Maternal hyperventilation helps preserve arterial oxygenation during high-altitude pregnancy

We examined arterial oxygenation during pregnancy and 3 mo postpartum in 35 nonsmoking residents of Leadville, CO (elevation 3,100 m) to determine how well and by what mechanisms maternal arterial oxygenation was maintained during pregnancy at high altitude. Hyperventilation raised arterial O2 saturation above that in the nonpregnant state. Respiratory alkalosis persisted throughout pregnancy, shifting the O2-hemoglobin dissociation curve to the left, further facilitating O2 loading in the lung. However, a decrease in blood hemoglobin concentration and a slight increase in the alveolar-arterial O2 gradient in the late pregnancy caused the arterial O2 content to fall below that in the nonpregnant state. Compared to published sea level values, the Leadville women had higher ventilation and hemoglobin values, yielding arterial O2 contents as high as in pregnant women at sea level. Thus, ventilation and hemoglobin concentration were important variables contributing to O2 ttransport during pregnancy at high altitude.

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Maternal hypoxic ventilatory response, ventilation, and infant birth weight at 4,300 m

Journal of Applied Physiology ◽

10.1152/jappl.1986.60.4.1401 ◽

1986 ◽

Vol 60 (4) ◽

pp. 1401-1406 ◽

Cited By ~ 73

Author(s):

L. G. Moore ◽

P. Brodeur ◽

O. Chumbe ◽

J. D'Brot ◽

S. Hofmeister ◽

...

Keyword(s):

Birth Weight ◽

Pregnant Women ◽

High Altitude ◽

Shape Parameter ◽

Ventilatory Response ◽

Hemoglobin Concentration ◽

Hypoxic Ventilatory Response ◽

Cerro De Pasco ◽

Arterial O2 Saturation ◽

Infant Birth

To test the hypothesis that increased hypoxic ventilatory responsiveness (HVR) raised maternal ventilation and arterial oxygenation during high-altitude pregnancy and related to the birth weight of the offspring, we studied 21 residents of Cerro de Pasco, Peru (4,300 m), while eight of them were 36 +/- 0 wk pregnant and 15 of them 13 +/- 0 wk postpartum. HVR was low in the nonpregnant women (mean +/- SE shape parameter A = 23 +/- 8) but increased nearly fourfold with pregnancy (A = 87 +/- 17). The increase in HVR appeared to account for the 25% rise in resting ventilation with pregnancy (delta VE observed = 2.4 +/- 0.7 l/min BTPS vs. delta VE predicted from delta HVR = 2.6 +/- 1.7 l/min BTPS, P = NS). Hyperoxia decreased ventilation in the pregnant women (P less than 0.01) to levels similar to those measured when nonpregnant. The increased ventilation of pregnancy raised arterial O2 saturation (SaO2) from 83 +/- 1 to 87 +/- 0%, and SaO2 was correlated positively with HVR in the pregnant women. The rise in SaO2 compensated for a 0.9 g/100 ml decrease in hemoglobin concentration to preserve arterial O2 content at levels present when nonpregnant. Cardiac output in the 36th wk of pregnancy did not differ significantly from values measured postpartum. The increase in HVR correlated positively with infant birth weight. An increase in HVR may be an important contributor to increased maternal ventilation with pregnancy and infant birth weight at high altitude.

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The Influence of Altitude on Erythropoietin Resistance Index in Maintenance Hemodialysis Patients: Data from Tibetan Plateau

Blood Purification ◽

10.1159/000510997 ◽

2020 ◽

pp. 1-6

Author(s):

Yan Wang ◽

Zong-hui Dang ◽

Liang-ying Gan ◽

Ciren Luobu ◽

Lei Zhang ◽

...

Keyword(s):

High Altitude ◽

Sea Level ◽

Resistance Index ◽

Hemoglobin Concentration ◽

Maintenance Hemodialysis ◽

Autonomous Region ◽

Tibet Autonomous Region ◽

Dialysis Vintage ◽

Peking University ◽

The Impact

Background: It is known that hypoxia influences many of the biologic processes involved in erythropoiesis; therefore, the high-altitude hypoxia may affect erythropoietin (EPO) responsiveness in maintenance hemodialysis (MHD) patients. This study aimed to evaluate the impact of altitude on EPO responsiveness in MHD patients. Methods: In this retrospective study, MHD patients from Tibet Autonomous Region People’s Hospital (3,650 m above sea level) and Peking University People’s Hospital (43.5 m above sea level) were recruited between May 2016 and December 2018. Patients were divided into 2 groups according to altitude. Variables including age, sex, dialysis vintage, dialysis modality, duration of EPO use, EPO doses, and laboratory tests were collected and analyzed. EPO responsiveness was measured in terms of the EPO resistance index (ERI). ERI was defined as the weekly weight-adjusted dose of EPO (IU/kg/week) divided by hemoglobin concentration (g/dL). The association between ERI and altitude was estimated using a multivariable linear regression model. Results: Sixty-two patients from Tibet Autonomous Region People’s Hospital (high-altitude [HA] group) and 102 patients from Peking University People’s Hospital (low-altitude [LA] group) were recruited. The ERI for HA group and LA group was 6.9 ± 5.1 IU w−1 kg−1 (g/dL)−1 and 11.5 ± 6.4 IU w−1 kg−1 (g/dL)−1, respectively. After adjusting for covariates by multivariable regression, altitude was independently associated with ERI (R2 = 0.245, p < 0.001). Conclusion: Altitude had an independent negative correlation with ERI. This result supported the hypothesis that altitude-associated hypoxia improved EPO responsiveness in MHD patients.

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Infant birth weight is related to maternal arterial oxygenation at high altitude

Journal of Applied Physiology ◽

10.1152/jappl.1982.52.3.695 ◽

1982 ◽

Vol 52 (3) ◽

pp. 695-699 ◽

Cited By ~ 72

Author(s):

L. G. Moore ◽

S. S. Rounds ◽

D. Jahnigen ◽

R. F. Grover ◽

J. T. Reeves

Keyword(s):

Birth Weight ◽

High Altitude ◽

Fetal Growth ◽

Growth Retardation ◽

Hemoglobin Concentration ◽

Late Gestation ◽

Fetal Growth Retardation ◽

Arterial Oxygenation ◽

Maternal Characteristics ◽

Infant Birth

Infant birth weight is reported to decrease at high altitude as a reulst of fetal growth retardation (McCullough, Reeves, and Liljegren. Arch. Environ, Health. 32: 36--39, 1977) but not all babies born at high altitude are small. We hypothesized that maternal characteristics acting to lower arterial O2 content would contribute to smaller infant birth weight. To test this hypothesis, we measured arterial oxygenation serially during pregnancy and again postpartum in 44 residents of Leadville, CO (elevation 3,100 m). We identified three maternal characteristics--ventilation, hemoglobin concentration, and smoking habits--that were related to the birth weight of the offspring. Mothers of smaller babies (less than 2,900 g) compared to mothers of larger babies (greater than 3,500 g) were characterized by hypoventilation, no change or a decrease in ventilation and arterial O2 saturation from early to late gestation, and a falling hemoglobin concentration that combined to lower arterial O2 content in the 3rd trimester. Maternal smoking at 3,100 m was associated with a two to threefold greater reduction in infant birth weight (-546 g) than reported from sea level. Thus, maternal arterial oxygenation during pregnancy may be important for predicting fetal growth retardation and the process of adaptation to high altitude.

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Oxygen transport of hemoglobin in high-altitude animals (Camelidae)

Journal of Applied Physiology ◽

10.1152/jappl.1975.38.5.806 ◽

1975 ◽

Vol 38 (5) ◽

pp. 806-810 ◽

Cited By ~ 45

Author(s):

C. Reynafarje ◽

J. Faura ◽

D. Villavicencio ◽

A. Curaca ◽

B. Reynafarje ◽

...

Keyword(s):

High Altitude ◽

Sea Level ◽

Oxygen Transport ◽

Fetal Hemoglobin ◽

Lactic Dehydrogenase ◽

Tissue Level ◽

Dissociation Curve ◽

Blood Characteristics ◽

Glucose 6 Phosphate Dehydrogenase ◽

2,3 Dpg

To clarify the mechanisms by which high-altitude Camelidae can adapt to hypoxia, the study of some blood characteristics were carried out in apacas and llamas. The results show that there is a peculiar dissociation curve of hemoglobin in alpacas which permits great affinity of hemoglobin for oxygen at lung level and the release of oxygen at the tissue level with a facility similar to that in man. Fetal hemoglobin was found high in adult alpacas (55 percent). Electrophoretic studies of hemoglobin showed that this pigment has two components, both of which have a very low mobility. Lactic dehydrogenase was found six times higher than in humans. RBC glucose-6-phosphate dehydrogenase was two times higher than in man living at the same altitude. Myoglobin was found to be higher than in man living at altitude. Alpacas have erythrocytes in which the amount of 2,3-DPG is approximately the same as in man. RBC are more resistent to hypotonic solutions than humans. The amount of lactic dehydrogenase, myoglobin, and glucose-6-phosphate dehydrogenase dimishes when alpacas are bought down to sea level.

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Effects of erythrocyte infusion on VO2max at high altitude

Journal of Applied Physiology ◽

10.1152/jappl.1996.81.1.252 ◽

1996 ◽

Vol 81 (1) ◽

pp. 252-259 ◽

Cited By ~ 35

Author(s):

A. J. Young ◽

M. N. Sawka ◽

S. R. Muza ◽

R. Boushel ◽

T. Lyons ◽

...

Keyword(s):

High Altitude ◽

Sea Level ◽

Carrying Capacity ◽

Hemoglobin Concentration ◽

Treadmill Running ◽

Control Group ◽

O2 Uptake ◽

Control Subjects ◽

And Control ◽

Experimental Group

This study investigated whether autologous erythrocyte infusion would ameliorate the decrement in maximal O2 uptake (VO2max) experienced by lowlanders when they ascend to high altitude. VO2max was measured in 16 men (treadmill running) at sea level (SL) and on the 1st (HA1) and 9th (HA9) days of high-altitude (4,300 m) residence. After VO2max was measured at SL, subjects were divided into two matched groups (n = 8). Twenty-four hours before ascent to high altitude, the experimental group received a 700-ml infusion of autologous erythrocytes and saline (42% hematocrit), whereas the control group received only saline. The VO2max of erythrocyte-infused [54 +/- 1 (SE) ml.kg-1.min-1] and control subjects (52 +/- 2 ml.kg-1.min-1) did not differ at SL before infusion. The decrement in VO2max on HA1 did not differ between groups, averaging 26% overall, despite higher (P < 0.01) arterial hematocrit, hemoglobin concentration, and arterial O2 content in the erythrocyte-infused subjects. By HA9, there were no longer any differences in hematocrit, hemoglobin concentration, or arterial O2 content between groups. No change in VO2max occurred between HA1 and HA9 for either group. Thus, despite increasing arterial O2-carrying capacity, autologous erythrocyte infusion did not ameliorate the decrement in VO2max at 4,300-m altitude.

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Hemoglobin at High Altitude as Related to Age

Clinical Chemistry ◽

10.1093/clinchem/9.6.710 ◽

1963 ◽

Vol 9 (6) ◽

pp. 710-716 ◽

Cited By ~ 6

Author(s):

D B Dill ◽

J W Terman ◽

F G Hall

Keyword(s):

High Altitude ◽

Sea Level ◽

Blood Volume ◽

Early Phase ◽

Hemoglobin Concentration ◽

The Other ◽

Other Hand

Abstract During the summer of 1962 the early phase of acclimatization to high altitude was studied in 6 of those who participated in the international high-altitude expedition to Chile in 1935. Ages of the 6 ranged from 58 to 71. Two also had taken part in a high-altitude study in 1929. In their earlier years these subjects had had an increase in hemoglobin concentration beginning with their arrival at high altitude. This response has been well established, especially by the Pike's Peak party led by Haldane and the work of Hurtado and associates in Peru. On the other hand, 5 of the 6 in the 1962 party exhibited a decrease in hemoglobin concentration during the first few days. The greatest decrease was observed in the oldest subject. His hemoglobin was 88% of his sea level value after 9 days at altitude and remained below his sea level value for another week. No observations were made on blood volume; hence, we can only speculate regarding possible related changes.

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Acid-base balance at high altitude in lowlanders and indigenous highlanders

Journal of Applied Physiology ◽

10.1152/japplphysiol.00757.2021 ◽

2022 ◽

Author(s):

Michael M. Tymko ◽

Christopher K. Willie ◽

Connor A. Howe ◽

Ryan L. Hoiland ◽

Rachel Stone ◽

...

Keyword(s):

High Altitude ◽

Sea Level ◽

Respiratory Alkalosis ◽

Indigenous Populations ◽

Acid Base Balance ◽

Acid Base ◽

Altitude Exposure ◽

Arterial Blood ◽

Blood Ph ◽

Base Balance

High-altitude exposure results in a hyperventilatory-induced respiratory alkalosis followed by renal compensation (bicarbonaturia) to return arterial blood pH(a) toward sea-level values. However, acid-base balance has not been comprehensively examined in both lowlanders and indigenous populations - where the latter are thought to be fully adapted to high-altitude. The purpose of this investigation was to compare acid-base balance between acclimatizing lowlanders, and Andean and Sherpa highlanders at various altitudes (~3,800, ~4,300, and ~5,000 m). We compiled data collected across five independent high-altitude expeditions and report the following novel findings: 1) at 3,800 m, Andeans (n=7) had elevated pHa compared to Sherpas (n=12; P<0.01), but not to lowlanders (n=16; nine days acclimatized; P=0.09); 2) at 4,300 m, lowlanders (n=16; 21 days acclimatized) had elevated pHa compared to Andeans (n=32) and Sherpas (n=11; both P<0.01), and Andeans had elevated pHa compared to Sherpas (P=0.01); and 3) at 5,000 m, lowlanders (n=16; 14 days acclimatized) had higher pHa compared to both Andeans (n=66) and Sherpas (n=18; P<0.01, and P=0.03, respectively), and Andean and Sherpa highlanders had similar blood pHa (P=0.65). These novel data characterize acid-base balance acclimatization and adaptation to various altitudes in lowlanders and indigenous highlanders.

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Beta-adrenergic blockade does not prevent the lactate response to exercise after acclimatization to high altitude

Journal of Applied Physiology ◽

10.1152/jappl.1994.76.2.610 ◽

1994 ◽

Vol 76 (2) ◽

pp. 610-615 ◽

Cited By ~ 31

Author(s):

R. S. Mazzeo ◽

G. A. Brooks ◽

G. E. Butterfield ◽

A. Cymerman ◽

A. C. Roberts ◽

...

Keyword(s):

High Altitude ◽

Sea Level ◽

Blood Lactate ◽

Lactate Concentration ◽

Blood Lactate Concentration ◽

Control Group ◽

Adrenergic Blockade ◽

Arterial O2 Saturation ◽

Response To Exercise ◽

Peak Blood

We examined the extent to which epinephrine influences blood lactate adjustments to exercise during both acute (AC) and chronic (CH) high-altitude exposure. Eleven male sea level residents were divided into a control group (n = 5) receiving a placebo or a drug group (n = 6) receiving 240 mg/day of propranolol. All subjects were studied at rest and during 45 min of submaximal exercise (approximately 50% of sea level maximal O2 uptake) at sea level (SL) and within 4 h of exposure to and after 3 wk residence at 4,300 m (summit of Pikes Peak). Blood samples were collected from the femoral artery for epinephrine and lactate concentration. Exercising blood lactate concentration was significantly different across all altitude conditions such that AC > CH > SL (P < 0.05). For a given arterial O2 saturation, mean exercising blood lactates were lower for the beta-blocked group compared with controls; however, both groups demonstrated similar patterns across all conditions. Epinephrine levels during exercise followed a similar pattern to that of lactate, averaging 0.67, 0.43, and 0.29 ng/ml for AC, CH, and SL, respectively. The correlation between lactate and epinephrine was 0.93 and 0.84 for control and beta-blocked subjects, respectively. Whereas during exercise epinephrine was consistently higher for the beta-blocked group than controls, this difference was only significant during CH exposure. The epinephrine response was related to the extent of hypoxia in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

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Internal carotid and vertebral arterial flow velocity in men at high altitude

Journal of Applied Physiology ◽

10.1152/jappl.1987.63.1.395 ◽

1987 ◽

Vol 63 (1) ◽

pp. 395-400 ◽

Cited By ~ 62

Author(s):

S. Y. Huang ◽

L. G. Moore ◽

R. E. McCullough ◽

R. G. McCullough ◽

A. J. Micco ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

High Altitude ◽

Flow Velocity ◽

Sea Level ◽

Internal Carotid ◽

Hemoglobin Concentration ◽

Subsequent Increase ◽

O2 Transport ◽

Flow Velocities

Cerebral blood flow increases at high altitude, but the mechanism of the increase and its role in adaptation to high altitude are unclear. We hypothesized that the hypoxemia at high altitude would increase cerebral blood flow, which would in turn defend O2 delivery to the brain. Noninvasive Doppler ultrasound was used to measure the flow velocities in the internal carotid and the vertebral arteries in six healthy male subjects. Within 2–4 h of arrival on Pikes Peak (4,300 m), velocities in both arteries were slightly and not significantly increased above sea-level values. By 18–44 h a peak increase of 20% was observed (combined P less than 0.025). Subsequently (days 4–12) velocities declined to values similar to those at sea level. At altitude the lowest arterial O2 saturation (SaO2) and the highest end-tidal PCO2 was observed on arrival. By day 4 and thereafter, when the flow velocities had returned toward sea-level values, hemoglobin concentration and SaO2 were increased over initial high-altitude values such that calculated O2 transport values were even higher than those at sea level. Although the cause of the failure for cerebral flow velocity to increase on arrival is not understood, the subsequent increase may act to defend brain O2 transport. With further increase in hemoglobin and SaO2 over time at high altitude, flow velocity returned to sea-level values.

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