1. Division of Pulmonary, Critical Care and Sleep Medicine
ABIM IM Board Review Pulmonary Physiology and Pulmonary Function Testing
Adam G. Cole, MD
Division of Pulmonary, Critical Care and Sleep Medicine

2. ~ 8-12 questions where pulmonary physiology knowledge is needed
Possibly more, harder to say. Out of approximately 20 pulmonary questions, probably a fair estimate that ½ of them will require at least some knowledge of clinical pulmonary physiology
~ 8-12 questions where pulmonary physiology knowledge is needed

3. Pulmonary Function Testing – Clinical Utility
Define airflow obstruction
Clues to many other pathologic states
Restrictive diseases
Diffusion impairments
Asthma, COPD, bronchiectasis, small airways diseases such as bronchiolitis (which can be from multiple etiologies)
Restricitve disease (DPLDs, neuromuscular diseases) and reduced DLCO in emphysema, fibrotic ILDs and pulmonary vascular disease

4. Spirometry How much gas can you forcefully exhale?
Forced Vital Capacity (FVC)
How quickly can you blow most of it out?
Forced Expiratory Volume in 1 second (FEV1)
Our most robust test in the PFT lab and the one you will probably see the most on the exam
Basically: How much can you blow out, and How fast?

5. If you remember one thing…..
FEV1/FVC ratio <70% = Airflow obstruction
For the test: most pulmonologists read by ATS/ERS standards which characterizes airflow obstruction by FEV1/FVC ratio as <LLN

7. Flow volume loop and volume time curve; graphic representation of spirometry

8. 22yoF cc severe dyspnea and wheezing
22yoF cc severe dyspnea and wheezing. Spirometry shows FEV1/FVC ratio of 0.8, FEV1 of 95% predicted and FVC of 101% predicted. There is no significant response to bronchodilator. Previous methacholine challenge testing was negative. Her flow volume loop is shown in the red (normal on right for comparison):
ATS/ERS Task Force: Standardisation of spirometry. Eur Respir J. 2005

9. What is the next best step in management?
Start inhaled corticosteroid
Prescribe albuterol as needed
Referral for laryngoscopy
HRCT chest
C: Referral for laryngoscopy for vocal cord dysfx

10. Patient had vocal cord dysfunction

11. What is the next best step in management?
46yoM non-smoker p/w inc’d cough, wheezing and mild dyspnea. These symptoms have been worsening, and are exacerbated by cold air and exercise. Spirometry shows a FEV1/FVC ratio of 0.81, FEV1 of 4.11L (95% predicted) and FVC of 5.05L (92% predicted). Post bronchodilator spirometry shows FEV1/FVC ratio of 0.81, FEV1 of 4.25L (99%) and FVC of 5.22L (95%).
What is the next best step in management?

12. What is the next best step in management?
Obtain methacholine challenge test
Start Inhaled corticosteroid
Start albuterol prn
HRCT chest
Prednisone burst
A: Obtain methacholine challenge test (?exercise-induced asthma)

13. Bronchodilator Challenge
≥ 12% ↑ FEV1 or FVC AND ≥ 200 mL ↑ |FEV1| or FVC
Wait 10 minutes between FVC efforts
A significant bronchodilator response in the proper clinical context can be evidence for asthma

14. Methacholine Challenge
Useful for evaluation for asthma in the setting of normal spirometry without response to bronchodilator
Positive test consistent w/ asthma
Negative test rules it out
Positive test: FEV1 ↓ ≥20% with challenge
Sequential challenges of increasing concentrations of methacholine, a cholinergic agent that directly stimulates bronchial smooth muscle to constrict
Need to know: why it’s ordered and what a positive test is

15. 67yoM cc DOE progressive over the past several years and now he can only walk short distances on flat ground. He has a dry cough, denies chest pain and wheezing. PE: bibasilar velcro rales, mild clubbing. Spirometry shows FEV1/FVC ratio of 0.75, FEV1 of 1.75 L (62% predicted) and FVC of 2.5L (65% predicted). Plethysmography shows a Total Lung Capacity of 62% predicted. What is the most appropriate next test?

16. What is the most appropriate next test?
Bronchoscopy with BAL (bronchoalveolar lavage)
Right heart catheterization
HRCT chest
Methacholine challenge test ?

17. Lung Volumes Body Plethysmography (Body Box) Nitrogen washout
Helium dilution
Radiographic
Don’t need to focus on the technical details of each of these, not relevant for the test
Plethysmography is really the best method and the only one you really need to know; in reality you’re just going to be given the numbers on the IM board exam

19. The Numbers…. TLC < 80% = Restrictive defect
TLC >120% = Hyperinflation
RV > 120% = Air Trapping
ATS/ERS criteria again would be TLC < LLN for restrictive defect but for the purposes of the test, remember < 80%. It shouldn’t be subtle…
80% is the second most important number to remember (anything less than 80% predicted, consider it abnormal)

20. Clinical Correlation TLC < 80% = Restrictive defect Fibrotic ILDs
NRO-MSK dz (ALS)
Pleural disease
Chest wall disorders
Obesity
IPF
ALS
Usually effusions
Kyphoscoliosis, scerloderma

21. Clinical Correlation TLC >120% = Hyperinflation
Obstructive diseases
RV > 120% = Air Trapping
COPD and asthma for test purposes
120% is the third most important number to remember

22. 36yoF cc DOE progressively worsening over 2 years
36yoF cc DOE progressively worsening over 2 years. She was previously active and liked to run, but now she can only walk short distances on flat ground. She denies any cough or wheezing or chest pain. She occasionally feels lightheaded with exertion. HRCT of the chest shows unremarkable lung parenchyma. Spirometry shows FEV1/FVC ratio of 0.86, FEV1 3.13L (98% predicted) and FVC 3.66L (99% predicted). Plethysmography shows a TLC of 104% predicted. Diffusing capacity (corrected for Hb) is 56% predicted. What is the next best step in management?

23. What is the next best step in management?
Methacholine challenge
Bronchoscopy with transbronchial lung biopsy
Transthoracic echocardiogram
Empiric trial of bronchodilators ?

24. Diffusing Capacity Measures ability of lung to take up oxygen
Difficult to directly measure for oxygen, but we can easily measure CO diffusion in the LAB
Don’t worry about technical aspects

25. Diffusing Capacity – What to know…
DLCO < 80% predicted = low
Usually corrected for Hb in questions because anemia reduces DLCO
Because anemia reduces diffusing capacity (less vehicles available for pick up)

26. Clinical Correlation Emphysema Fibrotic ILDs
Reasons for low corrected DLCO:
Emphysema
Fibrotic ILDs
Pulmonary vascular disease
Pulm HTN
The isolated reduced diffusing capacity is a good question for initiating the workup for pulmonary hypertension