RT-04 · Analysis & Monitoring

Pulmonary Function Test Interpretation

How to sort obstructive from restrictive patterns, grade severity, and read the bronchodilator and diffusion results that follow.

~22 min read5 concept sections·8 questions with rationale

What you'll be able to do

  • Use the FEV1/FVC ratio to classify obstruction before looking at any other value
  • Confirm restriction with total lung capacity rather than FVC alone
  • Grade severity from percent-predicted FEV1
  • Interpret DLCO and bronchodilator response in context
Concept breakdown
01

The ratio comes first

FEV1/FVC separates the two major patterns. Everything after that is severity and cause.

  • FEV1/FVC below 70% (or below the lower limit of normal) defines obstruction.
  • A normal or elevated ratio with a reduced FVC suggests restriction — but FVC alone cannot confirm it.
  • Restriction is confirmed by a total lung capacity below 80% predicted, which requires body plethysmography or gas dilution, not simple spirometry.
  • A reduced ratio and a reduced TLC together indicate a mixed defect.
Practice quiz

Check yourself before you read the rationale.

Question 1 of 1

Pre-bronchodilator FEV1 is 2.40 L; post-bronchodilator FEV1 is 2.58 L. How is this response best classified?

Practice questions

Answer first, then read why the distractors fail.

Question 1

Pre-bronchodilator FEV1 is 2.40 L; post-bronchodilator FEV1 is 2.58 L. How is this response best classified?

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4 more concept sections, 7 more questions, and the exam-day playbook for this module.

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