HIGH Altitude CArdiovascular REsearch in the ANDES

This is a parallel group, prospective, double-blind, placebo controlled randomized trial, comparing the effects of combination of two antihypertensive agents (telmisartan/nifedipine)with placebo in hypertensive subjects exposed to high altitude. The principal objectives are: 1. to assess the response of BP to high altitude exposure in hypertensive subjects residing at sea level 2. To assess the efficacy and safety of combination of telmisartan 80 mg with nifedipine GITS 30 mg in preventing a possible excessive BP increase in hypertensive subjects exposed to high altitude. The following data will be collected during the study at the different steps: * Clinical history * Symptoms and adverse events questionnaire * Conventional BP and heart rate (HR) measurement - seated measurements with a validated oscillometric device will be performed after at least 5 minutes rest on non-dominant arm; two measurements will be performed 1-2 minutes apart and their average will be used in the analyses * Vital signs: respiratory rate - will be measured manually over 60 seconds body height and weight, waist circumference blood oxygen saturation (SpO2) * Lake Louise Score * 24 h ambulatory blood pressure monitoring (ABPM; AND TM2430, AND, Japan) * Echocardiography * Arterial properties assessment * Six minute walking test (6MWT) * Cardiopulmonary Exercise Test (CPET) in a subgroup of subjects * Polysomnography with a portable device * Pulmonary function tests (only at sea level baseline visit) * Fluid balance chart * Blood and urine analyses: Visit 1: electrolytes, creatinine, estimated glomerular filtration rate (eGFR), glycemia, renin, angiotensin, aldosterone, plasma catecholamines, 24 h urinary sodium excretion, carbonic anhydrase activity and isoenzyme expression (in 50 randomly selected subjects), samples for genetic studies. Visit 2: electrolytes, creatinine, eGFR. Visit 3: complete blood count, electrolytes, creatinine, eGFR, glycemia, insulin, renin, angiotensin, aldosterone, plasma catecholamines, classic urinalysis, microalbuminuria, 24 h urinary sodium excretion, carbonic anhydrase activity and isoenzyme expression (in 50 subjects selected at Visit 1). Visit 4: electrolytes, creatinine, eGFR, glycemia, insulin, renin, angiotensin, aldosterone, plasma catecholamines, 24 h urinary sodium excretion, carbonic anhydrase activity and isoenzyme expression (in 50 subjects selected at Visit 1)