Influence of pregnancy on ventilatory and carotid body neural output responsiveness to hypoxia in cats

Hannhart, B.; Pickett, Cheryl A.; Weil, John V.; Moore, Lorna G.

doi:10.1152/jappl.1989.67.2.797

Cited by 46 publications

(37 citation statements)

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“…The rise in V E was greater than that which can be accounted for by increased CO 2 production, as demonstrated by the fall in PET CO 2 . We showed previously that about two-thirds of the V E rise can be attributed to elevated progesterone and estrogen hormones which act, in turn, to raise carotid body chemosensory sensitivity to hypoxia (20,22), central translation, and thus respiratory drive (11,12). The present study was consistent with these observations insofar as the women with the highest HVR had the highest alveolar V E (lowest PET CO 2 ).…”

Section: Discussionsupporting

confidence: 92%

Determinants of blood oxygenation during pregnancy in Andean and European residents of high altitude

Vargas

Julian

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

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High altitude decreases birth weight, but this effect is diminished in long vs. short-resident, high-altitude populations. We asked whether women from long vs. short-resident, high-altitude populations had higher arterial oxygenation levels by comparing 42 Andean and 26 European residents of La Paz, Bolivia (3,600 m), serially during pregnancy (weeks 20, 30, and 36) and again 4 mo postpartum. Pregnancy raised hypoxic ventilatory sensitivity threefold, resting ventilation (V E), and arterial O2 saturation (SaO 2 ) in both groups. Ancestry, as identified using 81 genetic markers, correlated with respiratory pattern, such that greater Andean ancestry was associated with higher respiratory frequency and lower tidal volume. Pregnancy increased total blood and plasma volume ϳ40% in both groups without changing red blood cell mass relative to body weight; hence, hemoglobin fell. The hemoglobin decline was compensated for by the rise in V E and SaO 2 with the result that arterial O2 content (Ca O 2 ) was maintained near nonpregnant levels in both groups. Birth weights were similar for all Andean and European babies, but after adjusting for variation in gestational age, maternal height and parity, Andeans weighed 209 g more than Europeans. Babies with heavier birth weights and greater ponderal indices were born to Andean women with higher V E during pregnancy. We concluded that while maternal V E and arterial oxygenation were important, some factor other than higher Ca O 2 was responsible for protecting Andeans from altitude-associated reductions in fetal growth.hypoxia; ventilation; ventilatory control; infant birth weight; fetal growth; genetics of birth weight; human adaptation; respiratory pattern RESIDENCE AT HIGH ALTITUDE (Ͼ8,000 ft, 2,500 m) exerts among the most powerful effects on birth weight with values falling, on average, 121 g per 1,000 m in Colorado high-altitude (Ͼ2,500 m, 8,000 ft) residents (15). This effect is due primarily to a slowing of fetal growth, not shortened gestation, and is greater than the effects of parity, the number of prenatal visits, or moderate maternal smoking on birth weight. Existing data indicate that the birth weight fall is not due to socioeconomic or other known risk factors (6, 15), but rather to the effects of hypoxia itself.Some 140 million persons live at high altitude, making them the largest single group at risk of low birth weight (16). While birth weight declines in all populations studied to date, the magnitude of fall varies, being least in long-and greatest in short-resident groups. For example, across a 2,700 -4,700 m (8,900 -15,500 ft) altitude range, birth weight decreases three times as much in Han ("Chinese") compared with Tibetans (24). In La Paz, Bolivia, at 3,600 m (11,880 ft), women of indigenous (Aymára or Quechua) ancestry give birth to heavier weight infants than European women, regardless of whether the data are adjusted for differences in maternal body size, nutrition, or the mother's own altitude of birth and development (9).On the basis of our previo...

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Section: Discussionsupporting

confidence: 92%

Determinants of blood oxygenation during pregnancy in Andean and European residents of high altitude

Vargas

Julian

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Previous reports have also suggested that endogenous and exogenous increases in progesterone markedly increase both the V E and carotid body neural output response to hypoxia (10,11,22,33). These effects appear to be intrinsic to the carotid body (i.e., peripheral chemoreflex) (10,11) and potentiated by increased plasma estrogen concentrations (10).…”

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confidence: 89%

mentioning

confidence: 99%

“…As a result, arterial (Pa CO 2 ), alveolar, and cerebrospinal fluid PCO 2 decrease throughout pregnancy (11,15,16). In addition, arterial PO 2 (Pa O 2 ) is either unchanged (11) or slightly increased (16). The pregnancy-induced respiratory alkalosis is partially compensated for by increased renal excretion of bicarbonate and a lowering of plasma bicarbonate concentration (16).…”

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confidence: 99%

“…Some studies have demonstrated an increase in the sensitivity and decrease in the threshold of the central ventilatory chemoreflex response to CO 2 (15,22), whereas Moore et al (21) observed no effect. In addition, Hannhart et al (11) reported that central chemoreflex sensitivity was greater in pregnant vs. nonpregnant cats. However, the threshold for CO 2 was similar in the two groups.…”

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confidence: 99%

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Effects of human pregnancy on the ventilatory chemoreflex response to carbon dioxide

Jensen¹,

Wolfe²,

Slatkovska³

et al. 2005

American Journal of Physiology-Regulatory, Integrative and Comp

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This study examined the effects of human pregnancy on the central chemoreflex control of breathing. Subjects were two groups ( n = 11) of pregnant subjects (PG, gestational age, 36.5 ± 0.4 wk) and nonpregnant control subjects (CG), equated for mean age, body height, prepregnant body mass, parity, and aerobic fitness. All subjects performed a hyperoxic CO2 rebreathing procedure, which includes prior hyperventilation and maintenance of iso-oxia. Resting blood gases and plasma progesterone and estradiol concentrations were measured. During rebreathing trials, end-tidal Pco2 increased, whereas end-tidal Po2 was maintained at a constant hyperoxic level. The point at which ventilation (V̇e) began to rise as end-tidal Pco2 increased was identified as the central chemoreflex ventilatory recruitment threshold for CO2 (VRTco2). V̇e levels below (basal V̇e) and above (central chemoreflex sensitivity) the VRTco2 were determined. The VRTco2 was significantly lower in the PG vs. CG (40.5 ± 0.8 vs. 45.8 ± 1.6 Torr), and both basal V̇e (14.8 ± 1.1 vs. 9.3 ± 1.6 l/min) and central chemoreflex sensitivity (5.07 ± 0.74 vs. 3.16 ± 0.29 l·min−1·Torr−1) were significantly higher in the PG vs. CG. Pooled data from the two groups showed significant correlations for resting arterial Pco2 with basal V̇e, central chemoreflex sensitivity, and the VRTco2. The VRTco2 was also correlated with progesterone and estradiol concentrations. These data support the hypothesis that pregnancy decreases the threshold and increases the sensitivity of the central chemoreflex response to CO2. These changes may be due to the effects of gestational hormones on chemoreflex and/or nonchemoreflex drives to breathe.

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Human adaptation to high altitude: Regional and life-cycle perspectives

Moore

Niermeyer

Zamudio

1998

Am. J. Phys. Anthropol.

325

231

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Studies of the ways in which persons respond to the adaptive challenges of life at high altitude have occupied an important place in anthropology. There are three major regions of the world where high-altitude studies have recently been performed: the Himalayas of Asia, the Andes of South America, and the Rocky Mountains of North America. Of these, the Himalayan region is larger, more geographically remote, and likely to have been occupied by humans for a longer period of time and to have been subject to less admixture or constriction of its gene pool. Recent studies of the physiological responses to hypoxia across the life cycle in these groups reveal several differences in adaptive success. Compared with acclimatized newcomers, lifelong residents of the Andes and/or Himalayas have less intrauterine growth retardation, better neonatal oxygenation, and more complete neonatal cardiopulmonary transition, enlarged lung volumes, decreased alveolar-arterial oxygen diffusion gradients, and higher maximal exercise capacity. In addition, Tibetans demonstrate a more sustained increase in cerebral blood flow during exercise, lower hemoglobin concentration, and less susceptibility to chronic mountain sickness (CMS) than acclimatized newcomers. Compared to Andean or Rocky Mountain high-altitude residents, Tibetans demonstrate less intrauterine growth retardation, greater reliance on redistribution of blood flow than elevated arterial oxygen content to increase uteroplacental oxygen delivery during pregnancy, higher levels of resting ventilation and hypoxic ventilatory responsiveness, less hypoxic pulmonary vasoconstriction, lower hemoglobin concentration, and less susceptibility to CMS. Several of the distinctions demonstrated by Tibetans parallel the differences between natives and newcomers, suggesting that the degree of protection or adaptive benefit relative to newcomers is enhanced for the Tibetans. We thus conclude that Tibetans have several physiological distinctions that confer adaptive benefit consistent with their probable greater generational length of high-altitude residence. Future progress is anticipated in achieving a more integrated view of high-altitude adaptation, incorporating a sophisticated understanding of the ways in which levels of biological organization are articulated and a recognition of the specific genetic variants contributing to differences among high-altitude groups.

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Influence of pregnancy on ventilatory and carotid body neural output responsiveness to hypoxia in cats

Cited by 46 publications

References 0 publications

Determinants of blood oxygenation during pregnancy in Andean and European residents of high altitude

Determinants of blood oxygenation during pregnancy in Andean and European residents of high altitude

Effects of human pregnancy on the ventilatory chemoreflex response to carbon dioxide

Human adaptation to high altitude: Regional and life-cycle perspectives

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