Lincoln Road in Peterborough was closed on Saturday night to allow the air ambulance to land and attend a medical incident.
Police were called by the ambulance service at 9.50pm on Saturday (May 13) to reports of a woman in cardiac arrest at a premises in Lincoln Road.
Officers assisted with a road closure to enable the air ambulance to attend the scene.
A spokesman for the East of England Ambulance Service said: “We were called at 9.43pm to Lincoln Road, Peterborough, on 13th May to a report of a woman who had collapsed and was not breathing.
“A community first responder, rapid response vehicle, ambulance officer, ambulance crew and response car from Magpas were dispatched.
They treated a woman in her 50s who was in cardiac arrest.
“Following treatment at the scene, she was resuscitated and taken by land ambulance to Papworth Hospital in a critical condition.”