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Respiratory > gas transport > Flashcards

gas transport Flashcards

1
Q

What does the prefixes P, F, S, C, Hb mean

A 
P - partial pressure
F - fraction
S - Hb saturation
C - content
Hb - volume bound to Hb
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2
Q

What do the following subscripts mean: I, E, A, a, v, P, D

A 
I - inspired
E - expired
A - alveolar
a - arterial
v- mixed venous
P - peripheral
D - dissolved
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3
Q

What is Dalton’s law

A

Pressure of a gas mixture is equal to the sum of the partial pressures of gases in that mixture

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4
Q

What is Fick’s law

A

Molecules diffuse from areas of high concentration to low concentration at a rate proportional to the concentration gradient, surface area and the diffusibility. Inversely proportionally to thickness

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5
Q

What is Henry’s law

A

At a constant temperature, the amount of a given gas that dissolves in a given type and volume liquid is directly proportional to the solubility 𝛼 of the gas and the partial pressure (P) of the gas in the equilibirum with that liquid

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6
Q

What is Boyle’s law

A

At a constant temperature, the volume (V) of a gas is inversely proportional to the pressure (P) of that gas

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7
Q

What is Charles’ law

A

At a constant pressure, the volume (V) of a gas is proportional to the temperature (T) of that gas

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8
Q

What is the partial pressure at sea level

A

21.3 kPa/ 160mmHg

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9
Q

How much can a nasal cannula or face mask increase inspired oxygen

A

increase by 60%

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10
Q

How does pressure change with altitude

A

As altitude increase, the ambient barometric pressure reduces. Although the gas fractions in inspired air are unchanged, they are taking fractions of a lower overall pressure.

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11
Q

What does respiratory conditioning involve and where does it occur

A

Structures with a high blood flow causally to the trachea. Blood is:
Warmed to a physiological temperature
Humidified to a PH20 of 6.3kPa (100% saturation)
Slowed
Mixed with air already in the lungs

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12
Q

Why is oxygen content reduced and carbon dioxide increased in the alveoli during ventilation

A

Fresh air entering the lungs mixes with the functional residue capacity (ERV + RV)

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13
Q

What is the total O2 delivery at rest

A

0.32 mL·dL-1
or
16 mL∙min-1

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14
Q

Describe haemoglobin

A

Hb is a tetrameric molecule consisting of 4 monomers with two parts
Haem and Globin

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15
Q

Describe haem

A

Ferrous iron ion (Fe2+) at the centre of a tetrapyrrole porphyrin ring. The ligand is able to reversibly bind to 1 O2. Once bound, haem and the connected chain change shape to affect other monomers, making them more receptive to binding oxygen (allosteric)

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16
Q

Describe globulin

A 
protein chain. There are 4 common protein chains encoded by genes:
Alpha chain (α) – produces Hbα
Beta chain (β) – produces Hbβ
Delta chain (δ) – produces Hbδ
Gamma chain (γ) – produces Hbγ
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17
Q

What are the 3 common variants of Hb

A

HbA, HbA2, HbF

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18
Q

How is haemoglobin transported in the blood

A

Packed in erythrocytes that account for 45% of the blood

150 g/L

19
Q

Explain cooperativity of haemoglobin

A

When Hb is fully deoxygenated, it shifts into a tense state where binding of the first oxygen is very difficult. As more oxygen binds it shifts to a relaxed state to increase infinity for oxygen. The affinity between the final binding site and oxygen is 300x greater than for the first.
Binding site for 2,3-DPG to bind which pushes Haemoglobin to have a tense state

20
Q

Describe foetal haemoglobin

A

OD curve shift to the left
2 alpha and 2 gamma
Greater affinity for oxygen as HbF must be able to bind to oxygen that is already bound to maternal Hb within the placenta
In utero, proportion of HbF is dominant but switches to HbA postpartum

21
Q

Describe methaemoglobin

A

Skin will become blue
0.5-1% of haemoglobin
Has a Fe3+ that does not bind oxygen

22
Q

Describe myoglobin

A

Much greater affinity than adult HbA to store oxygen from circulating blood. Found in muscle. Curve very greatly shifted to the left.

23
Q

What can be used to track how the oxygen dissociation curve changes

A

p50 (Partial pressure at 50% saturation)

24
Q

What may cause a shift of the OD curve to the left

A

Decrease in temperature
Alkalosis
Hypocapnia
Decrease in 2,3-DPG

25
Q

What may cause a shift of the OD curve to the right

A

Increase in demperature
Acidosis (Bohr)
Hypercapnia
Increase in 2,3-DPG

26
Q

What may cause an upwards shift of the OD curve

A

Changes as the amount of haemoglobin in the blood changes
Polycythaemia (tumour)
Increased oxygen-carrying capacity

27
Q

What may cause a downwards shift of the OD curve

A

Anaemia

Impaired oxygen-carrying capacity

28
Q

How will carbon monoxide poisoning affect the OD curve

A

Shifts the curve downwards and leftwards. There is an increased affinity while capacity decreases.

29
Q

What % saturation is haemoglobin arriving at the lung and when does oxygen stop diffusing

A

75%

13.5 kPa

30
Q

Why does blood arriving at tissues have a low partial pressure than at the lungs

A

bronchial drainage

A little amount drains into the pulmonary veins, diluting the blood.

31
Q

Where does the relative proportions of CO2 vary

A

moving from arterial to venous blood

32
Q

How can CO2 be transported

A

In solution
As bicarbonate (most)
Bound to haemoglobin (carbaminohaemoglobin)

33
Q

Explain how CO2 becomes bicarbonate

A

CO2 reacts with water to form carbonic acid. This dissolves into protons and bicarbonate to form an equilibrium
CO2 combines with water, catalysed by carbonic anhydrase

34
Q

What is transit time and give examples

A

Transit time = time that blood is in contact with the exchange surface
Pulmonary transit time is 0.75s for oxygen
For carbon dioxide, the time is 0.25s

35
Q

Describe ventilation perfusion matching

A

Lung tissue is under the influence of gravity, which pulls the alveoli to the bottom
Intrapleural pressure is different in the top and bottom of the lung

36
Q

Which end of the lung has greater ventilation and why

A

The bottom as alveoli are much easier to further inflate (Smaller transmural pressure gradient)
Alveoli smaller and more compliant so more ventilation

37
Q

Which end of the lung has reduced ventilation and why

A

The top as the alveoli are stretched and under a lot of pressure (greater transmural pressure -> gradient requires a greater pressure for further inflation)
The alveoli are larger and less compliant -> less ventilation and PPL is less negative

38
Q

Which end of the lung has greater perfusion and why

A

Bottom
Higher intravascular pressure so more recruitment
Less resistance and higher flow rate

39
Q

Which end of the lungs has reduced perfusion and why

A

Top
Lower intravascular pressure (gravity) so less recruitment
Greater resistance and lower flow rate

40
Q

What is the ventilation perfusion ratio

A

ventilation/perfusion

Greater at the apex

41
Q

Where is perfusion and ventilation wasted

A

wasted perfusion = bottom

waster ventilation = top

42
Q

Describe the partial pressures for ventilation perfusion matching in the 3 zones

A

Zone 1 - PA>Pa>Pv
Zone 2 - Pa>PA>Pv
Zone 3 - Pa>Pv>PA

43
Q

How does ventilation and perfusion change from the top to the bottom of the lung

A

Ventilation decreases

Perfusion decreases more

44
Q

What factors affect V/Q ratio

A

Exercise stimulates and increased effort to increase oxygen supply. V and Q increase proportionally
Increased ventilation force increases apical ventilation and perfusion

Respiratory (16 decks)

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