Respiratory neuronal networks in vertebrates appear to be able to generate a variety of rhythmic patterns in vivo, leading to the biological diversity of eupneic patterns as well as to life-threatening dyspneic patterns. Eupnea is best viewed as the collection of respiratory strategies preventing potential dyspneas, the major (and perhaps the only) criterion for a definition being that eupnea allows survival. Specific criteria can then be derived from the physiological identification of neurobiological mechanisms underlying identified dyspneic patterns, by exaggerating (pro-dyspneic mechanisms) or suppressing them (anti-dyspneic mechanisms). Because eupnea is vital, and one of the major targets of evolutionary pressure, identification of dyspnea-related neuronal systems seems to be important to understand the normal biological organization of the respiratory neuronal system.
Adaptation, Physiological Animals