Carlos Monge

Hematological Parameters in High Altitude Residents Living at 4355, 4660, and 5500 Meters Above Sea Level

There have been a number of reports describing the hematological indicators of Andean residents living at altitudes above 4,000 m, but several confounding factors have made the published results difficult to interpret. To clear up the effect of hypoxia on hemoglobin concentration (Hb, g/dL), hematocrit (Hct, %) and red blood cell concentration (RBC, cells/microL), this publication describes and analyzes these variables in children, men, and women from three large and homogeneous populations living at 4,355 m (n = 151), 4,660 m (n = 400), and 5,500 m (n = 273) in the Southern Peruvian Andes. Hb, Hct, and RBC increase with age in men (p < 0.001), as well as in women (p < 0.001) at the three altitudes of the study. In children (boys and girls) living at 5,500, Hb increases 11% when compared with children living at 4,355 m, and in adults, Hb increases 9.6% when comparing the same altitudes. The maximum percentage increase in Hb with age was 5.6% at 5,500 m, in men and 3.2% at 4,355 m, in women. The average percentage of difference for the Hb concentration between adult men and women is 6.6% at 4,355 m, 9.8% at 4,660 m, and 11.6% at 5,500 m. The differences in Hb concentration between men and women can only be seen after puberty. Finally, Hb is higher in older than younger women, which confirms the role of menopause in the development of erythremia. The result of this analysis reinforces the notion that Hb and Hct seem to be stable and useful parameters for acclimatization only at moderate altitudes; with aging or with increasing altitude, they may become excessive and lose their efficiency to protect the venous oxygen pressure.

Fetal and maternal blood oxygen affinity: A comparative study in llamas and sheep☆

We compared blood oxygen affinity (P50) and hemoglobin concentration among fetal and maternal llamas and sheep, as respective examples of species native to high and low altitudes. P50, hemoglobin concentration and blood oxygen content were determined at sea level in 16 pregnant llamas, 6 pregnant sheep and their respective fetuses. P50 was similar in fetal llamas and sheep, but maternal llamas had higher blood oxygen affinity than maternal sheep. As a consequence, the P50 difference between mother and fetus was less in llamas than in sheep. Fetal llamas had higher hemoglobin concentrations than fetal sheep. In contrast, the maternal hemoglobin concentrations were similar. The blood oxygen content was higher in fetal and maternal llamas than in fetal and maternal sheep. We conclude that the llama, a species native to the altiplano, has a higher blood oxygen content than the sheep, as determined in the fetus by a high hemoglobin concentration and in the mother by a low P50.

Variation in eggshell characteristics and gas exchange of montane and lowland coot eggs

SummaryThis study determined how structural features of the eggshells of coots (Fulica americana) laid at 4150 m in the Peruvian Andes differed from those at sea level in Peru and California and how these features affected exchange of water vapor, O2, and CO2. While barometric pressure at 4150 m was reduced to 60% of that at sea level, the conductance to water vapor, corrected to 760 torr, of montane eggs was 107% of the corresponding lowland value. When the effect of low barometric pressure on the diffusion coefficient of gases was considered, the ‘effective’ conductance of the montane eggs at altitude was 177% of that at sea level. As a result, daily water loss from the montane eggs was substantially greater than that from lowland ones. The oxygen consumption of montane embryos was lower than that of lowland embryos of all sizes, particularly at larger embryonic masses. Just before pipping, the oxygen consumption of montane embryos was about 60% of the corresponding value for lowland individuals. Air cell oxygen tensions in montane eggs varied between about 65 and 38 torr; these values were about 60–70 torr below those in lowland eggs at equivalent embryonic masses. Just before pipping, the air cell CO2 tension of montane eggs was about 20 torr below levels in sea level eggs. The eggshell conductance to gases of montane eggs appears to have been selected to promote oxygen delivery at the cost of increased losses of water vapor and CO2.

Ventilation and the control of erythropoiesis in high-altitude natives of Chile and Nepal

Previous studies have suggested that the hematocrit and hemoglobin values in Himalayan natives (Sherpas) are lower than those of Andean natives (Quechua Indians) living at the same altitude, perhaps because of genetic differences. To study these populations further, we selected healthy male subjects in Ollagüe, Chile (n = 29, age = 27.3 ± 15.9 years), and in Khunde, Nepal (n = 30, age = 24.7 ± 13.8 years). Both of these villages are located at 3,700 m above sea level. Hematologic measurements confirmed lower hematocrit values in Nepal (48.4 ± 1 4.5%) than in Chile (52.2 ± 1 4.6%) (P < 0.003). When subjects were matched for hematocrit, erythropoietin concentrations in Chile were higher than in Nepal (P < 0.01).

Blood gases, pH and hematology of montane and lowland coot embryos

Blood gases, air cell-blood gas differences, blood pH, and hematology were compared in embryonic coots (Fulica americana peruviana) at 4150 m and sea level in Peru. Neither arterialized nor venous O2 tensions differed significantly between montane and lowland groups but blood CO2 tensions of the two groups differed significantly. The air cell PO2-arterialized blood PO2 difference of montane eggs was less than half the value in lowland eggs. Both arterialized and venous CO2 tensions differed substantially between montane and lowland groups. Despite these differences, plasma pH at both altitudes was statistically indistinguishable, due in part to variation in plasma [HCO3-]. Hematocrits of montane embryos were significantly higher than that of their lowland counterparts.

Hemoglobin affinity in Andean rodents

Blood hemoglobin oxygen affinity (P50) was measured in three Andean species and in the laboratory rat (control), all raised near sea level. Chinchilla lanigera (Molina, 1792) has an altitudinal habitat range from low Andean slopes up to 3000 m., while Chinchilla brevicaudata (Waterhouse, 1848) has an altitudinal range from 3000 to 5000 m. The laboratory type guinea pig, wild type guinea pig (Cavia porcellus), (Waterhouse, 1748), and laboratory rat (Rattus norvegicus) were also raised at sea level. The Andean species had high hemoglobin oxygen affinities (low P50) compared with the rat. Chinchilla brevicaudata had a higher affinity than Chinchilla lanigera. The wild type guinea pig had a higher affinity than the laboratory type. As has been shown in other species, this is another example of an inverse correlation between the altitude level and the P50 values. This is the first hemoglobin oxygen affinity study in Chinchilla brevicaudata.

Shell Conductance, Daily Water Loss, and Water Content of Puna Teal Eggs

Characteristics of Puna teal (Anas versicolor puna) eggs laid at 4,150 m in the Peruvian Andes were compared with those of similarly sized eggs laid by other Anas species at sea level Mean eggshell conductance to water vapor (GH₂O, corrected to 760 Torr) was reduced below the average of most of the sea-level controls, but not to the same extent as the reduction in barometric pressure at the breeding site. In contrast to findings of previous studies, the reduction in GH₂O was not significant in three of four comparisons. Since the diffusion coeficient for water vapor increases inversely with barometric pressure, water loss during incubation was high, but relative water content of the eggs did not vary significantly during incubation. Variation in shell conductance was most likely due to alteration in the number of pores rather than to size. The characteristics of montane Puna teal eggs appear to reflect selection by conflicting requirements for preventing excessive loses of water vapor and CO₂ and for maximizing O₂ availability to the embryo.

Normal whole blood Bohr effect in Peruvian natives of high altitude

Measurements of whole blood O2 affinity were made with an automatic technique that allowed recording of O2 saturation continuously over a range of PO2 of 1 to 150 torr at constant pH and PCO2 with fresh samples of blood obtained from 5 natives of high altitude at Morococha, Peru (altitude, 4540 m). The results were not significantly different from those obtained with controls living at sea level with regard to the dlog P50/dpH slope at constant PCO2 or at constant base excess. Both results also agree with previous studies with normal sea-level blood. Thus earlier claims of an increased Bohr in Peruvian high-altitude natives is not supported.

Physiological Strategies of Oxygen Transport in High Altitude Bird Embryos

Abstract Because of the relative simplicity of factors governing gas exchange between the embryo and the environment, the avian embryo has been extensively studied at sea level as a model for describing the physical principles that govern the physiology of gaseous diffusion. Two patterns of response have been observed in the oxygen pressure (PO2) cascade of high altitude avian embryos: (1) At a fixed O2 conductance, a decrease in metabolic rate below levels typical of conspecific species at sea level results in a reduction of ΔPO2 between ambient air and air cell. The decrease in metabolic rate also affects each step in the gradient until the mitochondria is reached. This is illustrated by a Ficks-type equation: P O 2 = V O 2 / G O 2 (GO2 = oxygen conductance); (2) Maintenance of metabolic rate at roughly sea level values and a large GO2 will also keep the ΔPO2 unmodified or even reduced. We have observed both patterns in mountain avian embryos in the Peruvian Andes. We measured VO2 and the ΔPO2 cascade of embryos of Peruvian coots (Fulica americana peruviana), which breed both at sea level and in the puna (Andean high altitude plateau), and those of Puna teal (Anas versicolor puna), a species that breeds solely in the puna, both at 4150 m. These two different strategies result in similar arterial PO2 values in both values in both embryos. Because the a-v PO2 gradient remains protected, the PVO2 values are also similar in the embryos of both high altitude birds.

Gas exchange and blood gases of Puna teal (Anas versicolor puna) embryos in the Peruvian Andes

Oxygen consumption, air cell gases, hematology, blood gases and pH of Puna teal (Anas versicolor puna) embryos were measured at the altitude at which the eggs were laid (4150 m) in the Peruvian Andes. In contrast to the metabolic depression described by other studies on avian embryos incubated above 3700 m, O2 consumption of Puna teal embryos was higher than even that of some lowland avian embryos at equivalent body masses. Air cell O2 tensions dropped from about 80 toor in eggs with small embryos to about 45 toor in eggs containing a 14-g embryo; simultaneously air cell CO2 tension rose from virtually negligible amounts to around 26 torr. Arterial and venous O2 tensions (32–38 and 10–12 toor, respectively, in 12- to 14-g embryos) were lower than described previously in similarly-sized lowland wild avian embryos or chicken embryos incubated in shells with restricted gas exchange. The difference between air cell and arterial O2 tensions dropped significantly during incubation to a minimum of 11 torr, the lowest value recorded in any avian egg. Blood pH (mean 7.49) did not vary significantly during incubation. Hemoglobin concentration and hematocrits rose steadily throughout incubation to 11.5 g · 100 ml-1 and 39.9%, respectively, in 14-g embryos.