Sigh producing mechanism for positive pressure respirator

A positive pressure breathing apparatus having:

• a blower having an electrically operated blower motor controlled by a blower drive circuit and an intake and a discharge;
• a cyclic valve having at least one inlet and at least one outlet said inlet being in fluid communication with the discharge of said blower;
• and means for controlling of said cyclic valve in a timed manner according to inhalation and exhalation phases fluid communication between said inlet and said outlet;
• a breathing tube in fluid communication with the outlet of said cyclic valve, provided with means for exhausting air to produce an expiration cycle;
• and
• means for controlling the pressure output of said blower operatively associated with the blower motor to controllably produce a preselected air pressure in said breathing tube, said pressure control means includes a means in the blower drive circuit for changing motor speed, the improvement comprising:
• (a) a supplementary control means including a circuit shunting said motor speed changing means to increase the speed of the blower motor and thereby, the pressure at the breathing tube whenever the supplementary control means is activated;
• and
• (b) timer means adapted to activate the supplementary control means after a lapse time period sufficient to provide a large number of inspiration cycles at regular pressure and to continue such activation for a short sustained time period sufficient to provide a small number of inspiration cycles at increased pressure to produce a small number of sigh breaths in the breathing pattern of the respirator between lapse time periods.