Baxter Travenol Laboratories, Inc.

Respiratory Care, Inc.

Norman Shim

Vincent L Knigge

John E Gupton

The present invention comprises a cartridge humidifier assembly having a heating means for humidifying a gas supplied from a source and delivered to a patient. The cartridge humidifier has a cap which defines a chamber with a column. The cap includes a port which receives the gas from a ventilator and a port which permits the discharge of heated humidified gas to the patient. The cap also has a single air-vent port for the venting of air with the water supply from the chamber of cartridge assembly. Water is supplied to the bottom of the cartridge assembly from a one-way conduit in communication with the bottom of the water supply container. A float rises to close off the air-vent when the cartridge assembly is full. The float lowers itself, unblocking the vent to the water bottle supply from the cartridge assembly, as the water level in the cartridge is used up in the humidification process. The float air-vent control is thus automatic, preventing possible overflow or lack of flow of water in the system.

Cartridge humidifier vent valve

In a flow metering apparatus, a bubble detector for detecting bubble formation in tubing includes a light source and first and second light detectors. The first light detector is positioned on the opposite side of the tubing from the light source such that the light transmitted through the tubing to the detector is dependent on the focusing effect of fluid in the lumen of the tubing. A control circuit responsive to the output of the detector interrupts operation of the metering apparatus when the light transmitted through the tubing falls below a predetermined minimum level. The second light detector is positioned at an angle to the light path between the light source and the first detector so as to receive increased light from the light source in the absence of the focusing effect of fluid in the tubing. Intensity control means responsive to the output of the light source with increased incident light at the second detector to increase the responsiveness of the bubble detector to the absence of fluid in the tubing.

Bubble detector with feedback circuit for improved sensitivity

A crystal-controlled low-frequency power-conserving circuit for use in a controller operating with a casette to limit the rate of flow of an intravenous solution to a patient. The circuit uses a crystal oscillator operating below the stray frequencies often present in a hospital environment. The CMOS components in the circuit respond to the low frequencies of the oscillator, display no sensitivity to the higher stray frequencies, and consume a minimum of energy. Binary rate dividers reduce the frequency obtained from the oscillator by a positive integral power of two. Cascaded variable binary rate multipliers selectively permit the absorbtion of a least half of the pulses received from the rate divider. The inverted pulses of the binary rate multipliers pass to the S input of a D-type flip-flop. The pulses from the binary divider pass to the C input of the same flip-flop. On a pulse from the rate multiplier, the Q output of the flip-flop provides a positive pulse to a monostable multivibrator which then briefly turns on current to the coil of an electromagnet to allow fluid to enter the cassette. The monostable multivibrator allows current to flow for the short period of time required to change the position of an armature pivotably coupled to the electromagnet. After the flip-flop subsequently receives two pulses from the rate divider, its Q output goes negative and the Q output becomes positive. This allows another monostable multivibrator to provide a brief pulse of current, in the opposite direction, to the electromagnet to return the armature to the first position. The fluid in the casette may thus flow to the patient.

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Glenview, IL, United States of America

Norman Shim