Abstract: A pump piston assembly has a pump cylinder, at least one hollow piston slidably mounted for reciprocating motion in the pump cylinder, the piston having an inner surface of a first diameter and an outer surface of a second diameter, and a liner sleeve of a different material from the piston mounted on the inner or outer surface of the piston with a close or friction fit to the diameter of the piston surface on which it is mounted. The liner sleeve is of an acoustic dampening material which has a lower acoustic frequency than the piston material and is configured to absorb harmonic acoustic vibrations resulting from reciprocation of the piston in the cylinder.

Abstract: An enrichment device for mixing ambient air with a gas such as oxygen has a rigid outer housing defining a reservoir. The housing has an outlet port for attachment to a cyclic low pressure source, an ambient air inlet, and a second inlet for connection to a supply of pressurized gas. The reservoir has a plurality of internal walls defining a passageway having a plurality of turns defining a tortuous path for gas flow between the ambient air inlet and the outlet port, and the second inlet communicates with the passageway at a location at or close to the outlet port.

Abstract: A reciprocating drive apparatus has a driving device and a driven device, one of the devices comprising a reciprocating member mounted for movement along a longitudinal axis. At least one rotary member is coupled to one of the devices and a linear bearing assembly has a linear guide rail and a linear slide member with an end coupled to the other device. A connecting link has a first end pivotally connected to the rotary member and a second end pivotally linked to the slide member. Where the reciprocating member is the driven device, rotation of the rotary member will cause the reciprocating member to move back and forth along the longitudinal axis.

Abstract: A humidifier system for heating and humidifying respiratory gases has a housing with an inner chamber, a first port at the first end for connection to a ventilator breathing circuit and a second port at the second end for connection to a patient to supply respiratory gases to the patient and to receive exhaled gases from the patient. A body of heat moisture exchange (HME) material is located within the chamber, and a water permeable device is also located within the chamber. The housing has a water refill inlet communicating with the water permeable device. A water supply outside the housing is connected to the water refill inlet to supply water to the water permeable device. A heater mounted outside the housing supplies heat to the housing and maintains the housing at a selected temperature.

Abstract: A positive airway pressure assist breathing apparatus or ventilator system has a gas delivery unit, an inspiration line connected to the output of the gas delivery unit for connecting the gas delivery unit to a, patient during an inspiratory phase of each breath, and an expiratory unit for controlling exhausting of gases from the patient during an expiratory phase of each breath. A pressure sensor senses gas pressure in the system, and a control unit controls pressure of gas supplied to a patient in each inspiratory phase based on a pre-set target pressure.

Abstract: A system and method of controlling the termination of the inhalation phase in a pressure support ventilation system is disclosed, in which an expiratory trigger sensitivity, or ratio of inspiratory flow rate to peak inspiratory flow rate at which the inspiration phase is terminated, is varied in proportion to variations in a calculated respiratory time constant. The system includes sensors for monitoring pressure and flow of gas during each breath, and, based on the sensor outputs, calculates the respiratory time constant for one breath or a series of breaths. The expiratory trigger sensitivity is automatically increased with increasing patient respiratory time constant, providing a closed loop control of expiratory trigger sensitivity. The expiratory trigger sensitivity may also be varied in response to changes in supra-plateau pressure.