Specialist healthcare company BTG said it had completed its acquisition of US interventional pulmonology business PneumRx, which will cost the FTSE 250 group up to £315m.The acquisition had been conditional on the expiration or early termination of a waiting period under the Hart-Scott-Rodino Act in the US, which requires companies to check with the Federal Trade Commission and Department of Justice that the deal will not traverse antitrust laws."BTG is pleased to announce that the parties received early termination of the waiting period and the acquisition completed on Wednesday 7 January 2015," it said.The deal is based on an initial consideration of $230m (£152m) and up to $245m in performance-related milestone payments.BTG plans for PneumRx's flagship product, the RePneu Coil, to become the cornerstone of its growing interventional pulmonology business.The RePneu is a minimally invasive device intended to improve exercise capacity, lung function, and quality of life for patients with severe emphysema.Shares were up 1% to 820p by midday on Thursday.