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physiology > Ventilation/Perfusion > Flashcards

Ventilation/Perfusion Flashcards

1
Q

Respiration

A

Entire breathing process which includes both ventilation and oxygenation

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2
Q

Ventilation

A

Exchange of gases in the lungs on a molecular level caused by moving air in and out of the body
O2 in CO2 out

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3
Q

Oxygenation

A

Diffusion of oxygen from the air into the red blood cells where it is then delivered to the tissues

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4
Q

Perfusion

A

Blood flow, to the alveoli and the tissues

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5
Q

What drives ventilation?

A

High CO2

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6
Q

What is CO2

A

Waste product of energy production during the Kreb’s cycle

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7
Q

High levels of CO2 leads to formation of…

A

CO2 and water form carbonic acid, which is a weak acid that dissociates into bicarbonate and H+ ions

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8
Q

Increase of H+ leads to

A

Decrease in pH (More acidic)

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9
Q

Increase in CO2 leads to a/an _________ in pH

A

Decrease, more acidic from formation of H+ ions

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10
Q

Normal rage of pH

A

7.35 - 7.45

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11
Q

Chemoreceptors

A

Monitor the pH of the blood and can then trigger change in ventilation to alter amount of CO2 in the body which in turn can increase or decrease pH

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12
Q

Minute ventilation

A

Respiratory rate x tidal volume
RR x VT = MV
# of breaths x volume of each breath

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13
Q

Result of increase in tidal volume or RR

A

Increase amount of CO2 expelled, so decrease in amount of H+ ions and increase in pH (more basic)

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14
Q

Hypercapnia (hypercarbia)

A

CO2 retention
Elevation in PaCO2 (amount of CO2 in the blood) over 45 mmHg

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15
Q

Hypocapnia

A

A decrease in PaCO2 (CO2 in the blood) below 35 mmHg

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16
Q

Equation to determine acidity from CO2

A
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17
Q

Regulation of pH with respirations time

A

Seconds to minutes
Just breathing more or less to change CO2

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18
Q

Regulation of pH with kidneys time

A

Days to weeks

19
Q

How respirations change the pH equation

A

Change the amount of CO2 by breathing more or less
Left side

20
Q

How kidneys control pH equation

A

Right side of equation
Changing retention or excretion of bicarbonate and H+ into the urine

21
Q

Hypoventilation

A

Less breathing, so retaining CO2, not increased production
Decreases acidity

22
Q

Impact of chronic CO2 elevation

A

Down regulates chemoreceptors which makes it so they don’t respond to the consistent difference pH
Hypercapnia
Hypoxia becomes primary stimulus for ventilation

23
Q

Hypoxemia

A

Decrease amount of O2 in the blood
PaO2 is low (under 75 mmHg)

24
Q

Oxygen saturation

A

How much oxygen is currently bound to hemoglobin
Measured by pulse oximetry

25
Q

Hypoxia

A

When the tissue oxygen level is impaired
(Tissues now have decreased O2 amount)

26
Q

Anoxic

A

No oxygen delivery to a tissue
(Infarction, tissue death)

27
Q

Most common cause of hypoxia

A

Due to low oxygen available in the blood

28
Q

Hypoxemia without hypoxia

A

Means there is a decrease amount of O2 in the blood but not in the tissues
Increased delivery of O2 to compensate for low PaO2
(Increase in CO to maintain perfusion or hypothermia so tissues don’t need as much O2)

29
Q

Hypoxia without hypoxemia

A

O2 is in the blood but there is insufficient oxygen supply at the tissue level
Tissues are unable to use O2 effectively
O2 delivery is impaired (MI)

30
Q

V/Q mismatch used in cases of

A

Hypoxemia
So decrease amount of O2 in the blood

31
Q

V/Q mismatch

A

Ventilation/perfusion mismatch occurs when the ratio of ventilation to perfusion is abnormal in one or more areas of the lung. This can lead to a decrease in oxygen delivery to the tissues and an increase in carbon dioxide retention. Ventilation/perfusion mismatch is diagnosed by measuring the ratio of ventilation to perfusion in different areas of the lung.

32
Q

V/Q mismatch equation

A

1 = V divided by Q

33
Q

V =

A

Alveolar ventilation
Air entering lungs into alveoli

34
Q

Q =

A

Perfusion
Blood flow in capillaries past the alveoli

35
Q

What is V/Q mismatch looking at

A

Hypoxemia can occur when ventilation and perfusion aren’t matched
Seeing which is the cause

36
Q

Hypoxic pulmonary vasoconstriction

A

Try to maintain proper V/Q ratios by sensing areas of hypoxia and poor gas exchange and vasoconstricting flow to these poorly functioning areas
Healthy areas get the blood flow
Max out though when thinking about chronic disease issues

37
Q

5 most common causes of hypoxemia (V/Q mismatch)

A

Asthma
COPD
Pulmonary embolism
Cystic fibrosis
Interstitial lung disease

38
Q

Asthma V/Q mismatch

A

Bronchoconstriction = lower V (.75)
Blood flow is the same = Q of 1
.75 / 1 = .75
Low mismatch

39
Q

Pulmonary embolism V/Q mismatch

A

Blood clot is decreasing blood flow in artery so Q is lower = .5
Ventilation is the same so V= 1
1/.5 = 2
High mismatch

40
Q

Right to left shunt

A

When blood travels from the RV to the LA without ever being oxygenated
Extreme form of low ratio V/Q mismatch

41
Q

Diffusion limitation

A

Difficulty in getting oxygen from the alveolus into the capillary
Often due to scaring/fibrosis of the alveolar - capillary membrane or of reduced surface tension in the alveoli

42
Q

FiO2

A

Fraction of inspired oxygen
Room air is 21%
If less then less O2 for gas exchange leading to hypoxemia

43
Q

Carbon monoxide and Hb

A

Has 250X greater binding affinity for Hb than O2

44
Q

CO + O2 Hb

A

CO is a competitive antagonist
When CO binds it changes Hb shape to make it more difficult to unload oxygen into the tissues

physiology (5 decks)

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