Week 3 - Lung Function Tests

Question 1

What is the inspiratory reserve volume?

Answer 1

The volume not filled during a normal breath - e extra volume that can be achieved with work. Normally 2.5l

Question 2

What is the expiratory reserve volume?

Answer 2

The extra volume that can be can breathed out over that at rest. Normally 1.5l

Question 3

What is the residual volume?

Answer 3

The volume remaining after maximal expiration - cannot be measure by spirometry. Normally 0.8l

Question 4

What is the inspiratory capacity?

Answer 4

The total volume that can be breathed in from maximal expiratory volume. Normally 3l

Question 5

What is the functional residual capacity?

Answer 5

The amount of air left in the lungs after maximal expiration, normally 2.3l

Question 6

What is the vital capacity?

Answer 6

The measurement from max inspiration to max expiration - eg the biggest breath that can be taken. Normally about 5l in total. IRV + TV + EVR

Question 7

What factors affect the vital capacity?

Answer 7

Inspiration = compliance of the lungs, force of inspiratory muscles
Expiratory = airway resistance, increases as expiration proceeds

Therefore need a method to assess both

Question 8

How does spirometry work?

Answer 8

Patient fills lungs, breathes out as fully as possible and volume measured against time.

Question 9

What is the FVC and the FEV1.0 in regards to spirometry?

Answer 9

The fev1 is the volume expired in the first second, the FVC is the forced vital capacity so the maximum, normally 5l

Question 10

What is the relationship between the fev and fvc?

Answer 10

Normally the fev1 is more than 70% of the FVC

Question 11

What will you see with an obstructive pattern?

Answer 11

Lungs will still be easy to fill but the resistance will increase in expiration so air will come out more slowly and therefore the FEV1 will be rescued but FVC is normal

Question 12

What will you see in a restrictive pattern? Eg if lungs are difficult to fill because of stiff muscles or problem with chest wall?

Answer 12

The FVC is reduced but FEV is normal and probably more than 70%

Question 13

Why is the peak expiratory flow rate insensitive?

Answer 13

..?….

Question 14

What would a obstructive pattern in a flow volume curve look like?

Answer 14

Scoping out - lungs are compressed so more air expired but resistance will then increase and flow rate falls.

Question 15

What will a restrictive pattern look like in a flow volume curve?

Answer 15

Narrower - no problem getting the air out, problem filling in the first place.

Question 16

How do you measure the residual volume?

Answer 16

Helium dilution - helium is not metabolised - patient breathes a known concentration, start at functional residual capacity, as the patient breathes the helium concentration changes as it gets diluted because it is in a larger volume

Question 17

What is the tidal volume?

Answer 17

The volume of air displaced in one normal breath - normally 0.5l