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

~ 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

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

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?

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

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

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

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

Patient had vocal cord dysfunction www.uptodate.com

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?

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)

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

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

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?

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

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

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)

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

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

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?

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

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

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)

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