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Resp week 1 > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

What is ventilation?

A

air getting to alveoli L/min

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2
Q

What is perfusion?

A

local blood flow L/min

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3
Q

What is the ideal Ventilation-Perfusion Relationship

A

Ideally match (complement) each other

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4
Q

At the base of the lungs, is blood flow or ventilation higher and why

A

blood flow is higher than ventilation because arterial pressure exceeds alveolar pressure. This compresses the alveoli.

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5
Q

Is blood flow low or high at the apex of the lungs and why

A

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

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6
Q

Do blood flow and ventilation decrease with height across lung?

A

Yes, While both decline, blood flow declines faster than ventilation meaning blood flow>ventilation at the base, and ventilation>blood flow at the apex.

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7
Q

What is the Ventilation:Perfusion ratio at mis matched base and apex?

A

Base= <1 (Ventilation1 (Ventilation>Perfusion )

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8
Q

What % healthy lung perform well in ratio and wherewhere does most mismatch occur?

A

75%, most mismatch at apex. This is then auto regulated to keep the ventilation perfusion ratio close to 1.0

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9
Q

What is a “Shunt”. What happens in response to shunting?

A

term used to describe the passage of blood through areas of the lung that are poorly ventilated (ventilation &laquo_space;perfusion). Blood is “shunted” (moved) from right side of heart to left without undergoing ventilation.

Decreased ventilation in group of alveoli. Blood flowing past doesn’t get oxygenated, therefore causing dilution of oxygenated blood from better ventilated areas.

Perfusion > ventilation - Alveolar PO2 falls, PCO2 rises - Pulmonary Vasoconstriction (PO2) and Bronchial Dilation (PCO2).

Acts to match ventilation with perfusion (L/min)

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10
Q

How do local control mechanisms try to keep ventilation and perfusion matched?

A

Decreased tissue PO2 around underventilated alveoli constricts arterioles, diverting blood to better-ventilated alveoli.

Constriction in response to hypoxia is particular to pulmonary vessels (systemic vessels dilate)

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11
Q

What is “Alveolar Dead Space”

A

refers to alveoli that are ventilated but not perfused.

Occurs to small extent at apex of normal lung. Occurs pathologically in pulmonary embolus. Opposite of Shunt.

Ventilation > perfusion - Alveolar PO2 rises, PCO2 falls - Pulmonary Vasodilation (pO2) and Bronchial Constriction (pCO2)

Acts to match ventilation with perfusion (L/min)

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12
Q

What is Anatomical Dead Space

A

air in the conducting zone of the respiratory tract unable to participate in gas exchange as walls of airways in this region (nasal cavities, trachea, bronchi and upper bronchioles) are too thick.

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13
Q

What is Physiologic Dead Space

A

Alveolar DS + Anatomical DS

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14
Q

What is RSA and what does it aim to do

A

Respiratory Sinus Arrhythmia, ensures ventilation:perfusion ratio remains close to 1 (matched). mainly due to increased vagal activity during expiratory phase

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15
Q

O2 travels in what two forms in the blood? What amount of O2 is carried this way?

A

200ml O2 per litre whole blood, 197ml of which is bound to haemoglobin in red blood cells

Only 3ml O2 dissolve per litre plasma

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16
Q

How (and %) is CO2 transported?

A

Bulk (77%) of CO2 is transported in solution in plasma, 23% is stored within haemoglobin

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17
Q

What is cardiac output at rest?

A

5L/min

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18
Q

How much of arterial O2 is extracted by perhipheral tissues at rest?

A

25%

O2 demand of resting tissues = 250ml/min

200ml/L (O2ml/L via Haemoglobin = 197 and arterial O2 = 3ml/L) x 5L/min = 1000ml/min

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18
Q

How much of arterial O2 is extracted by perhipheral tissues at rest?

A

25%

O2 demand of resting tissues = 250ml/min

200ml/L (O2ml/L via Haemoglobin = 197 and arterial O2 = 3ml/L) x 5L/min = 1000ml/min

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19
Q

What % of the oxygen carried in blood is carried in red blood cells, bound to Haemoglobin

A

more than 98%

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20
Q

How many Haeme groups does 1 haemoglobin contain?

What does one Haeme group contain and what is its function?

A

Each haemoglobin molecule contains 4 haeme groups, each of which contains one Fe2+ which binds one O2 molecule. Each haemoglobin molecule therefore binds 4 molecules of oxygen.

21
Q

What is the major determinant of the degree to which haemoglobin binds (is saturated with) oxygen

A

partial pressure of oxygen in the blood.

22
Q

How long does it take for saturation of Haemoglobin to be complete? What is the average contact time?

A

Saturation is complete after 0.25s contact with alveoli (total contact time ~0.75s

23
Q

What is Anaemia

A

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

24
Q

What would happen to PO2 in anaemia?

A

Nothing!
PO2 is normal despite total blood O2 content being low

Possible to have normal plasma PO2, while total blood O2 content is low.
But:
Not possible to have low plasma PO2, and normal total blood O2 content.

25
Q

Is it possible for red blood cells to be fully saturated with O2 in anaemia?

A

YES! Red blood cells would still be fully saturated with oxygen as PO2 is normal

(only caveat is iron deficiency where number of O2 binding sites will be reduced, but those present will still be saturated)

26
Q

The affinity of haemoglobin for oxygen is decreased by…..
an increase/decrease pH
increase/decrease PCO2
increase/decrease Temparature
binding 2,3-diphosphoglycerate (2,3-DPG) synthesised by the erythrocytes?

What is this effect known as?

A

Decrease pH
Increase PCO2
INcrease in Temparature

Think about exercising. You want to lose the O2 at the tissues, so affinity to haemaglobin wants to be low. Lower pH caused by acidosis (exercising muscle), Increase in PCO2 (higher metabolic rate, more CO2 produced), and increasing temp (as a result!)

Known as the BOHR effect.
The affinity of haemoglobin for oxygen is decreased by binding 2,3-diphosphoglycerate (2,3-DPG) synthesised by the erythrocytes. 2,3- DPG increases in situations associated with inadequate oxygen supply (heart or lung disease, living at high altitude) and helps maintain oxygen release in the tissues.

27
Q

How much greater is the affinity of CO to Haemoglobin than O2?

A

250 times

28
Q

What is the PCO to cause progressive carboxyhaemoglobin formation?

A

0.4mmHg

29
Q

What is CO poisioning characterised by and what is the treatment?

A

Characterised by hypoxia, anaemia, nausea, headache, cherry red skin and mucous membranes as this is the colour of carboxyhaemoglobin. Respiration rate unaffected due to normal arterial PCO2. Potential brain damage and death.
Treatment involves providing 100% oxygen to increase PaO2

30
Q

What is the amount of oxygen that can bind to haemoglobin directly determined by?

A

PaO2, number of red blood cells and amount of haemoglobin in each and further influenced by further influenced by PaCO2, body temperature, plasma pH and levels of 2,3 DPG

31
Q

State the differences between partial pressure and gas content

A

Partial pressure of oxygen in the blood and oxygen concentration in the blood are not the same thing
Most of the time you will be dealing with partial pressure, which describes the amount of oxygen in solution in the plasma, not total oxygen content of the blood.

32
Q

Compare oxyhaemoglobin dissociation for adult haemoglobin with that of foetal haemoglobin (HbF) and myoglobin in relation to their physiological roles.

A

HbF and myoglobin have a higher affinity for O2 than HbA, this is necessary for extracting O2 from maternal/arterial blood

33
Q

Define the five different types of hypoxia.

A

Think SHAMH
Stagnant (O2 not moving - heart issue), Hypoxaemic (Low O2 perfusion at lungs), Anaemic (low O2 carrying ability), Metabolic (O2 to cells not meeting requirement), Histotoxic (poioning)

  1. Hypoxaemic Hypoxia: most common. Reduction in O2 diffusion at lungs either due to decreased PO2atmos or tissue pathology
    . Anaemic Hypoxia: Reduction in O2 carrying capacity of blood due to anaemia (red blood cell loss/iron deficiency).
    . Stagnant Hypoxia: Heart disease results in inefficient pumping of blood to lungs/around the body
    . 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.
34
Q

How much oxygen binds to each gram of haemoglobin? What is this process called?

A

1.34ml O2/gram haemoglobin. Called Oxygenation not oxidation.

35
Q

What percent haemoglobin in RBC is in the form HbA(Adult Haemaglobin)?

A

92%. Remaining 8% is made up of HbA2 (δ chains replace β), HbF (γ chains replace β), and glycosylated Hb (HbA1a, HbA1b, HbA1c.

36
Q

How else can oxygen be carried (found exclusivly in cardiac and skeletal muscle)

A

Myoglobin

37
Q

What is the difference anatomical dead space vs alveolar dead space vs physiologic dead space?

A

In both the air can’t participate in gas exchange.

Anatomical dead space = air in conducting zone of resp. tract unable to participate bc walls too thick (bronchioles/ bronchi etc)
Alveolar dead space = more air to blood flow
Physiologic dead space = Alveolar DS + Anatomical DS

37
Q

What is the difference anatomical dead space vs alveolar dead space vs physiologic dead space?

A

In both the air can’t participate in gas exchange.

Anatomical dead space = air in conducting zone of resp. tract unable to participate bc walls too thick (bronchioles/ bronchi etc)
Alveolar dead space = more air to blood flow
Physiologic dead space = Alveolar DS + Anatomical DS

38
Q

What does Respiratory Sinus Arrhythmia aim to to? How does it do this (through what nerve?)

A

Ensure ventilation:perfusion ratio remains close to 1 (matched).

(Increased HR during inspiration and decreased HR during expiration)

Does it through chnages in activity of parasympathetic vagus nerve that innervates the heart, whichs acts as a “heart brake” - parasympathetic vagus nerve increased innervation on expiration and decreased innervation on inspiration.

39
Q

What is cooperative binding in Haemoglobin?

A

That when Oxygen starts to bind there are conformational changes that make it easier for more Oxygen to bind. Likewise when Oxygen dissociates, there are further conformational changes that increase the ability of the Haemaglobin to release O2.

40
Q

How much Oxygen as a % of being fully saturated, does venous blood contain?

A

75%

41
Q

If body temp falls to 20deg.C what affect does this have on O2 retention of Haemoglobin?

A

If body temp falls to 20deg.C at PO2 Cells (40mmHg), haemaglobin is still 100% saturated

42
Q

If RBC have to work harder, they produce more of what compound? What effect does this have on the affinity of Haemoglobin to Oxygen?

A

DPG (diphosphoglycerate), which reduces affinity of haemoglobin with oxygen.

43
Q

What colour is normal oxyhaemaglobin compared with carboxyhaemaglobin (CO poisoning)

A 
Oxyhaemaglobin = bright red, scarlett colour. 
Carboxyhaemoglobin = cherry red, very red colour
44
Q
A

7% solution in plasma
93% into rbc, of which 23% combines with deoxyhaemoglobin (called that even tho its still 75% saturated with O2) to form carbamino compounds. The other 70% combines with water forming carbonic acid, which dissociates to H+ and bicarbonate ions. Most bicarbonate then exchanged for Cl- ions and left H+ binds to deoxyhaemoglobin. OPosite as CO2 moves capillary to alveoli.

45
Q

What is the Chloride Shift?

A

The exchange of bicarbonate ions for Chloride ions and then the bicarbonate travels in the blood (how 70% of ur CO2 travels)

46
Q

What enzyme helps form H2CO3 from H2O and CO2?

A

Carbonic Anhydrase

47
Q

Does Haemoglobin prefer CO2 or O2?

A

O2

48
Q

What are glycosylated Hb used to detect

A

How well diabetic patients have managed their glucose over a 3 month period

(lifespan 120 days, haemoglobin becomes glycosylated when exposed to high levels of glucose)

49
Q

Where is myoglobin stored, what is its role and when would it be found in the blood?

A

Exclusively in cardiac and skeletal muscle. It has a v high affinity for oxygen (higher than haemoglobin), function more in storing oxygen, Found in blood only with extensive muscle damag.

50
Q

Does Myoglobin and Foetal Haemoglobin have higher or lower affinity for oxygen compared with normal haemoglobin?

What are the advantages of this?

A

Both have higher affininity for oxygen.

Foetal Haemoglobin can therefore extract oxygen from maternal blood and equally muscle haemoglobin can extract O2 from the adult haemoglobin.

Resp week 1 (6 decks)

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