Importance

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Abstract

A flow head for ventilators includes a tubular open-ended breath transmission passage, and a tubular open-ended inside tube mounted axially inside the breath transmission passage. The inside tube is mounted in the passage by a fixed annular partition, and the ends of the inside tube extend slightly beyond a pair of perpendicular outlet ports on opposite sides of the partition. The inside tube produces a constriction to bi-directional gas flow in the passage which produces a pressure drop across the outlet ports. A pressure sensor connected across the outlet ports measures the pressure drop and therefore produces a measurement of gas flow in the passage. Various sizes of patient gas delivery tubes, endotracheal tubes for ventilator therapy, or tubes for spirometry or anesthesia can be connected to the upstream end of the flow head for producing accurate measurements of gas flow. The inside diameter of the inside tube in the flow head is equal to or slightly less than the inside diameter of the endotracheal tube, within a range progressing from about zero to about one mm less, across a range of endotracheal tube sizes from about 2.5 mm to about 9 mm, which produces a surprisingly smooth gas flow through the flow head and resulting stable pressure drop measurements. The invention also reduces the dead volume within the system by requiring the smallest possible size of breath transmission tube compared to the size of the inside tube. A pressure sensor can be used to measure gas flow as an alternative to a flow rate sensor with a source of bias gas.

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First Claim