Abstract: An exhalation assembly which includes a hollow flow-through body, having an air inlet port and an air outlet port. The inlet port is arranged to receive air for supplying to a patient, and the air outlet port is arranged to provide air to a patient. The device also includes an exhalation valve connected to the flow-through body, for facilitating selectable exhalation by a patient to whom air is being supplied.

Abstract: A reciprocating pump particularly useful in ventilator apparatus includes a piston reciprocatable axially within a cylinder and dividing its interior into an inlet chamber and an outlet chamber, a wall fixed within the inlet chamber, and a drive housing fixed to the wall. The drive housing includes a motor, a rotor rotatable by the motor, a nut rotatable within the drive housing, and a screw threadedly coupled at one end to the nut and fixed at its opposite end to the piston. The piston is substantially unrestrained for axial and rotary movement such that forward and reverse rotation of the nut by the motor reciprocates the screw and the piston axially of the cylinder, and also permits the screw and the piston to rotate with respect to the cylinder to thereby even out wear between the piston and cylinder.