Subir Mondal, a member of the team of experts attending on Sen at the Belle Vue Clinic here, said her oxygen saturation level is fluctuating and she is dependent on oxygen via non-invasive ventilation.
"Unless she is independent of the oxygen support, we must say she is critical. She is not out of danger," Mondal told IANS.
Her condition prompted West Bengal Chief Minister Mamata Banerjee to visit the hospital for the second consecutive day Friday.
The medical bulletin Friday claimed: "Her dependence and demand of oxygen still remains high. Her cardiac condition remains stable".
The actress, who has shunned media and public for decades since her retirement from the film industry, initially suffered chest infection. The 82-year-old actress was undergoing treatment for it at a nursing home since Dec 23. Her condition worsened Dec 28 night.
Following complications, Sen was put on the ventilator Jan 3.
Dubbed as the Greta Garbo of Bengali cinema, Sen is known for her performances in films "Deep Jwele Jaai" and "Uttar Falguni" in Bengali as well as Hindi movies "Devdas", "Bombai Ka Babu", "Mamta" and "Aandhi".
She won the best actress award for "Saat Paake Bandha" at the Moscow Film Festival in 1963.