Plasma osmolality and the strong ion difference predict respiratory adaptations in pregnant and nonpregnant women.
This study tested the hypothesis that plasma osmolality and the strong ion difference ([SID]) predict PaCO2 during rest and during exercise in physically active pregnant (n = 22; gestational age 37.0 +/- 0.2 weeks) and nonpregnant (n = 17) women. Nonpregnant subjects were in varying stages of the menstrual cycle. Arterialized blood gases, hydrogen ion concentration, plasma osmolality, [SID], and circulating levels of progesterone were measured at rest and during upright cycling at work rates corresponding to 70 and 110% of the ventilatory threshold. Pooled data from the two groups at rest revealed significant correlations (P < 0.05) between PaCO2 with plasma osmolality, [SID], and progesterone. Progesterone was also significantly correlated with [SID] and osmolality. Also, changes in PaCO2 with exercise correlated significantly with changes in [SID]. The results support the hypothesis that plasma osmolality and [SID] are important factors in the modulation of respiratory sensitivity in healthy women. Also, the effects of progesterone on PaCO2 may be expressed, at least in part, through progesterone-induced changes in [SID] and osmolality.
Heenan
A P
AP
School of Physical & Health Education, Queen's University, Kingston, Ontario K7L 3NG, Canada.
Wolfe
L A
LA
D000328:Adult; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood; D005080:Exercise Test; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D010949:Plasma; D011247:Pregnancy / Q000097:blood* / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology*; D012146:Rest
D002245:Carbon Dioxide