An inquiry is underway to discover why a switch which relays an emergency power supply around the hospital did not work after the main power failed at the Heartland's Hospital, Birmingham, on Wednesday evening.
Nursing staff operated ventilators and life-support machines manually as fire crews rigged up emergency lights so staff could reassure patients in 12 affected wards.
Robert Naylor, chief executive of the hospital, said that a mains cable had gone down at about 9.50pm and three emergency generators cut in automatically. This triggers a secondary supply of mains electricity, he said. However, one of the switches which transfers this power blew, and as a result the power failed in the main block of the 800-bed hospital, which included the intensive-care unit and the operating theatres.
'For half an hour those key departments were without power, and staff were forced to operate manually equipment such as life-support machines and ventilators,' Mr Naylor said. 'All the nurses are fully trained in that procedure and none of the patients anywhere in the hospital were adversely affected.' A substantial power supply was restored within half and hour, and full power by 1.30am.
Prisca Hall, who was duty-manager at the hospital on Wednesday said: 'It was a very traumatic night but thankfully none of the patients were adversely affected.'
A spokesman for Midlands Electricity said that a fault developed in an 11,000v mains cable. Two hundred homes were also cut off.