L7 Pulmonary function tests

Question 1

What are the main PFT ?

Answer 1

1. Spirometry
2. Assessment of the uniformity of ventilation
3. Assessment of the diffusion capacity of the respiratory membrane
4. Maximal respiratory pressures

Question 2

What are the main indications to use PFT ?

Answer 2

1. Primary assessment
   - pulmonary disease evaluation
   - non pulmonary disease evaluation
   - pulmonary exposure evaluation
2. Monitoring
   * pulmonary diseases :
   - treatment
   - prognosis
   - progression

• pulmonary impact of non-pulmonary diseases:
• vascular diseases
• heart diseases
• neuromuscular diseases

3. Screening
4. Evaluation of the disability

Question 3

How you can differentiate between asthma and COPD by using PEFR ?

Answer 3

1. In ASTHMA, the patient experience diurnal changes in PEFR with morning dipping ( so tha changes are in smaller scale )
2. In COPD, the patient experience changes in much longer time scale

Question 4

How we can measure lung volumes directly and indirectly ?

Answer 4

DIRECTLY:
- spirometry

INDIRECTLY :

1. Imaging techniques ( not accurate so not being used any more )
2. Gas diulational methods ( usually measuring FRC )
3. Whole body plethysmography

Question 5

What does the plethysmography measures ? And how ?

Answer 5

It is measuring indirectly:

1. RV
2. FRC
3. Airway resistance

By sitting in closed box and exhaling against closed mouth piece which will compress the lung volume and increase the pressure and in the same time decreases the box pressure

Question 6

What is The maximum voluntary ventilation (MVV) ?

Answer 6

The MVV is typically 30 to 40 x the patient’s FEV1 but may be reduced by

• upper airway obstruction
• respiratory muscle weakness
• poor maneuver performance.

Question 7

How we can asses the uniformity of ventilation ?

Answer 7

1. Single breath oxygen test o
2. Single breath nitrogen washout
3. Lung Clearance Index (LCI)

Question 8

What is happening for closing volume (CV ) in any airway obstruction ?

Answer 8

It will increases as the apical alveoli that contain nitrogen ( mixed air ) will empty with higher volumes ( earlier )

Question 9

What does DLCO/VA indicate ?

Answer 9

If the value is normal :
- it means that the main problem is in lung (alveolar ) volume

If the value is low :
- it means that the main problem is in the diffusion as DLCO is low