eLFH - Lung Function Tests

Question 1

Lung function test examples

Answer 1

Peak expiratory flow rate

Spirometry

Diffusing capacity

Question 2

Types of spirometry

Answer 2

Benedict Roth Spirometer

Vitalograph trace

Flow volume curves

Question 3

Peak flow meter description

Answer 3

Telescopic tube with a piston that expands as gas is blown into it, with longitudinal gas escape slot

Best of 3 measurements are taken

Question 4

Conditions which have reduced PEFR

Answer 4

Obstructive lung conditions:
- Asthma
- COPD

Question 5

PEFR prediction tables description

Answer 5

Gives predicted PEFR based on height and gender

Needs correction for ethnic groups that are not Caucasian

Question 6

Predicted PEFR correction in Afro-Caribbean population

Answer 6

Reduce values by 13%

Question 7

Predicted PEFR correction in Asian population

Answer 7

Reduce values by 7%

Question 8

Limitations of predicted FVC and FEV1 values

Answer 8

Less established for patients aged 70 years and older

Question 9

Calculation for predicted FVC in females over 70 years old

Answer 9

FVC = (0.0443 x height in cm) - (0.026 x age) - 2.89

SD +/- 0.43 L

Question 10

Calculation for predicted FEV1 in females over 70 years old

Answer 10

FEV1 = (0.0395 x height in cm) - (0.025 x age) - 2.60

SD +/- 0.38 L

Question 11

Calculation for predicted FVC in males over 70 years old

Answer 11

FVC = (0.0576 x height in cm) - (0.026 x age) - 4.34

SD +/- 0.61 L

Question 12

Calculation for predicted FEV1 in males over 70 years old

Answer 12

FEV1 = (0.043 x height in cm) - (0.029 x age) - 2.49

SD +/- 0.51 L

Question 13

Benedict Roth Spirometer use

Answer 13

Measures static lung volumes

Measures Tidal volume and vital capacity

Can then calculate Inspiratory reserve volume and Expiratory reserve volume

Question 14

Method to measure functional residual capacity

Answer 14

Helium dilution

or

Body plethysmography

Question 15

Volumes which can be calculated from FRC + other spirometry

Answer 15

Residual volume

Total lung capacity

Question 16

Tidal volume definition and volume

Answer 16

Volume of air inspired and expired with each breath

6-8 ml/kg

Question 17

Inspiratory reserve volume definition

Answer 17

Additional volume of air that can be forcibly inhaled after normal tidal volume inspiration

Question 18

Expiratory reserve volume definition

Answer 18

Additional volume of air that can be forcibly exhaled after normal tidal volume expiration

Question 19

Vital capacity definition

Answer 19

Maximal volume of air that can be exhaled after maximal inspiration

VC = TV + IRV + ERV

Question 20

Residual volume definition

Answer 20

Volume of air remaining in lungs after maximal expiration

RV = FRC - ERV

Question 21

Functional residual capacity definition

Answer 21

Volume of air remaining in lungs at the end of normal expiration

FRC = RV + ERV

Question 22

Total lung capacity definition

Answer 22

Total volume of air in lungs after maximal inspiration

TLC = FRC + TV + IRV
or
TLC = VC + RV

Question 23

Spirometry volumes and capacities graph and which cannot be calculated from it

Answer 23

Residual volume (and therefore also FRC and TLC) cannot be calculated from graph as lungs cannot be fully emptied

Question 24

Vitalograph definition

Answer 24

Plots time on x axis against forces expiratory volume (FEV) on y axis

Question 25

FEV1 definition

Answer 25

Volume of air forcefully exhaled in first second Reduced in obstructive lung disease

Question 26

Forced vital capacity definition

Answer 26

Volume of air that can be forcefully exhaled after maximal inspiration Reduced in restrictive lung disease

Question 27

High risk factor for general anaesthesia from vitalograph

Answer 27

FEV1 < 1L

Question 28

Flow volume curve definition

Answer 28

Derived from pneumotachograph studies of whole respiratory cycle Air flow is plotted against lung volume during forced inspiration and forced expiration

Question 29

Normal flow volume curve

Answer 29

On expiration - rapid rise to maximal expiratory flow, followed by steady decline

Question 30

Flow volume curve in obstructive lung disease

Answer 30

Expiration flow rate is low, with rapid decline after maximal flow giving scooped out appearance

Question 31

Flow volume curve in restrictive lung disease

Answer 31

Maximal flow rate reduced

Question 32

Flow volume curve with variable extra-thoracic obstruction e.g. goitre

Answer 32

Inspiratory part of curve is flattened, but expiratory part is preserved

Question 33

Flow volume curve with variable intra-thoracic obstruction e.g. tracheomalacia

Answer 33

Expiratory part of curve is flattened but inspiratory part is preserved

Question 34

Flow volume curve with fixed extra-thoracic obstruction

Answer 34

Flattening of curve in both inspiration and expiration

Question 35

Abnormal spirometry results by each measurement definition

Answer 35

Below are all considered abnormal results: FEV1 < 80% predicted FVC < 80% predicted FEV1/FVC < 0.7

Question 36

Diagnosis of obstructive lung disease

Answer 36

FEV1 < 80% and FEV1/FVC < 0.7

Question 37

Differentiating between COPD and Asthma on spirometry

Answer 37

Reversibility with bronchodilators

Question 38

Diagnosis of restrictive lung disease on spirometry

Answer 38

FEV1 < 80% FVC < 80% FEV1/FVC > 0.7

Question 39

Spirometry findings obstructive vs restrictive lung disease

Answer 39

Question 40

Diffusing Capacity of Lung for Carbon Monoxide (DLCO) alternate name

Answer 40

Transfer factor

Question 41

Diffusing Capacity of Lung for Carbon Monoxide (DLCO) definition

Answer 41

Test of the integrity of the alveolar-capillary surface area for gas transfer

Question 42

Normal carbon monoxide transfer limiting factor

Answer 42

CO rapidly taken up by Hb in blood Therefore transfer of CO mainly limited by diffusion and used to measure gas transfer

Question 43

Conditions where DLCO is reduced

Answer 43

COPD Interstitial lung disease Multiple PEs Anaemia

Question 44

Normal partial pressure changes in pulmonary capillary blood for N2O, O2, and CO

Answer 44

N2O is perfusion limited CO is diffusion limited O2 can be perfusion limited or partially diffusion limited

Question 45

Pathogenesis of Cor pulmonale or P pulmonale

Answer 45

Lung disease results in hypoxic pulmonary vasoconstriction Pulmonary hypertension results in right heart failure