20 research outputs found
THE INFLUENCE OF CARDIAC RESYNCHRONIZATION THERAPY IN CHRONIC HEART FAILURE ON RESPIRATORY PROFILE AND AUTONOMIC MODULATION
No full textDifferent determinants of left ventricular mass and relative wall thickness in male and female hypertensive patients undergoing 24 hour ambulatory blood pressure monitoring
No full textDisappearance of isocapnic buffering period during increasing work rate exercise at high altitude
No full textBackground At sea level, ventilation kinetics are characterized during a ramp exercise by three progressively steeper slopes, the first from the beginning of exercise to anaerobic threshold, the second from anaerobic threshold to respiratory compensation point, and the third from respiratory compensation point to peak exercise. In the second ventilation phase, body CO2 stores are used to buffer acidosis owing to lactate production; it has been suggested that this extra CO2 production drives the ventilation increase. At high altitude, ventilation increases owing to hypoxia. We hypothesize that ventilation increase reduces body CO2 stores affecting ventilation kinetics during exercise. Design In eight healthy participants, we studied the ventilation kinetics during an exercise performed at sea level and at high altitude (4559 m). Methods We used 30 W/2 min step incremental protocol both at sea level and high altitude. Tests were done on a cycloergometer with breath-by-breath ventilation and inspiratory and expiratory gas measurements. We evaluated cardiopulmonary data at anaerobic threshold, respiratory compensation point, peak exercise and the VE/VCO2 slope. Results At high altitude: (a) peak Vo(2) decreased from 2595 +/- 705 to 1745 +/- 545mi/min (P < 0.001); (b) efficiency of ventilation decreased (VE/VCO2 slope from 25 +/- 2 to 38 +/- 4, P < 0.0001); (c) at each exercise step end-tidal pressure change for CO2 was lower; and (d) the isocapnic buffering period disappeared in seven over eight participants and was significantly shortened in the remaining participant. Conclusion Exercise performed at high altitude is characterized by two, instead of three, ventilation slopes
Dynamic changes in indices of autonomic cardiovascular regulation induced by standing predict left ventricullar mass in hypertension
No full textAge related changes in indices of autonomic cardiovascular regulation and their relation to organ damage in hypertension
No full textThe strange story of the Sherpa and the tank of carbon monoxide: that is the story of a scientific adventure. A HIGHCARE 2008 substudy
No full textPulmonary vein isolation leads to transient alteration of cardiac baroreflex sensitivity
No full textBaroreflex sensitivity is reduced in patients with recurrent symptomatic atrial fibrillation
No full textEffects of slow deep breathing at high altitude on oxygen saturation, pulmonary and systemic hemodynamics.
Get PDFSlow deep breathing improves blood oxygenation (Sp(O2)) and affects hemodynamics in hypoxic patients. We investigated the ventilatory and hemodynamic effects of slow deep breathing in normal subjects at high altitude. We collected data in healthy lowlanders staying either at 4559 m for 2-3 days (Study A; N = 39) or at 5400 m for 12-16 days (Study B; N = 28). Study variables, including Sp(O2) and systemic and pulmonary arterial pressure, were assessed before, during and after 15 minutes of breathing at 6 breaths/min. At the end of slow breathing, an increase in Sp(O2) (Study A: from 80.2±7.7% to 89.5±8.2%; Study B: from 81.0±4.2% to 88.6±4.5; both p<0.001) and significant reductions in systemic and pulmonary arterial pressure occurred. This was associated with increased tidal volume and no changes in minute ventilation or pulmonary CO diffusion. Slow deep breathing improves ventilation efficiency for oxygen as shown by blood oxygenation increase, and it reduces systemic and pulmonary blood pressure at high altitude but does not change pulmonary gas diffusion
Effects of Beta-Blockade on Exercise Performance at High Altitude: A Randomized, Placebo-Controlled Trial Comparing the Efficacy of Nebivolol versus Carvedilol in Healthy Subjects
No full textAims Exposure to high altitude (HA) hypoxia decreases exercise performance in healthy subjects. Although beta-blockers are known to affect exercise capacity in normoxia, no data are available comparing selective and nonselective beta-adrenergic blockade on exercise performance in healthy subjects acutely exposed to HA hypoxia. We compared the impact of nebivolol and carvedilol on exercise capacity in healthy subjects acutely exposed to HA hypobaric hypoxia. Methods In this double-blind, placebo-controlled trial, 27 healthy untrained sea-level (SL) residents (15 males, age 38.3 +/- 12.8 years) were randomized to placebo (n = 9), carvedilol 25 mg b.i.d. (n = 9), or nebivolol 5 mg o.d. (n = 9). Primary endpoints were measures of exercise performance evaluated by cardiopulmonary exercise testing at sea level without treatment, and after at least 3 weeks of treatment, both at SL and shortly after arrival at HA (4559 m). Results HA hypoxia significantly decreased resting and peak oxygen saturation, peak workload, VO2, and heart rate (HR) (P < 0.01). Changes from SL (no treatment) differed among treatments: (1) peak VO2 was better preserved with nebivolol (22.5%) than with carvedilol (37.6%) (P < 0.01); (2) peak HR decreased with carvedilol (43.9 +/- 11.9 beats/min) more than with nebivolol (24.8 +/- 13.6 beats/min) (P < 0.05); (3) peak minute ventilation (VE) decreased with carvedilol (9.3%) and increased with nebivolol (+15.2%) (P= 0.053). Only peak VE changes independently predicted changes in peak VO2 at multivariate analysis (R= 0.62, P < 0.01). Conclusions Exercise performance is better preserved with nebivolol than with carvedilol under acute exposure to HA hypoxia in healthy subjects
