Respiratory Physiology

Question 1

what supplies bronchial circulation?

Answer 1

the bronchial arteries arising from the systematic circulation

Question 2

what does the pulmonary circulation consist of?

Answer 2

the left and right pulmonary arteries originating from the right ventricle which carries the entire cardiac output supplying a dense capillary network which surrounds the alveoli. oxygenated blood then returns to the left atrium via the pulmonary vein. high flow low pressure system.

Question 3

what is systolic pressure?

Answer 3

the maximum arterial pressure

Question 4

what is the…
> PAO2
> PACO2

Answer 4

> 100mmHg

>40mmHg

Question 5

what is the…
> PaO2
> PaCO2

Answer 5

> 100mmHg

> 40mmHg

Question 6

what is the…
> PvO2
> PvCO2

Answer 6

> 40mmHg

> 46mmHg

Question 7

what factors affect the diffusion of the rate of diffusion across a membrane?

Answer 7

> directly proportional to partial pressure gradient
directly proportional to gas solubility
directly proportional to surface area
inversely proportional to thickness of the membrane
diffusion distance

Question 8

how does emphysema reduce diffusion of gas between the blood and alveoli?

Answer 8

it destructs the alveoli reducing the surface area impairing ventilation

Question 9

how does fibrotic lung disease reduce gas exchange?

Answer 9

the fibrous tissue pushes the capillaries and type 1 cells apart increasing the diffusion distance

Question 10

how does a pulmonary oedema reduce gas exchange?

Answer 10

fluid build up between the alveoli and capillary increasing diffusion distance

Question 11

how does asthma reduce gas exchange?

Answer 11

increased airway resistance decreases ventilation so the is a low PO2

Question 12

Is blood flow higher at the base of the lung or the apex?

Answer 12

the base as arterial pressure exceeds alveolar pressure therefore vascular resistance is low. at the apex of the lung blood flow is low as arterial pressure is less than alveolar pressure.

Question 13

what happens if ventilation is lower than perfusion (or blood Flow)?

Answer 13

blood is effectively shunted from the right side of the heart to the left without being properly oxygenated. there is dilation of oxygenated blood from better ventilated areas.

Question 14

what is the local control mechanism to keep ventilation and perfusion matched?

Answer 14

the increase in PACO2 causes mild bronchial dilation.
hypoxia in tissue around under ventilated alveoli causes constriction of the pulmonary blood vessels (while systematic vessels dilate) diverting the blood to better ventilated areas.

Question 15

when does alveolar dead space occur?

Answer 15

if ventilation > blood flow as the alveoli are ventilated but not perfused, this is the opposite to shunt.

Question 16

what is anatomical dead space?

Answer 16

this is the air in the conduction zone of the respiratory tract that is unable to participate in gas exchange

Question 17

what does haemoglobin increase the red blood cells carrying capacity to?

Answer 17

200ml/L

Question 18

how is the arterial partial pressure of O2 determined?

Answer 18

O2 solubility and the partial pressure of oxygen in gaseous phase driving O2 into solution

Question 19

describe the different types of haemoglobin

Answer 19

HbA
HbA2 beta chains replaced with sigma chains
HbF beta chains replaced by gamma
glycosylated Hb

Question 20

how long does saturation of haemoglobin with oxygen take?

Answer 20

0.25 secs

Question 21

what decreases the affinity of haemoglobin for oxygen?

Answer 21

> decrease in pH

> increase in temperature, PCO2

Question 22

what affect does 2,3-diphosphoglycerate (2,3-DPG) have on haemoglobin?

Answer 22

it decreases it affinity for oxygen

Question 23

in what situation is 2,3-DPG useful to the body?

Answer 23

this increases in situations associated with inadequate oxygen supply; heart disease, lung disease, living in high altitude. it helps maintain oxygen release to the tissues.

Question 24

do foetal haemoglobin and myoglobin have a higher or lower affinity for oxygen than HbA?

Answer 24

a higher affinity which is necessary for extracting o2 from the maternal arterial blood.

Question 25

what is the structural difference between HbF and HbA?

Answer 25

in foetal haemoglobin the beta chain is replaced by gamma. beta has a higher affinity for oxygen.

Question 26

what is anaemia?

Answer 26

any condition where oxygen carrying capacity of the blood is compromised (iron deficiency, haemorrhage, vit.B12 deficiency)

Question 27

in anaemic patients is Po2 higher or lower?

Answer 27

It remains the same as partial pressure simply refers to the o2 in the blood not the o2 bound to haemoglobin

Question 28

describe the affects of CO binding to haemoglobin

Answer 28

since CO has an affinity for HbA that is 250 times higher than oxygen so it binds readily and dissociated very slowly.
symptoms: hypoxia, anaemia, nausea, headaches, cherry red skin and mucous membranes.

Question 29

describe hypoxic hypoxia

Answer 29

this is a reduction in o2 diffusion at the lungs due to PO2atoms or tissue pathology

Question 30

describe anaemic hypoxia

Answer 30

reduction in o2 carrying capacity of blood due to anaemia

Question 31

describe ischaemic hypoxia

Answer 31

heart disease results in inefficient pumping of blood around the body/lungs

Question 32

what is histotoxic hypoxia?

Answer 32

when poisoning prevents cells utilising oxygen delivered to them (carbon monoxide or cyanide)

Question 33

describe metabolic hypoxia?

Answer 33

when oxygen delivered to the tissues does not meet the increased demand of oxygen by the cells