Page stopped breathing a number of times and a defibrillator was used on him three times, Field told Seven News.
He was able to see Page in hospital after 3am and found the 48-year-old groggy and unable to remember much, he said.
But despite his own situation, the Wiggle original - who reunited with other original members of the children's group for sold-out concert - was thinking of his fans.
"He said, 'Did I finish the show?' I said, 'Yes mate, you finished the show. Bit of a melodramatic exit, but you did finish the show'."
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After Page's collapse, which happened about 10pm, the other band members returned to the stage to sing Hot Potato.
"We're going to sing it for Greg and hope he gets better real quick," Blue Wiggle Anthony Field said.
Page has suffered from fainting spells and chronic fatigue in the past. He hung up his yellow skivvy in 2006 after being diagnosed with orthostatic intolerance, which left him unable to perform and needing a cane to walk. However, he briefly returned to the group a few years later.
Yesterday's concert, which was being live-streamed online, was the first time the band's founding members had played together since 2012.