Climbers usually resident at moderate altitude exhibit less oygen desaturation during rapid ascent to 4559 m

Usual residence >900m is reported to reduce the incidence of acute mountain sickness (AMS) during rapid ascent >2500m. If this fact is due to a ever higher oxygen saturation (SpO2) is not known. AIM: to continuously monitor SpO2 during the climb from 1154m to 4559m with an overnight stay at 3647m. METHODS: 70 subjects (14 F) were recruited. Each subject was fitted with a 24-hour recording finger pulse oximeter. The subjects rode a cable car to 3275m and climbed to 3647m, where 60 subjects spent the night (S) whilst 10 subjects (3 F), permanently living at 1000-1200m, climbed directly to 4559m (D). We subsequently divided the subjects according to the presence of AMS (Lake Louise score ≥3). None of D suffered from AMS, whilst 24/60 S had a Lake Louise score ≥3 (AMS +, AMS - respectively)¹. The mean values of SpO2 during exercise from 3275m to 3647m (E1) and from 3647m to 4559m (E2), and % of time spent under different SpO2 values <90%, <85%, <80% are reported in Table 1 Comparison among groups was performed by repeated-measures ANOVA (mixed model). | | mean SpO2 E1 | mean SpO2 E2 | % of time < 90% | % of time<85% | % of time< 80% | || | D | 82±4 | 79±4 | 91±4∗ | 78±9∗ | 54±20∗ | | S-AMS - | 82±3 | 77±4 | 97±6 | 87±14 | 68±21 | | S-AMS + | 82±3 | 72±5° | 99±1 | 93±5 | 81±11 | * ∗p<0.05 as compared to S‚° p<0.05 as compared to D Conclusions: the introduction of the length and severity of oxygen desaturation allow us to state that climbers usually resident at moderate altitude have a higher oxygen saturation throughout the whole exposure to high altitude, in comparison to low-lander climbers. The less severe desaturation can explain the lower incidence of AMS even during a very fast ascent to 4559m. ¹Mandolesi et al WEM 2014.