A 32-year-old man is brought to the emergency department following a motor vehicle collision. He has severe chest pain, dyspnea, and tachycardia (HR 118/min). On examination, there is paradoxical movement of the left anterior chest wall during respiration. Chest X-ray shows fractures of ribs 4–7 on the left side. Oxygen saturation is 88% on room air. What is the most appropriate immediate management?