The 49-year-old came off at the Red Bull Ring, with a statement issued from Saiger Racing revealing the crash occurred when his brakes failed.
“Because of his numerous injuries, he is in an artificial coma. He is in a critical but stable condition,” the statement said.
“He needs time and we have to wait and hope that everything goes well. Thanks for keeping your fingers crossed and your positive thoughts.”
The statement was written on behalf of his partner Tamara and three sons.
The popular Austrian rider is also a regular competitor at the Macau Grand Prix.