Former West Bengal Chief Minister Buddhadeb Bhattacharya remained critical on Monday as he continued to be on mechanical ventilation, doctors treating him said.

Bhattacharya, 79, underwent a CT scan of his thorax in the morning, they said.

"Mr Bhattacharya's health condition is critical but stable. He is still on invasive ventilation. We have conducted a CT scan of his thorax this morning. He is responding to treatment," a senior doctor, who is a part of the multidisciplinary team that is treating him, said.

The veteran CPI(M) leader is likely to undergo a few tests later in the day, which will help in ascertaining the severity of the infection in his lungs that landed him in the hospital on Saturday afternoon.

The medical team would evaluate their next course of action depending on the test results, the doctor said.

"His blood pressure and oxygen saturation in the blood are at satisfactory levels, but he is still not out of danger. His lungs were badly affected after he was infected by coronavirus. We are trying to evaluate that as well. We have to wait for another 24 hours," he said.

Bhattacharya was rushed to the Woodlands Hospital in Alipore with breathing troubles, and he was diagnosed with lower respiratory tract infection and 'Type 2' respiratory failure. He has been suffering from COPD (chronic obstructive pulmonary disease), and other age-related ailments.

Bhattacharya took over as the chief minister of West Bengal in 2000 from party senior Jyoti Basu. He remained in the post till 2011, handling a tenure marked by agitations over the acquisition of land for industries led by now Chief Minister Mamata Banerjee.

As Bhattacharya lost the 2011 assembly elections to Banerjee's TMC, the CPI(M)-led Left Front's 34 years of rule in the state came to an end -- a loss from which it is yet to recover.

Over the last few years, Bhattacharya stayed away from the public glare due to his deteriorating health, and remained confined to his Palm Avenue apartment.

He was last seen in public when he surprised party workers by arriving unannounced at the Left's rally at Brigade Parade Ground in Kolkata, ahead of the 2019 Lok Sabha polls, with oxygen support.

Bhattacharya had stepped down from the CPI(M)'s Politburo and Central Committee in 2015, and gave up membership of the party's state secretariat in 2018.

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