The impact of human pregnancy on perceptual responses to chemoreflex vs. exercise stimulation of ventilation: A retrospective analysis

Abstract: We examined the impact of human pregnancy on breathlessness intensity at matched levels of ventilation during isoxic hyperoxic CO2 rebreathing and incremental cycle exercise tests in 21 healthy women in the third trimester (TM3) and again ∼5 months post-partum (PP). Pregnancy had no significant (P >0.05) effect on the slope or threshold of the breathlessness relationship during both exercise and rebreathing. By contrast, the slope of the breathlessness relationship was significantly higher, while the threshold of this relationship was consistently lower during rebreathing vs. exercise (both P <0.05), regardless of pregnancy status (P >0.05). As a result, breathlessness intensity was markedly higher at any given (e.g., by ∼4 Borg units at 40L/min) during rebreathing vs. exercise, regardless of pregnancy status. Inter-subject variation in breathlessness slopes during exercise was not associated with inter-subject variation in breathlessness slopes during rebreathing or with increased central chemoreflex responsiveness during pregnancy (both P >0.05). In conclusion, the intensity of perceived breathlessness for a given depends, at least in part, on the nature and source of increased central respiratory motor command output, independent of pregnancy status; and pregnancy-induced increases in activity-related breathlessness cannot be easily explained by increased central chemoreflex responsiveness. [Copyright &y& Elsevier]