3.20 - Spirometry Graphics

Question 1

What are the axes on a flow-volume loop?

Answer 1

Y-axis = flow (L/s); X-axis = volume (L)

Flow vs volume shows both inspiration and expiration patterns.

Question 2

What does PEF represent on a flow-volume loop?

Answer 2

Peak Expiratory Flow – the highest flow reached during a forced exhalation

Shows how quickly air leaves the lungs at the start of the maneuver.

Question 3

Define FEF 25%, FEF 50%, and FEF 75%.

Answer 3

• Flow rates measured when 25% of FVC exhaled
• Flow rates measured when 50% of FVC exhaled
• Flow rates measured when 75% of FVC exhaled

They reflect flow in the mid-to-small airways and indicate airway resistance.

Question 4

What does FVC stand for and what does it represent on an FVL?

Answer 4

Forced Vital Capacity – the total volume exhaled forcefully after full inspiration

It’s the width of the loop along the X-axis.

Question 5

Why can’t FEV₁ be precisely placed on a flow-volume loop?

Answer 5

Because FEV₁ is a time-based value (volume exhaled in 1 second)

The loop shows flow vs volume, not time.

Question 6

How do you identify inspiration and expiration on an FVL?

Answer 6

The upper (positive) curve = expiration; the lower (negative) curve = inspiration

This distinction helps in analyzing lung function.

Question 7

What shape indicates normal expiratory flow on an FVL?

Answer 7

A sharp rise to PEF followed by a linear or slightly concave decline

Smooth = healthy; “scooped-out” = obstructive.

Question 8

Fill-in-the-blank: “Peak up, _____ slows down.” → What concept does this describe?

Answer 8

Flow slows down

As the lungs empty, flow decreases due to less recoil and higher airway resistance.

Question 9

What are the axes on a volume-time graph?

Answer 9

Y-axis = volume (L); X-axis = time (seconds)

This graph is essential for assessing lung function over time.

Question 10

What does the steep initial rise on the expiration curve indicate?

Answer 10

Rapid early exhalation → good patient effort and high PEF

Indicates effective lung function.

Question 11

What does FEV₁ represent on this graph?

Answer 11

The volume exhaled in the first second of a forced exhalation

Key for detecting obstruction.

Question 12

What does the plateau on the volume-time graph indicate?

Answer 12

The point where no more air can be exhaled → FVC reached

A missing plateau = incomplete exhalation or poor effort.

Question 13

Fill-in-the-blank: The steeper the rise, the better the ______.

Answer 13

Effort

Steep rise = quick emptying of lungs.

Question 14

What does it mean to superimpose flow-volume loops?

Answer 14

Plot multiple loops (predicted, pre-, and post-bronchodilator) on one graph

To compare performance and reversibility.

Question 15

What does improvement in the post-bronchodilator loop suggest?

Answer 15

Reversible obstruction, as seen in asthma

Airways open better after medication.

Question 16

If there’s little or no change between pre- and post-bronchodilator loops, what does it suggest?

Answer 16

A fixed obstruction such as COPD

Where airways don’t respond to bronchodilators.

Question 17

Fill-in-the-blank: “Shift up = ______ up.” → What does this phrase help you remember?

Answer 17

opens up

The bronchodilator helped open airways.

Question 18

What does a normal expiratory limb look like on a flow-volume loop?

Answer 18

It decreases in a linear or slightly concave fashion after a sharp rise to PEF.

Question 19

After the first 25% of exhalation, what primarily determines airflow?

Answer 19

Airway resistance and elastic recoil (not effort).

Question 20

Before 25% → effort dependent; after 25% → ______ dependent.

Answer 20

Effort-independent (depends on airway mechanics, not muscle effort).

Question 21

Why do obstructive and restrictive diseases produce different FVL shapes?

Answer 21

Because they alter resistance and elastic recoil differently — obstruction changes flow rates; restriction reduces volumes.

Question 22

What is the expected relationship between FEF₅₀% and FIF₅₀% in a normal test?

Answer 22

They should be about equal, or expiratory flow is slightly less than inspiratory.

Question 23

What does the ratio FEF₅₀% / FIF₅₀% ≈ 1 indicate?

Answer 23

Normal airway function and good test quality.

Question 24

What can a large difference between FEF₅₀% and FIF₅₀% suggest?

Answer 24

A large-airway obstruction (fixed or variable).

Question 25

MEF₅₀ = ____________________

Answer 25

Maximum expiratory flow at 50% of the maneuver (same as FEF₅₀%).

Question 26

How can comparing inspiratory and expiratory flows help assess test quality?

Answer 26

If the loops are close and consistent, the test is likely technically sound.

Question 27

Why are flow-volume and volume-time graphs useful during testing?

Answer 27

They help spot errors quickly while the patient is still performing the test.

Question 28

How can using graphics save time in spirometry testing?

Answer 28

By identifying poor efforts or errors early, avoiding the need to re-check all values.

Question 29

What does “walk through the maneuver” mean?

Answer 29

Step-by-step comparison of what you expect to see vs. what actually appears on the graph.

Question 30

What are the six visual checkpoints when “walking through the maneuver”?

Answer 30

1. Rapid rise to PEF with no hesitation 2. Sharp PEF 3. Linear/slightly concave decline 4. Flow returns to zero 5. Flow at 50% insp ≈ 50% exp 6. FIVC ≈ FVC

Question 31

What does a missing sharp PEF or hesitation at the start indicate?

Answer 31

Poor effort or delayed start.

Question 32

What does a “scooped-out” expiratory limb suggest?

Answer 32

Obstruction (commonly COPD).

Question 33

If FIVC < FVC, it may suggest ____________.

Answer 33

Inconsistent effort or leak during inspiration.

Question 34

Why is comparing inspiratory and expiratory flows important during the walkthrough?

Answer 34

Major differences can reveal variable or fixed airway obstruction.

Question 35

What does a poor initial blast look like on a curve? How can we fix it via coaching?

Answer 35

- Rounded or flat peak - Coach --> Blast air out ***HARDER***

Question 36

What does a chart look like when a Pt hesitates, starts slow, or has large extrapolated volume? What can we do via coaching?

Answer 36

- Peak shifts to right - Coaching --> Blast Faster!

Question 37

What does a chart look like when no plateau before 15 sec? How can we fix this with coaching?

Answer 37

- Answer in the pic - Coaching --> Keep blowing until told to stop

Question 38

What does a chart look like if there is glottic closure or breath is holding? How can we fix it via coaching?

Answer 38

- Drops straight down! - Coach --> Initial big blast, then relax and keep blowing

Question 39

What does the chart look like if there is a leak? How can it be corrected via coaching?

Answer 39

- Curve moves backwards - Coach --> Check equipment + Connections

Question 40

What does the graph look like when partially blocked mouthpiece? How can we fix it via coaching?

Answer 40

- Curve has smaller peak and it wobbles a lot. - Coach --> Position mouthpiece between the teeth and top of the tongue + secure dentures

Question 41

Why are flow-volume loops more useful than volume-time graphs for identifying disease?

Answer 41

Because they visually show changes in flow patterns and shape, helping distinguish between obstructive and restrictive diseases.

Question 42

What do deviations from a normal loop pattern generally indicate?

Answer 42

Disease-related changes in volume or flow.

Question 43

Changes from normal FVL appearance may be ________.

Answer 43

Disease-related.

Question 44

What happens to FVL shape and size in restrictive disease?

Answer 44

Shape is normal, but smaller and narrower due to reduced volume.

Question 45

Why does restriction reduce lung volume?

Answer 45

Due to decreased lung compliance or limited expansion.

Question 46

Restrictive → small loop with ______ contour.

Answer 46

Normal contour.

Question 47

What are examples of restrictive diseases?

Answer 47

Pulmonary fibrosis, scoliosis, neuromuscular weakness, obesity.

Question 48

What does a “shoulder” or “knee” on a normal FVL mean?

Answer 48

A slight bend near PEF — normal variation seen in adolescents/young adults.

Question 49

Does a “shoulder” or “knee” indicate disease?

Answer 49

No, it’s a benign finding.

Question 50

lower airway obstruction

Answer 50

Diseases affecting small distal airways, like COPD and asthma.

Question 51

upper or large airway obstructions

Answer 51

Tracheal stenosis, vocal cord dysfunction, laryngeal obstruction.

Question 52

Upper = ________; Lower = ________.

Answer 52

- Upper = major airways (trachea, vocal cords) - Lower = small distal airways (bronchioles).

Question 53

What type of airways are affected in large airway obstruction?

Answer 53

Trachea, mainstem bronchi, or vocal cords.

Question 54

What is the difference between fixed and variable airway obstructions?

Answer 54

- Fixed: affects both inspiration and expiration - Variable: affects only one phase.

Question 55

Fixed = flow ↓ in _______ phases; Variable = flow ↓ in _______ phase.

Answer 55

Fixed = both; Variable = one (either inspiration or expiration).

Question 56

What happens in a variable extrathoracic obstruction?

Answer 56

Airway narrows on inspiration and dilates on expiration (pulled in by negative pressure).

Question 57

What happens in a variable intrathoracic obstruction?

Answer 57

Airway dilates on inspiration and narrows on expiration (pushed in by positive pressure).

Question 58

Fixed obstruction → airways narrow during _______ and _______.

Answer 58

Inspiration and expiration.

Question 59

Mnemonic to remember extrathoracic vs intrathoracic effects?

Answer 59

“Extra = Inspiration problem; Intra = Expiration problem.”

Question 61

What is this?

Answer 61

- Variable extrathoracic

Question 62

What is this?

Answer 62

- Variable Intrathoracic

Question 63

What is this?

Answer 63

- Fixed obstruction

Question 64

In a variable extrathoracic obstruction, which phase is affected and why?

Answer 64

Inspiration, because negative pressure pulls the airway inward → flattened inspiratory limb.

Question 65

In a variable intrathoracic obstruction, which phase is affected and why?

Answer 65

Expiration, because positive pressure during exhalation compresses intrathoracic airways → flattened expiratory limb.

Question 66

What does a fixed obstruction look like on an FVL?

Answer 66

Both inspiratory and expiratory limbs are flat (box-shaped or biphasic).

Question 67

Extra = ________ problem; Intra = ________ problem; Fixed = ________.

Answer 67

Inspiration; Expiration; Both.

Question 68

What does comparing FEF₅₀% / FIF₅₀% tell you?

Answer 68

Whether obstruction is fixed or variable (and which phase is affected).

Question 69

Normal FEF₅₀ / FIF₅₀ ratio ≈ ?

Answer 69

1.0 or slightly < 1.0.

Question 70

Ratio > 1.0 → likely ________ obstruction; Ratio < 1.0 → likely ________ obstruction.

Answer 70

Extrathoracic ; Intrathoracic.

Question 71

Flat inspiratory limb + normal expiratory limb = what pattern?

Answer 71

Variable extrathoracic obstruction.

Question 72

Flat expiratory limb + normal inspiratory limb = what pattern?

Answer 72

Variable intrathoracic obstruction.

Question 73

Flat both sides = ________ obstruction.

Answer 73

Fixed obstruction.

Question 74

In this diagram, flattened inspiration = ________; flattened expiration

Answer 74

Variable extrathoracic ; Variable intrathoracic. ## Footnote Upper airway

Question 75

What does a lower airway obstruction look like?

Answer 75

Question 76

What shape does a fixed obstruction loop have?

Answer 76

Box-shaped with plateaus on both inspiration and expiration.

Question 77

Fixed obstruction= what?

Answer 77

Biphasic.

Question 78

What breath sound is heard in variable extrathoracic obstruction?

Answer 78

Inspiratory stridor.

Question 79

What sound is heard in variable intrathoracic obstruction?

Answer 79

Expiratory wheezing.

Question 80

What sound is heard in fixed obstruction?

Answer 80

Biphasic (stridor on both inspiration and expiration).

Question 81

Vocal cord paralysis = ________; Tracheomalacia = ________; Post-intubation stenosis = ________.

Answer 81

Variable extrathoracic; Variable intrathoracic; Fixed.

Question 82

What does “malacia” mean in tracheomalacia?

Answer 82

Weakening or softening of tracheal cartilage, causing collapse during exhalation.