Pulmonary Disease
Obstructive and restrictive disease
Spirometry after bronchodilator is essential: an FEV1/FVC ratio below 0.70 defines obstruction, and a significant FEV1 improvement indicates reversible airflow limitation. In COPD, smoking cessation is the only intervention that slows decline; add long-acting bronchodilators, and reserve inhaled corticosteroids for frequent exacerbations or elevated eosinophils. Titrate oxygen to a saturation of about 88–92% in patients at risk of hypercapnia, but never withhold oxygen from a hypoxemic patient. In interstitial lung disease, obtain high-resolution CT and screen for connective tissue disease and drug exposures.
Pulmonary embolism
The trap is an inappropriate D-dimer in a high-pretest-probability patient. Use a validated pretest probability; a negative D-dimer excludes PE in low-probability patients only (age-adjust the cutoff). Confirm with CT pulmonary angiography and risk-stratify with vital signs, troponin, and BNP. Most stable patients can receive a DOAC.
Pleural effusion and nodules
Apply Light's criteria: an effusion is exudative if the pleural:serum protein ratio exceeds 0.5, the LDH ratio exceeds 0.6, or pleural LDH exceeds two-thirds of the upper limit of normal for serum.
Other essentials
Assess OSA with the STOP-BANG questionnaire and confirm with polysomnography. Evaluate an incidental nodule using size, risk, and Fleischner criteria. Recognize acute respiratory distress syndrome by acute onset, bilateral opacities, and hypoxemia not explained by cardiac failure.