Hyperpnea (or hyperpnoea in British English) is increased depth of breathing when required to meet metabolic demand of body tissues, such as during or following exercise, or when the body lacks oxygen (hypoxia), for instance in high altitude or as a result of anemia.
Hyperpnea may also occur as a result of sepsis, and is usually a sign of the beginning of refractory sepsis.
Hyperpnea is not the same as hyperventilation. In hyperpnea, the increased breathing rate is desirable as it meets the metabolic needs of the body. In hyperventilation, the rate of ventilation is inappropriate for the body's needs (except in respiratory acidosis, when CO2 needs to be breathed off). The resulting decrease in CO2 concentration results in the typical symptoms of light-headedness, tingling in peripheries, visual disturbances etc. In hyperpnea, there are generally no such symptoms.