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Yr 2 Sem 1 Resp > 3.3 Oxygen in the Blood > Flashcards

3.3 Oxygen in the Blood Flashcards

1
Q

How do you work out concentration of dissolved oxygen?

A

[O2]dissolved = Solubility x pO2

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2
Q

What is average cardiac output?

A

5L/min

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3
Q

What are the two oxygen binding pigments?

A

Haemoglobin

Myoglobin

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4
Q

Where is Hb found and how much oxygen can it bind?

A

Present in the blood

Tetramer - Binds 4 O2

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5
Q

Where can myoglobin be found and how much oxygen can it bind?

A

Present in muscle cells

Monomer - Binds 1 oxygen

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6
Q

What does the myoglobin dissociation curve look like?

A

Rectangular hyperbola

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7
Q

Why do we express saturation as a percentage in dissociation curves?

A

Because binding is saturated above a given pO2
The amount of O2 bounds depends on the amount of pigment when not using a percentage

Percentage is independent of pigment concentration

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8
Q

What are the two states of Hb?

A

Low affinity T state
- Difficult for oxygen to bind

High affinity R state
- Easier for oxygen to bind

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9
Q

Which state is Hb in at low PO2?

A

Tensestate

Hard for the first O2 molecule to bind

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10
Q

What shape is the Hb dissociation curve?

A

Sigmoidal

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11
Q

At what O2 KPa is Hb saturated?

A

Above 9-10kPa

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12
Q

At what oxygen kPa is Hb unsaturated?

A

1kPa

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13
Q

At what oxygen kPa is Hb half saturated?

A

3.5-4kPa

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14
Q

What is the oxygen content in arterial blood leaving the lungs?

A

8.8mmol/L

Normal Hb content = 2.2mmol/L
Each Hb molecule can bind 4 oxygen molecules
2.2 x 4 = 8.8mmol/L

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15
Q

What is the amount of oxygen given up in the tissues?

A

3mmol/L

Metabolically active tissue - pO2 = 5kPa
So Hb saturation drops to 65%
So 35% of oxygen is given up

8.8 x 0.35 = 3 mmol/L

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16
Q

How low can tissue pO2 get?

A

Most tissues 3kPa

Can be lower in metabolically active tissues where there is a higher capillary density (because it doesn’t have as far to diffuse)

17
Q

Briefly describe the Bohr shift

A

pH affects the affinity of Hb

Acidic conditions - shift to right - promotes T state - harder for oxygen to bind

Alkaline conditions - promotes R state

18
Q

What happens to oxygen in metabolically active tissues and why?

A

Given up

  • Lower pH
  • Increased temperature
19
Q

Why is improved extraction of oxygen by the tissues needed during extreme exercise?

A

Extreme exercise can increase metabolism by 10x but cardiac output only increased by 5x

20
Q

What is the normal RBC level of 2,3-BPG?

A

5mM

21
Q

Under what conditions may 2,3-BPG increase?

A

Anaemia

Altitude

22
Q

What affect does increased 2,3-BPG have on the dissociation curve?

A

Shifts to the right

Allows more oxygen to be given up in the tissues

23
Q

At what level in the blood is HbCO fatal?

A

> 50%

24
Q

Define hypoxemia

A

Low pO2 in arterial blood

25
Q

Define hypoxia

A

Low oxygen levels in body or tissues

26
Q

Why do you see a blue-ish tint in cyanosis?

A

Due to unsaturated Hb

Deoxygenated Hb is less red than oxygenated Hb

27
Q

What are the two types of cyanosis? Where are they found?

A

Peripheral - hands or feet

Central - mouth, tongue, lips, mucous membranes

28
Q

What causes peripheral cyanosis?

A

Poor local circulation

29
Q

What causes central cyanosis?

A

Poorly saturated blood in the systemic circulation

30
Q

Why may cyanosis be difficult to detect?

A

Poor lighting

Skin colouration

31
Q

What does pulse oximetry detect and how?

A

Detects level of Hb saturation

Detects different in absorption of light between oxygenated and deoxygenated Hb

32
Q

Disadvantages of pulse oximetry

A

Only detects pulsatile arterial blood
- Ignores levels in tissues and non-pulsatile venous blood

Doesn’t say how much Hb is present

Will not detect if someone is anaemic

33
Q

Which artery is used to get a sample of arterial blood for arterial blood gas and electrolyte analysis?

A

Radial artery

Yr 2 Sem 1 Resp (7 decks)

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