The role of the hering-breuer deflationary reflex in the control of spontaneous human respiration

The application of engineering control theory to biological systems is a challenge. Often, in initial engineering models or designs of systems to exert control over a certain aspect or part of a biological system, other control loops may be in operation within the biological system that are not accounted for. When the operation of such unconsidered hidden loops reveals themselves, this presents an opportunity to expand knowledge of biological control systems. A complimentary pair of reflexes involved in respiration was described by Hering and Breuer in 1868. Since that time, the manifestation of these reflexes has been controversial. In a recent group of studies seeking to apply an open-loop control system to assist or restore ventilation by electrically stimulating abdominal muscles, unexpected experimental results led to a more thorough study of the potential presence of the Hering-Breuer deflationary reflex in adult human subjects. This paper describes experiments in which abdominal compression (both manual and by electrical stimulation of abdominal muscles) provide evidence supporting the presence of the deflationary reflex control loop in adult human subjects. The results can be utilized to develop a comprehensive model of the human respiratory system considering both chemical and mechanical feedback