Browsing by Autor "Stuber, Thomas"

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Aymara children are protected from high-altitude-induced pulmonary hypertension
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2005) Stuber, Thomas
Pulmonary hypertension is a hallmark of the adaptation to ambient lack of oxygen. This assumption is also thought to hold true for high-altitude native children, since invasive studies showed elevated pulmonary-artery pressure in a few children studied at high altitude. However, the data to support this assumption is extremely sparse. We, therefore measured systolic pulmonaryartery pressure (Doppler-echocardiography) and arterial oxygen saturation in 36 Bolivian high-altitude native children of Aymara ethnicity (age 6 months to 13 years, mean SD 7.3 3.0 years) in La Paz (3600 m). We also studied 18 age- and sex-matched Caucasian children who were born or long-term residents of La Paz, and a group of healthy Caucasian children born and living in Berne, Switzerland (450 m). The major new finding was that systolic pulmonary-artery pressure in healthy Bolivian children of Aymara ethnicity was markedly lower than in children of Caucasian descent (25.1 4.1 vs 34.2 9.0 mmHg, P 0.001), and, indeed, was similar to the one measured in children at low altitude (450 m). At high altitude, the lower pulmonary-artery pressure in the Aymara children was not related to better arterial oxygenation, because arterial oxygen saturation was lower than the one measured in the Caucasian children (88.2 4.1 vs. 92.9 2.4%, P 0.0001). These data represent the first measurements of pulmonary-artery pressure in a large group of healthy children living at high-altitude. We found that at high altitude, despite lower arterial oxygen saturation, Aymara children had roughly 30% lower pulmonary artery pressure than well adapted Caucasian children, a value that was comparable to the normal values measured at low altitude. The data challenge the long held concept that high-altitude exposure in children invariably leads to pulmonary hypertension. Protection from hypoxia-induced pulmonary hypertension may represent a specific high-altitude adaptation of the Aymaran ethnicity.
Exaggerated pulmonary hypertension during mild exercise in chronic mountain sickness
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2010) Stuber, Thomas
Background: Chronic mountain sickness (CMS) is an important public health problem and is characterized by exaggerated hypoxemia, erythrocytosis, and pulmonary hypertension. While pulmonary hypertension is a leading cause of morbidity and mortality in patients with CMS, it is relatively mild and its underlying mechanisms are not known. We speculated that during mild exercise associated with daily activities, pulmonary hypertension in CMS is much more pronounced. Methods: We estimated pulmonary artery pressure by using echocardiography at rest and during mild bicycle exercise at 50 W in 30 male patients with CMS and 32 age-matched, healthy control subjects who were born and living at an altitude of 3,600 m. Results: The modest, albeit significant difference of the systolic right-ventricular-to-right-atrial pressure gradient between patients with CMS and controls at rest (30.368.0 vs 25.464.5 mm Hg, P5.002) became more than three times larger during mild bicycle exercise (56.4619.0 vs 39.868.0 mm Hg, P,.001). Conclusions: Measurements of pulmonary artery pressure at rest greatly underestimate pulmonary artery pressure during daily activity in patients with CMS. The marked pulmonary hypertension during mild exercise associated with daily activity may explain why this problem is a leading cause of morbidity and mortality in patients with CMS.
Respiratory nitric oxide and pulmonary artery pressure in children of aymara and european ancestry at high altitude*
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2008) Stuber, Thomas
Invasive studies suggest that healthy children living at high altitude display pulmonary hypertension, but the data to support this assumption are sparse. Nitric oxide (NO) synthesized by the respiratory epithelium regulates pulmonary artery pressure, and its synthesis was reported to be increased in Aymara high-altitude dwellers. We hypothesized that pulmonary artery pressure will be lower in Aymara children than in children of European ancestry at high altitude, and that this will be related to increased respiratory NO. We therefore compared pulmonary artery pressure and exhaled NO (a marker of respiratory epithelial NO synthesis) between large groups of healthy children of Aymara (n 200; mean SD age, 9.5 3.6 years) and European ancestry (n 77) living at high altitude (3,600 to 4,000 m). We also studied a group of European children (n 29) living at low altitude. The systolic right ventricular to right atrial pressure gradient in the Aymara children was normal, even though significantly higher than the gradient measured in European children at low altitude (22.5 6.1 mm Hg vs 17.7 3.1 mm Hg, p < 0.001). In children of European ancestry studied at high altitude, the pressure gradient was 33% higher than in the Aymara children (30.0 5.3 mm Hg vs 22.5 6.1 mm Hg, p < 0.0001). In contrast to what was expected, exhaled NO tended to be lower in Aymara children than in European children living at the same altitude (12.4 8.8 parts per billion [ppb] vs 16.1 11.1 ppb, p 0.06) and was not related to pulmonary artery pressure in either group. Aymara children are protected from hypoxic pulmonary hypertension at high altitude. This protection does not appear to be related to increased respiratory NO synthesis.