Lorient's goalkeeper Audard and striker Jeremie Aliadiere were forced off with injury midway through the first period, and the former's replacement Baptiste Reynet was picking the ball out of his net within 10 minutes of his introduction.
Marco Verrati picked up the first of two assists by laying the ball on a plate for Jeremy Menez to score his first goal of the season, moments after his shot had been cleared off the line.
Italian midfielder Verrati was again the provider when he crossed for Edinson Cavani to net PSG a third two minutes later, with the Uruguayan striker heading the hosts into a 3-0 half-time advantage.
The French champions took their foot off the gas a little in the second half, but Cavani did manage to net his sixth goal in his last four outings, pouncing on a rebound from close range on 80 minutes after Adrien Rabiot's header had been parried back into the danger area.
Laurent Blanc's side are now three points clear of Monaco, who were level with them prior to kickoff, at the Ligue 1 summit, while Lorient remain one place above the relegation zone.