Estimation of response slopes in respiratory control

The ventilatory response to changes in arterial CO₂ is an index of respiratory control behavior. Methodology for estimating these response slopes must consider that there may be error in both the independent (CO₂) and dependent (ventilation) variables. Recent work has suggested inherent problems in the traditional techniques of reduced major axis and has suggested more contemporary methods of directional statistics should be used. We have analyzed both techniques and developed a modified technique to overcome the problems of reduced major axis. Further, we point out several inherent problems in the use of directional statistics for respiratory data. Data from the literature serves to illustrate the concepts.