A commentary on eupnoea and gasping.

This commentary discusses the differences between patterns of bursting activity recorded from the phrenic nerves of different species, in several experimental preparations and under differing conditions. The spectrum of bursting activity patterns varies from that termed eupnoic to that termed gasping. Taking the pattern of activity recorded in the least reduced preparation as a standard for normality, i.e. eupnoea, consideration is given to the possible factors affecting the pattern of bursting activity in progressively reduced preparations. An examination of the conditions of these preparations leads to the conclusion that tissue gas exchange is a major determinant of bursting pattern, and consideration is given to the possible differences in respiratory rhythm generation that can be inferred from these different patterns.