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Respiratory > Pulmonary blood flow, gas exchange and perfusion > Flashcards

Pulmonary blood flow, gas exchange and perfusion Flashcards

1
Q

Describe the two types of blood supply to lungs

A

Bronchial circulation (nutritive): via bronchial arteries arising from systemic circulation to supply O2 to airway smooth muscle, nerves and lung tissue

Pulmonary circulation (gas exchange): L and R pul artieries originating from the right ventricle. Carry entire cardiac output. Supplies dense capillaries network around alveoli and return O2 blood to the left atrium via the pulmonary vein.

High flow, low pressure system.

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2
Q

What is the average systolic pressure?

A

25mmHg

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3
Q

What are the alveolar, arterial and venous partial pressures of O2 and CO2?

A

Alveolar: O2 is 100 and CO2 = 40
Artieral: O2 is 100 and CO2 is 40
Venous: O2 is 40 and CO2 is 46

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4
Q

What are the rules for the rate of diffusion in relation to partial pressure gradient and gas solubility?

A

Directly proportional

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5
Q

Which type of cell is alveoli capillaries

found beside?

A

Type 1

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6
Q

Describe effect of emphysema on alveoli and gas exchange

A

Destruction of alveoli wall and elastic fibres reduces surface area for gas exchange

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7
Q

Describe effect of fibrotic lung disease on gas exchange

A

Thickened alveolar membrane slows gas exchange. Loss of lung compliance may decrease the alveolar ventilation.

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8
Q

Describe effect of Pulmonary edema lung disease on gas exchange

A

Fluid in interstitial space increases diffusion distance. Arterial Pco2 may be normal due to higher CO2 solubility in water.

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9
Q

Describe effect of asthma on gas exchange

A

Increased ariway resistance decreases airway ventilation. There is no problem with diffusion, just ventilation

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10
Q

Does blood flow increase or decrease with height across the lung?

Compare it with the ventilation

A

It decreases alongside the ventilation however,

at the base of the lung, blood flow is higher because arterial pressure exceeds alveolar pressure which compresses the alveolar

Therefore, in apex the blood flow is low because artiral pressure is less than alveolar pressure which compresses the arterioles

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11
Q

Is apex or base better efficient at gas exchange?

A

Apex is less efficient

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12
Q

What is a shunt and when does it occur ?

A

Shunt – the blood passes by poorly ventilated area of the lung and opposite of alveolar dead space

Occurs in ventilation perfusion mismatch

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13
Q

What happens to pulmonary vessels in hypoxia?

A

Constriction

Instead, the blood is diverted to the better ventilated alveoli and that vessel dilates

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14
Q

What happens to systemic vessels in hypoxia?

A

Dilation

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15
Q

What is alveolar dead space?

A

Alveoli that are ventilated but not perfused (not enough gas exchange).

Also increase in alveolar PO2 which causes vasodilation

And decrease in alveolar PCO2 which causes mild bronchial constriction

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16
Q

What is anatomical dead space?

A

Air in conducting zone of the respiratory tract unable to participate in gas exchange as walls of airway in region are too thick

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17
Q

Partial pressure gradient for O2 is 10 times greater than Co2 even though rate of diffusion is similar, why?

A

Co2 more soluble than O2

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18
Q

What is the rate of diffusion proportional to?

A

Partial pressure gradient.
Gas solubility
Available surface area

most rapid over short distances.

*remember that its inversely proportional to the thickness of the membrane

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19
Q

What is the rate of diffusion inversely proportional to?

A

Inversely proportional to the thickness of the membrane

20
Q

How many ml of O2 dissolves in plasma?

A

3ml per litre

21
Q

How much does haemoglobin increase red blood cell carrying capacity?

A

200ml/L

22
Q

What does PaO2 refer to? (arterial partial pressure)

A

O2 in solution in the plasma and is determined by the solubility and partial pressure of O2 in the gaseous phase

23
Q

Why doesnt blood travel as gaseous in plasma?

A

Result in air embolism due to bubbles in blood

24
Q

Why is arterial partial pressure not the same as arterial O2 concentration?

A

Must consider the different phases that the gas moves from to liquid.

25
Q

What is the O2 delivery to tissues without and with haemaglobin?

A 
Without = 15ml/min
With = 1000ml/min

O2 demand if resting tissues is 250ml/min

26
Q

What percentage of arterial O2 is extracted by the peripheral tissues at rest?

A

25%

27
Q

How much ml of O2 binds to each gram of haemoglobin?

A

1.32ml

28
Q

Describe the structure of hemoglobin

A

Consists of 4 polypeptide chains ( 1 alpha and 2 beta ) each associated with an iron containing haeme group and haemoglobin cooperatively binds 4 molecules of oxygen, 1 each to haeme group.

29
Q

What is the major determinant of degree to which haemoglobin is saturated with oxygen?

A

Partial pressure of oxygen in arterial blood

30
Q

What is the percentage of the reserve capacity for PO2?

A

75%

31
Q

Describe the oxygen-haemoglobin dissociation curve

A

Sigmoid - very steep intial start

32
Q

Why does myoglobin foetal haemglobin have higher affinity for O2 than HbA?

A

Allows extraction out of mothers blood for the baby.

Myoglobin allows extraction of extra oxygen

33
Q

Define anaemia

A

Any condition where the oxygen carrying capacity of the blood is compromised

eg; iron deficiency

34
Q

What would happen to PaO2 in anaemia

A

It would be normal

35
Q

What is saturation for rbc for those with anaemia?

A

100%

36
Q

What factors are affected in the body by anaemia?

A

Number of rbc and Hb content

37
Q

What is the effect of pH, temp, Pco2 and DPG on saturation of the haemglobin?

A

as everything increases except pH which becomes more acidic, saturation decreases as the affinity decreases for oxygen

38
Q

What does CO bind to?

A

CO binds to haemoglobin to form carboxyhaemoglob which has affinity 250 times greater than O2

39
Q

What can 0.4mmHg of Pco cause?

A

Progressive carboxyhaemoglobin formation

40
Q

What are symptoms of CO?
Is their respiration rate affected?

Treatment?

A

Hypoxia and anaemia, nausea and headaches, cherry red skin and mucous membranes. Respiration rate unaffected due to normal arterial PCO2. Potential brain damage and death.

Treatment involves proviging 10% oxygen to increase PaO2

41
Q

Describe the 5 types of hypoxia?

A

Hypoxaemic hypoxia

42
Q

Hypoxaemic hypoxia

A

Most common, reduction in O2 diffusion at lungs either due to decreased Po2atmos or tissue pathology

43
Q

Anaemic hypoxia

A

Reduction of O2 carrying capacity of blood due to anaemia

44
Q

Stagnant hypoxia

A

HEart disease results in inefficient pumping of blood to lungs

45
Q

Histotoxic hypoxia

A

poisoning prevents cells utilising oxygen delivered to them

eg: CO/cyanide

46
Q

Metabolic hypoxia

A

Oxygen delivery to the tissues does not meet increased oxygen demand by cells

47
Q

What does hyper and hypo ventilation cause?

A

Hypoventilation, causing CO2 retention, leads to increased [H+] bringing about respiratory acidosis.

Hyperventilation, blowing off more CO2, lead to decreased [H+] bringing about respiratory alkalosis

Respiratory (23 decks)

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