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Semester 3: Respiratory > Session 2 > Flashcards

Session 2 Flashcards

1
Q

What is ventilation?

A

The process of inspiration and expiration

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2
Q

What is the tidal volume?

A

The volume of air which enters and leaves the lungs with each breath

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3
Q

Can the lungs be emptied completely?

A

No. Residual volume will remain

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4
Q

What are the lung capacities defined by?

A

Maximum inspiration
Maximum expiration
End of a quiet expiration

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5
Q

What is the volume of the conducting airways termed as?

A

Anatomical dead space

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6
Q

What is the physiological dead space?

A

Air in alveoli which are not perfused or are damaged do not take part in gas exchange, and ventilation of these alveoli are wasted

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7
Q

What is the equation for the total dead space?

A

Anatomical dead space + Physiological dead space

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8
Q

What is the equation for tidal volume?

A

Anatomical dead space + alveolar ventilation

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9
Q

What is the equation for total pulmonary ventilation?

A

Tidal volume X respiratory rate

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10
Q

What is the equation for the alveolar ventilation?

A

(Tidal volume - Dead space) X Respiratory rate

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11
Q

What is the inward force acting on the lung at rest?

A

The lung’s elasticity and surface tension generate an inwardly directed force that favours small lung volumes

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12
Q

What is the outward force acting on the lung at rest?

A

The muscles and various connective tissues associated with the rib cage also have elasticity. At rest these elastic elements favour outward movement of the chest wall.

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13
Q

What is the result of the inward and out ward force activist on the lung at rest?

A

They balance each other and create a negative pressure within the intrapleural space relative to atmospheric pressure

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14
Q

How does inspiration occur?

A
  • Contraction of the diaphragm and the external intercostal muscles expands the thoracic cavity outward from equilibrium position
  • Pleural seal ensure that the lungs expand along with the thorax.
  • Lung volume increase so air pressure within the lungs fall below atmospheric pressure. Air flows into the lungs
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15
Q

What happens in (quiet) expiration?

A
  • Muscle contraction ceases
  • Elastic recoil of the lung results in the thoracic cavity and lung returning to the original position
  • Passive process
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16
Q

What ensures that the chest wall and lung move together?

A

Surface tension as a result of the fluid lining the pleural space which holds the outer surface of the lungs to the inner surface of the chest wall. This ensure that the chest wall and lungs move together.

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17
Q

What happens to the intrapleural pressure during inspiration?

A

The intrapleural pressure becomes more negative and returns to resting pressure at the end of quiet expiration

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18
Q

What are the muscle of quiet inspiration?

A
  • Diaphragm

- External Intercostal muscles

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19
Q

What muscles are involved in quiet expiration?

A

None!

Due to elastic recoil

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20
Q

Which muscles are involved in forced inspiration?

A

Accessory muscles of inspiration.

  • Sternocleidomastoid
  • Scalene
  • Serratus anterior
  • Pectoralis major
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21
Q

What muscles are used in forced expiration?

A
  • lnternal intercostal muscles

- Abdominal wall muscles

22
Q

What is the stretchiness of the lung known as?

A

Compliance

23
Q

What is compliance defined as?

A

Volume change per unit pressure change

24
Q

What contributes to the elastic properties of the lung?

A
  • Elastic tissue in the lungs

- Surface tension forces of fluid lining the alveoli

25
Q

What is contained in the alveolar lining fluid?

A

Surfactant

26
Q

What is the purpose of surfactant?

A
  • Reduce surface tension thereby increasing lung compliance
  • Stabilise the lungs by preventing small alveoli collapsing into big ones
  • Prevents the surface tension in alveoli creating a suction force tending to cause transudation fluid from pulmonary
27
Q

How does surfactant increase surface tension as the alveolus expands?

A

Surfactant molecules spread further apart making them less efficient

28
Q

How does surfactant decrease the surface tension as the area of the alveolus decreases?

A

Surfactant molecules comes closer together increasing their concentration and act more efficiently thereby reducing the surface tension

29
Q

What is the effect of the increase in concentration of surfactant in the smaller alveoli?

A

The force required to expand smaller alveoli is therefore less than that required to expand the large one

30
Q

What would happen between the different sized alveoli if the surface tension was constant?

A

-Smaller alveoli would have a higher pressure within it.
-Therefore if two unequaled size alveoli were connected by an airway the smaller alveolus would empty into the larger alveolus due to having a higher pressure
Law of Laplace

31
Q

What would happens to the surface area for gas exchange if the surface tension was a constant in the variable alveolus sizes?

A
  • The smaller alveoli would collapse into larger alveoli to from huge air filled spaces
  • Combined surface area of a few large bubbles would be much less than combined surface area of thousands of small alveoli
  • Surface area for gas exchange would decrease
32
Q

What is the effect of surafactant on the alveoli as the size increases?

A

As the alveolus expands the surface tension and the radius increase as well.

33
Q

What is the effect of surfactant on the alveolus as the size decreases?

A

As the alveolus shrinks

  • Radius decreases
  • Surface tension reduces
34
Q

What is the overall effect of surfactant?

A

Different sized alveoli can have the same pressure within them. This stabilises the lungs preventing small alveoli collapsing into big ones.

35
Q

What is respiratory distress syndrome of the newborn?

A
  • Condition usually seen in premature babies particularly those less than 30 weeks old due to lack of surfactant.
  • Without surfactant, surface tension of alveolar sacs is high so increases tendency of the alveoli to collapse.
36
Q

What are the sign of RDS in the babies?

A
  • Cyanosis
  • Grunting
  • Intercostal and subcostal recessions
37
Q

What is the treatment for RDS?

A
  • Surfactant replacement via endotracheal tube

- Supportive treatment with oxygen and assisted ventillation

38
Q

What is the question for the minute ventilation?

A

Tidal volume X Breaths per minute

39
Q

How do you calculate the tidal volume entering the gas exchange region of the lung?

A

Resting tidal volume - Amount in anatomical deadspace

40
Q

What is alveolar ventilation?

A

Respiratory frequency X volume available for gas exchange

41
Q

Where in the bronchial tree is the main site of airways resistance?

A

The upper respiratory tract
-Although resistance increases sharply with lower radius the combined cross sectional area of the bronchioles is a lot bigger than the cross sectional area of the trachea.

42
Q

What are different mechanism for increased airways resistance?

A
  • Increased mucus
  • Hypertrophy of the smooth muscle, and/or oedema
  • Loss of radial traction
43
Q

What is the equation for resistance?

A

Pressure/Flow=Resistance

Resistance is also directly proportional to 1/r^4
Small change in r makes a big difference in resistance

44
Q

What are the different mechanisms of increased airways resistance associated with?

A

Increased mucus - Chronic Bronchitis
Hypertrophy of the smooth muscle - Asthma
Loss of radial traction - Emphysema

45
Q

Why do lungs collapse when air enter the pleural cavity?

A

Lack of negative pressure in the pleural cavity so the lungs aren’t held against the thoracic wall so they collapse

46
Q

How can damage to the intercostal vessels and nerves be avoided during procedure requiring insertion into the pleural space?

A

The costal groove runs underneath each rib so inserting into the lower border of the intercostal space

47
Q

Explain why lack of surfactant causes difficulty breathing?

A
  • Increased surface tension so alveolar walls held closer together
  • Smaller alveoli are not able to expand as well due to increased pressure
  • Bigger alveoli will expand
  • Higher volume in the thorax is need to lower the pressure in the alveoli
48
Q

Why is there indrawing of intercostal spaces during respiration?

A
  • Active contraction of external intercostal muscle in order to pull the thoracic wall upwards which will increase volume.
  • Pressure decreases as result
  • Indrawing is the presence of the active contraction
49
Q

How does fibrosis affect compliance?

A

Reduced compliance

50
Q

How does emphysema affect compliance of the lungs?

A

Increased compliance

Semester 3: Respiratory (4 decks)

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