Spirometry 2

Question 1

Spirometry Definitions 1

–> FEV1

Answer 1

FEV1 -> The maximum volume of gas which can be expired from the lungs in the first second of a forced expiration, from a position of full inspiration, measured in litres

Question 2

Spirometry Definitions 1

–> FVC

Answer 2

FVC -> The maximum volume of gas which can be expired from the lungs during a forced and complete exhalation, from a position of full inspiration measured in L

Question 3

FEV1/FVC Ratio %

Answer 3

Amount of air blown out in the first second during a forced attempt, expressed as a percentage of the total amount expired during a forced manoeuvre

Question 4

VC (EVC and IVC)

Answer 4

EVC - The maximum volume of gas which can be expired from the lungs during a relaxed but complete expiration from a position of full inspiration (TLC), measured in litres

IVC - The Maximum volume of gas which can be inspired into the lungs during a relaxed but complete inhalation from a position of full expiration (RV), measured in litres

Question 5

FEv1/VC ratio

Answer 5

Amount of air blown out in the first second during a forced manoeuvre, expressed as a percentage of the total amount expired during a relaxed vital capacity

Question 6

MEF 75

Answer 6

The maximum flow achievable during a forced manoeuvre when 25% of the FVC has been exhaled ( such as when 75% of FVC remains within the lungs, measured in litres per second)

Question 7

MEF 50

Answer 7

The maximum flow achievable during a forced manoeuvre when 50% of the FVC has been exhaled ( such as when 50% of FVC remains within the lungs, measured in litres per second)

Question 8

MEF 25

Answer 8

The maximum flow achievable during a forced manoeuvre when 75% of the FVC has been exhaled ( such as when 25% of FVC remains within the lungs, measured in litres per second)

Question 9

ATPS/BTPS

Answer 9

Ambient Temperature and Pressure Saturated Body Temperature and Pressure Saturated.

Question 10

Determination of Ambient Conditions

Answer 10

• Manual VS Automated Equipment
• Calculation of Correction Factors
• Met Office

Question 11

Why do we need to correct to BTPS?

Answer 11

• Not correcting a gas volume to BTPS can add up to a 10% error in the measurement of FEV1
• Exhaled air usually warmer than ambient air
• Spirometers usually measure volumes at room temperature
• Standardisation
• Repeat testing values not influenced by lab environment
  Reference values quoted at BTPS
• Need to look at the Gas Laws to look at effects of temperature and pressure on the volume of a measured gas

Question 12

Boyles Law:

Answer 12

• The volume of a gas is inversely proportional to the pressure (at a constant temperature)

Question 13

Charles Law:

Answer 13

• At a constant pressure, the volume of gas is directly proportional to it’s absolute temperature

Question 14

Selection of Spirometry Test Results:

Answer 14

• Technically Acceptable
• Meet Repeatability Criteria
• The best FEV1 and FVC are reported, irrespective of which manoeuvre they occurred
• FEV1/FVC ratio is calculated based on the best reported FEV1 and FVC
• Largest VC is reported
• Technical comments added to report

Question 15

Summary/Key Points:

Answer 15

• Spirometry results can be graphically displayed as FV and/or VT traces
• You can draw and label a normal flow-volume loop and define the measured parameters
• Measured gas values should be corrected to BTPS
• Spirometry tests should be technically acceptable and reproducible
• The best FEV1 and FVC should be reported irrespective of which blow they came from