The impact of human pregnancy on perceptual responses to chemoreflex vs. exercise stimulation of ventilation: a retrospective analysis.
We examined the impact of human pregnancy on breathlessness intensity at matched levels of ventilation (V˙E) 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 intensity-V˙E relationship during both exercise and rebreathing. By contrast, the slope of the breathlessness intensity-V˙E 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 V˙E (e.g., by ∼4 Borg units at 40 L/min) during rebreathing vs. exercise, regardless of pregnancy status. Inter-subject variation in breathlessness intensity-V˙E slopes during exercise was not associated with inter-subject variation in breathlessness intensity-V˙E 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 V˙E 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.
Jensen
Dennis
D
Respiratory Investigation Unit, Department of Medicine, Queen's University c/o Kingston General Hospital, Kingston, Ontario, Canada. dennis.jensen@queensu.ca
O'Donnell
Denis E
DE
D000328:Adult; D002245:Carbon Dioxide / Q000494:pharmacology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D005260:Female; D006801:Humans; D010465:Perception / Q000502:physiology*; D011247:Pregnancy / Q000502:physiology / Q000523:psychology; D011263:Pregnancy Trimester, Third / Q000502:physiology* / Q000523:psychology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D012018:Reflex / Q000187:drug effects / Q000502:physiology*; D012189:Retrospective Studies
D002245:Carbon Dioxide