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GENERAL MEDICINE CONFERENCE Interpreting pulmonary function tests Selim Krim, MD Assistant Professor Texas Tech University Health Sciences Center Objectives Be familiar with the indications for pulmonary function tests (PFT’s) Use a stepwise approach when interpreting PFT’s Know how to differentiate obstructive from restrictive pattern Be familiar with common etiologies of obstructive and restrictive diseases Know how to distinguish a mixed pattern from air trapping Know how to distinguish parenchymal from extra parenchymal causes of restrictive diseases Indications for PFT’s To evaluate symptoms and signs of lung disease (eg, cough, dyspnea, cyanosis, wheezing, hyperinflation, hypoxemia, hypercapnia) To assess the progression of lung disease To monitor the effectiveness of therapy To evaluate preoperative patients in selected situations To screen people at risk of pulmonary disease such as smokers or people with occupational exposure to toxic substances in occupational surveys. To monitor for the potentially toxic effects of certain drugs or chemicals (eg, amiodarone, beryllium) Lung volumes and capacities Flow-volume and flow-time loops Obstructive disease Decreased FEV1/FVC ratio (usually<70%) Asthma COPD ( Chronic bronchitis, emphysema) Response to bronchodilator therapy is defined by an increase of >12% in FEV1 Staging of obstruction I: Mild FEV1≥ 80% predicted II: Moderate 50%≤FEV1<80% predicted III: Severe 30%≤FEV1<50% predicted IV: Very severe FEV1 <30% predicted or FEV1 <50% predicted plus chronic respiratory failure Restrictive disease FEV1/FVC normal, FEV1 is decreased or normal, FVC is decreased, TLC decreased Intrinsic lung diseases, which cause inflammation or scarring of the lung tissue (interstitial lung disease) or fill the airspaces with exudates or debris (acute pneumonitis). Extrinsic disorders, such as disorders of the chest wall or the pleura, which mechanically compress the lungs or limit their expansion. Neuromuscular disorders, which decrease the ability of the respiratory muscles to inflate and deflate the lungs. Parenchymal vs. extra parenchymal causes of restriction Parenchymal Extraparenchymal TLC Decreased Decreased DLCO (corrected) Decreased Normal Mixed pattern vs. air trapping Mixed pattern Air trapping FVC Low Low TLC Low Normal or increased Pseudorestriction or air trapping Obstructive vs. restrictive Stepwise Approach to PFT’s Case 1 A 51-year-old woman presents for evaluation of shortness of breath, cough, and wheezing especially in the summer. Her symptoms are relieved with albuterol, salmeterol, and fluticasone inhalers. She does not smoke. Her PFT’s are as follow; FVC=83%, FEV1=63%, FEV1/FVC=58.2%. After bronchodilator therapy her FVC increases by 12%, FEV1 by 34%, and FEV1/FVC ratio by 29%. Which of the following patterns is present? A- Obstructive pattern without response to bronchodilators B- Restrictive pattern C- Obstructive pattern with response to bronchodilators What is the severity of this patient’s defect? 1- Mild 2- Moderate 3- Severe Case 2 A 68-year-old woman presents for evaluation of shortness of breath without cough or wheezing. She has systemic lupus erythematosus (for which she takes prednisone and methotrexate) and hypertension (for which she takes metoprolol and hydrochlorothiazide). Her oxygen saturation is 94% by pulse oximetry while breathing room air. Her hemoglobin concentration is 12.3 g/dL. FVC=60%, FEV1=70%, FEV1/FVC=88.6%, RV=38%, TLC=53%, DLCO=38%. Which of the following best describes the pattern seen on this patient’s pulmonary function tests? A- Obstructive pattern with suspicion of emphysema B- Restrictive pattern C- Obstructive pattern without emphysema D- Normal spirometry Case 3 A 68-year-old woman presents for evaluation of progressive shortness of breath. She describes 18 months of gradually increasing dyspnea on exertion. She has not noted any prominent cough, wheezing, chest pain, lightheadedness, or edema. Her review of systems is positive only for cold fingers and mild joint pains. She has never smoked and has no other medical history. Her only medication is hormone replacement therapy. Her FVC=96%, FEV1=101%, FEV1/FVC=81.7%, TLC=83%, DLCO=43%, Adjusted DLCO=59%. Which of the following are potential causes of this pattern? A- Anemia B- Pulmonary arterial hypertension C- Chronic thromboembolic disease D- Obesity E- All of the above Case 4 A 45-year-old man is evaluated for mild dyspnea on exertion. He has smoked 1.5 packs of cigarettes a day for 30 years. His personal and family medical history is unremarkable. On physical examination, the chest is clear; cardiac examination and chest radiograph are normal. Spirometry shows the FEV1 of 70%, FVC of 75%, FEV1/FVC of 68%. After administration of a bronchodilator, the FEV1 rises to 80% and the FVC to 85%; the FEV1/FVC ratio is 75%. The serum IgE concentration is normal, and there are no eosinophils on the peripheral blood smear. Which of the following is the most likely diagnosis? A- Chronic obstructive pulmonary disease, stage 0 B- Chronic obstructive pulmonary disease, stage 1 C- Chronic obstructive pulmonary disease, stage 2 D- Moderate persistent asthma E- Restrictive lung disease Case 5 A 64-year-old woman is evaluated for a 9-month history of progressive exertional dyspnea and nonproductive cough. She is an ex-smoker with a 30pack-year history. She has no constitutional symptoms or environmental exposures. There is no history of cardiovascular disease. She was recently treated with several courses of oral antibiotics for “bronchitis.” On physical examination, no exanthem or joint abnormalities are apparent. Cardiac examination is normal. Bibasilar, coarse mid to end-inspiratory crackles are noted. Chest radiograph shows increased bibasilar reticular markings in the periphery that were not evident 3 years ago. Pulmonary physiology shows a decreased total lung capacity (TLC), force vital capacity (FVC), and forced expiratory volume in 1 sec (FEV1), an increased FEV1/FVC ratio, and a decreased diffusing capacity for carbon monoxide (DLCO). Which of the following tests is most likely to provide specific diagnostic and prognostic information? A- Measurement of antinuclear antibodies and rheumatoid factor B- Timed walk test with oximetry (6-minute walk test) C- High-resolution computed tomographic scan (HRCT) D- Gallium scan E- Cardiopulmonary exercise test Case 6 A 53-year-old man is evaluated for a 6-month history of progressive dyspnea, mild cough, and fatigue. He had been previously healthy and has never smoked. His medical history includes systemic hypertension diagnosed 18 months ago, which is controlled with an ACE inhibitor. Results of his physical examination are normal. Chest radiograph and high-resolution computed tomography show increased basal and peripheral predominant reticular lines and moderate basal ground-glass opacity without honeycombing. Pulmonary function studies show a forced vital capacity (FVC) of 73% of predicted and a carbon monoxide diffusing capacity (DLCO) of 56% of predicted. Oximetry is normal at rest, but desaturation to 84% is noted with brisk walking. What is your diagnosis? A- Non specific pneumonitis B- Asthma C- COPD D- Emphysema E- Idiopathic pulmonary fibrosis Case 7 An 18-year-old male high school football player is evaluated for recurrent episodes of dyspnea, chest tightness, and cough that have occurred during a game and limited his ability to participate. The symptoms resolve spontaneously in 20 to 30 minutes. The patient's father has known allergies but no known lung disease. On physical examination, the patient is a healthy young man; the lungs are clear on auscultation. Office spirometry shows an FEV1 of 90% predicted and FEV1/FVC 80%. Which of the following is the most appropriate next step in the evaluation of this patient? A Measure lung volumes and diffusion capacity B Perform an exercise challenge test C Perform allergy skin testing D Prescribe a physical conditioning program Case 8 A 44-year-old woman is hospitalized because of respiratory failure. She has had flu-like symptoms with arthralgias, low-grade fever, cough, and rare hemoptysis for 2 months. Respiratory failure developed during the past 48 hours. Three days ago a chest radiograph revealed bibasilar alveolar infiltrates. Physiology revealed an FVC 85% of predicted, FEV1 88% of predicted, and a DLCO of 120%. On physical examination there is no exanthem. Loud end-inspiratory bilateral crackles are heard. Mild anemia is present. The PaO2 is 48 mm Hg, and the PaCO2 is 29 mm Hg. The current chest radiograph shows extensive bilateral infiltrative lesions. Intravenous therapy with appropriate antibiotics for overwhelming community-acquired pneumonia is begun; 24 hours later respiratory failure continues. Which of the following is the best management option for this patient? A- Surgical lung biopsy B- Corticosteroids C- Bronchoscopy with bronchoalveolar lavage D- High-resolution computed tomography of the chest Key points Along with PFT’s a good history and physical exam usually help getting the right diagnosis First look at the ratio FEV1/FVC, if low think obstructive disease the next step in that case is to assess for the severity of the obstruction by looking at the FEV1 If FEV1/FVC is normal, think either restrictive disease or normal pattern. The next step is to check for the FVC, if FVC is low the diagnosis is restrictive disease. A normal FVC indicates a normal pattern Finally when dealing with a restrictive pattern, a decreased corrected DLCO indicates parenchymal disease were as a normal corrected DLCO indicates extra parenchymal disease. Questions?