Pulmonary blood flow, gas exchange and transport Flashcards by Anna Coull

In 1 litre of systemic arterial blood there is how many ml of O2

200 ml

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how many ml of O2 is dissolved in free water of plasma?

3 ml

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what happens if gases in the gaseous state are present in plasma

a fatal air embolism

bubbles in the blood

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gas that travels in the blood travels in what state

solution

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which two ways are blood supplied to the lungs

bronchial arteries- Supply oxygenated blood to the smooth muscle, nerves and lung tissue. Arises from systemic circulation- separate to pulmonary.

pulmonary circulation- gas exchange. Returns oxygenated blood to L atrium

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difference between bronchial and pulmonary circulation

bronchial circulation is small, only carries about 1% of cardiac output. It is part of the general systemic circulatory system.

pulmonary circulation carries entire cardiac output from the right ventricle to the lungs

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how does air diffuse across membranes?

down partial pressure gradient

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what does A stand for in partial pressure

alveolar

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what does a stand for

arterial blood

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what does ṽ stand for

mixed venous blood

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What are the normal values for partial pressure of O2 in both arterial and alveolar blood?

100 mmHg
13.3 kPa

this reflects/ is the same as the lung values

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normal values for partial pressure of CO2 in both

arterial blood and alveolar blood

40 mmHg
5.3 kPa

this reflects/ is the same as the lung values

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normal values for partial pressure of O2 in mixed venous blood- this reflects tissue values

40 mmHg
5.3 kPa

reflects/ is the same as the tissues value

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normal values for partial pressure of CO2 in mixed venous blood

46 mmHg
6.2 kPa

reflects/ is the same as the tissues value

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which 2 key features of alveoli help with gas exchange

thin membrane, short diffusion distance

larfe surface area

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which has a higher partial pressure gradient? PO2 or PCO2?

PO2

250ml/min

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what is emphysema

destruction of alveoli which reduces SA for gas exchange

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what is pulmonary oedema

fluid in the interstitial space increases diffusion distance

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describe what fibrotic lung disease is

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

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what does fibrosis look like on chest x-ray?

shadows that indicate scar tissue- (not fully black which means it isn’t air)

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describe the ventilation- perfusion relationship

ideally they compliment/ match each other concentration
ventilation= air getting to alveoli
perfusion= local blood flow

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blood flow is higher than ventilation where in the lung?

At the base because arterial pressure exceeds alveolar pressure.

Gravity pulls blood to the base of the lung and so blood vessels push on alveoli. This compresses the alveoli

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why is blood flow low at the apex of the lungs

because arterial pressure is less than alveolar pressure. This compresses the arterioles.

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what does ‘shunt’ mean

moving blood from the right to the left side of the heart without it being properly oxygenated- movement of blood through areas of lung that are poorly ventilated

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what happens when ventilation is less than blood flow

when ventilation decreases in a group of alveoli ultimately PO2 decreases and PCO2 increases -blood is poorly oxygenated and this means it's harder to remove CO2 shunt would occur

how does the body try to keep ventilation and perfusion matched?

pulmonary vessels constrict (bronchial constriction) in response to hypoxia and this diverts blood to better-ventilated alveoli. When pulmonary vessels constrict systemic ones dilate

what is alveolar dead space and when does it occur

alveoli that are ventilated but not perfused ie ventilation is higher than blood flow. Low blood flow around alveoli means gas exchange cannot occur and air can't pass through

what is physiological dead space

alveolar DS + anatomical DS

what does haemoglobin in RBCs help increase

the O2 carrying capacity to 200ml/L

how is CO2 transported through blood

in solution in plasma

true or false: O2 solubility in water is low

true

what is the O2 demand of resting tissues?

250 ml/min

with red blood cells (increased haemoglobin) what happens to the amount of O2 getting to tissues

it increases- demand is met

what is reserved O2 used for

we can tap into it when we need to during periods of hypoxia but when O2 demand increases in tissues we tend to increase respiratory and cardiovascular rates to meet this instead

in systemic arterial blood, is there more O2 in haemoglobin or plasma

haemoglobin- it is more than 98% saturated normally

is pulmonary arterial pressure low

yes

how much oxygen does each litre of systemic arterial blood contain?

200 ml

how much oxygen is bound to each gram of haemoglobin?

1.34 ml

what is the process called where O2 binds to haemoglobin

oxygenation

what is the main determinant of the degree of haemoglobin oxygen saturation

PaO2 (arterial blood)

what two molecules have a higher affinity for oxygen than haemoglobin? and why?

myoglobin foetal haemoglobin higher affinity needed to extract O2 from maternal/ arterial blood to get O2 into muscle cells or foetus

what use is myglobin and HbF?

necessary for extracting o2 from maternal/arterial blood

if there is a low partial pressure of O2 in arterial blood then haemoglobin...

releases O2

if there is a high partial pressure of O2 in arterial blood then haemoglobin..

accepts/ takes up O2 from plasma

where is myoglobin found

oxidative muscle fibres

what is aneamia

Anaemia is defined as any condition where the oxygen carrying capacity of the blood is compromised

examples of aneamia

. iron deficiency, haemorrhage, vit B12 deficiency (needed to resynthesise RBC's

Affinity of haemoglobin for O2 changes in response to certain ______ factors?

chemical

what is normal extracellular fluid pH

7.4

which way does the ox-haem curve shift when there is a decrease in pH (acidosis) but increase in CO2 and body temp?

to the right... | meaning haemoglobin has a lower affinity for O2 and so more O2 can be stripped and given to metabolically active tissues

which way does the ox-haem curve shift when there is a increase in pH (alkalosis), but decrease in CO2 and body temp?

to the left... | meaning haemoglobin has a higher affinity for O2 and so more O2 is pulled from the plasma by the haemoglobin

what is 2,3-DPG?

A metabolite produced by RBCs

when do levels of DPG rise?

when RBCs are stressed ie when there is inadequate O2 supply

when DPG binds what happens to the affinity of haemoglobin for O2?

It decreases. Curve shifts to the R

Why is CO so dangerous?

it has an affinity for haemoglobin 250 times greater than O2 so it can bind readily but it dissociates very slowly- hard to get rid of.

how do you treat CO poisoning

provide 100% O2 to increase PaO2

when you have carbon monoxide poisoning, why do you still have normal respiration rate?

because you have normal PCO2 level normal pO2, because the carbon monoxide concentration required to cause poisoning is low enough that it does not alter the amount of oxygen physically dissolved in the plasma.

what is hypoxaemic hypoxia?

most common | reduction in O2 diffusion at the lungs either due to decreased PO2 or tissue pathology

what is anaemic hypoxia?

reduction in O2 carrying capacity of blood due to anaemia (RBC loss or iron deficiency

what is stagnant hypoxia?

heart disease results in inefficient pumping of blood to lungs/around the body- cardiovascular problem

histotoxic hypoxia?

poisoning prevents cells utilising oxygen delivered to them e.g carbon monoxide/ cyanide

metabolic hypoxia

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

how is CO2 transported?

in solution it goes down partial pressure gradient into plasma from tissues (biproduct of metabolic processes) a lot of CO2 enters RBCs

alveolar vs anatomical dead space - what is the difference?

Alveolar dead space is sum of the volumes of those alveoli which have little or no blood flowing through their adjacent pulmonary capillaries, i.e., alveoli that are ventilated but not perfused, and where, as a result, no gas exchange can occur. Anatomical dead space is the total volume of the conducting airways from the nose or mouth down to the level of the terminal bronchioles, and is about 150 ml on average. The anatomic dead space fills with stale air at the end of each inspiration, but this air is exhaled unchanged.

what is arterial blood?

the oxygenated blood in the circulatory system found in the pulmonary vein, the left chambers of the heart, and in the arteries

what % of arterial O2 is extracted by tissues at rest?

only 25% 200ml/L of O2 in blood and 5L/min cardiac output so 1000ml/min the O2 demand of resting tissues is 250ml/min so that's 25% of 1000