PFT

Question 1

What are the ideal characteristics of a lung function test for clinical use?

Answer 1

The test should:
* be easy and quick to perform
* have standard operating procedures and robust reference data
* discriminate between healthy children and those with respiratory disease with high specificity and sensitivity
* be feasible at any age for longitudinal follow-up
* be cheap and widely available.

Question 2

At what age can lung function be measured in infants?

Answer 2

Lung function can be measured as early as in the first days of life.

Question 3

What is the most common source of error in infant lung function testing?

Answer 3

Leak around the mask.

Question 4

When should lung function be measured in unsedated infants?

Answer 4

During non-REM sleep.

Question 5

What monitoring is mandatory when infants are sedated for lung function testing?

Answer 5

Monitoring of oxygen saturation.

Question 6

Is sedation recommended for neonates and preterm babies during lung function tests?

Answer 6

No, sedation is contraindicated.

Question 7

What is the most frequently used lung function test in children above 6 years of age?

Answer 7

Spirometry.

Question 8

What is Functional Residual Capacity (FRC)?

Answer 8

The volume of gas present in the lungs at the end of a tidal expiration.

Question 9

Which lung volume can be measured at any age?

Answer 9

Functional Residual Capacity (FRC).

Question 10

What are the two techniques used for measuring lung volumes?

Answer 10

• Body plethysmography
• Gas dilution technique.

Question 11

What does the gas dilution technique measure?

Answer 11

It measures only the communicating compartments of the lungs.

Question 12

What is Whole Body Plethysmography used for?

Answer 12

Measurement of total thoracic gas volume, including nonventilating areas.

Question 13

What physiological law underlies the measurement of FRCp?

Answer 13

Boyle’s law.

Question 14

What is the assumption made during plethysmography?

Answer 14

If the temperature is constant, the product of pressure and volume is constant.

Question 15

What is vital capacity (VC)?

Answer 15

The volume between the maximal inspiratory and expiratory levels.

Question 16

What is the residual volume (RV)?

Answer 16

The volume remaining in the lungs after a maximal expiration.

Question 17

What does Total Lung Capacity (TLC) represent?

Answer 17

The volume that the lungs contain at maximum inspiration.

Question 18

What is the main limitation of the gas dilution technique?

Answer 18

Underestimation of FRC in severe airway obstruction.

Question 19

What is the most common multiple breath washout (MBW) test in preschool-age children?

Answer 19

N2 washout with pure O2.

Question 20

What is a key quality control criterion for FRCg measurements?

Answer 20

At least 3 recordings should be within 25% of each other.

Question 21

How does FRC correlate in healthy children?

Answer 21

FRC correlates with height and weight.

Question 22

What conditions can lead to low FRC in infants?

Answer 22

• Surfactant deficiency
• Bronchopulmonary dysplasia (BPD)
• Chest wall conditions (e.g., muscular disease).

Question 23

What is a common mechanism underlying changes in FRC in children?

Answer 23

Airway obstruction.

Question 24

What does DLCO measure?

Answer 24

The rate at which oxygen is transferred from the lungs to the circulation.

Question 25

What factors can increase DLCO values?

Answer 25

* Increased pulmonary blood flow * Exercise * Increased hemoglobin levels.

Question 26

What can cause decreased DLCO values?

Answer 26

* Cigarette smoke * Uneven distribution of ventilation-perfusion * Pulmonary emboli.

Question 27

What is flow limitation during forced expiration?

Answer 27

Flow cannot increase further at low lung volumes even if transpulmonary pressure increases.

Question 28

What are the two techniques used to obtain flow-volume curves in infants?

Answer 28

* Rapid thoracoabdominal compression (RTC) * Raised volume RTC.

Question 29

What is the significance of measuring forced expiration?

Answer 29

It is the most frequently used lung function test in clinical practice.

Question 30

What is associated with the fall in expiratory flow until it stops on reaching the RV?

Answer 30

Increase in expired volume ## Footnote The increase in expired volume relates to lung mechanics and flow dynamics.

Question 31

What factors can narrow the airways leading to flow limitation?

Answer 31

* Inflammation * Mucus production * Bronchoconstriction * Airway wall remodeling ## Footnote These factors contribute to obstructive lung diseases.

Question 32

What happens to expiratory flow as expiratory volume increases?

Answer 32

Expiratory flow drops faster, the flow-volume diagram becomes concave, and lung emptying is delayed ## Footnote This reflects changes in lung mechanics.

Question 33

What is FEV1?

Answer 33

Volume expired in the 1st second ## Footnote FEV1 is a key measure in assessing lung function.

Question 34

What is the success rate of spirometry in children older than 6 years of age?

Answer 34

Above 85% ## Footnote Spirometry is the most common lung function test.

Question 35

What are the main outcome measures reported in older children for spirometry?

Answer 35

* FVC * FEV1 * FEV1/FVC * FEF25-75 ## Footnote These metrics help characterize lung function and flow limitation.

Question 36

What is the plateau phase of the flow-volume curve?

Answer 36

The phase during which the volume is not changing anymore with time ## Footnote Important for valid spirometry results.

Question 37

What indicates premature termination during spirometry?

Answer 37

Expiration stopped at a flow > 10% of the peak flow ## Footnote This is a common reason for unsuccessful tests in children.

Question 38

What is the most common clinical lung function test during infancy?

Answer 38

Flow-volume curve measurement ## Footnote This can be measured at both FRC and RV-RTC.

Question 39

What is Rapid Thoracoabdominal Compression (RTC)?

Answer 39

A technique to record a partial flow-volume curve ## Footnote RTC provides insights into lung function without the variable effects of lung inflation.

Question 40

How is flow limitation detected in infants?

Answer 40

With minimal influence of the nasal pathway ## Footnote This is crucial for accurate assessment of lung function.

Question 41

What characterizes obstructive lung disease in terms of flow-volume curve?

Answer 41

* Flow limitation appears at higher lung volumes * Normal or increased FVC * Decreased FEV1 * FEV1/FVC ratio below 80% ## Footnote These indicators help in diagnosing obstructive conditions.

Question 42

What is the significance of FEV1/FVC ratio?

Answer 42

More sensitive indicator of early lung disease than FEV1 alone ## Footnote It helps identify lung dysfunction before significant changes occur.

Question 43

What does FEF25-75 measure?

Answer 43

Small airway function ## Footnote It is a sensitive marker of early disease.

Question 44

What is the best method for measuring maximum or peak expiratory flow (PEF)?

Answer 44

Using a peak flow meter ## Footnote The child is instructed to take a big inspiration and blow out quickly.

Question 45

What spirometry measure indicates the need for lung transplant in cystic fibrosis?

Answer 45

FEV1 < 30% predicted ## Footnote It signifies severe lung function impairment.

Question 46

What is a positive bronchial hyperresponsiveness test?

Answer 46

A positive BDR showing improvement of ≥12% and/or 200 mL in FEV1 ## Footnote This supports the asthma diagnosis.

Question 47

What does respiratory resistance describe?

Answer 47

The relationship between pressure and flow ## Footnote It combines determinants of energy dissipation in the airways and respiratory tissues.

Question 48

What does compliance characterize in the respiratory system?

Answer 48

The ability of the tissues to expand in response to distending pressure ## Footnote It is crucial for understanding lung mechanics.

Question 49

What is the significance of the single-breath occlusion technique?

Answer 49

Estimates compliance of the respiratory system ## Footnote It involves occlusion pressure and recorded expired volume.

Question 50

What is interrupter resistance (Rint)?

Answer 50

Resistance measured during tidal breathing via short occlusions ## Footnote It is feasible in children but may underestimate airway resistance.

Question 51

What does the forced oscillation technique measure?

Answer 51

* Respiratory resistance (Rrs) * Reactance (Xrs) ## Footnote It provides insights into airway dynamics in health and disease.

Question 52

What is the limitation of the multiple breath washout technique?

Answer 52

Inconsistent methodology and time required for the test ## Footnote It affects its clinical potential.