Wicked Local As the Shawsheen Valley Regional Vocational Technical High School class of 2021 prepared to walk one last time out onto the football field to graduate they had no idea the life of a graduate's family member in the process of being saved on that same turf. Six-minutes. This is how long it takes to reverse the damage that starts after the body begins to lose oxygen after a heart attack, according to Shawsheen Health Assisting Instructor Karen Meister, RN BSN. Meister knows this not only from years of teaching, but from practical experience as a critical care nurse, and put her know-how to the test on Thursday, June 3, when a man collapsed in the minutes prior to graduation.