RESULTS	In contrast , cleaning of the CSC with a valve in situ resulted in non-significant lung volume changes and maintenance of normal ventilation during MHI and SIMV-VC , respectively ( 188 impedance units , 95 % CI -136 to 511 , P = .22 ; and 22 impedance units , 95 % CI -342 to 299 , P = .89 ) .\