A triage nurse has four clients arrive in the emergency department within 15 minutes. Which client should the triage nurse send back to be seen first?

The correct answer is the teenager who suffered singed facial hair while camping. This client is in the greatest danger with a potential risk of respiratory distress. Singed facial hair indicates exposure to heat or fire in close range, which could have caused serious damage to the interior of the lungs. It's crucial to prioritize this client as the interior lining of the lungs has no nerve fibers, so swelling may not be immediately noticeable. The other choices, while concerning, do not present an immediate life-threatening situation. The infant's condition may be serious but does not pose an immediate danger of respiratory distress. The elderly client's symptoms could indicate gastrointestinal issues, which are important but not as urgent as potential respiratory compromise. The middle-aged client's pain behind the right scapula, while uncomfortable, does not indicate an acute life-threatening condition requiring immediate attention.