GB2508897A

GB2508897A - Automatic oxygen flow regulator using a pulse oximeter

Info

Publication number: GB2508897A
Application number: GB201222587A
Authority: GB
Inventors: Bahram Kandar
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-12-14
Filing date: 2012-12-14
Publication date: 2014-06-18
Anticipated expiration: 2032-12-14
Also published as: GB201222587D0; GB2508897B

Abstract

A combined pulse oximeter and oxygen flow controller having feedback control from the oximeter to the flow controller is provided in a common housing, in one embodiment adapted for use in place of a basic oxygen flow controller at a hospital bedside during oxygen therapy. In one embodiment the device is adapted to plug in to and to be supported by a wall mounted hospital oxygen supply outlet. The device allows automatic, closed-loop feedback from the pulse-oximeter. The housing may have an inlet for oxygen at the rear. The device may calculate an average SpO2 reading over a chosen period, have an alarm in response to disconnection of the pulse-oximeter, loss of power or blockage, and the maximum and minimum oxygen flow rate may be settable by the user. The device may also have a manual operating mode.

Description

Oxygen flow controller for medical use

Field of the Invention

The present invention relates to a medical oxygen flow controller and in particular to a compact oxygen flow control device suitable for use at a patient's hospital bedside,

Background

Oxygen flow rate controllers and oxygen concentration control systems for control of oxygen concentration in gas to be breathed by a patient are known in the prior art, and in general are adapted to be used with a separate pulse oximeter and to form part of a control system for a ventilator or incubator. Simple mechanical oxygen flow controllers are in wide use in hospitals to provide bedside oxygen-enhanced breathing assistance. Guidelines for use of oxygen include recommendation for monitoring of a patient's blood oxygen saturation level (SpO2) at intervals of between and 30 minutes. This is a drain on staff time and leads to slow response to changing Sp02 levels. A compact replacement for the bedside oxygen flow controller having combined monitoring and control capability would have therapeutic and commercial value.

Prior Art

Accordingly a number of patent applications have been filed in an attempt to resolve the problem or similar, including the following: W0201 122242 discloses a method and system for controlling a ventilator. Oxygen saturation values from pulse oximeters may be used to adjust the settings of a ventilator. Multiple sensors and multiple oxygen saturation values in a fault tolerant pulse oximeter configuration may be used to provide a backup value or confidence measure, thereby increasing reliability and patient safety.

W0200970186 discloses a mechanical ventilator system that is a compact and portable artificial respiration system. A negative pressure vortex generator delivers an Fi02 mix from an air-oxygen blender to the patient during the patient's inhalations, but remains idle during the patient's exhalations. Exhaust gases generated by the patient are released through an exhaust gas valve. During operation, the patient's oxygen saturation level is measured by an infrared pulse-oxygen probe, and an Fi02 autoregulator is in communication with the probe to receive oxygen saturation level signals. The Fi02 autoregulator is coupled with the air-oxygen blender to control the oxygen proportion of the Fi02 mix. An automatic pressure flow sensor is fluidly coupled with the patient's airway to control actuation of the negative pressure vortex generator. The automatic flow sensor is coupled with a controller, which actuates a vortex generator trigger circuit in communication with the vortex generator.

US20080156328 discloses a pair of solenoid air/oxygen mixing systems used by an adaptive controller for delivering fractional inspired oxygen to a patient. The solenoid control system comprises either a bi-moda! solenoid or a proportional solenoid air/oxygen mixing system to derive a fraction of inspired oxygen delivered to a patient. In the bi modal solenoid air/oxygen mixing system, a derived fraction of insipid oxygen is delivered to a patient. The bi-modal mixer uses a three-way valve solenoid. The solenoid has two input gas ports and one output gas port. TOggling between the two input port gases generates an output gas oxygen concentration. In contrast with the bi-modal solenoid, variation or proportionality between the two input port gases generates an output gas oxygen concentration. Both solenoid systems use a mini-computer and digital controller with software to control the fraction of inspired oxygen delivered to a patient. Finally, several therapeutic applications are described.

US2010121314 discloses a drug delivery device for regulating delivery of a drug to a patient that provides a controlled rate of delivery which accounts for changes in health or required dose and, in systems with inherent lag, enables a rapid and accurate response whilst maintaining system stability. The device comprises a drug delivery or dose regulator; a sensor for measuring a biochemical or physiological property associated with the drug or the condition to be treated; and a controller configured to control the rate of delivery or dose of drug via the regulator in response to the difference in a measured biochemical or physiological property with respect to a target. In order to maintain the system stability, the controller comprises an anti-wind up component for minimizing wind up effects, and/or a filter sub-component to ensure that the controller does not generate output signals to control the regulator in response to noise or erroneous signals.

EP1893269 discloses a method and apparatus for operating a ventilator to control the fraction of pressure inspired oxygen (Fi02) to a patient that includes: providing a ventilator controller that includes a software algorithm, a pulse oximeter and a Fi02 flow rate controller; measuring the pulse oximetry of the patient and computing an average pulse oximetry value over a time period; selecting a first, second and third pulse oximetry levels as set points for the ventilator controller; selecting an update time interval; decreasing the Fi02 flow rate by a first incremental amount when the average pulse oximetry value is greater than the first level; increasing the Fi02 flow rate by a second incremental amount when the average pulse oximetry value is less than the second level; increasing the Fi02 flow rate to the maximum and initiating an alarm condition when the average pulse oximetry value is less than the third level W0200247741 discloses a system and method for delivering fractionally inspired oxygen (Fi02) to a patient in response to receiving an arterial hemoglobin oxygen saturation signal (Sp02). The Sp02 is measured, for example, by using a pulse oximeter. An algorithm receives a signal indicating the Sp02. The algorithm determines wither the Sp02 is in the normoxemia range, hypoxemia range or hyperoxemia range. The algorithm also determines trends by calculating a slope of second-to-second changes in the Sp02. Based on the current Sp02 and the trend, the algorithm determines the appropriate Fi02 for the patient and instructs a device such as a mechanical ventilator or an air oxygen mixer as to the appropriate Fi02 to be delivered to the patient. The system initializes various parameters with default values, but a user (e.g., a nurse) can also update the settings at any time. The system also provides alerts for various conditions, for example, standard pulse oximeter alarms, as well as notification when an episode of hyperoxemia or hypoxemia occurs, when it lasts for more than a specified period of time (e.g., two minutes) in spite of Fi02 adjustments and when the adjustments set the Fi02 at certain levels. The user is also alerted when 5p02 signal is lost.

U320010039951 discloses a medical ventilator system which automatically controls and modifies the oxygen support provided to the patient. The system includes a source of pressurized oxygen and a fluid conduit extending between the pressurized oxygen source and a patient. A valve is fluidly connected in series with the conduit which is variably controllable to vary the oxygen support for the patient. A pulse oximeter provides an Sp02 signal representative of the blood saturation of the patient. A controller is responsive to the magnitude of the 5p02 signal as well as the rate of change of the Sp02 signal for varying the oxygen support (Fi02) to the patient by variably actuating the valve. Preferably1 the controller utilizes fuzzy logic to determine the proper oxygen support for the patient.

The above patents and patent applications all disclose complex and multi-component systems for achieving controlled oxygen assisted breathing. Typically the control system and flow controller are combined in a common piece of equipment, coupled to a separate standard pulse oximeter. In other cases the control system is adapted to control a mechanical ventilator and in some cases to be part of it.

In contrast the present invention provides a compact replacement for a conventional oxygen flow controller, having a pulse oximeter, flow controller and control means in a common housing adapted for use at a patients bedside.

Summary of the Invention

According to the present invention there is provided an oxygen flow control device comprising: A housing having a front and a rear surface and comprising: A pulse oximeter having an input for an optical pulse oximetry sensor An inlet coupling for an oxygen supply An outlet coupling for the controlled oxygen supply A flow controller in series with the inlet coupling and the outlet coupling A control means adapted to receive data from the pulse oximeter and to provide an output to the flow controller A display means adapted to display data from the control means An input means adapted to allow input of parameters to the cDntrol means Wherein the control means is adapted to generate difference data from the data from the pulse oximeter and at least one input parameter and to control the flow controller in response to that data.

Preferably the control means comprises a memory and controls the flow controller in accordance with a program in the memory.

Preferably the device is adapted to display data from the oximeter and the oxygen flow rate.

Preferably the control means implements a PID (proportional-integral-derivative) function to control the flow controller.

Preferably the control means comprises a filter function to filter the data from the pulse oximeter.

Preferably the flow controller is calibrated to give a known flow rate as a function of the input data or signal.

In preferred embodiments the device further comprises a flow sensor adapted to measure flow of oxygen through the flow controller and the control means is adapted to receive data from the flow sensor. In this way the device may use a non-calibrated flow controller and a calibrated flow sensor to provide an accurate flow rate.

In preferred embodiments the flow controller may comprise a continuously variable flow controller such as a servo-operated needle valve, butterfly valve or ball valve. In other embodiments the flow controller may comprise an open or shut solenoid valve, flow control being achieved by the ratio of open to shut periods over time. In some such embodiments the device comprises an oxygen reservoir or accumulator to smooth out the open and shut flow pulses.

In preferred embodiments the device is adapted to plug into a standard wall oxygen outlet. Preferably in this embodiment the inlet coupling is provided on the rear surface of the housing.

In further preferred embodiments the device is adapted to be mounted on a pole or trolley and comprises fixing means adapted to fix the housing to a pole.

In preferred embodiments the device has a manual operating mode in which the desired oxygen flow rate is set and an automatic mode in which a desired Sp02 level is set and the device reads pulse oxirnetry data to control the flow rate of oxygen to the patient.

Preferably in the automatic mode the device is adapted to have a maximum and a minimum oxygen flow rate and to control the oxygen flow rate between the maximum and the minimum. Preferably the maximum and minimum flow rates are settable by the user. In some embodiments the minimum flow rate may be zero.

Preferably in the automatic mode the control means averages the Sp02 reading over a chosen period to produce the pulse oximetry data. In this way the pulse oximetry data being used by the comparator has reduced fluctuation and hence the oxygen flow rate is adjusted in a smoothed manner even if the pulse oximetry data fluctuates.

In this way the automatic mode means the device is suitable for uses in cases of type 1 respiratory failure, which will cover the majority of patients who require oxygen therapy in hospitals. The manual mode may be used in cases of type 2 respiratory failure, for example patients suffering from COPD -chronic obstructive pulmonary disease).

In preferred embodiments the device is adapted to receive input parameters comprising one or more of: Manual mode enabled Chosen oxygen flow rate Automatic mode enabled Chosen Sp02 level Maximum and minimum oxygen flow rates when in automatic mode Preferably the device further comprises means to record measured Sp02 levels in the memory.

Preferably the unit comprises a power supply comprising a mains power supply and battery. Preferably the unit is adapted to give warning of the loss of power supply sufficient to control the oxygen flow. In one embodiment the battery is sufficient to sound an alarm and to record measured Sp02 levels for a longer period ti and to control oxygen levels for a shorter period t2. In some embodiments the device is adapted to sound an alarm and to record Sp02 levels only while on battery power.

Preferably the device further comprises alarm means to notify an alarm in response to one or more of: Pulse oximetry sensor is decoupled from the patient or disconnected from the device No oxygen flow or pressure at the inlet Oxygen flow outlet is blacked Lass of power to the unit, br example mains power or low batteries.

In one embodiment the device is adapted to have an alarm mode in which the oxygen flow control is set to a predetermined alarm flow rate. In some embodiments that predetermined alarm flow rate may be set by a user. In this way, if the unit loses power or pulse oximetry measurement, the oxygen flow rate is set at a safe level while the alarm is sounded.

In preferred embodiments the device is adapted to allow device data to be read from the memory, the device data including one or more of: input parameters and times at which they were set by a user record of measured Sp02 levels over time record of oxygen flow rates set by the unit in automatic mode in response to measured Sp02 levels record of actual flow rates meaured by a flow sensor if present record of alarm events and times at which they were cleared by a user.

In preferred!mbodiments the device further comprises data communication means adapted to communicate device data to a remote device such as a computer, for example by means of wired LAN or RF means.

According to a second aspect of the invention there is provided a method for supplying oxygen to a patient comprisi.pg providing an oxygen flow control device substantially as described herein, coupling the device to an oxygen supply, entering parameters to the device and connecting the output tube to a patient breathing means.

In preferred embodiments-the patient breathing means may comprise a face mask, a nasal or tracheal tube.

The invention has been described by way of examples only and it will be appreciated that variation may be made to the above-mentioned embodiments without departing from the scope of invention.

With respect to the above description then, it is to be realised that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.

Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Brief Description of Figures

Figure 1 shows a front view of a first embodiment of a device according to the invention Figure 2 shows a rear view of the embodiment shown in figure 1 Figure 3 shows a top view of the embodiment shown in figure 1 Figure 4 shows a bottom view of the embodiment shown in figure 1 Figure 5 shows a left side view of the embodiment shown in figure 1 Figure 6 shows a right view of the embodiment shown in figure 1 Figure 7 shows a rear isometric view of the embodiment shown in figure 1 Figure 8 shows a front isometric view of the embodiment shown in figure 1 Figure 9 shows an exploded isometric view of the embodiment shown in figure 1 Figure 10 shows a block diagram of a device according to the invention

Detailed Description of Figures

Figures 1 to 9 show a first embodiment of a device according to the invention, adapted to connectdirectly to a wall Tounted hospital oxygen supply outlet as found typically at a patient's bedside.

Figure 1 shows a front view showing user controls on the left side of the fascia including controls for automatic function; a knob to set oxygen flow rate manually; up and down buttons to choose from menus provided by the control means and to input parameters and data. The device comprises a display screen at the right hand side of the fascia, not shown in figure 1. In a preferred embodiment the display is mounted behind a gradient plastic housing, and visible through it. Preferably the user controls are adapted to be rugged and splashproof. User controls may take 5. other forms and the fascia may have other layouts from that shown in figure 1, according to the embodiment. The oxygen outlet is shown as a tube line attached at the bottom of the housing. The mains power cable is shown entering the housing at the bottom, and the connection for the pulse oximetry sensor is shown at the bottom right. In preferred embodiments the pulse oximetry sensor has a plug connection to the device.

Figure 2 shows a rear view of the embodiment shown in figure 1. The connection to the hospital oxygen supply is provided on the rear surface of the housing, the device being adapted to mount directly on and to be supported by the wall mounted oxygen supply outlet. In this way this embodiment provides a simple and compact replacement for existing mechanical oxygen flow controllers.

Figure 3 shows a top view and Figure 4 shows a bottom view of the embodiment shown in figure 1, with the wall-mounting oxygen connection projecting from the rear surface. This connection is shown here as a screw thread, but in alternative embodiments it may comprise a plug adapted to interfit with the hospital oxygen supply outlet. In some embodiments the device comprises an adaptor to connect the oxygen connector to the wall oxygen outlet.

Figure 5 shows a left side view and Figure 6 shows a right view of the embodiment shown in figure 1. Figure 7 shows a rear isometric view and Figure 8 shows a front isometric view of the embodiment shown in figure 1. The housing is visible as comprising a front and a rear portion fastened together.

Figure 9 shows an exploded isometric view of the embodiment shown in figure 1.

From left to right in figure 1, i.e. from front to back in the assembled device, the components are: A control knob for example to set manual oxygen flow rate A fascia having cut-outs for the knob and control buttons A front housing portion shown as having the main power cable and the pulse oximetry sensor cables attached to the front housing portion Control buttons and push switches Oxygen flow controller comprising a flow valve and actuator and a ridged outlet spigot -this is preferably a calibrated flow controlled providing a known flow rate for a given control input from the control means Oxygen outlet tubing leading to the patient Oxygen inlet connection tubing that connects with the flow controller and the oxygen supply Rear housing portion and assembly screws.

The device additionally comprises a circuit board (not shown) housing the control means, display, and valve control means mounted in the housing.

In an alternative embodiment (not illustrated) the device is adapted to mount on a pole, for example on a trolley that may be placed near a patient's bedside. In such embodiments the oxygen inlet may be provided as a spigot on the upper edge, a side, or the front surface ol the device.

Figure 10 shows a block diagram of a device according to the invention, showing the main functional units of the device. A pulse oximeter sensor is connected to a patient, for example a dual wavelength optical sensor attached to a finger end or to an ear, that is connected to an oximeter forming part of the unit. The output from the oximeter is preferably amplified and filtered and compared in a comparator with a set point input by the user or provided as a default setting by the device. The output from the comparator is passed to a PLD (proportional integration and differential) controller that controls the valve actuation means, here a servo valve driver, hence controlling the oxygen flow rate via the servo valve. The patient breathes the oxygen and their Sp02 level changes as a result. The new pulse oximetry value is then read and passed to the comparator, and the oxygen flow rate is changed by the PID controller accordingly.

It will be understood that the functions shown in figure 10 may be implemented in some embodiments in analogue electronics, in alternative embodiments in digital electronics, and in further embodiments wholly or partially in software in a computing means. The control means forming part of the device may therefore be partially analogue, wholly or partially digital or implemented in a computing means.

The housing may be formed from suitable engineering plastics such as moulded polycarbonate. The tube connections may be formed from moulded ABS for example. The inlet oxygen connector is preferably formed from metal in order to support the weight of the unit. In embodiments adapted to mount on a pole or tube, the mountings preferably comprise metal rings adapted to tighten onto the pole or tube.

The device is preferably dimensioned to be small enough to be wall mounted.

Typically the housing may be less than 20cm wide and 20cm tall by 10 cm deep, more preferably less than or approximately equal to 15cm wide and 10 cm tall by 5 cm deep, though the invention is not limited to any specific size, aspect ratio or appearance of the housing.

Claims

Claims 1. An oxygen flow control device comprising: A housing having a front and a rear surface and comprising: A pulse oxirneter having an input for an optical pulse oximetry sensor An inlet coupling for an oxygen supply An outlet coupling for the controlled oxygen supply A flow controller in series with the inlet coupling and the outlet coupling A control means adapted to receive data from the pulse oximeter data and to provide an output to the flow controller A display means adapted to display data from the control means An input means adapted to allow input of parameters to the control means Wherein the control means is adapted to generate difference data from the data from the pulse oximeter and at least one input parameter and to control the flow controller in response to that data.
2. A device as claimed in claim 1 adapted to plug into a standard hospital wall oxygen outlet.
3. A device as claimed in claim 2 wherein the inlet coupling is provided on the rear surface of the housing.
4. A device as claimed in any claim above having a manual operating mode in which the desired oxygen flow r?te is set by user and an automatic mode in which a desired Sp02 is set by a user and the device reads pulse oximetry data to control the flow rate of oxygen to the patient.
5. A device as claimed in claim 4 where in the automatic mode the control means averages the Sp02 reading over a chosen period to produce the pulse oximetry data.
6. A device as claimed in claim 4 or claim S where in the automatic mode the device is adapted to have a maximum and a minimum oxygen flow rate settable by a user and to control the oxygen flow rate between the maximum and the minimum.
7. A device as claimed in any claim above further comprising means to record measured Sp02 levels in the memory.
8. A device as claimed in any claim above further comprising alarm means to notify an alarm in response to one or more of: Pulse oximetry sensor is decoupled from the patient or disconnected from the device No oxygen flow or pressure at the inlet Oxygen flow outlet is blocked Loss of power to the unit, for example mains power or low batteries.
9. A device as claimed in any claim above wherein the device is adapted to have an alarm mode in which the oxygen flow control is set to a predetermined alarm flow rate.
10. A device as claimed in any claim above comprising a power supply comprising a mains power supply and battery wherein the battery is sufficient to sound an alarm and to record measured SpO2 levels for a longer period ti and to control oxygen levels for a shorter period t2.
11. A device as claimed in any claim above further comprising a flow sensor readable by the control means.
12. A method for supplying oxygen to a patient comprising providing an oxygen flow control device substantially as described herein, coupling the device to an oxygen supply, entering parameters to the device and connecting the oUtput tube to a patient breathing means.Amendment to the claims have been filed as follows Claim Amendment 1.An oxygen supply control comprising an inlet for an oxygen source an outlet for controlled oxygen delivery a flow control between inlet and outlet responsive selectively to a manual flow rate setting and/or averaged oxygenation measurement data a pulse oximeter for connection to an optical pulse oximetry sensor with an output of oxygenation measurement data to the control to allow manual and/or automated setting of oxygen supply. 2.A device as claimed in claim I adapted to plug into a standard hospital wall oxygen outlet. 3.A device as claimed in claim 2 wherein the inlet coupling is provided on the rear surface of the housing. 4.A device as claimed in any claim above having a manual operating mode in which the desired oxygen flow rate is set by user and an automatic mode which a desired Sp02 is set by a user and the device reads pulse oximetry data to control the flow rate of oxygen to the patient. 5.CV) A device as claimed in claim 4 where in the automatic mode the control means averages the SPO2 reading over a chosen period to produce the pulse oximetry data. 6.0 A device as claimed in claim 4 or claim 5 where in the automatic mode the device is adapted to have a maximum and a minimum oxygen flow rate settable by a user and to control the oxygen flow rate between the maximum and the minimum. 1 7.CA device as claimed in any claim above further comprising means to record measured SPO2 levels in the memory. 8.A device as claimed in any claim above further comprising alarm means to notify an alarm in response to one or more of: Pulse oximetry sensor is decoupled from the patient or disconnected from the device No oxygen flow or pressure at the inlet Oxygen flow outlet is blocked Loss of power to the unit, for example mains power or low batteries. 9.A device as claimed in any claim above wherein the device is adapted to have an alarm mode in which the oxygen flow control is set to a predetermined alarm flow rate. 10.A device as claimed in any claim above comprising a power supply comprising a mains power supply and battery wherein the battery is sufficient to sound an alarm and to record measured SpO2 levels for a longer period tl and to control oxygen levels for a shorter period t2. II.A device as claimed in any claim above further comprising a flow sensor readable by the control means. 12.A device substantially as show and herein described, by reference to the accompanyingdrawings and description of the embodiments.