Spirometry and paediatric pulmonary-function testing — branching viva

Station opening

Examiner: "Tell me what spirometry measures and the three values you take from it." [1]

Strong candidate (must-hit)

• Explains that spirometry records a single maximal forced expiration and yields the forced vital capacity (the total volume exhaled), the forced expiratory volume in one second (the volume exhaled in the first second), and their ratio, which reflects how fast the lungs empty; adds that the effort is displayed as a flow-volume loop whose shape carries diagnostic information beyond the numbers. [1] [6]

Weak candidate

• "It measures how good the lungs are and gives you a percentage of normal." [2]

Branch A — Obstruction versus restriction

Examiner: "How do you tell an obstructive from a restrictive pattern?" [6]

Strong candidate (must-hit)

• States that the FEV1/FVC ratio decides it: below the lower limit of normal means obstruction, with a scooped expiratory loop; a normal or high ratio with a reduced FVC suggests restriction, with a small but normally shaped loop. Explains that obstruction empties slowly so the FEV1 falls more than the FVC, whereas restriction reduces both together and preserves the ratio. [6] [2]

Examiner: "You call a low FVC restrictive. Are you sure?" [9]

Strong candidate (must-hit)

• Corrects course: a low FVC only suggests restriction and is far more often submaximal effort, early termination or air trapping; true restriction requires a reduced total lung capacity measured by body plethysmography or gas dilution, which spirometry cannot measure. [9] [2]

Branch B — Bronchodilator response and asthma

Examiner: "The child has obstruction. How do you test reversibility and what counts as significant?" [2]

Strong candidate (must-hit)

• Describes giving an inhaled bronchodilator after baseline spirometry and repeating the test after ten to fifteen minutes; states that under the 2022 ATS/ERS standard a significant response is a rise in FEV1 or FVC greater than ten percent of the predicted value, and notes this replaces the older twelve-percent-from-baseline definition. Adds that reversibility supports asthma but a negative test does not exclude it. [2] [10]

Weak candidate

• "If it goes up at all after the puffer, that's asthma." [10]

Branch C — Deciding what is normal

Examiner: "How do you decide whether a value is abnormal?" [3]

Strong candidate (must-hit)

• Explains interpretation with the Global Lung Function Initiative 2012 equations, which convert a raw value into a z-score against healthy people of the same age, height, sex and ancestry, with the lower limit of normal at the fifth percentile (a z-score of about minus 1.64); rejects the fixed 0.70 ratio and the eighty-percent-predicted habit as adult shortcuts that misclassify children. [3] [2]

Branch D — Quality and safety

Examiner: "Before you interpret anything, what must be true, and when is testing unsafe?" [1]

Strong candidate (must-hit)

• States that the test must be acceptable (good hesitation-free start with a small back-extrapolated volume, no cough in the first second, no early termination or leak) and repeatable (the two largest FVC and FEV1 values agreeing within the accepted margin), and that an unacceptable test is repeated, not interpreted. Lists the contraindications (recent pneumothorax, recent thoracic, abdominal or eye surgery, active haemoptysis, an unstable state) and describes stopping for provoked bronchospasm, treating it as acute asthma. [1] [6]

Weak candidate

• "As long as the machine prints a number, you read it." [1]