Respiratory Physiology

Question 1

What is tidal volume?

Answer 1

1. Volume inspired or expired with each breath at rest
2. 500ml males/350ml females

Question 2

What is inspiratory reserve volume?

Answer 2

1. IRV=2.3L
2. Max vol inspired at end of normal tidal insp
3. Inspiratory capacity = TV+IRV

Question 3

What is the expiratory reserve volume (ERV)

Answer 3

1. ERV=750ml
2. Max vol expired at end of normal tidal expirat

Question 4

What is the residual volume?(RV)

Answer 4

1. Volume of air remaining after max expiration
2. Increases with age
3. RV=FRC-ERV
4. 1.2L

Question 5

What is the vital capacity (VC)?

Answer 5

1. Max vol of air exp after max inspiration
2. 4.5L males/3.5L females
3. Decreases with age
4. VC = insp capacity + ERV

Question 6

What is total lung capacity?

Answer 6

1. VC+residual volume

Question 7

What does the oxygen dissociation curve describe?

Answer 7

It describes the relationship between the percentage of saturated haemoglobin and partial pressure of oxygen in the blood. Not affected by the haemoglobin concentration.

Question 8

When the curve shifts to the left what happens?

Answer 8

For a given oxygen tension there is increased saturation of HB with oxygen ie < oxygen delivery to the tissues

Question 9

When the curve shifts to the right what happens?

Answer 9

For a given oxygen tension there is reduced saturation of Hb with oxygen ie enhanced oxygen delivery to the tissues.

Question 10

What causes the curve to shift to the left?

Answer 10

1. HbF: methaemoglobin, carboxyhaemoglobin
2. Low H+ (alkali)
3. Low 2,3-DPG
4. Low temperature

Question 11

What mnemonic helps us to remember things that cause a left shift ( lower O2)?

Answer 11

The L rule! Shifts to L - lowers oxygen delivery caused by:

1. Low H+ alkali
2. Low pCO2
3. Low 2,3-DPG
4. Low temperature

Question 12

What causes the curve to shift to the right?

Answer 12

Shifts to right = raised oxygen delivery

1. Raised H+ acidic
2. Raised pCO2
3. Raised 2,3 - DPG
4. Raised temperature

Question 13

What mnemonic helps to remember what causes shifts to the right?

Answer 13

‘CADET, face right!’

• CO2
• Acid
• 2,3 DPG
• Exercise
• Temperature