A former mayor of Worthing chained himself to an NHS building to protest at plans to downgrade two hospitals.
More than 136,000 people have signed the petition
Tom Wye was among a group, including two women in wheelchairs, who chained themselves to the front door of West Sussex Primary Care Trust (PCT) HQ.
The trust, in Goring-by-Sea, has started a public consultation on plans for the county's three major hospitals.
It wants only one to have the full range of A&E, emergency surgery and consultant-led maternity services.
The three hospitals whose services are in doubt are St Richard's at Chichester, Worthing and Southlands, and the Princess Royal, in Haywards Heath.
Police attended the protest on Tuesday, where the group were chained to the HQ for four hours, but no arrests were made.
"It was a peaceful protest to draw attention to the options the PCT are offering West Sussex," said Mr Wye.
"We arrived at 5am and it was no problem at all to chain ourselves to the door - it was like a slick military operation."
A series of public meetings to discuss the hospital options begins on Thursday at Clair Hall in Haywards Heath.
It continues until 18 October, with a final meeting at Martlets Hall in Burgess Hill.
Chief executive of the PCT, John Wilderspin, said: "We intend to use the consultation process to talk to people about their concerns, explain our proposals and to hear people's views.
"We are strongly committed to our local NHS and want to see it being improved in the future.
"Keeping things as they are is not the best way to ensure the highest quality of care for the future, and we need to make change now to be able to respond to this challenge."