Respiration Lecture 07: Movement of Gas from Alveoli to Blood Flashcards Preview

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Flashcards in Respiration Lecture 07: Movement of Gas from Alveoli to Blood Deck (19)
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0
Q

increased CO2 –> PO2 in lung?

A

decreases, because CO2 also occupies space

1
Q

Why is PO2 in lung lower than PO2 in air?

A

air in lung is saturated with water vapor, which occupies some of the total gas volume. PO2 in lung = FO2 * (Pb - 47). PO2 in air = FO2 * Pb

2
Q

What is normal net PO2 in the alveolus?

A

100 mmHg (after equilibrating with PO2 in alveolus and PO2 in arterial blood)

3
Q

normal venous blood returns with a PCO2 of

A

45 mmHg

4
Q

Normal net PCO2 in alveolus after equilibrating with arterial blood

A

40mmHg

5
Q

hyperventilation –> PCO2 and PO2?

A

decrease PCO2, increase PO2

6
Q

hypoventilation –> PCO2 and PO2?

A

PCO2 increases, PO2 decreases

7
Q

hyperventilation –> alveolar ventilation

A

increases

8
Q

hypoventilation –> alveolar ventilation

A

decreases

9
Q

Why do CO2 and O2 diffuse at similar rates even though O2 has a larger gradient than CO2?

A

O2 is less soluble than CO2 so it needs a greater gradient to achieve the same rate of diffusion

10
Q

What does blood pressure actually measure?

A

SYSTEMIC arterial pressure from L heart

11
Q

PO2 in venous blood compared to alveolus

A

PO2 in venous blood = 40mmHg. PO2 in alveolus = 100mmHg (net driving force for O2 to enter venous blood and leave alveolus)

12
Q

Fick’s Law of Diffusion

A

The rate at which a molecule crosses a membrane is determined by the properties of the molecule and the membrane. J = DAa[change in P/X] where J= rate of molecular movement (flux), D= diffusion constant, A= area of membrane, a= solubility, and X = membrane thickness. Aka the consumption rate of O2, VO2, and release rate of CO2 and VCO2

13
Q

VO2

A

rate at which O2 diffuses

14
Q

VCO2

A

rate at which CO2 diffuses

15
Q

Layers separating alveolus and the blood (5)

A
alveolar epithelium
basement membrane
interstitial space
capillary basement membrane
capillary epithelium
16
Q

Diffusing capacity (DL)

A

DL= Vgas/change in Pgas = (DAa)/X = J/PA

17
Q

Which gas is commonly used to measure DL?

A

CO

18
Q

What will decrease DLCO?

A

Any condition that affects the effective alveolar surface area and/or thickness. Ex:

1) Hindrance to the alveolar wall (fibrosis, alveolitis, vasculitis)
2) decrease in total lung area
3) uneven spread of air in lungs (i.e. emphysema)
4) pulmonary embolism
5) cardiac insufficiency
6) pulmonary hypertension
7) anemia due to decrease in blood volume
8) pulmonary edema

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