Police said the Arcadia woman, 23, was driving her Commodore along Cattai Ridge Road at 5.40pm on Saturday.

She was approaching a left turn, 100 metres from Smiths Lane, when the driver's side of the car collided with a tree.

The NRMA CareFlight helicopter team doctor said the woman was unconscious with no pulse and a tree was protruding half a metre into the car. The CareFlight specialist trauma doctor and duty paramedic started resuscitation before the woman was freed after 40 minutes by Castle Hill Fire Brigade officers.

She was given a general anaesthetic and placed on a ventilator to control her breathing and given IV fluids to compensate for the loss of blood. She was taken by ambulance to the hospital for emergency surgery for head, chest and abdominal injuries.