Lung Function Assessment

Question 1

A 58-year-old male patient has a normal FEV₁/FVC ratio but a reduced FVC on spirometry. What is the most likely interpretation and what additional finding would you expect?

A
Obstructive pattern — FEV₁ is disproportionately reduced relative to FVC, with a concave expiratory limb on flow volume loop

B
Normal pattern — a reduced FVC alone with normal ratio is within acceptable variation and requires no further investigation

C
Restrictive pattern — a normal FEV₁/FVC ratio with a low FVC indicates restriction, usually associated with a reduction in lung volumes

D
Mixed obstructive-restrictive pattern — FVC reduction with normal ratio indicates both air trapping and parenchymal disease simultaneously

Answer 1

C

Question 2

Why cannot FRC be estimated through spirometry alone, and which of the following methods would allow precise measurement of residual volume?

A
FRC cannot be measured by spirometry because the manoeuvre requires full inspiration from TLC; body plethysmography, nitrogen washout or helium dilution are required to measure RV precisely

B
FRC cannot be measured by spirometry because flow-volume loops only measure expiratory flow; inspiratory manometry is required to derive RV

C
FRC cannot be estimated by spirometry because it requires patient effort which introduces variability; only CT volumetry allows accurate measurement

D
FRC cannot be estimated by spirometry because it includes the residual volume which cannot be exhaled; techniques such as nitrogen washout, helium dilution, or body plethysmography are required

Answer 2

D

Question 3

During a forced expiratory manoeuvre in spirometry, what physiological mechanisms account for the progressive fall in flow rate after the initial peak?

A
Increasing elastic recoil as lung volume decreases, combined with progressive airway widening as transmural pressure increases

B
Dynamic airway compression due to high pleural pressure and lowering lung volume secondary to reduced elastic recoil causing progressive airways narrowing

C
Diaphragmatic fatigue reducing expiratory muscle force, combined with increased airway resistance from mucus accumulation at lower lung volumes

D
Collapse of large central airways due to loss of cartilaginous support, combined with increasing viscosity of airflow at low lung volumes

Answer 3

B

Question 4

A flow volume loop shows a concave expiratory limb with reduced expiratory flows but relatively preserved inspiratory flows. Which condition does this pattern most suggest, and why?

A
Emphysema — expiratory flows are suddenly attenuated due to loss of elastic recoil causing airway collapse during expiration

B
Diaphragm weakness — reduced inspiratory effort produces a flattened inspiratory loop with preserved expiratory mechanics

C
Extra-thoracic tracheal obstruction — fixed upper airway narrowing limits both inspiratory and expiratory flow equally, producing an oval loop

D
Early small airways obstruction such as asthma or chronic bronchitis — producing a concave expiratory limb with reduced flows at lower lung volumes

Answer 4

D

Question 5

What is the approximate volume of FRC in a 70kg average-sized male, and from which two lung volume components is it derived?

A
Approximately 3600ml — derived from the sum of inspiratory reserve volume (IRV) and tidal volume (VT)

B
Approximately 1200ml — derived from the residual volume (RV) alone, as ERV is negligible at end-passive expiration

C
Approximately 4800ml — derived from the sum of vital capacity (VC) and residual volume (RV), representing total lung capacity at rest

D
Approximately 2400ml — derived from the sum of expiratory reserve volume (ERV) and residual volume (RV)

Answer 5

D

Question 6

In which obstructive lung disease pattern does spirometry show a reduction in FEV₁ with relative preservation of FVC, and what does a low FEV₁/FVC ratio specifically indicate?

A
Restrictive pattern — a low FEV₁/FVC ratio indicates fibrotic lung disease with proportional reduction of both volumes

B
Obstructive pattern — a low FEV₁/FVC ratio indicates airway obstruction, as FEV₁ is disproportionately reduced relative to FVC

C
Mixed pattern — a low FEV₁/FVC ratio always indicates concurrent restriction and obstruction requiring further volumetric testing

D
Normal variant — a low FEV₁/FVC ratio within 2SD of predicted is acceptable and should not trigger further investigation

Answer 6

B

Question 7

How are abnormal spirometry values defined, and what patient-specific variables are used when calculating predicted values?

A
Abnormal values are defined as those more than 1SD below the predicted mean, calculated using weight, smoking history, and symptom duration

B
Abnormal values are those outside 2SD of the normal range, approximately a 15% reduction from predicted; predicted values are calculated using sex, height, age, and race

C
Abnormal values are defined as an absolute FEV₁ below 1.0L or FVC below 2.0L, with no adjustment for patient demographics

D
Abnormal values are defined as those outside 3SD of predicted — approximately 20% reduction; predicted values use sex, weight, and BMI

Answer 7

B

Question 8

A patient with a history of emphysema has a flow volume loop performed. Which finding most specifically distinguishes their loop from one showing early small airways obstruction?

A
In emphysema, both inspiratory and expiratory flows are markedly reduced and equal in magnitude, producing a symmetrical loop

B
In emphysema, expiratory flows are suddenly attenuated while inspiratory flows are relatively well preserved, contrasting with the concave expiratory limb seen in early small airways obstruction

C
In emphysema, the loop is oval in shape with plateau formation on both limbs, reflecting fixed large airway obstruction

D
In emphysema, the inspiratory limb is disproportionately reduced compared to expiratory flow, reflecting diaphragmatic involvement

Answer 8

B

Question 9

Why might a slow vital capacity manoeuvre yield a greater vital capacity than a forced manoeuvre in a patient with airway disease?

A
A slow manoeuvre allows greater diaphragmatic recruitment, increasing inspiratory capacity and therefore measured VC

B
A slow manoeuvre avoids activation of the Hering-Breuer reflex, which would otherwise terminate expiration prematurely during forced manoeuvres

C
A slow manoeuvre prevents dynamic airway compression that occurs during forced expiration, allowing more complete emptying of air from obstructed airways

D
A slow manoeuvre is more effort-independent and therefore less subject to patient cooperation bias, giving consistently higher values

Answer 9

C

Question 10

What does the PEFR ‘yellow zone’ represent, and what is the clinical implication for a patient performing daily readings who enters this zone?

A
Yellow zone represents 80–100% of normal PEFR, indicating the patient is well-controlled and no action is required

B
Yellow zone represents less than 50% of normal PEFR, indicating severe obstruction requiring emergency medical attention

C
Yellow zone represents 50–85% of normal PEFR, suggesting worsening airway obstruction and the need to follow action plans regarding GP or hospital contact

D
Yellow zone represents 85–95% of normal PEFR, indicating mild variability within normal diurnal variation requiring only monitoring

Answer 10

C

Question 11

Which statement most accurately describes the difference between restrictive and obstructive disease patterns in terms of lung volume changes?

A
Restrictive diseases cause reduced capacities overall, while obstructive diseases are characterised by reduced ERV and increased RV due to air trapping

B
Obstructive diseases reduce all lung capacities proportionally, while restrictive diseases selectively reduce RV with preservation of TLC

C
Restrictive diseases increase RV and reduce IRV, while obstructive diseases reduce TLC and increase ERV

D
Both obstructive and restrictive diseases reduce TLC, but only obstructive disease shows a concurrent increase in FRC

Answer 11

A

Question 12

When should pulmonary function tests generally not be ordered, and what clinical scenario illustrates the risk of confusing results even when tests are technically valid?

A
PFTs should not be ordered in patients under 18 or over 75; results are confounded in asthma because bronchospasm prevents reliable FVC measurement

B
PFTs are not generally indicated in asymptomatic patients; results may be confusing when non-pulmonary diseases affecting the pulmonary system are active, such as congestive heart failure

C
PFTs should not be ordered in smokers as nicotine artificially elevates FEV₁, leading to false-normal results; PEFR is preferred in this population

D
PFTs are not indicated following recent bronchodilator use; results from patients with obesity are unreliable due to diaphragmatic restriction inflating FVC

Answer 12

B