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Respiratory System > Gas Exchange And Transport > Flashcards

Gas Exchange And Transport Flashcards

1
Q

Bronchial circulation

A

Is systemic but small, brings nutrients to bronchioles

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2
Q

Pulmonary circulation

A

High flow, low pressure (25mmHg, normal is 120)

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3
Q

PACO2

A

40mmHg

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4
Q

PaCO2

A

40mmHg

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5
Q

PAO2

A

100mmHg

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6
Q

PaO2

A

100mmHg

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7
Q

PvCO2

A

46mmHg

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8
Q

PvO2

A

40mmHg

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9
Q

Things that affect rate of diffusion across membrane

A

Partial pressure gradient, gas solubility, available surface area, thickness of membrane

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10
Q

Why does CO2 diffuse faster than O2

A

It is much more soluble

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11
Q

Emphysema

A

Destruction of alveoli decreases surface area for gas exchange, PAO2 decreases

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12
Q

Fibrotic lung disease

A

Thickened alveolar membrane slows gas exchange, PAO2 decreases. Shows on xray

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13
Q

Pulmonary oedema

A

Fluid in interstitial space increases diffusion distance, PACO2 may still be normal as CO2 is very water soluble

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14
Q

Asthma

A

Bronchioles are constricted, O2 low in both

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15
Q

Ventilation perfusion relationship

A

Should ideally match each other in L/min

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16
Q

Blood flow and ventilation in Base of lungs

A

Blood flow > ventilation as arterial pressure>alveolar pressure, alveoli are compressed

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17
Q

Blood flow and ventilation in apex of lungs

A

Blood flow < ventilation as arterial pressure < alveolar pressure so arterioles are compressed.

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18
Q

Where does ventilation match perfusion

A

Rib 3

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19
Q

Ventilation perfusion ratio

A

Mostly mismatches at apex, 75% works well

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20
Q

Autoregulation when ventilation < blood flow

A

Creates a shunt which dilutes oxygenated blood. Decreased PO2 around these alveoli constricts their arterioles and blood is diverted. This response only happens in pulmonary vessels. Increased PO2 also causes mild bronchodilation.

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21
Q

Autoregulation when ventilation > blood flow

A

Alveolar dead space is created. Increased PO2 causes pulmonary vasodilation and decreased PCO2 causes mild bronchial constriction.

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22
Q

Physiologic dead space

A

Anatomical DS + Alveolar DS

23
Q

How much O2 dissolves per litre plasma

A

3ml

24
Q

What is the O2 carrying capacity in blood due to Hb

A

200ml

25
Q

How is CO2 transported in the blood

A

In solution

26
Q

Why is arterial PO2 different to arterial O2 concentration

A

PaO2 is just the dissolved oxygen not what is carried by Hb. It is determined by O2 solubility and the partial pressure of O2 in the gaseous phase driving it into solution.

27
Q

Oxygen tension

A

100mgHg in arteries

28
Q

Cardiac output

A

5L/min (1000ml/min of O2)

29
Q

How much oxygen binds to each gram of Hb

A

1.34ml

30
Q

92% of Hb is in

A

HbA (adult form)

31
Q

HbA2

A

Lambda chains replace beta chains

32
Q

HbF

A

Gamma chains replace beta chains (higher affinity for O2)

33
Q

Glycosylated Hb

A

Caused by high blood sugar especially in diabetes can be used as a marker for uncontrolled diabetes

34
Q

What determines Hb saturation

A

PaO2

35
Q

Time for saturation of Hb to take place

A

0.25s (total contact time is 0.75s)

36
Q

Until where is Hb 90% saturated

A

60mmHg

37
Q

Myoglobin

A

Higher affinity for O2 even than HbF

38
Q

Anaemia

A

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

39
Q

Factors increasing Hb affinity for O2

A

Increase in pH, decrease in PCO2, decrease in temperature, decrease in DPHG (produces when RBC working hard eg high altitude or heart/lung diseases). They will be less likely to let go of oxygen.

40
Q

Factors decreasing Hb affinity for oxygen

A

Decreasing pH, increasing PCO2, increasing temperature, increasing DPG. Oxygen more likely to get to tissues

41
Q

How can alkalosis or acidosis be compensated for

A

Hypo or hyperventilating

42
Q

CO + Hb

A

Carboxyhaemoglobin

43
Q

Affinity of Hb for CO

A

250x more than O2

44
Q

Concentration of CO needed to form carboxyhaemoglobin (in mmHg)

A

0.4mmHg

45
Q

Symptoms of carbon monoxide poisoning

A

Hypoxia and anaemia, nausea and headaches, cherry red skin. Normal resp rate as PCO2 is normal. Can cause potential brain damage and death.

46
Q

5 causes of hypoxia

A

Hypoxaemic, anaemic, stagnant, histotoxic, metabolic

47
Q

Hypoxaemic hypoxia

A

Most common, less O2 diffusion at lungs due to low atmospheric O2 or tissue pathology

48
Q

Anaemic hypoxia

A

Blood can’t carry O2

49
Q

Stagnant hypoxia

A

Inefficient pumping of blood to lungs and body due to heart disease

50
Q

Histotoxic hypoxia

A

Cells are poisoned by CO or cyanide etc and can’t use oxygen

51
Q

Metabolic hypoxia

A

Oxygen delivery to tissues doesn’t meet an increased demand

52
Q

CO2 transport in blood

A

7% dissolved in plasma and erythrocytes, 23% combines with deoxyheamoglobin to form carbamino compounds, 70% forms carbonic acid in erythrocytes to yield hco3 and H ions which chlorine shift into blood mostly.

53
Q

Hypoventilation on CO2

A

Retention and acidosis

54
Q

Hyperventilation on CO2

A

Getting rid of more CO2 and alkalosis

Respiratory System (25 decks)

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