After deriving a WAVE model based on all data , training-set performance demonstrated that the model increased its predictive power when applied to patients conventionally considered high risk : a WAVE score > 0.5 in patients with RSBI > 105 and perceived high risk of failure yielded a fold increase in risk of extubation failure of 3.0 ( 95 % confidence interval ( CI ) 1.2 to 5.2 ) and 3.5 ( 95 % CI 1.9 to 5.4 ) , respectively .