There were 81 minutes on the clock and Barcelona led 2-0 when it became apparent there was a problem behind the south goal.
Players from both sides looked on in concern and Cadiz goalkeeper Conan Ledesma could be seen sprinting across the pitch with a defibrillator towards the incident.
Barcelona defender Ronald Araujo and his Cadiz counterpart Fali could be seen praying as the delay continued and it became clear that the situation had not been resolved.
The game was suspended for an hour and Cadiz president Manuel Vizcaino told Spanish radio that the fan had been successfully resuscitated and taken to hospital.
Fati scored just five minutes after the restart as he guided the ball into an empty net, having been teed up by Robert Lewandowski.
The Spain international refused to celebrate and he put his palms together to gesture an apology to the home supporters.
Ousmane Dembele struck in the second minute of injury-time to cap off a strong performance which maintained Barcelona’s unbeaten start to the season.
Earlier on, it was Frenkie de Jong who gave Xavi’s side the lead before Lewandowski doubled it with his sixth Laliga goal after 66 minutes.
Speaking after the game, Xavi was asked about the incident. He said: ‘It was not a nice situation for anyone. Health and people’s lives always come before anything else. Luckily they were able to revive the person and they are healthy and safe.
‘We felt, both teams, that it was right to restart the game. We hope the supporter recovers quickly. If it had gone another way, we would have suspended the match.’
The win against Cadiz means Barcelona stay third in the table, two points behind Real Madrid, who thrashed Mallorca 4-1 on Sunday.
Up next for the Catalonian side is Bayern Munich in the Champions League on Tuesday night.
