Measuring the respiratory chemoreflexes in humans

Breathing responds to changes in CO2 and O2 detected by respiratory chemoreceptors. In this paper I examine the methodologies for a quantitative assessment of the respiratory chemoreflex characteristics in humans. My intention is to provide the investigator unfamiliar with these methods an overview and introduction that allows them to choose the methodology that answers their needs. Included are brief background histories of such testing techniques and the way in which they have been refined and improved over time, a description of current techniques and tips for their implementation, and a comparative assessment of their relative strengths and weaknesses. I begin with a statement of the problem that provides a brief review of the chemoreflex control of breathing, and difficulties in measuring the chemoreflex characteristics. Then each of the two major methodologies, steady-state and rebreathing techniques are described in detail. Lastly, I compare and contrast these two methodologies.