Gas Exchange And Transport

Question 1

Bronchial circulation

Answer 1

Is systemic but small, brings nutrients to bronchioles

Question 2

Pulmonary circulation

Answer 2

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

Question 3

PACO2

Answer 3

40mmHg

Question 4

PaCO2

Answer 4

40mmHg

Question 5

PAO2

Answer 5

100mmHg

Question 6

PaO2

Answer 6

100mmHg

Question 7

PvCO2

Answer 7

46mmHg

Question 8

PvO2

Answer 8

40mmHg

Question 9

Things that affect rate of diffusion across membrane

Answer 9

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

Question 10

Why does CO2 diffuse faster than O2

Answer 10

It is much more soluble

Question 11

Emphysema

Answer 11

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

Question 12

Fibrotic lung disease

Answer 12

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

Question 13

Pulmonary oedema

Answer 13

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

Question 14

Asthma

Answer 14

Bronchioles are constricted, O2 low in both

Question 15

Ventilation perfusion relationship

Answer 15

Should ideally match each other in L/min

Question 16

Blood flow and ventilation in Base of lungs

Answer 16

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

Question 17

Blood flow and ventilation in apex of lungs

Answer 17

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

Question 18

Where does ventilation match perfusion

Answer 18

Rib 3

Question 19

Ventilation perfusion ratio

Answer 19

Mostly mismatches at apex, 75% works well

Question 20

Autoregulation when ventilation < blood flow

Answer 20

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.

Question 21

Autoregulation when ventilation > blood flow

Answer 21

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

Question 22

Physiologic dead space

Answer 22

Anatomical DS + Alveolar DS

Question 23

How much O2 dissolves per litre plasma

Answer 23

3ml

Question 24

What is the O2 carrying capacity in blood due to Hb

Answer 24

200ml

Question 25

How is CO2 transported in the blood

Answer 25

In solution

Question 26

Why is arterial PO2 different to arterial O2 concentration

Answer 26

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.

Question 27

Oxygen tension

Answer 27

100mgHg in arteries

Question 28

Cardiac output

Answer 28

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

Question 29

How much oxygen binds to each gram of Hb

Answer 29

1.34ml

Question 30

92% of Hb is in

Answer 30

HbA (adult form)

Question 31

HbA2

Answer 31

Lambda chains replace beta chains

Question 32

HbF

Answer 32

Gamma chains replace beta chains (higher affinity for O2)

Question 33

Glycosylated Hb

Answer 33

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

Question 34

What determines Hb saturation

Answer 34

PaO2

Question 35

Time for saturation of Hb to take place

Answer 35

0.25s (total contact time is 0.75s)

Question 36

Until where is Hb 90% saturated

Answer 36

60mmHg

Question 37

Myoglobin

Answer 37

Higher affinity for O2 even than HbF

Question 38

Anaemia

Answer 38

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

Question 39

Factors increasing Hb affinity for O2

Answer 39

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.

Question 40

Factors decreasing Hb affinity for oxygen

Answer 40

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

Question 41

How can alkalosis or acidosis be compensated for

Answer 41

Hypo or hyperventilating

Question 42

CO + Hb

Answer 42

Carboxyhaemoglobin

Question 43

Affinity of Hb for CO

Answer 43

250x more than O2

Question 44

Concentration of CO needed to form carboxyhaemoglobin (in mmHg)

Answer 44

0.4mmHg

Question 45

Symptoms of carbon monoxide poisoning

Answer 45

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

Question 46

5 causes of hypoxia

Answer 46

Hypoxaemic, anaemic, stagnant, histotoxic, metabolic

Question 47

Hypoxaemic hypoxia

Answer 47

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

Question 48

Anaemic hypoxia

Answer 48

Blood can't carry O2

Question 49

Stagnant hypoxia

Answer 49

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

Question 50

Histotoxic hypoxia

Answer 50

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

Question 51

Metabolic hypoxia

Answer 51

Oxygen delivery to tissues doesn't meet an increased demand

Question 52

CO2 transport in blood

Answer 52

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.

Question 53

Hypoventilation on CO2

Answer 53

Retention and acidosis

Question 54

Hyperventilation on CO2

Answer 54

Getting rid of more CO2 and alkalosis