Figure 3.

Schematic representation of a simple model of ventilatory control (see Nicolò and Sacchetti [22] for further information). While respiratory rate (the behavioral component of minute ventilation) is substantially influenced by non-metabolic stressors, V_T (the metabolic component of minute ventilation) satisfies the metabolic requirements of the human body. As such V_T is fine-tuned according to the levels of respiratory rate and the magnitude of metabolic inputs, while f_R is influenced by V_T to a lesser extent. This model explains why f_R is more sensitive than V_T to a variety of non-metabolic stressors and corroborates the importance of f_R monitoring in different fields of use.