He has given us images of dead babies crawling across ceilings, small Indian children plunging into steaming pools of excrement and a trio of Edinburgh flatmates hacking apart a dead body. But with his latest film, 127 Hours, Danny Boyle may just have delivered the ultimate hands-over-the-eyes moment.

Reports suggest that, at the feature's Toronto film festival debut on Sunday night, three people fainted and one experienced a seizure after viewing scenes in which a mountain climber hacks off his own arm to free himself from a fallen boulder.

127 Hours tells the true-life story of Aron Ralston, an adventurer who was trapped for five days in an isolated canyon while hiking in Utah. With no mobile phone and the knowledge that rescue services did not know his whereabouts and would be unlikely to come looking for him, Ralston was forced to amputate his crushed limb above the wrist in order to escape. Boyle's film, which is set to close the London film festival on 28 October, shows the incident in all its gruesome glory.

John H Foote of thewrap.com, who attended the screening, wrote: "So overwhelmed were these members by what was happening on screen at Sunday night's premiere they simply could not take it. No one at the theatre will comment on the seizure – which may not have been related to the film at all – but make no mistake, the scenes of mountain climber Ralston taking off his own arm to free himself after a fall are among the most realistic of graphic gore ever put on film, and not for the faint of heart.

"At the screening on Monday, once again there were several mad dashes to the door when these scenes came on, and more than a few moviegoers were looking anywhere but at the screen. You could clearly see people in shock, struggling to stay in their seats, working to get past the intensity of what was going on in front of them."

Ralston, 34, who is played on screen by James Franco, told reporters in Toronto that he himself struggled to keep his eyes on the screen during the amputation scene. He said: "The experience of the very gruesome arm-removing [was], like, 'Whoa, I can't believe we're watching this!' I was ecstatic to be getting out of there. And at that point, I'm sitting there in the theatre and I'm munching my popcorn."

The adventurer survived the ordeal in 2003 despite having to hike eight miles to his truck after abseiling down a 65ft wall before alerting the emergency services. He told his story in a book, Between a Rock and a Hard Place, which Boyle optioned for his film.