Defining eupnea.

Abstract

To describe a pattern of rhythmic activity as "breathing" or "respiration" inevitably leads to the conclusion that this rhythmic activity is "normal" or "eupneic". Initially, it must be noted that, by strictest definition, "eupnea" can only be applied to "breathing" in an unanesthetized preparation. Any experimental perturbation, including anesthesia, changes eupnea, primarily by reducing the frequency of "breathing". However, a "eupneic pattern", in terms of the pattern of airflow of individual breaths, remains. Also remaining are patterns of neural and neuronal activities which are characteristic of individual breaths of eupnea. In this commentary, we consider these patterns of activities, which define a eupneic pattern and contrast these with patterns during apneusis and gasping. It has long been recognized that these three different patterns of "respiratory activity", eupnea, apneusis and gasping, can be generated in preparations in which all of the central nervous system has been removed, exclusive of the brainstem and spinal cord.