3. Lung Function Tests + Common Lung Conditions

Question 1

What is an obstructive lung disease ?

Answer 1

Obstruction to airflow, especially on expiration

Question 2

What are some obstructive lung diseases ?

Answer 2

Asthma- over reactive constriction of bronchial smooth muscles, increases resistanceCOPD- chronic obstructive pulmonary disease- chronic bronchitis- inflammation of bronchi- emphysema- destruction of alveoli, loss of elasticity

Question 3

What is a restrictive lung disease ?

Answer 3

Restriction of lung expansionLoss of compliance

Question 4

What are some restrictive lung diseases ?

Answer 4

Fibrosis- formation of excess fibrous connective tissue that creates a stiff lung- idiopathic, 50:100,000 new cases per year UK- asbestosisInfant respiratory distress syndrome- insufficient surfactant productionoedema-fluid builds up around alveoli creating pressure which requires more force to inflatepneumothorax- air in the pleural cavity

Question 5

What is spirometry ?

Answer 5

Technique used to measure lung functionMeasurements can be static or dynamic

Question 6

What does static mean ?

Answer 6

Where the only consideration made is volume exhaled

Question 7

What does dynamic mean ?

Answer 7

Where the time taken to exhale a certain amount is what is being measured

Question 8

What can spirometry directly measure ?

Answer 8

Tidal volumeIRVERVInspiratory capacityVital capacity

Question 9

What is the FEV1 in a young healthy male ?

Answer 9

4L

Question 10

What is the FVC in a young, healthy male ?

Answer 10

5L

Question 11

What is the normal value of FEV1/FVC ?

Answer 11

80%

Question 12

What are the FEV and FVC for an obstructive respiratory disorder ?

Answer 12

Rate at which air is expelled is exhaled much slowerTotal expired volume (FVC) is also reduced (FRC may be increased)Major effect is on airways and so FEV1 is reduced to a greater extent than FVCRatio also reduced - 42%

Question 13

What are the FEV and FVC for an restrictive respiratory disorder ?

Answer 13

Absolute rate of airflow is reduced (FEV reduced)Total volume is reduced due to limitations to lung expansion (FVC)Ratio remains constant or can increase as a large proportion of volume can be exhaled in the first second

Question 14

What are the limitations of FEV1/FVC ?

Answer 14

Obstructive: both FEV and FVC fall but FEV more so. So ratio is reducedRestrictive: both FEV and FVC fall so ratio remains normal, or may even increase, despite severe compromise of functionTherefore normal FEV1/FVC ratio not always indicative of health

Question 15

What is a forced expiratory flow?

Answer 15

Average expired flow over the middle of a forced vital capacity