Oxygen masks and nasal cannulas are vital devices for delivering supplemental oxygen to patients with respiratory distress, such as those with COPD, pneumonia, or post-surgical recovery needs. Nasal cannulas, featuring lightweight tubes with prongs inserted into the nostrils, provide low-flow oxygen (1-6 L/min, 24-44% FiO2), allowing patients to eat, speak, and move freely while being comfortable for long-term home use. Oxygen masks, covering the nose and mouth, deliver higher concentrations: simple masks (40-60% at 6-10 L/min), non-rebreathers (60-90% at 10-15 L/min for emergencies), and Venturi masks (precise 24-60% for CO2 retainers). Cannulas suit mild hypoxemia; masks are preferred when higher flows are required, though they may cause claustrophobia or skin irritation. Both connect to concentrators or tanks and require monitoring to avoid dryness or oxygen toxicity.