Abstract: A gas blending system for use with a medical ventilator blends a pressurized gas with ambient air for delivery to the ventilator in response to the ventilator's demand for gas during the gas intake phase of its cycle. The system comprises a demand valve that discharges a flow of the pressurized gas in proportion to the demand applied to its outlet. The demand valve outlet is coupled to a first inlet of a blending valve, a second inlet of which is open to the atmosphere. The blending valve has a blended gas outlet adapted to be coupled to the ventilator. The total demand applied by the ventilator to the blended gas outlet is transmitted to the first and second inlets. A proportioning mechanism in the blending valve adjusts the demand that is transmitted to the demand valve outlet through the blending valve first inlet as a percentage of the total demand applied to the blended gas outlet.

Abstract: An external, self-contained laryngeal prosthesis is adapted for use by a tracheostomized patient having a surgically-formed "pseudoglottis" separating the trachea and the hypopharynx. The prosthesis includes a housing and a fitting for attaching the housing to the tracheostoma formed in the patient's neck. The housing contains an inhalation valve to allow inhaled air to pass through a first conduit into the trachea, and an exhalation valve for directing exhaled air from the first conduit into the housing downstream from the inhalation valve toward a second conduit. The second conduit is adapted for communicating between the housing and the hypopharynx through the fitting and through an incision in the pseudoglottis. Downstream from the exhalation valve is a tone-generating mechanism responsive to air pressures in a range normally produced by a speech effort.

Abstract: A pneumatic speech simulator has a vibratory tone-generating element which produces an audible tone in response to the flow of pressurized air within a predetermined pressure range, said tone being transmitted to a patient's pharyngeal region by a conduit, such as a nasal catheter. The simulator includes a pressure compensation valve, upstream from the tone-generating element, which maintains the pressure experienced by the tone-generating element within its operating range as the pneumatic resistance of tone-transmitting conduit is increased due to partial or total blockage.