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Cardiorespiratory Science > Control of Tidal Volume and Frequency > Flashcards

Control of Tidal Volume and Frequency Flashcards

1
Q

What is the primary role for the cardiorespiratory system?

A

Support metabolism and promote homeostasis.

This support centres on tissue O2 delivery and CO2 removal which relies on gas exchange in the lungs.

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2
Q

What is dead space?

A

area or volume where gas exchange does not occur.

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3
Q

Where does gas exchange in the respiratory system work?

A

Gas exchange only works in the alveoli.

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4
Q

What are conducting zones?

A

Air is conducted through to the gas exchange regions.

(no alveoli) generations 0-16

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5
Q

What is the transitional and respiratory zone?

A

Gas exchange occurs in these regions. Throughout the transitional and into the respiratory zones, there is an increasing number of alveoli present.

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6
Q

What is anatomic dead space?

A

Areas where there is no alveoli (conducting zones) and therefore no gas exchange takes place.
Average volume about 150ml

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7
Q

What factors affect dead space volume?

A

Body size
Age
Head position
Drugs

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8
Q

What is the alveolar dead space?

A

0ml since gas exchange takes place as long as ventilation and perfusion takes place.
(temporary dead space may exist in disease states)

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9
Q

What is physiological dead space?

A

Anatomical and alveolar dead space added together.

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10
Q

What are methods for measuring physiological and anatomical dead space?

A

Physiological - Bohrs method

Anatomical - Fowler’s method

If these are not the same then it tells se that there is some alveolar dead space.

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11
Q

How does branching affect cross-sectional area?

A

Branching increases the cross-sectional area and thus surface area.

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12
Q

What affects velocity of gas in the respiratory system?

A

Diameter of the tubes down throughout the respiratory system. Smaller tubes decreases velocity

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13
Q

How do you calculate the total flow in the respiratory system?

A

Flow = Velocity x Area

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14
Q

What is the effect on velocity when increasing the cross-sectional area?

A

This causes the velocity to decrease and vice versa.

By generation 17 velocity is down to the speed of diffusion (has been decreased massively)

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15
Q

What is generation 17 in the respiratory system?

A

A transition point
Above generation 17 (0-16 which are found above), gas velocity is faster than diffusion and therefore there are no alveoli since the exchange mechanism in alveoli is diffusion. Therefore this means that it would be wasted to have alveoli in these areas. Once the velocity is slower, the alveoli can then function and exchange gas via diffusion.

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16
Q

How does cross-sectional area and velocity in the airways relate to the cardiovascular system?

A

Functions in the same way and therefore when a blood vessel branches increasing the cross sectional area, the velocity decreases.

17
Q

What is the average minute ventilation and how is it calculated?

A

Tidal volume - 500ml
Respiratory frequency - 12 breaths per min
Minute ventilation = 500 x 12 = 6000ml/min

18
Q

How is tidal volume calculated?

A

VD(wasted) + VA (useful)

D - dead space
A - alveolar volume

Only the useful ventilation (gas exchange) can support metabolism

19
Q

How is homeostasis achieved when related to alveolar ventilation?

A

Alveolar ventilation must be matched to metabolism to achieve homeostasis. As a result of homeostasis, this keeps the alveolar gas composition constant.

20
Q

What is the partial pressure of gas in the lungs dependent on?

A

The ventilation
Cardiovascular system
metabolism

21
Q

For oxygen and carbon dioxide, explain the effect of ventilation and metabolism on the concentrations in the body.

A

Oxygen:
Ventilation - Adds O2
Metabolism - Removes O2

Carbon Dioxide:
Ventilation - Removes CO2
Metabolism - adds CO2

22
Q

What is the relationship between alveolar partial pressure of Oxygen and carbon dioxide?

A

PaO2 and PaCO2 are inversely related.

23
Q

What is a hyperventilation

A

when there is more ventilation than required for the metabolism, and the CO2 levels fall this is hyperventilation

24
Q

What is a Hypoventilation?

A

When there is a ventilation that is too small for the metabolism, and the CO2 levels rise, this is hypoventilation.

25
Q

What is a hyperaemia?

A

Increase in ventilation at an appropriate level to a change in metabolism.

26
Q

What is end tidal CO2?

A

The alveolar CO2 pressure which should be around 5kPa

27
Q

Why do we measure ETCO2?

A

By measuring the composition of the air when you breath in and breath out. The CO2 concentration should be almost 0 during inspiration and similarly these levels would be the same during the first few ms of exhilation. This is because some of the gas has come from the dead space where no gas exchange has taken place and thus the composition is the same. The concentrations will then increase as the alveolar gas starts to be exhaled.

28
Q

What is the consequence for arterial blood gases if alveolar gas compositions were not constant?

A

Can lead to hyper/hypoventilation if the oxygen levels fluctuate and thus the carbon dioxide levels will do the opposite. What is seen in the alveolar will be reflected in the blood since the alveolar pressures set the blood pressures.
Eg. if short breaths were taken, then O2 is reduced and hence the effect on metabolism would mean that CO2 increases to the point where it may lead to hypoventilation.

29
Q

What is tidal volume?

A

VT which is the volume expired in each breath

500ml

30
Q

What is the respiratory frequency?

A

fR which is the Number of breaths per minute

12 breaths/min

31
Q

What is minute ventilation?

A

VE which is the volume of air expired per minute

6000ml/min

32
Q

How do you calculate the total volume of air breathed per minute is not available for gas exchange?

A

V’D = VD x fR

eg. 1800 ml/min = 150ml x 12 breaths/min

33
Q

How do you calculate the total volume of air breathed that is useful for gas exchange?

A

V’A = Va x fR

eg. 4200ml/min = 350 ml x 12

34
Q

What are the average alveolar partial pressures for CO2 and O2 (PA CO2 / PA O2)

A

PA CO2 = 5kPa

PA O2 = 13 kPa

35
Q

What is the average alveolar ventilation rate?

A

4.2L/min

36
Q

What is hyperpnea?

A

Deep and rapid respiration occurring normally after exercise or abnormally due to fever or various disorders.

Cardiorespiratory Science (15 decks)

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