Analysis and statistics Data will be described as n, mean, median, standard deviation, minimum and maximum for quantitative variables and frequencies for qualitative variables. The percentage of time in normal breathing range and normal saturation range will be compared between the last hour with S1 ventilator, and the first hour in conventional ventilation; and between the last hour with S1 ventilator and last hour in conventional ventilation 2 groups using a Wilcoxon's test.