PFT Lab

Question 1

Indications for Spirometry/PFT

Answer 1

• 1. Evaluation of symptoms and signs of lung disease (e.g., dyspnea, cough, wheezing, cyanosis, hypoxemia, hypercapnia).
• 2. Monitoring disease course and response to therapy.
• 3. Risk evaluation of pre-operative patients in selected situations (e.g., thoracic or upper abdominal surgery).
• 4. Evaluation for adverse effects of occupational exposures (e.g., dusts or chemicals) or toxic effects of drugs (e.g., amiodarone or chemotherapeutic agents).

Question 2

Answer 2

Question 3

Answer 3

Question 4

Answer 4

Question 5

Lung Volumes

Answer 5

• Spirometry alone unable to determine some of the lung volumes

• Residual Volume (RV)
• Functional Residual Capacity (FRC)
• Total Lung Capacity (TLC)

• Require special techniques

• Body plethysmography
• Nitrogen washout
• Helium dilution

• Determine FRC and derive RV and TLC

Question 6

Answer 6

Question 7

LLN

Answer 7

• Normal values determined from studies of non-smoking healthy subjects (height, age, sex).
• Lower limit of normal (LLN) defined as value that identifies the lower 5th percentile of the healthy population.

Question 8

FEV1/FVC Ratio -What is the problem with using LLN = 70% for everyone?

Answer 8

• Underestimate disease in younger patients
• Overestimate disease in older patients

Question 9

Interpretation of Spirometry

Answer 9

• First step is to assess the FEV1/FVC ratio.

• Is the pattern obstructive?
• If the FEV1/FVC ratio is less than the LLN, obstruction is present.
• If the FEV1/FVC ratio is within the normal range, the test is normal or restriction is present.
• Next step is to examine the FVC. If the FVC is less than the LLN, a restrictive defect is present.