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Phase I Medicine > B2 Physiology of Respiration > Flashcards

B2 Physiology of Respiration Flashcards

1
Q

What is the term for the extent of elastic recoil during respiration (i.e. volume at expiration depending on what it was at inspiration)?

A

Hysteresis

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2
Q

What is hysteresis?

A

The idea that the volume that the lungs decrease by at expiration depends on how much they increased on inspiration

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3
Q

What three factors does lung stiffness depend on?

A
  1. Elasticity of lung tissue
  2. Surface Tension
  3. Role of Surfactant
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4
Q

What are the problems with having high surface tension in the alveoli?

A

a) high stiffness (low compliance)
b) alveolar instability, with small alveoli emptying into large alveoli; can cause atelectasis
c) movement of interstitial fluid into the alveoli (life threatening!)

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5
Q

What is the relationship between surface tension and surfactant?

A

Surfactant reduces alveolar surface tension

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6
Q

What is atelectasis?

A

Alveolar collapse

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7
Q

How is ventilation measured?

A

Litres/ Minute

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8
Q

What is tidal volume?

A

The volume of each breath

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9
Q

What is vital capacity?

A

Volume of maximum expiration following maximum inspiration

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10
Q

What is residual volume?

A

Air remaining in lungs after maximal expiration

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11
Q

What is inspiratory reserve volume?

A

Vital capacity - expiratory reserve volume

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12
Q

What is expiratory reserve volume?

A

Vital capacity - inspiratory reserve volume

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13
Q

True or false? residual volume can be measured by spirometry?

A

False

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14
Q

True or false? functional residual capacity can be measured by spirometry?

A

False

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15
Q

How is residual volume measured?

A

Helium dilution method

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16
Q

What does PEFR stand for?

A

Peak expiratory flow rate

17
Q

How is PEFR measured

A

Mini peak flow meters

18
Q

What is PEFR

A

The maximum flow at the outset of forced expiration

19
Q

Why is PEFR measured in asthma and COPD patients?

A

Forced expiration would be reduced in proportion to the severity of airway obstuction; can monitor effects of drugs

20
Q

How is carbon dioxide carried in the blood?

A

7% dissolved
70% HCO3
23% As carbamino compounds

21
Q

What is the Haldane effect?

A

CO2 reacts more with deoxygenated Hb than oxygenated Hb
Deoxygenated Hb is less acidic so accepts more H+
This means that deoxygenation increases the CO2 carrying power of blood

22
Q

Does the Haldane effect occur in the lungs?

A

No, the reverse reaction occurs

Oxygenation will decrease the CO2 carrying ability of blood, releasing it

23
Q

What effect does expiring CO2 have on pH?

A

Decreases H+ -Increasing pH

24
Q

What effect does inspiring CO2 have on pH?

A

Increases H+- Decreases pH

25
Q

True or false? Ventilation is sensitive to PO2?

A

False. It’s sensitive to PCO2

26
Q

What does hyperventilation cause?

A

Alkalosis

27
Q

What is hyperventilation usually a result of?

A

Acidosis

28
Q

Why does hyperventilation cause alkalosis?

A

Lungs lose excess CO2
HCO3 falls so pH rises
Kidney compensates by retaining H+ and excreting HCO3
pH is closer to normal but you’ve lost CO2 and HCO3

29
Q

What do low partial pressures of oxygen cause?

A

Hypoxic sensitive ventilation

30
Q

Why does hypoventilation cause acidosis?

A

Lungs keep the CO2
HCO3 rises so pH falls
Kidney compensates by keeping HCO3 and getting rid of H+
pH is closer to normal but CO2 and HCO3 are high

31
Q

What is a metabolic cause of alkalosis?

A

Vomiting

32
Q

What are metabolic causes of acidosis?

A

DKA and Renal failure

33
Q

What are the body’s responses to pH changes?

A

Buffering - HCO3 - rapid but limited
Changes in ventilation - rapid but impossible if the cause is respiratory
Kidney compensation - Slow but limited if the problem is kidney failure

34
Q

Are dead space and residual volume the same?

A

No

35
Q

What is dead space?

A

The volume of the lung that isn’t available for gas exchange

36
Q

What is anatomical dead space?

A

The conducting respiratory system that don’t take part in gas exchange anyway (about 150ml)

37
Q

What is physiological dead space?

A

Anatomical, plus the alveoli that will get air but don’t have enough of a blood supply (about 150ml)

38
Q

What type of V/Q ratio will alveoli with an insufficient blood supply have?

A

Increased/ >1

39
Q

What is P50?

A

PO2 at 50% saturation of Hb (Normally about 27mm Hg)

Phase I Medicine (46 decks)

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