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Respiratory > Ventilation and gas exhange > Flashcards

Ventilation and gas exhange Flashcards

1
Q

What is hyperventilation?

A

Excessive ventilation of the lungs atop of metabolic demand (results in reduced PCO2 - alkalosis)

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2
Q

How to calculate minute ventilation? ( L/min )

Typical range?

A

Tidal Volume L x breathing frequency min

6 L/min

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3
Q

How to calculate Alveolar ventilation ( L/min )

A

Gas entering and leaving the alveoli

( Tidal volume - Dead space ) x Breathing frequency

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4
Q

What factors affect lung volume and capacities?

A

Body size - height

Sex

Disease

Age

Fitness

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5
Q

What is the conductive zone?

A

Equivalent to anatomical dead space
150 mL in adults at FRC
16 generations

Gas exchange doesn’t occur here, e.g. bronchi, trachea, larynx etc

In comparison to respiration zone

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6
Q

What is the non-perfused parenchyma?

A

Alveolar dead space
Alveoli with no blood supply
No gas exchange
0 mL in adults

Parenchyma: should be functional not supportive tissue, in this case it is alveoli which is not functioning ( non-perfused )

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7
Q

How to increase volume of dead space?

A

Anaesthethic circuit snorkelling

intubation

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8
Q

How to decrease volume of dead space?

A

Tracheostomy

Cricothyroctomy

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9
Q

The chest wall has a tendency to ( a ) , and the lung has a tendency to ( b ) inwards

A

a - spring outwards

b - recoil inwards

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10
Q

What is the FRC?

A

Functional residual capacity which is the neutral position of the intact chest

  • FRC also represents the point of the breathing cycle where the lung tissue elastic recoil and chest wall outward expansion are balanced and equal.
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11
Q

Inspiratory muscle effort + chest recoil > lung recoil ?

A

INSPIRATION

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12
Q

Chest recoil < lung recoil + expiratory muscle effort ?

A

EXPIRATION

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13
Q

Describe the basic chest wall anatomy?

A

The lungs are surrounded by a visceral pleural membrane

The inner surface of the chest wall is covered by a parietal pleural membrane

The pleural cavity (the gap between pleural membranes) is a fixed volume and contains protein-rich pleural fluid

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14
Q

What diseases affecting lung anatomy can cause issues with ventilation ?

A

Haemothorax - intrapleural bleeding

Pneumothoriax - performated chest wall / lung

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15
Q

What is negative pressure breathing?

A

Pressure alv is reduced below Pressure atm

  • normal healthy breathing
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16
Q

What is positive pressure breathing?

A

Pressure atm increased above P alv

  • recusitation
17
Q

Describe the three compartment model?

A

Transmural pressures
(Pinside – Poutside)

A negative transrespiratory pressure will lead to inspiration

A positive transmural pressure leads to expiration

18
Q

What is Dalton’s Law?

A

Pressure of a gas mixture is equal to the sum (Σ) of the partial pressures (P) of gases in that mixture

19
Q

What is Fick’s Law

A

Molecules diffuse from regions of high concentration to low concentration at a rate proportional to the concentration gradient (P1-P2), the exchange surface area (A) and the diffusion capacity (D) of the gas, and inversely proportional to the thickness of the exchange surface (T)

20
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 of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid

21
Q

What is Boyle’s Law?

A

At a constant temperature, the volume of a gas is inversely proportional to the pressure of that gas

22
Q

What is Charle’s law?

A

At a constant pressure, the volume of a gas is proportional to the temperature of that gas

23
Q

What ‘type’ of air could a patient be breathing?

A

Room air

Oxygen therapy: + O2

Smoke: -O2 +CO2 +CO

High altitude: Same proportion as room air but all increased

24
Q

How is Inspired air modified in airways?

warmed, humid, slower going down

A

Dry air outside:
PO2 = 21.3 kPa
PCO2 = 0 kPa
PH2O = 0 kPa

Conducting airways:
PO2 = 20 kPa
PCO2 = 0 kPa
PH2O = 6.3 kPa

Respiratory airways
PO2 = 13.5 kPa
PCO2 = 5.3 kPa
PH2O = 6.3 kPa

25
Q

What chest wall relationship causes inspiration?

A

Inspiratory muscle effort + chest recoil > lung recoil

26
Q

What chest wall relationship causes expiration?

A

Chest recoil < lung recoil + expiratory muscle effort

27
Q

What is the total O2 delivery at rest?

A

16 mL-min-1

  • Resting V̇O2 is approx. 250 mL·min-1 so obviously relying on dissolved oxygen alone is not conducive with life.
28
Q

What does a Oximeter measure?

A

Detect binding to Hb not Oxygen concentration itself.

29
Q

How may someone have a high Pulse Oximeter reading and still be ischaemic?

A

If all the Hb is bound to oxygen = high saturation reading however a person may have very little Hb in the first place.

30
Q

What causes left shift?

A

Increased affinity (loading)

↓ Temperature
Alkalosis
Hypocapnia
↓ 2,3-DPG

31
Q

What causes right shift?

A

↑ Temperature
Acidosis
Hypercapnia
↑ 2,3-DPG

( Bohr effect )

  • conditions of excersize
32
Q

What is Polycythaemia?

A

Increased oxygen-carrying capacity
( increased Hb )

dissoaciation curve goes up

  • opposite to anaemia
33
Q

What does carbon monoxide do to the partial pressure graph?

A

Downwards and left shift : decreased capacity and increased affinity.

34
Q

How does Myoglobin look on the partial pressure graph?

A

Much much greater affinity than adult HbA to ‘extract’ oxygen from blood and store it

35
Q

How is Oxygen transported?

A

2% in solution

98% bound to H monomers

36
Q

How is Carbon dioxide transported?

A

CO2 transported in solution, as bicarbonate (HCO3-) and as carbamino compounds (e.g. HbCO2)

  • In plasma very small amount will react without enzymes = CO2 + H2O –> H2CO3 which disociates

In red blood cells carbonic anhydrase increases this reaction greatly

37
Q

What is the chloride shift?

A

Negative chloride ions enter the RBC to maintain resting membrane potential as HCO3- leaves.

Respiratory (5 decks)

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