Self-compensating blood pressure bleed valve

Abstract

A bleed flow valve for venting air from a blood pressure cuff includes a valve body having an axially extending central bore. The central bore has a transition section, a fluid inlet port opening into the central bore upstream of the transition section and a fluid outlet port opening into the central bore downstream of the transition section. A piston is disposed within the central bore of the valve body and is axially translatable within the central bore of the valve body. An annular orifice is defined between an outer circumferential surface on the piston and the transition section of the central bore. The bleed valve is self-compensating as the pressure within the cuff decreases in that the piston self adjusts axially within the central bore to adjust the area of the annular orifice so as to maintain a relatively constant cuff pressure change rate throughout the deflation process.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates generally to the field of blood pressure measurement devices and, more particularly, to a nearly constant flow rate bleed valve for use in either manual or automatic blood pressure measurement devices. [0002] Blood pressure measurement devices, also referred to as sphygmomanometers, of the type commonly used to measure arterial blood pressure include an inflatable sleeve, commonly referred to as a cuff, adapted to fit around a limb, e.g. an arm or leg, of a patient. The cuff includes an interior chamber that is in fluid communication with a device for selectively inflating the interior chamber of the cuff with pressurized air. A gage is operatively connected in fluid communication with the interior chamber of the cuff for monitoring the air pressure within the cuff. A bleed valve is also operatively connected in fluid communication with the interior chamber to permit selective depressuring of the interior chamber when ...

AI Technical Summary

Benefits of technology

[0019] In a further aspect of the invention, a method is provided for venting an inflated blood pressure cuff through a bleed valve at a relatively constant cuff pressure change rate. The method includes the steps of: providing an annular orifice having a variable flow area between an upstream cavity and a downstream cavity; passing air under pressure from the blood pressure cuff to the upstream cavity; venting air from the downstream cavity; and varying the flow area of the flow path between the upstream cavity and the downstream cavity in response to a change in the pressure of the air within the upstream cavity so as to maintain a relatively constant cuff pressure change rate. Further, the method may include the step of preventing an increase in the flow area of the flow path between the upstream cavity and the downstream cavity in response to a decrease in the pressure of the air within the upstream cavity to a predetermined maximum flow area at a predetermined relatively low pressure. The method may also include the step of preventing a decrease in the flow area of the flow path between the upstream cavity and the downstream cavity in response to a change in the pressure of the air within the upstream cavity to a predetermined minimum flow area at a predetermined relatively high pressure.

Problems solved by technology

Maintaining a relatively constant bleed flow rate has been a problem when using many prior art sphygmomanometers, particularly when used by untrained personnel.

Over repeated flexing, the potential exists for such flexible members to lose some degree of flexibility and even to crack or otherwise fail from fatigue after repetitive flexure under pressure.

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