Lung function tests

Question 1

what is peak expiratory flow?

Answer 1

maximal speed of airflow as the patient exhales in L/min

Question 2

what does (1) increase or (2) decrease in PEF value reveal

Answer 2

increase:

• lung function is better

decrease:

• lung function has gotten worse

Question 3

what is FVC (forced vital capacity)

Answer 3

maximal amount of air (L) that a patient can forcibly echale after taking in maximal inhalation

Question 4

what does a spirometer record and what can it generate

Answer 4

• records:volume of air that is breathed in and out
• generates: tracings of air flow called a pneumotachograph

Question 5

what 3 things can tracings on a pneumotachograph allow you to observe

Answer 5

• tidal volume
• vital capacity
• flow rate of air movement

Question 6

what is always bigger, FVCstanding or FVCseated

Answer 6

FVCstanding is always larger than FVseated

Question 7

what 2 things can high intrathoracic pressure result in and what can this lead to when observing FVCstanding of patients?

Answer 7

• reduced cardiac output
• reduced cerebral blood flow

can lead to patients becoming unsteady on their feet in FVCstanding patients

Question 8

outline 4 steps of how a spirometer works

Think:
1. water seal
2. Pressure and jar
3. Pen
4. Relationship to pen and volume breathed in and out

Answer 8

1. expired gas passes into water seal
2. increased pressure causes jar to rise
3. movement is then transmitted to a pen
4. pen movement is proportional to volume breathed in and out

Question 9

how is inspiration displayed as on a spirometer pen trace?

Answer 9

it is displayed as an upward deflection

Question 10

how is expiration displayed as on a spirometer pen trace?

Answer 10

it is displayed as an downward deflection

Question 11

how do you calculate inspiratory capacity from a spirogram?

Answer 11

Tidal volume (Vt) + Inspiratory reserve volume (IRV)

Question 12

how do you calculate functional residual capacity from a spirogram?

Answer 12

Expiratory reserve volume (ERV) + residual volume (RV)

Question 13

what 5 things can forced flow volume measurements show us (FVC and FEV1)

think:
- blowing out
- expelling air from lungs
- treatment
- diases
- age/growth

Answer 13

can show us:

• how much air can the subject blow out
• how fast the air is expelled from lungs
• response to treatment
• progression of disease
• change with age/growth

Question 14

what 2 things reduce how much air a subject can blow out in forced flow-volume measurements

For second part think narrowing and closure

Answer 14

• restrictive disorders
• airwary narrowing precipitating early airway closure (asthma or CF)

Question 15

what can a pattern change in flow-volume curve indicate?

Answer 15

can indicate site of obstruction

Question 16

1. what is FEV1 on spirogram

Answer 16

maximal volume exhaled in the first second

Question 17

what are the 3 typical patterns of Forced flow-volume measurements in obstructive airway diseases and give a reason for why

think FVC, FEV1 and FEV1/FVC ratio

for the reason think speed of air

Answer 17

• FVC nearly normal
• FEV1 markedly reduced
• FEV1/FVC ratio is less than 70%

1 reason why is that narrowed airways reduces the speed at which air can be breathed out

Question 18

what obstructive disease does it indicate someone has if there is improvement of a volume-time graph curve, towards the normal, after treatment with a bronchodilator?

Answer 18

it indicates the person has Asthma

Question 19

what obstructive disease does it indicate someone has if there is NO improvement on a volume-time graph curve after treatment with a bronchodilator?

Answer 19

it indicates the person has COPD

Question 20

what are the 3 typical patterns of Forced flow-volume measurements in restrictive airway diseases

think FVC, FEV1 and FEV1/FVC ratio

Answer 20

• low FVC
• low FEV1 but is proportionality to FVC is normal
• FEV1/FVC ratio is ≥ 70% (elevated)

Question 21

why is there low FVC in restrictive diseases like lung fibrosis?

Answer 21

because lungs are stiff so cannot expand adequately

Question 22

what does the width of a volume flow loop show?

Answer 22

• shows the vital capacity/forced vital capacity

Question 23

what does the rapid rise at the beginning of the expiratory portion of the flow volume loop show?

Answer 23

shows large airway movement

Question 24

what type of airway movement does the sloped section of the expiratory section of a flow-volume loop show?

Answer 24

shows small airway movement

Question 25

outline the differences in a flow volume loop between someone with an obstructive disease (e.g COPD, asthma, tracheal-stenosis) and a normal flow volume loop ## Footnote **hint: think**: - **expiration line** - think what does this look like if the **small airways** are **obstructed** - think waht this line looks like if the **large airways** are **obstructed**

Answer 25

**NORMAL** flow-volume loop: - relatively linear expiratory slope - normal/expected **steep rise in the inital portion of the expiration line** **OBSTRUCTIVE disease** flow-volume loop: - if **smaller/lower airways ** are obstructed, there is a **smaller angle** or ***caving in*** of the usually linear expiratory slope on the flow-volume loop - if **upper/large airways** are obstructed, initial portion of expiration line can also have **shorter** steep line.

Question 26

what is the physiological reason for why flow-volume loops are narrowed in restrictive lung diseases

Answer 26

- This is because the lungs suffering from restrictive diseases are not able to expand to the same **volume** as healthy lungs, meaning the **Vital capacity**/**Forced vital capacity** is reduced, thus narrowing the loop.

Question 26

outline the differences in a flow volume loop between someone with a restrictive disease (e.g lung fibrosis, interstitial lung disease) and a normal flow volume loop ## Footnote **hint:** - difference lies in the **width** of the flow volume loop

Answer 26

**NORMAL** flow-volume loop: - relatively linear expiratory slope - normal/expected **steep rise in the inital portion of the expiration line** - normal **width** of the flow-volume loop, meaning normal **VC/FVC** **RESTRICTIVE disease** flow-volume loop: - relatively linear expiratory slope - normal steep rise in initial portion of expiration line - **Difference is that there is low VC/FVC, therefore the width of the flow-volume loop is lower, narrowing the loop**

Question 27

what is the physiological reason for why flow-volume loops have a **shorter steep line** and/or **caved in** slopes in **obstructive diseases**?

Answer 27

this is because the **obstruction** to the upper and/or lower airways reduces the speed at which air in the airways can be breathed out.