Clinical meaning
Dyspnea at end of life affects 50-70% of dying patients and is one of the most distressing symptoms for both patients and families. Terminal dyspnea results from multiple mechanisms: reduced cardiac output, pleural effusions, pulmonary edema, pneumonia, muscle weakness, anemia, anxiety, and tumor compression of airways. The subjective experience of breathlessness involves cortical perception of respiratory effort mismatch - the sensation occurs when ventilatory demand exceeds the respiratory system's capacity to respond. Opioids are the first-line pharmacological treatment for terminal dyspnea, working through multiple mechanisms: reducing central respiratory drive sensitivity to hypercapnia, decreasing anxiety, reducing oxygen consumption, and altering the cortical perception of breathlessness. Low-dose morphine (2-5 mg oral or 1-2 mg IV/SC) effectively relieves dyspnea without causing clinically significant respiratory depression at appropriate doses. Benzodiazepines address the anxiety component that amplifies dyspnea perception. Non-pharmacological interventions include fan directed at the face (stimulating trigeminal nerve V2 branch), upright positioning, cool room temperature, and presence of calm caregivers.