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I've got hypertension > Lecture 16 > Flashcards

Lecture 16 Flashcards

1
Q

How does breathing pattern affect alveolar ventilation?

A
  • fast and shallow breathing: the tidal volume decreases but the frequency increases so the total ventilation remains the same
    alveolar ventilation decreases
  • slow and deep breathing: the frequency is a low slower but the volume is more so the total ventilation remains the same
    alveolar ventilation increases
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2
Q

What is the effect of fast shallow breathing on alveolar ventilation?

A

There is a decrease in alveolar ventilation which causes hypoxia (decreased partial pressure of alveolar O2) and hypercapnia (increased partial pressure of alveolar CO2) and acidity.
From a gas exchange point of view, there is a decrease in the transfer of O2 from the alveoli into the capillaries and the CO2 is not being removed and so it wastes ventilation in the dead space. It is energetically costly for the respiratory muscles.

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3
Q

What is the effect of slow deep breathing on alveolar ventilation?

A

There is an increase in alveolar ventilation. This causes hyperoxia (increased partial pressure of O2 in the alveoli) and hypocapnia (decreased partial pressure of CO2 in the alveoli) and alkalinity. There is an increase on gas exchange but it is energetically costly for the respiratory muscles and so they are working harder to get air in.

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4
Q 
The respiratory quotient (RQ) is:
A.
V̇ O2/V̇ CO2
 B. a measure of cell metabolism.
C.
V̇ CO2/
̇VO2
D. A and B are both correct.
E. B and C are both correct.
A

E

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5
Q

We need to exchange _____ and ______ between alveolar air and ______ in lung ________ by ______

A 
O2 
CO2
blood
capillaries
diffusion
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6
Q

We need to exchange ________ and _______ between _________ in tissue _______ and cells in the __________ by _________

A 
O2
CO2
blood
capillaries
tissues
diffusion
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7
Q

Gases move across the alveolar capillary membrane by ____________

A

diffusion

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8
Q

What are three different names for the barrier between the lungs and the blood?

A
  • air-blood barrier
  • blood-gas barrier
  • alveocapillary membrane
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9
Q

What three things make up the air blood barrier?

A
  1. alveolar epithelial cells (type 1)
  2. basement membrane
  3. endothelial cell
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10
Q

Which direction does O2 flow through the air-blood barrier?

A

from the type 1 epithelial cells, through the basement membrane and through the endothelial cell into the blood

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11
Q

What direction doesCO2 flow through the air-blood barrier?

A

From the blood endothelial layer, through the basement membrane then through the alveolar type 1 cell into the lungs

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12
Q

What does Fick’s Law of diffusion describe?

A

the gas exchange through the membranes

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13
Q

What is Fick’s Law of diffusion?

What do each of the components mean?

A 
F = A/T D (P1-P2)
F = flux (ie. amount flowing)
A = surface area of the alveoli
T = thickness of the membrane
D = diffusion constant ie. how easy it is to move stuff across the membrane
P1-P2 = pressure difference
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14
Q

What does the diffusion constant depend on?

A

the solubility of the gas, and the molecular weight (as described by Graham’s Law)

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15
Q

Which diffuses faster, CO2 or O2? Why is this?

A

CO2 diffuses about 20x faster than O2 due to CO2 having a higher solubility

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16
Q

What can we do to increase the area of the alveoli?

A

we can breathe in which increases the ventilation which increases the area

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17
Q

What is a disease that results in a decrease in the area of the alveoli?
Explain this

A

This is a disease characterised by dilation of the alveolar spaces and destruction of the alveolar walls. There is a decrease in the surface area of the lung. This means that patients have less air flow through the alveoli and therefore there is decreased PO2 in blood

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18
Q

What is the thickness of the air-blood barrier?

A

0.3μm

19
Q

What is a condition that affects the thickness of the membranes?
Explain this

A

Pulmonary fibrosis this involves the thickening and scarring of the alveolar membrane.
Deposit of fibrotic tissue between alveolar and endothelial cells leads to thickening and scarring of the alveolar membranes.
This means there is an increase in the thickness in the alveoli and so patients have less air flow through the alveoli and therefore there is decreased PO2 in blood

20
Q

What is pulmonary oedema and how does it affect diffusion capacity?

A

This is water accumulation in the alveoli. This increases the diffusion distance and so there is reduced diffusion capacity

21
Q

What is the main factor affecting diffusion capacity/flow?

A

the pressure difference

22
Q

What are the pressure differences that drive diffusion?

A
  • Partial pressure of O2 in the alveoli vs partial pressure of O2 in the blood
  • partial pressure of CO2 in the alveoli vs partial pressure of CO2 in the blood
23
Q

If there is more O2 in the alveoli than in the blood, which way does O2 move?

A

there is movement of O2 from the alveoli into the capillaries

24
Q

What is the approximate partial pressure of oxygen in the alveoli?

A

100mHg (it is reduced reduced from PB (159 mmHg) by water vapour in alveoli)

25
Q

What three things does PAO2 depend on?

A
  1. PIO2 (partial pressure of oxygen in the inspired air)
  2. alveolar ventilation ie. how much O2 you are bringing into the alveoli
  3. oxygen consumption
26
Q

The atmospheric PO2 is usually constant so it is the balance between oxygen ________ and alveolar _________ that is the most important

A

consumption

ventilation

27
Q

What is the approximate partial pressure of CO2 in the alveoli?

A

it is kept constant at 40mmHg

28
Q

What three things does PACO2 depend on?

A
  1. alveolar ventilation ie. how much CO2 we are breathing out
  2. carbon dioxide production
  3. PICO2 of inspired air
29
Q

Alveolar PACO2 is usually determines only by the balance between _________ production and ________ ventilation, because __________ _________ is negligible

A

CO2
alveolar
atmospheric PCO2

30
Q

Where do we measure partial pressures in arterial blood, PaO2 and PaCO2?

A

we measure these from arterial blood sample

31
Q

What is the usual value for PaO2?

A

100 mmHg

32
Q

What is the usual value for PaCO2?

A

40mmHg

33
Q

The movement of oxygen by diffusion between the alveoli and the pulmonary capillary blood is:
A. inversely related to the area of the alveolar membrane. B. inversely related to the diffusion constant
C. directly related to the thickness of the alveolar membrane.
D. proportional to the partial pressure gradient between air-blood barrier.

A

D. proportional to the partial pressure gradient between air-blood barrier.

34
Q

Describe the movement of O2 from the alveolus into the capillary

A

The partial O2 pressure in the alveolus is greater than that in the capillary so O2 flows in until the pressures are the same (and they are the same as the original PAO2)

35
Q

Describe the movement of of CO2 from the capillary into the alveolus

A

The partial CO2 pressure in the capillary is greater than that in the alveolus so CO2 flows in until the pressures are the same (and they are the same as the original PACO2)

36
Q

How is diffusion changed during exercise and how does this relate to Fick’s Law?

A

When you exercise, there is more O2 burned in the muscle. There is increase tidal volume and increased alveolar ventilation (rate) and so the alveolar surface increases. The lung diffusion capacity for O2 also increases.
Because of the increase in alveolar ventilation (rate), there is an increase in the partial pressure of alveolar O2. Because of the increased oxygen ventilation, there is a decrease in the partial pressure of arterial O2. This means that there is an increase in P1-P2
All these things mean that there is more gas exchanged. More capillaries are perfused and so there is increased capillary surface area and reduced diffusion distance for capillaries so O2 gets into the blood faster

37
Q

What is the ratio of ventilation to perfusion? What are the normal values? What is the effect of a change in this ratio?

A

This is the ratio of how much air you are bringing in and how much blood is being brought close to the alveoli.
In a healthy lung, alveolar ventilation = 4L/min and pulmonary blood flow = 5L/min so the normal V/Q (both with dots as they are rates) = 0.8
Any change in the ratio impairs O2 and CO2 transfer

38
Q

What are three examples of

Ventilation and perfusion mismatch?

A
  • anatomical shunt
  • physiological shunt
  • low ventilation/perfusion
39
Q

Describe an anatomical shunt and explain how it causes a mismatch of V and Q

A

This is when there is an additional pulmonary artery which may not take part in picking up O2. It bypasses the alveoli and goes to the pulmonary veins. When they reach the veins, no balance is reached ie. there is less O2 and more CO2

40
Q

Describe a physiological shunt and explain how it causes a mismatch of V and Q

A

This is when there is an alveoli which is blocked so the O2 in that alveoli is less than the other one. The veins leaving the alveoli are not balanced so there is decreased ventilation

41
Q

Describe low ventilation and explain how it causes a mismatch of V and Q

A

Ventilation decreases reducing PO2 in alveoli and so the ratio is altered

42
Q

What are three lung diseases that leas to impaired ventilation?

A
  • atelectasis (fibrosis)
  • emphysema
  • pulmonary oedema (fluid)
43
Q

What are three vascular diseases cause impaired perfusion?

A
  • pulmonary hypertension
  • heart failure
  • COPD

I've got hypertension (47 decks)

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