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):
0

Why is PO2 in lung lower than PO2 in air?

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

1

increased CO2 --> PO2 in lung?

decreases, because CO2 also occupies space

2

What is normal net PO2 in the alveolus?

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

3

normal venous blood returns with a PCO2 of

45 mmHg

4

Normal net PCO2 in alveolus after equilibrating with arterial blood

40mmHg

5

hyperventilation --> PCO2 and PO2?

decrease PCO2, increase PO2

6

hypoventilation --> PCO2 and PO2?

PCO2 increases, PO2 decreases

7

hyperventilation --> alveolar ventilation

increases

8

hypoventilation --> alveolar ventilation

decreases

9

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

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

10

What does blood pressure actually measure?

SYSTEMIC arterial pressure from L heart

11

PO2 in venous blood compared to alveolus

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

12

Fick's Law of Diffusion

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

VO2

rate at which O2 diffuses

14

VCO2

rate at which CO2 diffuses

15

Layers separating alveolus and the blood (5)

alveolar epithelium
basement membrane
interstitial space
capillary basement membrane
capillary epithelium

16

Diffusing capacity (DL)

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

17

Which gas is commonly used to measure DL?

CO

18

What will decrease DLCO?

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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