Respiratory Emergencies
What to know
Respiratory items reward pattern recognition. Asthma and COPD exacerbations are treated with inhaled short-acting beta agonists plus ipratropium, systemic corticosteroids, and magnesium for severe cases; epinephrine is appropriate for severe asthma or anaphylaxis. Pulmonary embolism presents with sudden dyspnea, pleuritic pain, tachycardia, and hypoxemia; risk-stratify with Wells, use D-dimer in low-risk patients, CT angiography for higher risk, and thrombolysis for massive PE with hemodynamic instability. Tension pneumothorax is a clinical diagnosis requiring immediate needle decompression before imaging. ARDS is defined by acute onset, bilateral infiltrates, and hypoxemia not explained by cardiac failure; ventilation is lung-protective at roughly 6 mL/kg predicted body weight with plateau pressure under 30 cm H2O. Distinguish type 1 (hypoxemic) from type 2 (hypercapnic) respiratory failure.
Traps
A "silent chest" in asthma is worsening obstruction, not improvement. A normal PaCO2 in a tachypneic, exhausted asthmatic is a warning of impending failure rather than reassurance. The COPD "hypoxic drive" is largely a myth; titrate oxygen to a target saturation rather than withholding it. Not every wheeze is asthma - consider anaphylaxis, PE, heart failure, and foreign body.
Worked example
A 24-year-old in status asthmaticus has diminishing breath sounds, a PaCO2 of 44 mm Hg, and increasing drowsiness. These findings signal fatigue and impending respiratory arrest; call for help and prepare for intubation rather than simply repeating nebulizers. Rule of thumb: in severe asthma, a rising CO2 means the patient is tiring.