A simple 'constraint-satisfaction' model illustrating the inter-relatedness of Mechanical ventilatory variables. Simply defining two points within any coloured triangle also defines the third point within the triangle of the same colour. If another point is selected from a triangle of a different colour, the whole picture is completed. Only 3 independent variables can be selected at a given time. While setting up the Mechanical Ventilator, this diagram helps understand the relation between the ventilatory variables.