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pulmonary function test (PFT)

Classification: - spirometry used to assess airflow obstruction - flow-volume loop - can help identify anatomy of airway obstruction - lung volume - total lung capacity - vital capacity - functional residual capacity - expiratory reserve volume - residual volume - diffusion capacity of carbon monoxide (DLCO) - evaluates gas transport across the alveolar membrane Indications: - dyspnea - classification of lung disease - obstructive lung disease - chronic obstructive lung disease - asthma - bronichiectasis - restrictive lung disease - interstitial lung disease - assessment of lung disease severity [4] Contraindications: - spirometry alone is insufficient to rule out lung disease in smokers & former smokers [7] Procedure: 1) spirometry is used to measure airflow 2) DLCO is a measurement of gas exchange Clinical significance: 1) obstructive lung disease a) indicated by decrease in FEV1, FEV1/FVC & FEF[25-75] b) FEV1/FVC of < 70% c) asthma, bronchitis, emphysema - residual volume increased with emphysema d) resistance to expiratory airflow causes air trapping leading to elevated intrathoracic pressure (auto-PEEP) 2) asthma a) obstruction to airflow during inspiration & expiration b) provocation inhalation challenge test 3) reversible airway disease (asthma, bronchitis) - indicated by increase in flow rate (FEV1 or FVC) of > 12-20% & > 200 mL from baseline after bronchodilator therapy* [4] 4) restrictive lung disease a) limitation of full expansion of the lungs 1] lung parenchymal disease 2] chest wall or diaphragm dysfunction b) volumes FEV1 & FVC are similarly diminished (includes pneumonectomy) c) total lung capacity < 80% d) flow rates are normal 5) combination of restrictive & obstructive a) COPD; smokers may have interstitial lung changes along with emphysema [5] b) pulmonary fibrosis 6) neuromuscular disease a) restrictive lung disease pattern - vital capacity < 50% of predicted b) decreased maximal voluntary ventilation (MVV) - arterial pCO2 > 45 mm Hg c) normal flow rates - minimal inspiratory pressure: -60 cm H2O - maximal expiratory pressure: +40 cm H2O d) DLCO is normal 7) upper airway obstruction shows inspiratory abnormalities in flow loop 8) no obstruction & no restriction a) isolated low DLCO is consistent with 1] anemia 2] pulmonary embolism 3] pulmonary hypertension b) isolated high DLCO is consistent with 1] pulmonary hemorrhage 2] obesity 3] left-to-right cardiac shunt 4] polycythemia c) nonspecific pattern - normal total lung capacity - normal FEV1/FVC - low FEV1 or FVC (or both) - generally does not evolve into obstructive lung disease or restrictive lung disease [6] d) preserved ratio impaired spirometry - associated with increased risk for mortality & adverse cardiovascular & respiratory outcomes [11] * in a large cohort, bronchodilator responsiveness failed to distinguish asthma & COPD [13] Interpretation: - results below 80% of predicted indicate impairment [4] - race-based corrections not useful for predicting adverse respiratory events [12]

Related

age-associated changes in pulmonary function dyspnea (shortness of breath {SOB}) lung lung disease pulmonary

Specific

cardiopulmonary exercise testing diffusion capacity of carbon monoxide (DLCO) flow-volume loop forced expiratory flow forced expiratory flow (FEF[25-75]) forced expiratory volume in 1 second (FEV1) forced vital capacity (FVC) fraction of exhaled nitric oxide (FeNo) maximal voluntary ventilation (MVV) nitrogen washout peak expiratory flow rate (PEFR, PER) pneumogram preserved ratio impaired spirometry provocation inhalation challenge test; methacholine challenge test respiratory residual volume static lung volume total lung capacity (TLC)

General

clinical procedure

References

  1. Diagnostic History & Physical Examination in Medicine, Chan & Winkle, Current Clinical Strategies, Laguna Hills, CA 1996
  2. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
  3. American Thoracic Society, Am Rev Respir Dis 144:1202-18, 1991
  4. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 17, 19. American College of Physicians, Philadelphia 1998, 2006, 2015, 2022. - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  5. Washko GR et al. Lung volumes and emphysema in smokers with interstitial lung abnormalities. N Engl J Med 2011 Mar 10; 364:897 PMID: 21388308 - King TE Jr. Smoking and subclinical interstitial lung disease. N Engl J Med 2011 Mar 10; 364:968 PMID: 21388315
  6. Iyer VN et al. The nonspecific pulmonary function test: Longitudinal follow-up and outcomes. Chest 2011 Apr; 139:878. PMID: 20724741
  7. Regan EA et al Clinical and Radiologic Disease in Smokers With Normal Spirometry. JAMA Intern Med. Published online June 22, 2015 PMID: 26098755 http://archinte.jamanetwork.com/article.aspx?articleid=2323415
  8. Miller MR, Hankinson J, Brusasco V et al Standardisation of spirometry. Eur Respir J. 2005 Aug;26(2):319-38. PMID: 16055882
  9. Pellegrino R, Viegi G, Brusasco V et al Interpretative strategies for lung function tests. Eur Respir J. 2005 Nov;26(5):948-68. PMID: 16264058
  10. Redlich CA, Tarlo SM, Hankinson JL et al Official American Thoracic Society technical standards: spirometry in the occupational setting. Am J Respir Crit Care Med. 2014 Apr 15;189(8):983-93 PMID: 24735032
  11. Wan ES, Balte P, Schwartz JE et al. Association between preserved ratio impaired spirometry and clinical outcomes in US adults. JAMA 2021 Dec 14; 326:2287. PMID: 34905031 https://jamanetwork.com/journals/jama/fullarticle/2787116
  12. Elmaleh-Sachs A et al. Race/ethnicity, spirometry reference equations, and prediction of incident clinical events: The Multi-Ethnic Study of Atherosclerosis (MESA) Lung Study. Am J Respir Crit Care Med 2022 Mar 15; 205:700 PMID: 34913853 https://www.atsjournals.org/doi/10.1164/rccm.202107-1612OC - Schluger NW. The vanishing rationale for the race adjustment in pulmonary function test interpretation. Am J Respir Crit Care Med 2022 Mar 15; 205:612 PMID: 35085469 https://www.atsjournals.org/doi/10.1164/rccm.202112-2772ED
  13. Beasley R et al. Prevalence, diagnostic utility and associated characteristics of bronchodilator responsiveness. Am J Respir Crit Care Med 2024 Feb 15; 209:390. PMID: 38029294 PMCID: PMC10878375 Free PMC article https://www.atsjournals.org/doi/10.1164/rccm.202308-1436OC