System*/physiology	Example	History	Physical examination	Diagnostic studies
Pulmonary
Alveolar	Chronic†/recurrent pneumonia	Fever, productive cough, shortness of breath	Fever, productive cough, fremitus, bronchophony	Chest radiography, chest CT, workup for bacterial and fungal organisms and noninfectious causes
Interstitial	Idiopathic fibrosis	Exertional dyspnea, dry cough, malignancy, drugs/medications, chemical exposure	Hypoxia, clubbing, persistent inspiratory crackles	Chest radiography (fibrosis interstitial markings), chest CT, bronchoscopy, biopsy
Obstruction of air flow	Chronic obstructive pulmonary disease	Tobacco use, cough, relief with bronchodilators, increased sputum production, weight loss	Wheezing, barrel chest, decreased breath sounds, accessory muscle use, clubbing, paradoxical pulse	Peak flow, spirometry, chest radiography (hyperinflation), pulmonary function test
Restrictive	Pleural effusion	Pleuritic chest pain, dyspnea not improved with supplemental oxygen	Decreased breath sounds, chest morphology, pleural rub, basal dullness	Chest radiography, spirometry, pulmonary function test
Vascular	Chronic pulmonary emboli	Fatigue, pleuritic chest pain, prior emboli/deep venous thrombosis, thrombosis, syncope	Wheezing, lower extremity swelling, pleural rub, prominent P2, murmur, right ventricular heave, jugular venous distention	d-dimer, ventilation-perfusion scan, CT angiogram, echocardiography right heart catheterization
Cardiac
Arrhythmia	Atrial fibrillation	Palpitation, syncope	Irregular rhythm, pauses	ECG, event recorder, cardiac stress testing once stable
Heart failure	Ischemic cardiomyopathy	Dyspnea on exertion, orthopnea, chest pain, prior coronary artery disease, atrial fibrillation	Edema, jugular venous distention, S3, displaced cardiac apical impulse, hepatojugular reflex, murmur, crackles, wheezing, tachycardia, S4	ECG, brain natriuretic peptide, echocardiography, stress testing, coronary angiography
Restrictive or constrictive pericardial disease	Tumors	Viral infection, malignancy, mycobacterial infection, chest radiation, inflammatory disease	Decreased heart sounds	Echocardiography
Valvular	Aortic stenosis	Dyspnea on exertion	Murmur, jugular venous distention	Echocardiography
Gastrointestinal
Aspiration	Gastroesophageal reflux disease	Postprandial, nighttime cough	Intermittent crackles and wheezes	Chest radiography, esophageal pH, esophagography
Neuromuscular
Respiratory muscle weakness	Phrenic nerve palsy	Known disorder, weakness	Atrophy	Maximal inspiratory and expiratory pressures
Hematologic
Anemia	Iron deficiency	Fatigue, weakness, irritability, postural dizziness, dyspnea with exertion	Conjunctival pallor, tachycardia, orthostatic hypotension, tachypnea, rales, hepatosplenomegaly or splenomegaly	Complete blood count with attention to the red blood cell indices
Psychological
	Anxiety	Anxiety, depression, history of trauma or abuse	Validated screening scales (e.g., GAD-7)	Diagnosis of exclusion
Endocrine
Thyroid	Hypothyroid	Cold sensitivity, fatigue, constipation, dry skin	Hair loss, dry skin, brittle nails, enlarged thyroid, bradycardia, weight gain	Thyroid-stimulating hormone
Musculoskeletal
Deformity	Sever kyphosis	Long-term history of kyphosis	Visible and palpable deformity	Radiography, pulmonary function tests