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Biomedical subjects

C C Monge

Publications and source records attributed to C C Monge.

11 recordsLinked to original sources
PubMed2000

Hematological parameters in high altitude residents living at 4,355, 4,660, and 5,500 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.

Acclimatization↗
PubMed2000

Reduced oxygen diffusion across the shell of Gray gull (Larus modestus) eggs.

Gray gulls, Larus modestus, nest 1500 m above sea level in northern Chile's Atacama Desert, one of the driest in the world. Their eggshell gas permeability, one third of that found in other Larus species, is an adaptation that reduces water loss, but at the expense of oxygen diffusion into the air cell with resultant hypoxia and reduced metabolic rate. This contrasts with characteristics found in birds nesting at very high altitudes where oxygen diffusion across the egg shell is maximized at the expense of water conservation. The oxygen consumption (MO2) of Larus modestus is 66% that of Larus argentatus; the oxygen conductance (GO2) is equivalent to 48% of that obtained in 5 other bird species. The oxygen partial pressure (PAO2) in the air chamber of Larus modestus (84 Torr) is lower than that of 10 other bird species whose average (PAO2) is 106 Torr. The CO2 partial pressure (PACO2) in the air chamber of Larus modestus is 68 Torr, a higher value than that found in 9 other bird species whose average (PACO2) is 39 Torr.

Adaptation, Physiological↗
PubMed1991

Serum immunoreactive erythropoietin in high altitude natives with and without excessive erythrocytosis.

We report the estimation of blood hemoglobin (Hb), arterial blood oxygen saturation (SaO2), and serum immunoreactive erythropoietin (siEPO) in a group of Peruvian workers residing in Cerro de Pasco at 4300 m showing "excessive erythrocytosis" (EE, Monge's disease, chronic mountain sickness). These estimates were compared with those of humans residing either in Cerro de Pasco and showing "normal erythrocytosis" (NE) or in Lima (sea level, SL) to determine whether Hb and SaO2 are related to siEPO in high altitude (HA) natives with NE or EE. The three parameters showed statistically significant differences between HA and SL groups--the values in SL being lower. Significant differences were also found between NE and EE groups in Hb and SaO2. There was no statistical difference in siEPo between the two groups. The results indicate, therefore, that HA residents who develop EE are not distinguishable from residents who develop NE on the basis of estimates of siEPO. As a result, siEPO and Hb do not show a dose-response relationship in HA residents, and variation in EPO does not explain the striking variation in Hb at high altitudes.

Adult↗
PubMed1989

Different hematologic responses to hypoxia in Sherpas and Quechua Indians.

Previous studies of the erythropoietic response to hypoxia in high-altitude natives suggest that the hematocrit and hemoglobin values in Himalayan natives (Sherpas) are lower than expected for the altitude, perhaps because of a genetic adaptation. However, differences in sampling techniques and experimental methods make comparisons difficult. Our studies were carried out to compare the erythropoietic response with the same altitude in age-matched natives of the Himalayas and Andes by the same experimental techniques. Healthy male subjects were selected in Ollagüe, Chile (n = 29, 27.3 +/- 5.9 yr) and in Khunde, Nepal (n = 30, 24.7 +/- 3.8 yr). Both of these villages are located at 3,700 m above sea level. Hematologic measurements confirmed lower hematocrit values in Nepal (48.4 +/- 4.5%) than in Chile (52.2 +/- 4.6%) (P less than 0.003). When subjects were matched for hematocrit, erythropoietin concentrations in Chile were higher than in Nepal (P less than 0.01). Detailed measurements of blood O2 affinity in Nepal showed no differences in shape or position of the O2 equilibrium curve between Sherpas and Western sojourners. Our results indicate that although Quechua Indians have higher hematocrits than Sherpas living at the same altitude, nevertheless they may be functionally anemic.

Adult↗
PubMed1985

A technique to continuously measure arteriovenous oxygen content difference and P50 in vivo.

In hypoxemic high-altitude polycythemic natives whose arterial O2 saturation (SaO2) normally ranges between 70 and 80%, three polyurethane catheters with both optical and polarographic sensors were inserted into the radial artery to measure SaO2 and O2 tension (PaO2), and three thermodilution fiber-optic balloon-tipped catheters were floated into the pulmonary artery to measure mixed venous O2 saturation (SvO2). Correlation of the in vivo SaO2, PaO2, and SvO2 values with the in vitro measurements was high (r = 0.97, 0.99, and 0.98, respectively). Both catheters were inserted in one polycythemic subject before and 4 days after isovolemic hemodilution. Data from the sensors were used to calculate arteriovenous O2 content difference (CaO2 - CvO2) and the O2 half-saturation pressure of hemoglobin (P50). The mean +/- 1 SD of the in vivo and in vitro P50 calculated with the Hill equation was 27.61 +/- 2.15 Torr and 27.35 +/- 1.60 Torr, respectively. The mean +/- 1 SD of the absolute difference between the in vivo and in vitro measurements was 1.16 +/- 1.21 Torr. The in vivo CaO2 - CvO2 correlated well with the in vitro measurements (r = 0.93), and the mean +/- 1 SD of the error in the catheter CaO2 - CvO2 measurements was 0.47 +/- 0.50 ml/dl. This technique appears to provide a useful measurement of blood gas exchange parameters and should be applicable to the study of exercise physiology and clinical regulation of O2 transport.

Arteries↗
PubMed1985

Effects of hemodilution on O2 transport in high-altitude polycythemia.

A native of the Peruvian Andes (4,250 m) was studied before and after isovolemic hemodilution of the hematocrit from 62 to 42%. O2 transport was studied with newly developed catheters in the radial and pulmonary arteries. These catheters allowed continuous measurement of arteriovenous O2 content and intermittent cardiac output by thermodilution. During exercise tests, breath-by-breath gas exchange measurements also allowed cardiac output to be calculated by the O2-Fick technique. A complex series of interrelated physiological changes occurred in response to hemodilution. These included increased ventilation, increased arterial and mixed venous PO2, increased cardiac output (both heart rate and stroke volume), and improved ventilation-flow match. The general improvement in symptoms that followed hemodilution correlated well with increased anaerobic threshold and mixed venous PO2 during exercise.

Altitude↗
PubMed1982

Renin and aldosterone at high altitude in man.

Measurements have been made of hormonal changes relevant to salt and water balance during prolonged exposure to hypoxia to improve our understanding of the syndrome of acute mountain sickness. We have attempted to delineate the detailed inter-relationships between the renin-aldosterone and the vasopressin systems by a metabolically controlled study, involving an orthostatic stress (45 degrees head-up tilt) and an injection of a standard dose of ACTH to test adrenal responsiveness. Three Caucasian medical students underwent a 7-day equilibration at 150 m (Lima, Peru), followed by a 6-day sojourn at 4350 m (Cerro de Pasco, Peru) and a final 7 days at 150 m. Measurements were made of sodium and potassium balance, body weight and the 24-h renal excretion of vasopressin, cortisol and aldosterone 18-glucuronide. These variables showed little change, except for that of aldosterone 18-glucuronide, which fell sharply at altitude and rebounded even more sharply on return to sea level. At altitude, basal plasma levels of renin activity and aldosterone fell, and the response to orthostasis was attenuated, but the fall of plasma renin activity, as compared to plasma aldosterone, was delayed; on return to sea level this dissociation was exacerbated with the return of normal renin responsiveness lagging behind that of aldosterone. We suggest that unknown factors which dissociate the orthodox renin-aldosterone relationship, other than the activity of the angiotensin I-converting enzyme, are operative on exposure to hypoxia.

Adult↗
PubMed1981

Variability of oxygen affinity of blood: human subjects native to high altitude.

Whole blood O2 equilibrium curves (OEC) were measured in 46 Peruvians native to high altitude (4,540 m) and in 25 sea-level controls. A method was employed that records the entire OEC from 0 to 150 Torr with constant pH and PCO2. The data were analyzed by fitting the Adair equation describing the successive oxygenation of hemoglobin. At pH 7.4 the PO2 at which hemoglobin is half-saturated with O2 (P50) was significantly higher in the high-altitude population (31.2 +/- 1.9 Torr) than in controls (29.2 +/- 1.8 Torr, P less than 0.001). The acid-base status of the high-altitude subjects, however, was that of compensated respiratory alkalosis (plasma pH 7.439 +/- 0.065), and when the P50's were corrected to the subjects' plasma pH the values (30.1 +/- 2.2 Torr) could no longer be distinguished from the controls. We conclude that, on the average, increased P50 resulting from increased red cell 2,3-diphosphyoglycerate concentration at high altitude is offset by compensated respiratory alkalosis with the net result that the position of the OEC more closely approaches that of sea-level humans than has hitherto been thought. Considerable variation exists in P50, both at sea level and high altitude. This variation might have important consequences for acclimatization and survival under adverse environmental conditions.

2,3-Diphosphoglycerate↗
PubMed1976

Chronic mountain sickness.

Chronic mountain sickness was first described in the Peruvian Andes. It consists of an excesive polycythemia for the altitude of residence. Its main symptoms are of cerebral congestion and occasionally of right heart insufficiency. The authors postulate that it is caused by a decay of the ventilatory rate with age with the corresponding increase in hematocrit.

Adolescent↗