Lung Function Measurement

Question 1

Describe the reasons for performing lung function tests like spirometry. (4)

Answer 1

Helps with diagnosis
Assesses response to therapy
Pre-surgery assessment
Epidemiology

Question 2

What is a vitalograph? (2)

Answer 2

Spirometer that records expired volume.

Question 3

What does FVC depend on? (4)

Answer 3

Health, age, gender, height.

Question 4

Describe the normal time volume graph and how they’re produced. (3)

Answer 4

Steep line up, flattens off.

Patient inspired to vital capacity, rapid forced expiration.

Question 5

Explain the volume time graph see in obstructive disease. (3)

Answer 5

FVC not markedly reduced if given enough time.
Narrow airways means that FEV1 reduced lots.
FEV1/FVC ratio <70%

Question 6

Explain the volume time graph seen in restrictive disease (4)

Answer 6

FVC is markedly reduced.
Fraction of air expelled in one second is high (less air to start with) but volume is reduced.
FEV1/FVC ration > 70%

Question 7

Explain the shape and axis of the spirogram/ flow-volume Loop. (6)

Answer 7

Y axis: flow l/s
X axis: reversed volume l
Graph: time, clockwise
Above x axis is expiration, first bit is straight up because it’s fast flow large airway expiration, then gently down because then it’s small airway slower flow.
Below the x axis is inspiration, gentle curve of slower flow.

Question 8

Explain the flow-volume loop seen in obstructive disorder. (3)

Answer 8

Much lower peak, scalloping of small airways - collapse of small airways slows flow.

Question 9

Describe where peak expiratory flow, vital capacity and residual volume fit on the flow-volume loop. (3)

Answer 9

PEF - top of the expiration curve
Residual vol - bit of x axis on the right with no curve on it.
Vital capacity - width of the curve.

Question 10

Explain the flow-volume loop seen in Restrictive disorders. (3)

Answer 10

Low VC (narrow) and low PEF (short). 
Lungs cannot expand as much, so can’t draw in much air.

Question 11

Explain the flow-volume loop seen in mixed restrictive and obstructive disorders. (3)

Answer 11

Low VC, scalloping.

Collapse of small airways on expiration and restriction of lungs on inspiration.

Question 12

Explain the flow-volume loop seen in variable upper airway obstruction (eg laryngeal polyp) (3)

Answer 12

Expiration normal, inspiration variable in flow and reduced because polyp in the way, but large and small airways unaffected.

Question 13

Explain the flow-volume loop seen in fixed upper airway obstruction (eg tracheal stenosis). (2)

Answer 13

Both inhalation and exhalation reduced because air struggles to get in and out.