The 82-year-old actress was put on BIPAP therapy through an endotracheal tube to control her oxygen saturation level in blood.
Critical care specialist Dr Subarata Maitra told reporters that they were worried as to how her system would react after the withdrawal of the tube but her oxygen saturation remained satisfactory.
He said the doctors were trying to remove the excess fluid accumulation in her lungs through nebulisation and antibiotics.
The actress was admitted on December 23 following a respiratory tract infection.
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Physiotherapy would be resumed to ease the lung congestion, doctors said adding that she was also being given potassium supplements.
A medical bulletin issued in the afternoon said her heart rate fluctuates occasionally but in general it remains in a normal rhythm with satisfactory blood pressure readings.
Sen's actress-daughter Moon Moon has been staying at the hospital for very long hours. Her grand-daughters, starlets Riya and Raima are frequenting the clinic with their father.
Leader of the Opposition in the West Bengal Assembly and CPI(M) leader Surya Kant Mishra visited Sen at the hospital where security cover has been increased by the Kolkata Police as anxious fans wait outside the clinic to get the latest information about her well-being.
Sen has starred in memorable Hindi films like 'Devdas', 'Aandhi' and 'Saat Paake Bandha', 'Agnipariksha', 'Saptapadi' and 'Deep Jwele Jai' in Bengali.