A liquid crystal display having specific dispositions of pixels of a liquid crystal display so as to prevent the coupling defect and the stripe defect in high speed driving. The method includes driving a helical coil resonator at an RF frequency to generate an RF electric-magnetic field sufficient to generate an electrical discharge in the high pressure gas. The electrical machine is coupled to the rear plate of the impeller such that the electrical machine is positioned entirely outside the central chamber. The signalling compound itself does not possess the detectable property or does so only to a very weak degree. A flexible flapped curtain at the outer end of the bite block may be provided to largely enclose the inner volume of the bite block to enable more accurate capnographic sampling under conditions of wide-open mouth breathing.