Pulmonary function tests

Question 1

What pulmonary aspects are measured in pulmonary function tests

Answer 1

1. Airflow (also called Spirometry) 2. Lung Volumes 3. Gas Exchange (Diffusing Capacity) 4. Respiratory System Compliance 5. Airway Responsiveness 6. Respiratory Muscle Strength
2. Airflow (also called Spirometry) 2. Lung Volumes 3. Gas Exchange (Diffusing Capacity) 4. Respiratory System Compliance 5. Airway Responsiveness 6. Respiratory Muscle Strength

Question 2

1. Identify the three major components of routine pulmonary function tests and how they are measured

Answer 2

Lung volumes (spirogram), airflow (spirometry) and gas exchange.

Question 3

Obstructive diseases

Answer 3

asthma, COPD, bronchiolitis

Question 4

restrictive diseases

Answer 4

pulmonary edema, interstitial lung disease, neuromuscular weakness, pleural disease, obesity

Question 5

2. Identify components of and distinguish between volumes and capacities

Answer 5

volumes are single entities while capacities are composed of two or more volumes.

Question 6

3. Define the determinants of FRC (aka TGV)

Answer 6

functional residual capacity = residual volume + expiratory reserve volume

Question 7

tidal volume

Answer 7

This is the amount of gas volume moved during a normal inspiration

Question 8

Inspiratory reserve volume

Answer 8

This is the volume of gas that a subject can inhale above what they would normally inhale during a tidal breath. This requires maximum effort of the respiratory muscles.

Question 9

Expiratory reserve volume

Answer 9

This is the volume of gas from the end of a tidal breath that can be expelled by the subject. Requires active work of respiratory muscles

Question 10

Residual volume

Answer 10

This is the volume of gas retained in the lung even after a maximal exhalation

Question 11

Functional residual capcity

Answer 11

This capacity represents the sum of the RV and ERV and represents the amount of gas in the lung at the end of a normal exhalation. It is also the point at which the respiratory system is in equilibrium

Question 12

Inspiratory capacity

Answer 12

Inspiratory capacity. This is the sum of the tidal volume and Inspiratory reserve volume and represents the amount of gas that can be inhaled from Functional residual capcity. This requires maximum effort of the respiratory muscles to perform.

Question 13

vital capacity

Answer 13

Sum of expiratory reserve volume + tidal volume + inspiratory reserve volume. is the amount of gas that can be inhaled from the end of a maximum expiration (starting at RV) to the maximum inflation.

Question 14

Total lung capacity

Answer 14

. This represents the total of all 4 volumes of the lung. It is VC plus RV

Question 15

what does spirometry measure

Answer 15

pulmonary function

Question 16

Forced vital capacity

Answer 16

The FVC represents the total volume of gas (in liters) exhaled from total lung capacity down as far as possible. Should be the same as vital capacity.

Question 17

Forced expiratory volume

Answer 17

The FEV1 denotes the volume of gas (in liters) exhaled in the first second from total lung capacity. Most people exhale 70-80% of the VC in the first second

Question 18

FEV/FVC

Answer 18

This ratio compares the volume of gas expelled in the first second in relation to the total amount of gas exhaled. It normalizes lung mechanics for people with different lung volumes. Most people exhale 70 to 80% of air in the first second, making a normal ratio 0.7-0.8.

Question 19

4. Identify effort dependent and independent components to pulmonary function testing

Answer 19

effort dependent: expiratory reserve volume, inspiratory reserve volume, inspiratory capacity, vital capacity, total lung capcity. Effort independent: tidal volume (exhalation)

Question 20

5. Distinguish between obstructive and restrictive patterns on pulmonary function tests

Answer 20

Obstructive: reduced FEV/FVC ratio b/c it takes longer to expire. Restrictive: may have FEV1/FVC’s greater than 0.8 but airflows are not diagnostic of restrictive lung disease

Question 21

flow volume loops in obstructiv and restrictive diseases

Answer 21

Obstructive: increased lung volumes (curve shifts to left), airflow is decreased with coving of expiratory flow loop. Restrictive: curve is shifted to right (lower total lung capacity), max airflow is decreased b/c total volume of gas in lungs Is decreased.

Question 22

intrathoracic resistance

Answer 22

Within the thorax, the airway is held open during inspiration by negative pleural pressure. During forced expiration, however, positive pleural pressure surrounding the airway compresses it, reducing airway diameter. Consequently, intra-thoracic airway resistance is increased during expiration.

Question 23

extrathoracic resistance

Answer 23

extra-thoracic airways (namely the trachea above the clavicles) are subjected to atmospheric pressure that is transduced through the tissues of the neck to the exterior walls of the trachea. Thus, negative intraluminal pressure is generated in extra-thoracic airways during inspiration resulting in airway narrowing. During expiration, the intraluminal pressure becomes positive, making the airway diameter larger.

Question 24

Variable intrathoracic vs extrathoracic obstruction

Answer 24

Extrathoracic obstruction will be evident during inspiration (inspiration curve will be smaller), and intrathoracic obstruction will be evident during expiration (expiration curve will be smaller)

Question 25

Fixed obstruction pressure volume loop

Answer 25

Curve is flattened in both inspiration and expiration due to circumferential lesions such as tracheal stenosis from prior intubation or a circumferential airway neoplasm.

Question 26

Increased lung volumes are seen in what diseases? Decreased lung volumes are seen in what diseases?

Answer 26

increased lung volumes: obstructive diseases (air trapping b/c decreased ability to exhale). Decreased lung volumes: restrictive processes

Question 27

How are lung volumes measured? Which one is more accurate

Answer 27

Helium dilution (C1V1=C2(V1+V2)) and Body Plethysmography (P1V1= P2V2). Helium dilution requires uniform diffusion of gas in lungs, so if obstructive disease it may be innacurate and underestimate FRC.

Question 28

What is air trapping

Answer 28

residual volume is >140% but TLC and FRC are normal.

Question 29

6. Identify the 3 major factors contributing to DLCO

Answer 29

Diffusing capacity depends on surface area, membrane thickness, diffusion gradient of gas/presence of hemoglobin
Diffusing capacity depends on surface area, membrane thickness, diffusion gradient of gas/presence of hemoglobin

Question 30

How is DLCO measured

Answer 30

single breath of CO, held for 10 seconds, then exhaled. The amount of CO absorbed into blood depends solely on diffusing capcity.

Question 31

Causes of increased DLCO and decreased DLCO

Answer 31

increased (>120%):Things that increase blood in lung such as Polycythemia, Interstitial edema, Asthma and Alveolar hemorrhage. Decreased (120%):Things that increase blood in lung such as Polycythemia, Interstitial edema, Asthma and Alveolar hemorrhage. Decreased (<80%): emphysema, pulm vascular disease, interstitial lung disease, anemia, pulm edema or pneurmonia.

Question 32

How do you measure respiratory muscle strength

Answer 32

Pimax measures maximum inspiratory pressure (inspiration against closed valve) and Pemax measures max expiratory pressure (expiration against occluded airway)

Question 33

Causes of respiratory muscle weakness

Answer 33

neuropathies and myopathies (durgs, collagen vascular diseases, paraneoplastic syndromes)

Question 34

compliance and elastance

Answer 34

compliance is a measure of how easily the lung inflates (∆V/ ∆P). A more compliant lung means that it takes less pressure to increase the volume in the lung. Elastance is the reciprocal of compliance. Increased elastance means that it takes more pressure to get the same change in lung volume.

Question 35

8. Understand how pressure – volume curves are performed and assist in the interpretation of abnormal pulmonary function tests (specifically in emphysema, asthma, obesity and fibrotic lung disease).

Answer 35

. Patient exhales slowly from TLC (at left) and flow is interrupted at several points and pressure at the mouth (equivalent to alveolar pressure) is measured with no flow (i.e. static pressure).

Question 36

Pulmonary fibrosis pressure volume curve

Answer 36

Flat curve that is down shifted

Question 37

emphysema pressure volume curve

Answer 37

Steep curve, left and up shifted

Question 38

asthma pressure volume curve

Answer 38

Curve is similar in shape to normal, but slightly up shifted

Question 39

obesity pressure volume curve

Answer 39

curve is similar in shape ot normal, but slightly down shifted

Question 40

What is bronchoprovocation. What is a positive bronchodilator response

Answer 40

Bronchoprovocation tests stimulate bronchoconstriction. A significant response to bronchodilator is defined as >12% improvement in FEV1 or FVC and > 200cc increase in volume of FEV1 or FVC.

Question 41

Methacholine challenge

Answer 41

The patient inhales progressively higher concentrations of nebulized methacholine (or histamine), which stimulates bronchoconstriction in both healthy and asthmatic subjects. In asthmatics, the concentration required to reduce airflow by 20% (PC20) is several orders of magnitude lower than in healthy subjects. No bronchodilator is used

Question 42

Exercise induced bronchoprovocation

Answer 42

For people with exercise induced asthma, The patient performs spirometry before the test, and then exercises on a treadmill breathing cold air. Spirometry is performed at intervals post exercise to see if there is >20% decrease in FEV1.