Teaching Pearls:

• FEV1/FVC Ratio <0.7 suggestive of obstructive parenchymal disease
• DLCO – ability for gas to diffuse across alveolar capillary membrane.  CO (inhaled) – CO (exhaled). CO has a high affinity for Hb. If CO (exhaled) is higher than expected, DLCO is low and this is suggestive of diffusion problem.
  • False Positive
    • Anemia
    • Pulmonary hypertension
  • False Negative
    • Pulmonary hemorrhage
• Pulmonary Function Tests
  

  	FEV1	FVC	FEV1/FVC	DLCO	TLC	RV	F-V
  Emphysema	Decrease	Decrease/No change	<70%	Decrease	Normal/increase	Normal/increase	C
  Chronic Bronchitis	Decrease	Decrease/No change	<70%	Normal	Normal/increase	Normal/increase	C
  ILD	Normal/Decrease	Normal/Decrease	Normal/Increase	Decrease	Decrease	Decrease	A
  Tracheal stenosis	Decrease	Decrease/normal	Decrease	Normal	Normal	Normal	B
  Resp muscle weakness	Decrease	Decrease	Normal	Normal	Decrease	Increase	D

  A.  

  B.

• C.
• D.