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Respiratory system

Upper respiratory tract disorders

Choanal atresia


Allergic rhinitis

Nasal polyps

Upper respiratory tract infection



Retropharyngeal and peritonsillar abscesses

Bacterial epiglottitis

Nasopharyngeal carcinoma

Lower respiratory tract disorders

Tracheoesophageal fistula

Congenital pulmonary airway malformation

Pulmonary hypoplasia

Neonatal respiratory distress syndrome

Transient tachypnea of the newborn

Meconium aspiration syndrome

Apnea of prematurity

Sudden infant death syndrome

Acute respiratory distress syndrome

Pulmonary changes at high altitude and altitude sickness

Decompression sickness

Cyanide poisoning



Chronic bronchitis


Cystic fibrosis


Alpha 1-antitrypsin deficiency

Restrictive lung diseases


Idiopathic pulmonary fibrosis

Hypersensitivity pneumonitis



Bacterial tracheitis

Lung cancer

Pancoast tumor

Superior vena cava syndrome

Pleura and pleural space disorders


Pleural effusion


Pulmonary vascular disorders

Pulmonary embolism

Pulmonary edema

Pulmonary hypertension

Apnea and hypoventilation

Sleep apnea

Apnea of prematurity

Respiratory system pathology review

Respiratory distress syndrome: Pathology review

Cystic fibrosis: Pathology review

Pneumonia: Pathology review

Tuberculosis: Pathology review

Deep vein thrombosis and pulmonary embolism: Pathology review

Pleural effusion, pneumothorax, hemothorax and atelectasis: Pathology review

Obstructive lung diseases: Pathology review

Restrictive lung diseases: Pathology review

Apnea, hypoventilation and pulmonary hypertension: Pathology review

Lung cancer and mesothelioma: Pathology review




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USMLE® Step 1 questions

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High Yield Notes

13 pages



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USMLE® Step 1 style questions USMLE

of complete

A 61-year-old man comes to the clinic for a routine evaluation. He has had a chronic productive cough for the past 5 years, with occasional dyspnea and wheezing. He smoked a pack of cigarettes a day for 40 years, but stopped several months ago. Vitals are within normal limits. Physical examination reveals bilateral diffuse crackles and rales on chest auscultation. Pulmonary function testing (PFT) is performed, which confirms the diagnosis of chronic bronchitis-predominant chronic obstructive pulmonary disease. Which of the following PFT findings are most likely present in this patient?  

External References

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α1 -antitrypsin deficiency p. 50, 401

emphysema p. 698

Centriacinar emphysema p. 698


emphysema p. 720

Elastase p. 382

activity in emphysema p. 698

Emphysema p. 698

α1 -antitrypsin deficiency p. 401

compliance in p. 689

diffusion in p. 690

diffusion-limited gas exchange p. 690

elastin in p. 50

panacinar p. 402

presentation p. 720


emphysema p. 720

Panacinar emphysema p. 402, 698


emphysema p. 698, 720


Content Reviewers

Rishi Desai, MD, MPH

Kara Lukasiewicz, PhD, MScBMC


Tanner Marshall, MS

Emphysema means “inflate or swell”, which makes sense because in the lungs of people with emphysema, the alveolar air sacs, which are the thin walled air spaces at the ends of the airways where oxygen and carbon dioxide are exchanged, become damaged or destroyed.

The alveoli permanently enlarge and lose elasticity, and as a result, individuals with emphysema typically have difficulty with exhaling, which depends heavily on the ability of lungs to recoil like elastic bands.

Emphysema’s actually lumped under the umbrella of chronic obstructive pulmonary disease (or COPD), along with chronic bronchitis.

The two differ in that chronic bronchitis is defined by clinical features, like the productive cough, whereas emphysema is defined by structural changes, mainly enlargement of the air spaces.

That being said, they almost always coexist, probably because they share the same major cause—smoking.

With COPD, the airways become obstructed, the lungs don’t empty properly, and that leaves air trapped inside the lungs.

For that reason, the maximum amount of air people with COPD can breath out in a single breath, known as the FVC, or forced vital capacity, is lower.

This reduction is especially noticeable in the first second of air breathed out in a single breath, called FEV1—forced expiratory volume (in one second), which typically is reduced even more than the FVC.

A useful metric therefore is the FEV1 to FVC ratio, which, since the FEV1 goes down even more than FVC, causes the FEV1 to FVC ratio to go down as well.

Alright so say normally your FVC is 5 L, and your FEV1 is 4 L, your FEV1 to FVC ratio would end up being 80%.

Now, someone with COPD’s FVC might be 4 L instead, which is lower than normal, but the volume of air that he or she can expire in the first second is only 2 L, so not only are both these values lower, but their ratio is lower as well—and this is a hallmark of COPD.

All that had to do with air breathed out right? Conversely, for air going in, the TLC, or total lung capacity, which is the maximum volume of air that can be taken in or inspired into the lungs, is actually often often higher because of the air trapping.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease" American Journal of Respiratory and Critical Care Medicine (2013)
  6. "Flow limitation and dynamic hyperinflation: key concepts in modern respiratory physiology" European Respiratory Journal (2005)
  7. "Screening for Chronic Obstructive Pulmonary Disease" JAMA (2016)
  8. "Endocarditis" JAMA (2018)
  9. "Infective endocarditis" The Lancet (2016)
  10. "Endocardite infectieuse. Épidémiologie, physiopathologie et anatomopathologie" La Presse Médicale (2019)

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