Condition of Sehgal (97), who was admitted to the private hospital on July 19, is "deteriorating" and she has been kept on life support system, Sehgal's daughter and CPI(M) leader Subhashini Ali said.
A team of doctors is constantly keeping an eye on her situation.
Senior CPI(M) leader Brinda Karat and Sehgal's grandson and filmmaker Shaad Ali are camping at the hospital.
Earlier, Union Coal Minister and MP from Kanpur Sri Prakash Jaiswal also visited the hospital to enquire about her health.
Captain Sehgal was very active during the Independence movement and had commanded the 'Rani of Jhansi Regiment' of INA, formed by Subhash Chandra Bose.
A doctor by profession, she was working as a medical practitioner and a social worker. She was awarded Padma Vibhushan in 1998.