Respiratory function tests

Question 1

What does spirometry measure? When is it used?

Answer 1

Measures expired and inspired air (volume, time, flow)
Uses:
- assess lung disease
- quantify lung impairment
- monitor effects of occupational/ environmental exposures
- determine effects of medication

Question 2

What is the correct technique when performing spirometry?

Answer 2

• deep breath in
• place mouth tightly around the mouthpiece
• take full expiration
• no glossitis closure or cessation of airflow
• exhaling for 6 seconds with 50 ml exhlaed in last 2 seconds

Question 3

What is tidal volume?

Answer 3

amount of air moved into and out of lungs during rest

Question 4

What is inspiratory reserve volume?

Answer 4

volume of air drawn into lungs

Question 5

What is expiratory reserve volume?

Answer 5

volume of air expelled from lungs

Question 6

What is residual volume?

Answer 6

volume of air remaining in the lungs even after maximal exhalation

Question 7

What is forced vital capacity?

Answer 7

maximum amount of air moved into and out of the lungs during a single respiratory cycle

FVC = IRV + TV + ERV

Question 8

What is the FEV1:FVC in restrictive and obstructive diseases?

Answer 8

Restrictive= >0.75-0.8
Obstructive= <0.75-0.8

Question 9

What tests can be done to measure respiratory gas transfer?

Answer 9

DLCO and TLCO test
DLCO is measured in “ml/min/kPa” and TLCO is measured in “ml/min/mmHg”
DLCO = diffusing capacity of lungs for carbon monoxide
TLCO = transfer factor of lungs for carbon monoxide

Question 10

How is the DLCO/TLCO test performed? What exactly is it measuring?

Answer 10

1. Unforced exhalation to residual volume
2. followed by rapid inhalation of CO/Helium to TLC
3. Hold for 10 seconds
4. Another unforced exhalation <4 seconds
5. Sample the exhaled breath

Measuring the quantity of CO transferred per minute from alveolar gas to RBCs

Question 11

How is DLCO result calculated? What results are normal and abnormal?

Answer 11

DLCO = lung surface area x rate of capillary blood CO uptake

Normal: 75-140% of predicted value
Mild decrease: 60-74%
Moderate decrease: 40-59%
Severe: <40%

Question 12

What might be the cause of a reduced DLCO?

Answer 12

1. Hindrance in the alveolar wall. e.g. fibrosis, alveolitis, vasculitis
2. Decrease of total lung area, e.g. Restrictive lung disease or lung resection (partial or total).
3. Chronic obstructive pulmonary disease (COPD) {except asthma and chronic bronchitis} due to decreased surface area in the alveoli, as well as damage to the capillary bed
4. Pulmonary embolism
5. Cardiac insufficiency
6. Pulmonary hypertension
7. Bleomycin (upon administration of more than 200 units)
8. Chronic heart failure
9. Anaemia - due to decrease in blood volume
10. Amiodarone high cumulative dose; more than 400 milligrams per day

Question 13

What might increase DLCO?

Answer 13

1. Polycythaemia
2. Asthma
3. Increased pulmonary blood volume (exercise)
4. L–>R intracardiac shunting
5. Mild left heart failure
6. Alveolar haemorrhage

Question 14

Why are exercise tests used clinically?

Answer 14

• assess how much exercise a patient can manage
• asses the benefit of extra O2 for daily activities
• assess pre-op fitness

Question 15

What exercise tests are usually performed?

Answer 15

1. 6 minute walk
   - assess breathlessness before and after
   - record blood O2 saturation
2. Shuttle walk
   - distance + speed without rest
3. Cardiopulmonary exercise
   - use cycle ergometer or treadmill
   - measure O2 consumption/ECG/SpO2