Intercept shift in the breathlessness/ventilation relationship in response to progressive increase in workload: change in exercise breathlessness response.

The relationship between breathlessness based on the visual analog scale (VAS) and expired pulmonary ventilation (VE) has been investigated under different experimental conditions. The 'Newcastle effect' revealed for the first time that a repetitive exercise protocol over a period of ten days increased the intercept without change in the slope of VASNE relationship!. Whether experiments were conducted daily or weekly, the time course of the intercept plateaued after around 5 to 6 weeks of exercise training. A similar effect has been shown to occur during volitional tracking of an inspiratory resistive breathing pattem. In another study, hypercapnia has been shown to decrease the intercept and increase the slope3.4. Inspiratory resistive loading increased the slope without any change in the intercept• The VASNE relationship, when examined in patients pursuing a COPDrehabilitation program, showed a decrease in the slope without change in the intercept• The analysis of the intercept and slope dynamics, being the quantitative indices of breathlessness in contrast to VAS scores alone, may open avenues in modeling and understanding the mechanisms of breathlessness. The aim of this study, firstly, was to see if the 'Newcastle effect' could be reproduced. Secondly, since in clinical practice the recording of heart rate is simpler and easier then that of expired pulmonary ventilation, the dynamics of VAS-heart rate relationship has been additionally investigated. Thus we have a representation of both respiratory and cardiovascular control systems being examined with reference to a change in the degree of breathlessness.