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  • Title: The impact of human pregnancy on perceptual responses to chemoreflex vs. exercise stimulation of ventilation: a retrospective analysis.
    Author: Jensen D, O'Donnell DE.
    Journal: Respir Physiol Neurobiol; 2011 Jan 31; 175(1):55-61. PubMed ID: 20850571.
    Abstract:
    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.
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