Former Bengal chief minister Buddhadeb Bhattacharjee, 76, was rushed to a south Calcutta hospital on Wednesday with acute breathing problems.

He was “critical” and put on invasive “mechanical ventilation”, a bulletin issued by Woodlands Hospital on Wednesday evening.

He tested negative for Covid-19 upon hospitalisation. But his HRCT (high-resolution CT scan) thorax showed features of old patches of pneumonia, the bulletin said.

Bhattacharjee was admitted to the hospital at 2.40pm after his oxygen saturation level fell to 70 per cent and he became unconscious at home, an earlier bulletin said.

“He was put on non-invasive ventilation and his oxygen saturation went up to 95 per cent, but the arterial blood gas test showed accumulation of carbon dioxide and low PH levels. So we had to put him on invasive ventilation after taking permission from his family,” said Woodlands official.

Chief minister Mamata Banerjee visited Bhattacharjee in the hospital. “We want him to get well soon,” she told journalists.

Bhattacharjee has been suffering from breathing issues, CoPD and other age-related issues for a while. He was rushed to the hospital last year with breathing troubles and an acute drop in blood pressure.