Pulmonary
PFT Interpretation
Pulmonary

PFT Interpretation

FEV1/FVC + lung volumes + DLCO algorithm.

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◆Stepwise algorithm

  • •Step 1: FEV1/FVC ratio. ≤0.7 = obstructive; >0.7 = restrictive
  • •Step 2 (obstructive): ↑TLC + ↑RV (air trapping). Test reversibility with albuterol
  • •Reversible (↑FEV1 ≥12%) = asthma
  • •Not reversible: ↓DLCO = emphysema; normal DLCO = chronic bronchitis
  • •Step 2 (restrictive): ↓TLC + ↓RV. Check DLCO
  • •↓DLCO = intrinsic (pulmonary fibrosis)
  • •Normal DLCO = extrinsic (obesity, chest wall, NMD)

High-yield pearls

  • ◆Methacholine challenge: ↓FEV1 ≥20% confirms asthma when reversibility test equivocal
  • ◆Severe asthma exacerbation + rising PCO₂ in hypoxic patient = ominous, anticipate respiratory failure
Quick check

5-question quiz on this note

Test yourself before moving on. ~1 min.

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