The 42-year-old has won this event at the last two Paralympics and it is hard to see who will prevent her from making it three, given she is 14.16 ahead of Song Lingling who was second fastest through.
Bruhn touched in 1:35.03, 1.20 outside her own world record, which could well be under threat tonight before she bows out of competition.
There were two Paralympic records in as many races in the women's 100m Breaststroke - SB6.
Liz Johnson is the defending champion and she set a new Games mark of 1:41.09 in the first heat.
However, Great Britain team-mate Charlotte Henshaw lowered it by a significant 1.45 in the next heat.
Henshaw, fourth in Beijing, said: 'I was really surprised. I just wanted to go in and do a solid heat and I think a lot of the nerves really pushed me on, I really wanted to post a good time.
'I think that's the best time I have done in near enough 18 months so it is a massive confidence-booster because I had a little bit of a dip at the beginning of the year, trials weren't particularly great.'
Jessica Long will aim for her sixth medal in the pool after she set a Paralympic record en route to reaching the final of the women's 200m Individual Medley - SM8.
Long, who has already won golds in the S8 class in the 400m Freestyle, 100m Butterfly and 100m Breaststroke as well as two silver medals, did not appear too happy at the finish of her race this morning despite her time of 2:40.42.
The men's 400m Freestyle - S10 promises to be a thriller with a little over six seconds separating the field.
There was a world record of 1:01.35 for Yang Yang in the 50m Backstroke - S2.