This is a recent study from the Danish Anaesthesia Register and they looked at predictors for difficulties with facemask ventilation.
Interestingly if their score is between 6–10 points these patients need special attention as it could turn out difficult mask ventilation compared to those with lower score. Higher the risks are obvious. A clear cut off value was not to establish and their proposed score needs prospective validation in clinical practice. All in all a new attempt to solve a nearly impossible task - predicting what happens in the future but still a needed task - pre-anaesthesia evaluation to focus attention to possible problems of the patients, the process or the anaesthesia personnel which includes all of us.
Have fun in reading the article
Lundstrøm LH, Rosenstock CV, Wetterslev J, Nørskov AK: The DIFFMASK score for predicting difficult facemask ventilation: a cohort study of 46,804 patients, Anaesthesia. 2019 May 20. doi: 10.1111/anae.14701. [Epub ahead of print]