Pittsburgh The U.S. District Court for the Western District of Pennsylvania dismissed the third of four patent infringement charges made by San Diego-based ResMed Inc. against Respironics Inc., Pittsburgh.

The Sept. 30 decision closes another chapter in the legal battle that dates to January 1995, when ResMed originally sued Respironics for patent infringement on one of its respiratory masks. The latest dismissed charge involved Respironics' alleged infringement of ResMed's patented delay timer feature, referred to as "ramp," found on its CPAP device. The remaining infringement charge by ResMed against Respironics also relates to the ramp patent.