Lung function tests

Question 1

How do you calculate forced vital capacity? [1]

Answer 1

Forced vital capacity (maximum volume of air air forcibly exhaled out of your lungs after a deep full breath) = Inspiratory reserve volime + tidal volume + expiratory reserve volume

Question 2

How should a patient be positioned when undertaking spirometry? [2]

What is correct technique for spirometry? [3]

Answer 2

Position:
- Sat upright
- Feet flat on floor, legs uncrossed

Technique:
- Deep breath
- Exhale hard and fast for as long as possible (6 seconds)
- Mouth placed tightly around moutpiece

Question 3

What dose peak expiratory flow measure?
What technique is used for PEF?

Answer 3

Forced exhalation: HARD AND FAST
Peak expiratory flow (PEF) 3 best attempts
PEF is best used to provide an estimate of variability of airflow from multiple measurements made over at least two weeks

Question 4

What happens to FEV1 and FVC to asthma patients compared to normal? [1]

Answer 4

FEV1 and FVC are reduced

Question 5

What is A?
What is B?

Answer 5

A: PEF
B: FVC

Question 6

What is FEV1 / FVC ratio for healthy patients? [1]
What is FEV1 / FVC ratio for COPD patients? [1]

Answer 6

FEV1 / FVC: Values above 70-80% = normal
FEV1 / FVC: Below 70% = COPD.

Question 7

What’s a limitation of PEFR for diagnosis? [1]

Answer 7

Lots of variability between people (even within a day), hard to know what normal values are !!!

Question 8

What are ethnic variabilities in predicted FEV1 values?

Answer 8

Question 9

DCLO technique

Answer 9

Rapid inhalation of CO/Helium to TLC → Breath hold (10 sec) → unforced exhalation (< 4 sec)
Sample: exhaled breath

Question 10

What is a normal DLCO value?

Answer 10

above 75 % of predicted value

Question 11

How do you calculate DLCO?

Answer 11

DLCO = Lung surface area available for gas exchange (Va) X rate of capillary blood CO uptake (Kco)

Question 12

Name 3 conditions that reduce DLCO xx [3]

Answer 12

• Interstitial lung diseases (e.g. idiopathic pulmonary fibrosis)
• Pulmonary emphysema
• Pulmonary vascular disease (Pulmonary arterial hypertension & chronic venous thromboembolism)

Question 13

Interstitial lung disease affects which part of DCLO? [1]

Answer 13

↓DLCO primarily due to ↓Kco

Question 14

Technique for DCLO test?

Answer 14

Unforced exhalation to RV → Rapid inhalation of CO/Helium to TLC → Breath hold (10 sec) → unforced exhalation (< 4 sec)
Sample: exhaled breath

Question 15

What are the main causes of variability in spirometry date? [4]

Answer 15

In adults, age, height, sex and race are the main determinants

Question 16

What is FEV1 and FVC like in asthma patients?

Answer 16

Depends if they’re on medication.

Acute asthma: reduced
Well managed Ptx: normal

Question 17

Why is DCLO raised in asthma Ptx?

Answer 17

Expiration is decreased, so air is trapped in the lungs.

Have a lot of blood vessel recruitment

Question 18

Name 3 & explain 3 excercise tests

Answer 18

Assess pre-operative fitness/fitness state/extent of breathlessness/benefit of oxygen therapy