Is it ok to train at 95% of your maximum heart rate?

when I do cardio my average hear rate for 1 hour is 160bpm. My bp at doc last week was 123/71 with 60bpm heart rate. What I would like to know is - is it ok to train at say 95% of max heart rate? sometimes when i go flat our for a less than a minute etc I can get my heart rate up to 180 but can't sustain it... am I doing damage to my heart if I train at say 95% o f heart rate 3 days week?