GB2547022B

GB2547022B - An automated system for inducing hypoxia

Info

Publication number: GB2547022B
Application number: GB1602071.1A
Authority: GB
Inventors: Polsek Dora; Bago Marcell
Original assignee: Of Zagreb, University of
Current assignee: Of Zagreb, University of
Priority date: 2016-02-05
Filing date: 2016-02-05
Publication date: 2019-10-02
Anticipated expiration: 2036-02-05
Also published as: GB201602071D0; GB2547022A

Description

AN AUTOMATED SYSTEM FOR INDUCING HYPOXIA

FIELD OF THE INVENTION

The present invention relates to an automated system for inducing hypoxia in which length and pattern of exposure to hypoxia can be continuously and automatically controlled by means for regulating and adjusting of a hypoxia chamber microenvironment; to a process for continuous and automatic control and adjustment of a hypoxia chamber microenvironment; and to the use of said automated system for inducing hypoxia in conducting in vivo models for diseases, disorders and/or conditions with a hypoxic component. More particularly, said system is useful for inducing intermittent hypoxia (IH), in particular for inducing chronic intermittent hypoxia (CIH). Particularly, said automated system for inducing hypoxia is useful in conducting in vivo models for sleep apnea syndrome (SAS), specifically for conducting in vivo models for obstructive sleep apnea (OSA).

BACKGROUND OF THE INVENTION

Hypoxia (also known as hypoxiation) is a condition in which the body or a region of the body is deprived of adequate oxygen supply. Hypoxia may be classified as either generalized, affecting the whole body, or local, affecting a region of the body. Although hypoxia is often a pathological condition, variations in arterial oxygen concentrations can be part of the normal physiology, for example, during hypoventilation training or strenuous physical exercise. Hypoxia differs from hypoxemia in that hypoxia refers to a state in which oxygen supply is insufficient in general, whereas hypoxemia refers specifically to the low oxygen levels in the blood. However, in some publications these terms are used interchangeably. Hypoxia in which there is complete deprivation of oxygen supply is referred to as "anoxia". Within the body, hypoxemia can lead to tissue hypoxia in various organs with the most severe being cerebral hypoxia that can rapidly result in brain damage or death.

Symptoms of hypoxia and/or hypoxemia may be acute, chronic, mild or severe. Common acute symptoms are: shortness of breath, rapid breathing and a fast heart rate. Severe symptoms include: the inability to communicate, confusion, possible coma, and may result in death. Symptoms in children include irritableness, anxiousness, and inattentiveness. Treatment of hypoxia and/or hypoxemia is to provide supplemental oxygen to the body as soon as possible.

In general, hypoxia is usually diagnosed by oxygen monitors placed on fingers or ears (pulse oximeter) and/or by determining the oxygen level in a blood gas sample (a sample of blood taken from an artery). Normal readings are about 94% to 99% oxygen saturation levels; generally, oxygen is supplied if the level is about 90% or below. Other tests may be ordered to determine if other potential problems such as carbon monoxide poisoning are responsible. Pulmonary function tests may also be ordered along with other studies to help determine the cause of unexplained low oxygen saturation.

Hypoxia can be acute or chronic, depending on the length of exposure, and can be continuously sustained or intermittent, depending on the pattern of exposure (Trevi A. Ramirez et al: “Chronic and intermittent hypoxia differentially regulate left ventricular inflammatory and extracellular matrix responses” Hypertension Research (2012) 35, 811-818). The physiological and pathological responses to hypoxia differ depending on these characteristics.

There are a variety of causes of any type of hypoxia. Sustained hypoxia occurs when oxygen levels fall from atmospheric levels of 21% to values that generally range from 8-12%. For example, in humans sustained hypoxia occurs in high altitude and in patients with chronic lung diseases such as chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF).

Intermittent hypoxia occurs when oxygen levels fall for brief episodes. Clinical and environmental conditions such as sleep apnea syndrome (SAS), bronchial asthma, and transient exposure to high altitudes are characterized by intermittent hypoxia (IH).

Sleep apnea syndrome (SAS) is a common disorder in which one has one or more pauses in breathing or shallow breaths during sleep. Breathing pauses can last from a few seconds to minutes. They may occur 30 times or more during an hour. Typically, normal breathing then starts again, sometimes with a loud snort or choking sound. Sleep apnea usually is a chronic (ongoing) condition that disrupts sleep. The most common type of sleep apnea syndrome is obstructive sleep apnea (OSA). In this condition, the airway collapses or becomes blocked during sleep. This causes shallow breathing or breathing pauses. Central sleep apnea (CSA) is a less common type of sleep apnea. This disorder occurs if the area of the brain that controls breathing doesn't send the correct signals to breathing muscles. As a result, patient will not make effort to breathe for brief periods. CSA can affect anyone. However, it's more common in people who have certain medical conditions or use certain medicines. CSA can occur with obstructive sleep apnea (OSA) or alone.

Likewise, there are a variety of hypoxia induced conditions and/or diseases. For example, it has been reported that SAS is a major independent risk factor for cardiovascular diseases such as systemic and pulmonary hypertension, congestive heart failure, and stroke (Lattimore JD, et al. Obstructive sleep apnea and cardiovascular disease" J Am Coll Cardiol A) (2003) p. 1429-1437), as well as myocardial infarction, cerebrovascular dysfunction, and idiopathic sudden death (Bradley TD, Floras JS. Obstructive sleep apnoea and its cardiovascular consequences" Lancet 373 (2009) p. 82-93).

In animals and humans, long or frequent hypoxic episodes and chronic hypoxia (CH) are also associated with cardiovascular changes such as persistent polycythemia, systemic and pulmonary arterial hypertension, and right ventricular hypertrophy (Nagai, etal.: “A novel system for inducing hypoxia" Int. J. of Clin, and Exp. Physiology) (2014) p. 307-310).

In the field of systems for inducing hypoxia task of controlling and adjusting of a hypoxia chamber microenvironment is a complex technical problem.

Every time a hypoxia chamber door is opened, room air flows in and hypoxic conditions are temporarily lost and have to be re-established. Even if hypoxia chamber with gloves is used the major problem is that current technology provides either static oxygen supply or, if it recognizes that oxygen requirements change over the time, it offers only manual oxygen adjustment.

There is also a problem of adjustability of existing hypoxia chambers to diverse experimental protocols, e.g. if there is a need for fine tuning of length and pattern of exposure to hypoxia in order to easily set up the appropriate in vivo model for diverse diseases, disorders and/or conditions with a hypoxic component with currently manually conducted systems this can be again a complex challenge.

From what is said above it is clear there is a need to meet any hypoxic challenge in any existing hypoxia chamber, i.e. workstation. Thus, there is a need to develop automatically controllable and user-friendly system that can be easily adjusted to diverse experimental protocols, e.g. in which fine tuning of length and pattern of exposure to hypoxia can be easily achieved. Especially, to develop controllable system that can be simply applied to any existing hypoxia chamber, i.e. workstation.

For that reason there is a constant need for development of improved systems for inducing hypoxia, in particular for development of a highly controlled system for inducing hypoxia wherein length and pattern of exposure to hypoxia can be continuously and automatically controlled within hypoxia chamber, and thus suitable to be used for diverse in vivo and/or in vitro models in which subjects can be exposed to hypoxic microenvironment as required for a particular model (for example to intermittent (IH), particularly to chronic intermittent hypoxia (CIH) microenvironment conditions) for a desired period of time, and thus suitable in research of variety diseases, disorders and/or conditions with a hypoxic component, in particular for development and conducting in vivo models for breathing and/or lung diseases and/or disorders with a hypoxic component, such as sleep apnea syndrome, in particular OSA.

Surprisingly, applicants have discovered that by using a system for inducing hypoxia of the present invention an automatic control of hypoxia microenvironment within hypoxia chamber can be achieved, i.e. control of a length and pattern of hypoxia exposure can be quickly, simply and more precisely adjusted.

The system for inducing hypoxia of the present invention which consists essentially of a hypoxia chamber; two independent oxygen sensors which continuously measure oxygen levels: the first one is arranged immediately after a mixing antechamber (gas mixing point) where gases (air/oxygen and nitrogen) are mixed together, while the second oxygen sensor is arranged within the hypoxia chamber together with a muffler system in combination with means for regulating and adjusting a hypoxia chamber microenvironment, i.e. a controller that is arranged at the top of the hypoxia chamber and implemented as integral part of the hypoxia chamber, wherein said controller is based on a control panel system consisting of a field programmable gate array (FPGA) development card with PID controller implementation. Proportional-Integral-Derivative (PID) controllers are widely used in automation systems. They are usually implemented either in hardware using analog components or in software using computer-based systems. They may also be implemented using Application Specific Integrated Circuits (ASICs). Building of the PID controller on Field Programmable Gate Arrays (FPGAs) improves speed, accuracy, power, compactness, and cost effectiveness. In control systems, the majority of actuating signals and sensor returns are analog signals. Therefore, analog to digital and digital to analog conversion plays an important role in digital controllers. These converters are located at the boundary of the digital controller. Usually there are some modules within the digital system that facilitate communication with these converters. In addition, digital controllers usually encompass input/output (I/O) modules to communicate with users. Pushbuttons and displays are well suited to small size and compact controllers.

Consequently, the precise, continuous and automatic system for inducing hypoxia in which microenvironment conditions within the hypoxia chamber are automatically and continuously controlled as provided by the present invention is not described in the art. In particular, there is no mention or suggestion of the technical solution as provided by specific arrangement in the system for controlling hypoxia microenvironment conditions within the hypoxia chamber according to the present invention which is technically simple, not expensive and applicable to diverse hypoxia chamber boxes and to diverse hypoxia microenvironment conditions. The continuous and automatic system for inducing hypoxia microenvironment conditions within the hypoxia chamber according to the present invention is easily adjustable to specific needs and therefore applicable for development and conducting diverse and specific in vivo and in vitro models.

SUMMARY OF THE INVENTION

In one embodiment, the present invention relates to an automated system for inducing hypoxia in which length and pattern of exposure to hypoxia can be continuously and automatically controlled by means for regulating and adjusting of a hypoxia chamber microenvironment.

In further embodiment, the present invention relates to a process for continuous and automatic control and adjustment of a hypoxia chamber microenvironment.

In another embodiment, the present invention relates to an automated system for inducing hypoxia in which length and pattern of exposure to hypoxia can be continuously and automatically controlled by means for regulating and adjusting of a hypoxia chamber microenvironment for use in conducting in vivo models for diseases, disorders and/or conditions with a hypoxic component.

Other objects and advantages will become apparent to those skilled in the art from a consideration of the ensuing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and/or other aspects, features and advantages of the present invention will become apparent and more readily appreciated from the following detailed description, taken in conjunction with the accompanying drawings of which:

Figure 1: Illustrates block diagram of an automated system for inducing hypoxia according to the present invention;

Figure 2: Illustrates block diagram of a control panel system according to the present invention; and

Figure 3: Illustrates Block diagram of FPGA-based PID controller.

DETAILED DESCRIPTION OF THE INVENTION

DEFINITIONS

It will be understood that the present invention covers all combinations of aspects, suitable, convenient and preferred groups described herein.

The term "hypoxia" refers to a condition in which subject’s body or a region of the body is deprived of adequate oxygen supply to the blood. Hypoxia can be acute or chronic, depending on the length of exposure, and can be continuously sustained or intermittent, depending on the pattern of exposure. For example, hypoxia can refer to intermittent hypoxia (IH), specifically to chronic intermittent hypoxia (CIH), in particular hypoxia refers to repetitive intermittent hypoxia in mice (RIHM), more particularly to repetitive chronic intermittent hypoxia in mice (RCIHM).

The term "intermittent hypoxia" refers to a condition in which subject’s body or a region of the body is temporarily deprived of adequate oxygen supply for a brief period of time, i.e. the repeated episodes of hypoxia are interspersed with episodes of normoxia, where the actual length and pattern of hypoxic episodes used in experimental protocols vary. Whereas "chronic intermittent hypoxia" refers to a condition in which subject’s body or a region of the body is temporarily deprived of adequate oxygen supply for a long period of time.

The term "hypoxic microenvironment" refers to the environment in which oxygen concentration is reduced below normal physiological level, i.e. oxygen level is insufficient, within desired period of time in the hypoxia chamber and thus induces diseases, disorders and/or conditions with a hypoxic component in the subject exposed to such microenvironment. According to the present invention the "hypoxic microenvironment" refers to oxygen level below 21 % in the hypoxia chamber controlled with up to 0.1% precision.

The term "disease, disorder and/or condition with a hypoxic component" refers to breathing and/or lung diseases and/or disorders with a hypoxic component as well as to the hypoxia induced conditions and/or diseases.

The term "breathing and/or lung diseases and/or disorders with a hypoxic component" refers to diseases and/or disorders selected from sleep apnea syndrome (SAS) such as obstructive sleep apnea (OSA) and central sleep apnea (CSA), chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), asthma, bronchitis, emphysema, pulmonary edema, pneumonia, pneumothorax, lung cancer and a like. In particular, said breathing and/or lung disease and/or disorder with a hypoxic component is SAS, specifically it is OSA.

The term “hypoxia induced conditions and/or diseases” refers to conditions and/or diseases selected from cardiovascular diseases such as systemic and pulmonary (arterial) hypertension, congestive heart failure, heart attack, myocardial infarction, persistent polycythemia, right ventricular hypertrophy; and cerebrovascular diseases including stroke and transitory ischemic attacks; as well as pathologies that are still poorly understood such as idiopathic sudden death.

The term "means for regulating and adjusting of the hypoxia chamber microenvironment" refers to a controller (5) based on control panel system consisting of a field programmable gate array (FPGA) development card (9) with PID controller implementation, an analog-digital converter (10-1) and a digitalanalog converter (10-2), and a two channel analog amplifier (11).

The term "hypoxia chamber(s)" and/or "hypoxia chamber(s) of the (present) invention" refers to an airtight chamber, box or cage which may be of diverse size and construction, in particular it relates to a chamber wherein a subject which is exposed to hypoxic microenvironment for a desired period of time is situated.

Specifically, it relates to animal cage wherein experimental animals are exposed to a hypoxic microenvironment for a desired period of time.

The term "subject" refers to an animal, in particular a mammal and more particular to an animal serving as a model of disease, disorder and/or condition with a hypoxic component (for example mice, rats, guinea pigs, gerbils, fish, birds, cats, rabbits, dogs, horses, cows, monkeys, chimpanzees or a like). In particular, the subject is a rodent, such as mouse or rat. In specific embodiment "subject" can refer also to a human, in particular to a human in a clinical study. The terms "patient" and "subject" are used interchangeably herein.

The term "effective amount" refers to the reduced concentration of oxygen to which subject is exposed within desired period of time in hypoxia chamber in order to achieve desired level of hypoxia, i.e. to the "effective amount" that is sufficient to achieve desired disease, disorder and/or condition with a hypoxic component in the subject exposed to such microenvironment. The "effective amount" can vary depending on the desired level of hypoxia which need to be achieved in particular experiment to achieve the model of the desired disease, disorder and/or condition with a hypoxic component in the subject exposed to such microenvironment, i.e. the desired level of hypoxia damage as per desired symptoms severity. In addition, the "effective amount" can vary depending on the age, weight, sex, and type of the subject exposed to such microenvironment.

EMBODIMENTS OF THE INVENTION

The present invention is based on the identification that by using a system for inducing hypoxia of the present invention which consists essentially of a hypoxia chamber; two independent oxygen sensors which continuously measure oxygen levels: the first one is arranged immediately after a mixing antechamber (gas mixing point) where gases (air/oxygen and nitrogen) are mixed together, while the second oxygen sensor is arranged within the hypoxia chamber together with a muffler system in combination with a means for regulating and adjusting a hypoxia chamber microenvironment, i.e. a controller that is arranged at the top of the hypoxia chamber implemented as integral part of the hypoxia chamber, wherein said controller is based on a control panel system consisting of a field programmable gate array (FPGA) development card with PID controller implementation and a timer for a continuous and automatic control of an intermittent hypoxia microenvironment within the hypoxia chamber, a length and pattern of exposure to hypoxia can be quickly, simply and precisely adjusted.

The first aspect the present invention relates to an automated system for inducing hypoxia in which length and pattern of exposure to hypoxia can be continuously and automatically controlled by means for regulating and adjusting of a hypoxia chamber (7) microenvironment, characterized in that the automated system consists essentially of a hypoxia chamber (7); a controller (5) arranged at the top of the hypoxia chamber (7) and implemented as integral part of the hypoxia chamber (7); two independent oxygen sensors (4-1; 4-2) which continuously measure an oxygen level, wherein the first oxygen sensor (4-1) is situated right after a mixing antechamber (3) in which gases are mixed together and sends analog signal via a first channel of an analog-digital converter (9-1) to the controller (5), and wherein the second oxygen sensor (4-2) is arranged within the hypoxia chamber (7) together with a muffler system (6) which is directly connected to an inlet (8) of the hypoxia chamber (7), where the second sensor (4-2) measures the oxygen level inside the hypoxia chamber (7) and sends an analog signal via an analog-digital converter (10-1) to the controller (5), wherein the controller (5) operates with the work of a proportional solenoid valve (1-PSV) which is directly connected to a pressure regulator (1-PR) of a nitrogen gas source (1) and with an on-off solenoid valve (2-SV) which is directly connected to a pressure regulator (2-PR) of air or an oxygen gas source (2).

The present invention also relates to a means for regulating and adjusting of the hypoxia chamber microenvironment, wherein the means for regulating and adjusting of the hypoxia chamber microenvironment is the controller (5) based on the control panel system, characterized in that the controller (5) consists essentially of the field programmable gate array (FPGA) development card (9) with PID controller implementation, the analog-digital converter (10-1), an digital-analog converter (10-2) and a two channel analog amplifier (11), wherein two independent oxygen sensors (4-1; 4-2) send signals via the analog digital converter (10-1) to the controller (5), wherein the controller (5) sends signals to the proportional solenoid valve (1-PSV) and the on-off solenoid valve (2-SV) via the 2-channel amplifier (11). The controller (5) is via a DC-DC converter (14) connected to a main power supply (13-2). The core voltages for most FPGAs, range from 1.2V to 2.5V. Some mature products have 3V, 3.3V or 5V core voltages. Each FPGA family has a specific quiescent supply current, ranging from under 100mA to about 2A. The DC/DC converter (14) is provided for an optimal power supply solution for systems using FPGAs. The main power supply (13-2) gives power for the whole system. Additional power supplies for sensors are provided by a sensor power supply (13-1).

With reference now to Figure 1 Illustrating block diagram of the automated system for inducing hypoxia according to the present invention, said system consists essentially of the airtight hypoxia chamber (7); two independent oxygen sensors (4-1; 4-2) which continuously measure the oxygen level [%], the (FPGA) based controller (5) with PID controller implementation wherein the controller (5) is being implemented as integral part of the hypoxia chamber (7), the proportional solenoid valve (1-PSV), the on-off solenoid valve (2-SV), the nitrogen source (1) and the air or oxygen (2) source with pressure regulators (1 -PR; 2-PR). Gas conditions are formed by two parallel flow lines. One-line supplies air containing 21% oxygen and 79% nitrogen and is fed by the air source (2); the second line supplies the system with nitrogen (99.5%) provided by a nitrogen high pressure tank (1). Two flow lines are connected in the gas mixing point, i.e. the mixing antechamber (3) in which gasses are mixed and directed through one flow line to the hypoxia chamber (7). To avoid the noise effect of the gas flow, the muffler system (6) is directly connected to an input hole (8) of the hypoxia chamber (7). An output hole arranged on the hypoxia chamber (7) is open in order to avoid the pressure rising inside the hypoxia chamber (7). The proportional solenoid valve (1-PSV) is directly connected to the pressure regulator (1-PR) arranged after the nitrogen source (1), whereas the on-off solenoid valve (2-SV) is directly connected to the pressure regulator (2-PR) arranged after the air source (2).

The first oxygen sensor (4-1) is arranged immediately thereafter the mixing antechamber (3) where gases are mixed together and sends analog signal of the oxygen level [%] via the first channel of the analog-digital converter (10-1) to the controller (5); and the second oxygen sensor (4-2) is arranged within the hypoxia chamber (7) together with the muffler system (6) which is directly connected to the inlet (8) of the hypoxia chamber (7), the second sensor (4-2) measures the oxygen level [%] inside the hypoxia chamber (7) and sends the analog signal to the second channel of the analog-digital converter (10-1). After the oxygen level is stabilized at a set point, i.e. gas mixing point in the mixing antechamber (3), the controller (5) waits the signal from the second sensor (4-2). If both sensors show the same value of the oxygen level [%] that means the oxygen level is at the set point inside the cage. In this case the controller (5) turns off said valves to save the gas.

With reference now to Figure 2: the means for regulating and adjusting chamber microenvironment is the controller (5), the controller (5) is placed at the top of the hypoxia chamber (7) and arranged as its integral part, based on the control panel system consisting essentially of the field programmable gate array (FPGA) development card (9) with PID controller implementation, the analog-digital converter (10-1), the digital-analog converter (10-2) (for example Digilent PMOD-DA2), and the two channel analog amplifier (11). Necessary power supplies, i.e. the sensor power supply (13-1) and the main power supply (13-2) are arranged. The proportional solenoid valve (1-PSV) is directly connected to the pressure regulator (1-PR) of the nitrogen gas source (1), whereas the on-off solenoid valve (2-SV) is directly connected to the pressure regulator (2-PR) of the air/oxygen source (2).

The FPGA development card (9) receives signals from both oxygen sensors (4-1 and 4-2) through the analog-digital converter (10-1). After processing the values, the FPGA development card (9) sends the control signals to the two channel analog amplifier through the digital-analog converter (10-2). Both solenoid valves (1-PSV and 2-SV) are connected to the two channel analog amplifier (11). The main power supply (13-2) gives power for the whole system.

According to the one embodiment of the invention supply of the air is performed by using a compressor tank, wherein air is pressured at certain effective pressure level.

According to one embodiment of the invention gas sources are an air gas source and a nitrogen gas source, yet according to another embodiment of invention gas sources are an oxygen gas source and the nitrogen gas source.

In embodiment wherein a first gas inlet coupling is configured to be coupled to the source of oxygen and a second gas inlet coupling is configured to be coupled only to the source of nitrogen, the oxygen level can be adjusted between 00.00 % -100 % of oxygen. In this embodiment the source of oxygen is a compressed oxygen container and the source of nitrogen is a compressed nitrogen container. Settings of pressure in the compressor for the nitrogen are set to 250000 Pa and for the oxygen to 15000 Pa.

In embodiment wherein the first gas inlet coupling is configured to be coupled to the source of air and the second gas inlet coupling is configured to be coupled only to the source of nitrogen, the oxygen level can be adjusted between 00.00 % - 30.00 % of oxygen. A process for inducing hypoxia in which a length and pattern of exposure to hypoxia can be continuously and automatically controlled by means for regulating and adjusting of a hypoxia chamber microenvironment according to the present invention is suitable for oxygen glucose deprivation experiments (OGD) and for intermittent hypoxia experiments. Desired conditions can be easily set up.

The process for continuous and automatic control and adjustment of a hypoxia chamber (7) microenvironment; an oxygen level being based on a set and maintained oxygen level in a hypoxia chamber (7) over two predetermined time intervals, characterized in that said process consists essentially of following steps: - programming a controller (5) with a gas mixture profile in which the concentration of the oxygen level varies over two-time intervals to achieve the desired hypoxia chamber (7) microenvironment; wherein said controller (5) continually controls the oxygen level in the hypoxia chamber (7) by changing a concentration of the oxygen level in said chamber (7) by introducing an additional flow of gas mixture to keep the oxygen level at a desired level over a predetermined time interval; - measuring continually the concentration of the oxygen level within the hypoxia chamber (7); - measuring continually the concentration of the oxygen level in a mixing antechamber (3); - comparing continually measured values of the oxygen levels within hypoxia chamber (7) and in the mixing antechamber (3), wherein according to the said measured values the controller (5) regulates a gas mixture flow by turning off or on valves (1-PSV; 2-SV) of a nitrogen gas source (1) or respectively an air or oxygen gas source (2), wherein if the said measured values are equal the controller (5) turns off said valves to save the gas.

The process includes reiterating the steps of measuring and regulating the gas mixture flow in accordance with measured values of the oxygen levels from previous steps of measuring to arrive at a desired oxygen level concentration in hypoxia chamber (7) during the predetermined time interval.

The process further includes adjusting parameters of the system and a timer on a menu profile arranged at a front panel interface with associated switches, wherein the timer can be set to measure duration of first and second time interval.

Adjustable parameters of the system are the oxygen level in the hypoxia chamber (7) in the first and second time interval, duration of the first-time interval, duration of the second-time interval, and number of performed iterations of changing the oxygen level in the hypoxia chamber (7) within pre-set first and second time interval.

Parameters of the system can be adjusted in following ranges: - the oxygen level can be adjusted between 00.00%-30.00% of oxygen, when the air source and the nitrogen source is used; - the oxygen level can be adjusted between 00.00%-100.00% of oxygen, when the oxygen source and the nitrogen source is used; - duration of the first-time interval in seconds which can be adjusted between 0000-9999s; - duration of the second-time interval in seconds which can be adjusted between 0000-9999s; and - a number of iterations can be adjusted between 0000-9999.

The software on the FPGA (9) controls the menu profile arranged at the front panel interface with associated switches, the timer and a PID controller. The controlling software was written in VHDL language. In the menu profile we can see and adjust the parameters of the system and the timer. At the front panel interface is arranged the set-point menu profile of set-point values over time. The menu profile contains six values: (a) an actual oxygen level (displayed text: A o2); (b) a first oxygen level (displayed text: o2 1); (c) a second oxygen level (displayed text: o2 2); (d) a first-time interval (displayed text: t1); (e) a second-time interval (displayed text: t2); (f) a number of iterations (displayed text: LooP).

The first menu profile on the display shows the signals of the two oxygen sensors. It is possible to see the actual oxygen levels in the mixing antechamber (3) and in chamber itself on the same display by changing between the signals of the sensors with the second switch on the FPGA. This menu point is the only one that cannot be adjusted and modified in set mode. All of the other menu points can be adjusted in set mode.

The second menu point shows the oxygen level to be achieved in the first-time interval. It can be adjusted between 00.00%-30.00% of oxygen.

The third menu point shows the oxygen level to be achieved in the second-time interval. It can be adjusted between 00.00%- 30.00%.

The fourth menu point shows the duration of the first-time interval in seconds. It can be adjusted between 0000-9999s.

The fifth menu point shows the duration of the second-time interval in seconds. It can be adjusted between 0000-9999s.

The sixth menu point shows the number of iterations. It can be adjusted between 0000-9999. Oxygen level dynamic set-point is ranging from 0,1% to 99,9%.

The system will start only if the number of iterations and at least one of the time intervals are not zero. If only one-time interval is set up with an iteration time than the system will set and maintain the first oxygen level in the cage (OGD function). If both time intervals are given, then the system will function as an intermittent hypoxia chamber. In this case the timer always starts with the first-time interval. After the parameter adjustment the timer can be started.

To reach the given oxygen level continuous gas mixing is used. The air flow is fixed in a certain amount and the controller adjusts the proportional solenoid valve (1-PSV) to reach the given gas mixture. PID controller is used for this purpose. After the oxygen level is stabilized at the set point the same signal from the second sensor has to be awaited. If both sensors show the same value that means the oxygen level is at the set point inside the hypoxia chamber. In this case the controller turns off the valves to save the gas.

According to the embodiment, the present invention relates to an automated system for inducing hypoxia in which length and pattern of exposure to hypoxia can be continuously and automatically controlled by means for regulating and adjusting of a hypoxia chamber microenvironment and to a process for continuous and automatic control and adjustment of a hypoxia chamber microenvironment. More particularly, said system is useful for inducing intermittent hypoxia (IH), in particular for inducing chronic intermittent hypoxia (CIH).

Particularly, said automated system for inducing hypoxia is useful in conducting in vivo models for diseases, disorders and/or conditions with a hypoxic component in a subject in need thereof consisting of exposing said subject to the effective amount of hypoxia microenvironment induced by an automated system for inducing hypoxia in which length and pattern of exposure to hypoxia can be continuously and automatically controlled by the means for regulating and adjusting of the hypoxia chamber microenvironment according to the present invention.

Said diseases, disorders and/or conditions with a hypoxic component are selected from breathing and/or lung diseases and/or disorders with a hypoxic component; and from hypoxia induced conditions and/or diseases. More particularly, breathing and/or lung disease and/or disorder with a hypoxic component is SAS, specifically it is OSA.

Claims

CLAIMS:

1. An automated system for inducing hypoxia in which length and pattern of exposure to hypoxia can be continuously and automatically controlled by a means for regulating and adjusting of a hypoxia chamber (7) microenvironment, characterized in that the automated system consists essentially of a hypoxia chamber (7); a controller (5) arranged at the top of the hypoxia chamber (7) and implemented as integral part of the hypoxia chamber (7); two independent oxygen sensors (4-1; 4-2) which continuously measure an oxygen level, wherein the first oxygen sensor (4-1) is situated right after a mixing antechamber (3) in which gases are mixed together and sends analog signal via a first channel of an analog-digital converter (9-1) to the controller (5), and wherein the second oxygen sensor (4-2) is arranged within the hypoxia chamber (7) together with a muffler system (6) which is directly connected to an inlet (8) of the hypoxia chamber (7), where the second sensor (4-2) measures the oxygen level inside the hypoxia chamber (7) and sends the analog signal via an analogdigital converter (10-1) to the controller (5), wherein the controller (5) operates with the work of a proportional solenoid valve (1-PSV) which is directly connected to a pressure regulator (1-PR) of a nitrogen gas source (1) and with an on-off solenoid valve (2-SV) which is directly connected to a pressure regulator (2-PR) of an air or oxygen gas source (2).

2. The automated system according to claim 1, characterized in that the controller (5) consists essentially of a field programmable gate array (FPGA) development card (9) with PID controller implementation, the analog-digital converter (10-1), a digital-analog converter (10-2) and a two channel analog amplifier (11), wherein two independent oxygen sensors (4-1; 4-2) send signals via the analog digital converter (10-1) to the controller (5), wherein the controller (5) sends signals to the proportional solenoid valve (1-PSV) and the on-off solenoid valve (2-SV) via the 2-channel amplifier (11).

3. The automated system according to claims 1 and 2, characterized in that the controller (5) further comprises a set-point menu profile arranged at a front panel interface with associated switches and a timer, wherein in the set-point menu profile the parameters for inducing hypoxia and the timer are adjusted.

4. The automated system according to claim 3, characterized in that the setpoint menu profile contains six values: (a) an actual oxygen level (displayed text: A o2), (b) a first oxygen level (displayed text: o2 1), (c) a second oxygen level (displayed text: o2 2), (d) a first-time interval (displayed text: t1), (e) a second-time interval (displayed text: t2), and (f) a number of iterations (displayed text: LooP).

5. The automated system according to claim 4, characterized in that the first value on the set-point menu profile on a display shows signals of the two oxygen sensors displaying the actual oxygen level in the hypoxia chamber (7) and the mixing antechamber (3).

6. The automated system according to claims 3 and 4, characterized in that the second menu point shows the oxygen level to be achieved in the first time interval and can be adjusted between 00.00%-30.00% of oxygen; the third menu point shows the oxygen level to be achieved in the second time interval and can be adjusted between 00.00%- 30.00%; the fourth menu point shows the duration of the first time interval in seconds and can be adjusted between 0000-9999s; the fifth menu point shows the duration of the second time interval in seconds and can be adjusted between 0000-9999s; and the sixth menu point shows the number of the repeating of the cycles and can be adjusted between 0000-9999, wherein an oxygen level dynamic set-point is ranging from 0,1% to 99,9%.

7. A process for continuous and automatic control and adjustment of a hypoxia chamber (7) microenvironment; an oxygen level being based on a set and maintained oxygen level in a hypoxia chamber (7) over two predetermined time intervals, characterized in that said process consists essentially of following steps: - programming a controller (5) with a gas mixture profile in which an concentration of the oxygen level varies over two-time intervals to achieve the desired hypoxia chamber (7) microenvironment; wherein said controller (5) continually controls the oxygen level in the hypoxia chamber (7) by changing the concentration of the oxygen level in said chamber (7) by introducing an additional flow of the gas mixture to keep the oxygen level at a desired level over a predetermined time interval; - measuring continually the concentration of the oxygen level within the hypoxia chamber (7); - measuring continually the concentration of the oxygen level in a mixing antechamber (3); and - comparing continually the measured values of oxygen levels within the hypoxia chamber (7) and in the mixing antechamber (3), wherein according to said measured values the controller (5) regulates a gas mixture flow by turning off or on the valves (1-PSV; 2-SV) of a nitrogen gas source (1) or respective air or an oxygen gas source (2), wherein if said measured values are equal the controller (5) turns off said valves to save the gas.

8. The process according to claim 7, characterized in that it includes reiterating the steps of measuring and regulating the gas mixture flow in accordance with the measured values of oxygen levels from the previous steps of measuring to arrive at the desired oxygen level concentration in the hypoxia chamber (7) during the predetermined time interval.

9. The process according to claim 7, characterized in that it further includes adjusting parameters of an automated system and a timer on a menu profile arranged at a front panel interface with associated switches, wherein the timer can be set to measure duration of a first and a second-time interval.

10. The process according to claim 9, characterized in that adjustable parameters of the automated system are the oxygen level in the hypoxia chamber (7) at both intervals, duration of the first-time interval, duration of the second-time interval, and a number of performed iterations of changing the oxygen level in the hypoxia chamber (7) within pre-set the first and the second-time interval.

11. The process according to claim 10, characterized in that parameters of the automated system can be adjusted in following ranges: - the oxygen level can be adjusted between 00.00% - 30.00% of oxygen in both time intervals, when an air source and a nitrogen source is used; or - the oxygen level can be adjusted between 00.00% - 100.00% of oxygen in both time intervals, when an oxygen source and the nitrogen source is used; - duration of the first-time interval in seconds which can be adjusted between 0000-9999s; - duration of the second-time interval in seconds which can be adjusted between 0000-9999s; and - the number of iterations can be adjusted between 0000-9999.