a normal breath; RV + ERV = 40%TLC
2 Reasons why we can't exhale completely:
1. The chest wall can't contract all the way
2. The airway will collapse long before the alveoli will
What is required in order to reach FRC?
Nothing; no muscle activity, just passive expiration.
What is reached when expiratory muscle activity is maximal?
Residual volume
What % of TLC is:
FRC = 40% TLC
RV = 20% TLC
Does the same amount of air that is inspired during normal breathing equal that which reaches the alveoli? Why/why not?
No; because the first air that reaches the lungs during inspiration is the same air that just left the lungs
What do we call that air that first reaches the alveoli during inspiration?
Dead space volume
What is Ve?
(w/ a dot over it)
Air expired - the total amt of air exiting the lungs in one minute
What is Vi?
(w/ a dot over it)
Total amount of air reaching the lungs in one minute
What is Vd?
(w/ a dot over it)
Dead space volume - the volume of airways.
What is VA?
Volume of fresh atmospheric air reaching the alveoli/lungs per minute
What is Va equivalent to?
Ve - Vd
How do you calculate Ve, Vi, or Vd?
That volume x frequency
Are Ve and Vi always equivalent?
No; if you're burning pure glucose they are, but normally they're not exactly equal.
What is the normal ratio of Ve:Vi?
What does a spirometer measure?
The fractional percentage of O2 and CO2 at the mouth during inspiration and expiration.
What happens to the composition of expired air as airflow changes?
Composition changes when breathing flow rate changes.
How does air composition change when you exhale more quickly?
%CO2 increases
%O2 decreases
Define dead space volume:
The air in the conducting airways that did not reach the alveoli during inspiration; first air to reach them next time.
What is the dead space air composition?
Same as that of atmospheric air
When you increase the flowrate of expiration what is the final peak PCo2 and nadir PO2 levels after time? what are normals?
PO2 = 13.5% (vs 15.5% normal)

PCo2 = 6.4% (vs 5.5% normal)
What happens to the air composition during normal breathing (not changeing flowrate)?
It also changes
What is the initial air exhaled?
Dead space air - same in comp as atmospheric air.
What happens to expirate after all the dead space air is cleared out of the lungs?
The gas levels become the same as alveolar levels - higher CO2 and lower O2
How are end tidal PO2 and PCO2 levels useful?
Allow us to estimate alveolar and arterial blood gas levels b/c once gas exchange has occurred PCO2 is identical in these values - BUT NOT PO2!!
How does the PO2 value differ in alveolar vs arterial blood?
Alveolar O2 is 6 mm Hg higher than arterial PO2
Formula for estimating partial pressure of a gas from expirmnt measured fraction:
(%)(Pb-47) = partial press
What is the 47 value?
Water vapor pressure
If the fractional concentration of CO2 at end of exhalation is 0.05 (5%), what is the PCO2? Where?
.05 x (740-47) = 34.7 mm Hg
-This is equiv to both alveolar and arterial PCO2
What is the normal PCo2 value for a healthy young person?
40 mm Hg
If the fractional concentration of O2 at end of exhalation is 0.17 (17%), what is the PO2? Where?
.17 x (740-47) = 117.8 mm Hg
-This is equiv to only alveolar PO2 -> arterial is 6 mm hg lower (111 mm Hg)
What is the normal atmospheric PO2?
150 mm Hg
What is the normal alveolar PO2?
Why do alveolar O2 and CO2 levels differ from atmospheric?
(3 reasons)
1. Dead space
2. FRC
3. Continuous alveolar-cap exchange
Why does dead space make alveolar O2/CO2 levels different from atmospheric?
Because we reinhale some gas with every inspiration that we exhaled on the previous breath.
How does FRC contribute to the alveolar O2/CO2 levels being different from atmospheric?
We never completely empty the lungs with each breath
How does humidity affect the gas percentage that we inhale?
It reduces the O2 level of inhalate
How would Po2 and PCO2 levels differ in end-expirate samples vs a mixture of all expirate?
End-expirate would have less O2 and more CO2
(mixed has more O2 and less CO2)
What type of air was in the bag of expirate from Josh? What was its composition like?
Alveolar air + Deadspace Air
-More O2 than alveolar air
-Less Co2 than alveolar air
How is the difference between mixed expirate vs end-expirate gas levels useful?
Allows calculation of dead space volume
What is the equation for dead space volume?
Tidal Vol x(FACo2 - FECO2)/FACo2
What is FACO2?
Fractional concentration of alveolar CO2
What is FECO2?
Fractional concentration of mixed expired air CO2 (in bag)
What is the normal tidal volume?
500 mL
What is the normal respiratory rate?
10 breaths / min
What is a typical calculation for dead space?
Vd = 500 x (5%-3%)/5% = 200 mL
How do you calculate Dead Space Ventilation?
Vd x RR = 200 x 10 bths/min = 2L per min
What does calculating dead space ventilation allow us to calculate?
Alveolar ventilation
What is the formula for Alveolar ventilation?
Va = Vtotal - Vd
Va = 5L/min - 2L/min = 3L/min
So what percent of inhalation goes to alveoli and dead space?
Dead space gets 40% of TV
Alveoli get 60% of Tidal vol
What is Anatomic dead space?
The volume of the conductive airways themselves - trachea and bronchi.
What is Alveolar dead space?
A component of the underperfused alveoli in a diseased person; gets added to normal anatomic dead space volume.
What is Physiologic dead space?
Anatomic + Alveolar dead space
What type of dead space is calculated via the bohr equation?
Physiologic - anatomic plus alveolar.
What happens to PACO2 if breathing decreases or ceases without a decrease in metabolic rate?
-PACO2 will increase -> called
Alveolar hypoventilation
What is alveolar hypoventilation?
An increased PACO2 without an increased metabolic rate
What happens to PACo2 if alveolar ventilation is increased without an increase in metabolic rate?
PACO2 will decrease -> called alveolar hyperventilation
Define alveolar hyperventilation:
Increase in PAO2 without an increased metabolic rate
What is apnea?
Cessation of breathing
What is hypopnea?
Reduced or slower breathing
What is the Respiratory Quotient?
Formula for R
R = VCO2/VO2

CO2 production/O2 utilization
Formula for calculating PAco2:
Formula for calculating PAo2:
PIO2 - PaCO2/R
What is the respiratory quotient (R) when you're burning pure glucose?
What is the normal resp quotient?
If you take a dog and put him in a warm environment, he starts to pant; is he hyperventilating?
no; even tho breathing freq and his expirate volume (Ve) increase, his PACO2 doesn't increase so NOT hyperventilating.
What is it called when a dog pants?
Tachypnic hyperpnea
What is the measurement that best assesses hypo or hyperventilation?
How is pleural pressure distributed during normal breathing in upright position?
-More negative at top of chest
-Less negative at bottom of chest
Why is the top of the lung more negative when you're upright than the bottom of it?
Because gravity makes the weight of the lung hang down, expanding upper regions, creating more neg pressure at the top of the lung.
What happens to the vertical pressure gradient in the lung if a person lies down horzontally?
It becomes a horizontal pressure gradient
What is the result of inspired air distrubution due to the vertical Ppl gradient?
The top of the lung is relatively more full than the bottom of the lung. (more sucking force up high)
2 factors that cause non-uniform distribution of inspirational air:
1. Vertical Ppl gradient
2. The fact that the compliance curve is nonlinear
When starting from FRC, where will air flow preferentially? Why?
To the bottom of the lung because it is more compliant
When starting from RV where will inspired air flow preferentially? Why?
To the top - because now it's more compliant.
At FRC, how full is the:
-Upper lung
-Lower lung
Upper is almost 70% full
Lower is almost 30% full
When inspiring a tidal breath, where does most of the air go?
To the bottom of the lung
Why does more air go to the lower lung during TV breathing?
Because the upper part of the lung is less compliant, and less air is exchanged during breathing.
How does the decreasing pleural pressure during inhalation distribute over the lungs?
Equally in both upper and lower portions; the Ppl gradient is maintained, but negativity is increased.
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