Objective: Slow controlled breathing has been reported to reduce blood pressure (BP) in hypertensive patients, decreasing sympathetic nerve activity. In hypoxic conditions associated with high altitude, slow deep breathing has also been shown to improve oxygen saturation and to infl uence BP and heart rate. In the present teaching experiment conducted during the ESH 2018 Summer School, we have evaluated the impact of slow breathing on hemodynamic parameters and O2 saturation when acutely ascending from les Diablerets (altitude 1150 m) to Glacier 3000 (at 3010 m). Design and method: Blood pressure(ABPM, Novacor System, oscillometric validated device), heart rate and O2 saturation were measured at baseline, 30 minutes after arriving at 3010 m, during slow breathing, after 2 hours at altitude and after returning to baseline. Results: Eleven subjects (4 males/7 females) participated in the experiment. Mean age was 34.3 y and mean BMI was 24.3 km/m2. At baseline, systolic (S) BP and diastolic (D) BP were 132 ± 19/86 ± 11 mmHg, heart rate (HR) was 72.5 ± 8 b/min and O2 saturation was 98.2%. Breathing rate was 13.6 per min. Upon arrival at 3000m, O2 saturation decreased to 91.7% (p < 0.01) and breathing rate increased to 16.5 per min. Both SBP and DBP decreased signifi cantly to 123 ± 14 and 78 ± 9 mmHg respectively (P < 0.01) due to the acute vasodilating effects of hypoxemia. Heart rate increased to 94.8 b/min (p < 0.001). Slow breathing to 6 per min, lowered SBP to 118.8 ± 14 and increased DBP 80.9 ± 8.8 mmHg (p = ns). O2 saturation increased slightly to 92.5%. After 2 h, the subjects adapted their oxygenation but heart rate remained elevated (94.5 b/min). When returned to baseline, all values were normalized. Conclusions: Even short terms changes in altitude induce signifi cant changes in BP, heart rate and O2 saturation in healthy subjects. Slow breathing tends to improve BP and O2 saturation