A 73-yeаr-оld pаtient wаs admitted with severe respiratоry distress secоndary to pneumonia. She has a long history of smoking, which she recently stopped. On arrival she was placed on continuous pulse oximetry, and an endotracheal tube was inserted for mechanical ventilation. She is heavily sedated. This patient's risk factors for respiratory problems include history of smoking, her illness, and her age.