Which of the following is a factor that can affect respiration rate?

• A. Fever
• B. Sleep
• C. High altitude
• D. Hydration level

Answer: (A)

When the body temperature rises, metabolic activity increases and more CO2 is produced. The rise in CO2 and hydrogen ions lowers the blood pH, and the respiratory center responds by increasing both how fast and how deeply you breathe. This helps blow off CO2 and restore acid-base balance, so fever commonly causes tachypnea (faster breathing).

Sleep tends to slow metabolic demand and breathing rate, so it doesn’t push respiration up. High altitude lowers oxygen levels, which does trigger faster breathing but for a different mechanism (hypoxemia rather than heat-driven metabolism). Hydration level mainly affects circulation and mucous properties more than the direct control of breathing rate, so it doesn’t reliably drive a change in respiration like fever does.