Chronic obstructive pulmonary disease (COPD)

An acute exacerbation of COPD is a change in baseline dyspnea, cough, or sputum that requires a change in therapy, most often triggered by viral or bacterial respiratory infection. Severity is graded by the treatment required, and management is a stepwise sequence of bronchodilators, glucocorticoids, targeted oxygen, and, when hypercapnic acidosis is present, noninvasive ventilation.

Asthma is a chronic inflammatory airway disorder causing episodic, reversible airflow obstruction confirmed by spirometry or bronchial challenge testing. Management is a stepwise ladder led by inhaled glucocorticoids plus as-needed SABA or ICS-formoterol, escalating to biologics for severe type 2-high disease, with an oral glucocorticoid burst and frequent SABA for exacerbations.

Alpha-1 antitrypsin deficiency is an autosomal codominant disorder in which a deficient or misfolded protease inhibitor causes unopposed neutrophil elastase activity in the lung and toxic protein accumulation in the liver, producing early basilar-predominant panacinar emphysema and, in some patients, cirrhosis. Diagnosis rests on a low serum level confirmed by phenotype or genotype testing, and management centers on smoking cessation, standard COPD therapy, and, for qualifying patients, weekly IV augmentation with pooled alpha-1 proteinase inhibitor.

Cor pulmonale is right ventricular structural and functional impairment caused by group 3 pulmonary hypertension from chronic lung disease or hypoxemia. Diagnosis rests on echocardiographic screening confirmed by right heart catheterization, and management centers on treating the underlying lung disease, correcting hypoxemia, and cautious diuresis.

Bronchiectasis is chronic, irreversible bronchial dilation from a cycle of infection, inflammation, and airway destruction, diagnosed by high-resolution CT and managed with airway clearance, treatment of the underlying cause, and antibiotics for exacerbations.

Lung cancer is the leading cause of cancer death worldwide, split into non-small cell lung cancer (NSCLC, 80% of cases: adenocarcinoma, squamous cell, large cell) and small cell lung cancer (SCLC, 10-15%), both driven overwhelmingly by cigarette smoking. Diagnosis requires tissue histopathology, staging drives treatment (TNM staging for NSCLC, limited versus extensive stage for SCLC), and management ranges from lobectomy in early-stage disease through concurrent chemoradiation and consolidation immunotherapy in locally advanced disease to targeted tyrosine kinase inhibitors, immune checkpoint inhibitors, or platinum-based chemotherapy in metastatic disease.

Pulmonary hypertension is a resting mean pulmonary artery pressure of 20 mmHg or greater on right heart catheterization, classified into five WHO groups by mechanism. Diagnosis requires screening echocardiography followed by confirmatory right heart catheterization, and management is group-specific, with PAH-targeted vasodilator therapy reserved for group 1 disease.

Obstructive sleep apnea is repetitive upper airway collapse during sleep, diagnosed by an apnea-hypopnea index of 5 or more per hour with symptoms, or 15 or more per hour regardless of symptoms, and treated first with weight loss plus positive airway pressure.

Tobacco use is the leading cause of preventable death in the United States, and every smoker should be asked about use at every visit and offered combined behavioral counseling plus pharmacotherapy, since neither alone matches the quit rate of both together. Varenicline is the most effective single agent, combination nicotine replacement therapy (long-acting patch plus a short-acting form) is equally first-line, and bupropion is an alternative, all started before a set quit date and continued for a 7- to 12-week course.

Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading global cause of infectious death and presents as latent infection, primary/secondary pulmonary disease, or extrapulmonary and disseminated (miliary) disease. Diagnosis rests on AFB smear, NAAT, and mycobacterial culture (the gold standard), and drug-susceptible active disease is treated with a four-drug regimen (isoniazid, rifampin, pyrazinamide, ethambutol) for 2 months followed by isoniazid plus rifampin for 4 to 7 months.