Roger Ebert, right, seen here with partner-in-criticism Gene Siskel, opened up his life to documentarian Steve James. (Kevin Horan)

A nurse has placed a tube into the trachea of the most famous film critic in the world and is using it to suck out the saliva and mucus that, due to cancer-related surgery, he can no longer cough out or swallow. A machine whirs and slurps as the movie scene continues, and continues, and continues. 

It’s one of the pivotal scenes in “Life Itself,” the new documentary based on Roger Ebert’s 2011 memoir of the same name, and it almost didn’t make it in. 

“Before we even started filming, we were meeting with Roger and [his wife] Chaz,” says Steve James, the film’s director. “And she said, ‘You guys need to step out of the room for a little while and then you can come back.’ She explained that he has to have his windpipe suctioned. She said [to Roger], ‘I know you don’t care, but I do. I just don’t want them to see.’ But the way their apartment was set up I could see it happening, and I said to my colleagues, ‘We need to film this; this is a regular part of his life.’ ” 

On the first day of filming, a week later, Chaz was out of the room, so James let the camera roll. “Once I filmed it I totally understood why she felt that way,” he says. It’s an intrusive, ugly, visceral scene that would have ended up on the cutting room floor if not for an email Ebert sent that night congratulating James on “getting great stuff today.” 

“It was like him saying to me, ‘Whatever you’re feeling about that [scene], it’s good you did what you did because this is the kind of film we’re going to make,’ ” James says.

Ebert — who singled out James’ 1994 doc “Hoop Dreams” as the best film of the 1990s — knew how “Life Itself” would end up. “He said, ‘This is what I prize in documentaries I watch: I want the whole story,’ ” James says. “ ‘I want the excess, I want the candor. If I want that in some other movie, then I should want that for myself.’ ”

That doesn’t mean Ebert had control over the film, and he understood that, James says. 

“I said, ‘I welcome your feedback, I welcome your thoughts anytime you want to share them,’ ” James says. “ ‘As long as you understand I don’t have to take them.’ ”

More than a decade after he was diagnosed with thyroid cancer, Ebert died on April 4, 2013, during the filming of “Life Itself.” (One of his last emails to James, seen onscreen, reads simply, “I’m fading.”) But he remained a strong presence for James. 

“Especially during editing, I literally thought about him perching on my shoulder, watching the film through his critic’s eyes — not his personal eyes,” James says. That’s why James included the suction footage, and other scenes that show Ebert was no saintly invalid; he still had his furious temper and strong stubborn streak. 

“I thought about him a lot in terms of making sure the film didn’t turn into hagiography,” James says. “I would have felt really bad if people’s reaction to the movie was, ‘Oh, it’s a tribute film to Roger Ebert. It’s good, but it’s a tribute film.’ I would have felt like I had failed.” 

By including everything that Ebert faced at the end of his life — all the crap, big and small, that serious illness brings — James shows us all the angles of a man we all felt we knew. Just like Ebert wanted. 

Want more film?

‘Life Itself’ is the story of Roger Ebert & dad & me

Five documentaries you should see before you see “Korengal”

“The Railway Man” doesn’t quite get the gray areas of PTSD

“The Fault in Our Stars” shows the blunt force of cancer