Steady insufflation of a gas starts before the beginning of each inhalation, and a pulse-like peak flow insufflation of the gas is superposed on the steady insufflation for a short period of times at the beginning of the inhalation, and the steady insufflation is terminated before the end of the inhalation,...http://www.google.com/patents/US4686974?utm_source=gb-gplus-sharePatent US4686974 - Breath synchronized gas-insufflation device and method therefor
