APPARATUS AND METHOD FOR PULSE CYCLE PRESSURE MODULATION AND NEGATIVE PRESSURE THERAPY

Abstract

The present invention relates to a system and method for pulse cycle pressure modulation and negative pressure therapy in a cardio synchronous manner to improve distal limb blood flow applying negative or variable pressure to a portion of the body. The invention relates to methods and apparatus for the application of a sequential and gradient pulse wave for treating wounds that are difficult to heal or livelihood limiting claudication and/or ischemic rest pain. An integral part of the present invention includes methods to determine blood flow and effects of treatments on tissue.

Claims

1. An apparatus for pulse cycle pressure modulation and negative pressure therapy treatment of a limb of a mammal comprising a pneumatic system for exerting negative pressure upon a tissue of the limb of the mammal which pressure is synchronized with a transduced real time signal representative of the mammal's cardiac cycle.

2. The apparatus of claim 1 wherein the apparatus alternately applies negative pressure to improve arterial blood flow and positive pressure to increase venous blood flow and the apparatus comprises a transducer for signal input of the cardiac cycle, a microcontroller-based control module and an associated computing system, an air compressor, an air reservoir, one or more inflation valves, conduits, electronic circuitry for controlling the inflation valves, and one or more inflation air cells adapted to compress tissue.

3. The apparatus of claim 2, wherein the inflation air cells comprise inflatable double walled chambers for exerting negative pressure on a mammalian limb.

4. The apparatus of claim 3, wherein the double walled chambers each comprise inner and outer inflatable shells wherein once a fluid is introduced between the inner inflatable shell and outer inflatable shell using a valve on the outer shell, the double walled chamber resists deformation during subsequent inflation or suction.

5. The apparatus of claim 3, wherein the double walled inflatable chamber is positioned over the mammal's limb, and the limb is padded and sealed to the inner shell by a curable material.

6. The apparatus of claim 1, wherein the negative pressure is varied in timed relation to a transduced signal that is indicative of cardiovascular activity.

7. The apparatus of claim 6, wherein negative pressure is exerted at the distal segment of the mammal's limb.

8. The apparatus of claim 7, wherein the negative pressure is varied in timed relation to inflation of the immediately proximal inflatable chamber.

9. A method for pulse cycle pressure modulation and negative pressure therapy, wherein at least one of the following steps is performed simultaneously or sequentially: (i) applying positive pressure at a limb during systole; (ii) applying negative pressure at a wound site during systole; (iii) applying positive pressure at a tissue site on the limb during diastole.

10. The apparatus of claim 1, wherein the negative pressure is applied by progressively decreasing negative pressure to the limb.

11. The apparatus of claim 10 comprising a multi-compartment pneumatic device having fluid conduits between adjacent compartments.

12. The apparatus of claim 11, wherein the fluid conduits are sized to provide progressive changes in negative pressure within each more distal compartment when such pressure is changed in the adjacent proximal compartment.

13. The apparatus of claim 12, wherein each fluid conduit comprises a valve.

14. The apparatus of claim 12 wherein the pressure, flow rate, flow volume, and timing of fluid flows is selectively controllable.

15. The apparatus of claim 14, wherein the pressure, flow rate, flow volume, and timing of fluid flows varied in timed relation to a transduced signal that is indicative of cardiovascular activity.

16. The apparatus of claim 1, wherein the transduce signal is derived from a pulse oximeter.

17. A method of treating a vertebrate organism using the apparatus of claim 1 wherein the following treatment parameters may be independently varied: (a) delay in time from largest detected signal of cardiac activity at which time the most proximal compartment inflation begins; (b) exerting negative pressure at the distal segment of the organism's limb, e.g., the foot or hand or any other optionally selected body-part; (c) maximal pressure in one or more compartments; (d) duration of compartment inflation; (e) time after inflation of most proximal compartment when the next compartment inflation begins; (f) pressure of each successive compartment, relative to its most immediate neighboring proximal compartment; and (g) duration of treatment.

18. A method of treating a wound of a vertebrate organism comprising the steps of (a) detecting cardiovascular activity of the organism; (b) applying varying sub-atmospheric pressures to a wound site of the organism in timed relation with the detected cardiovascular activity.

19. A method of treating one or more of the following human conditions: peripheral arterial obstructive disease; microangiopathy; vasculitis; vasa vasorum disease; complex regional pain syndrome; frostbite; erythromelalgia; trauma induced limb wound; chronic limb wound; diabetic neuropathic wounds; trench foot; Raynaud's disease; vasa nervosum disease; peripheral neuropathy; and peripheral arterial diseases in which traditional or standard treatments are contraindicated or not advised; by the steps of (a) detecting cardiovascular activity of the human; (b) applying varying sub-atmospheric pressures to one or more somatic sites on the human in timed relation with the detected cardiovascular activity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0083] FIG. 1: Represents complete schematic plan for applying the components of the system for pulse cycle pressure modulation and negative pressure therapy; particularly towards enhancing arterial blood-flow and also for improving venous return;

[0084] FIG. 2: Schematic presentation of the inflatable double walled plastic chamber (foot model), showing its structural and functional provisions for negative pressure therapy, directly employed at the distal tissues of the limb;

[0085] FIG. 3: Schematic graphical representation of arterial and venous blood flow and their respective enhancements, demonstrating an illustrative scenario of treating a patient with impaired blood flow and suffering from edema of distal wound; particularly wherein various waveform inputs may comparatively be analysed towards understanding the effect of applying the positive and negative pressure therapy during the cardiac cycle using the apparatus of the present invention, involving Arterial Pulse Enhancement Technology (APET) and Venous Flow Enhancement Technology (VFET) principals of pressure therapy of the present invention as explained hereinbelow.

DETAILED DESCRIPTION OF THE EMBODIMENT OF THE INVENTION

[0086] Referring to FIG. 1 in more detail, Simplified block diagram of device. Below is identification of all the components in FIG. 1.

[0087] 1. EKG signal

[0088] 2. Blood flow sensor, actuating PPG signal,

[0089] 3. User interface

[0090] 4. Computing system with the controller module for the system

[0091] 5. External database

[0092] 6. Air Compressor

[0093] 7. Air Reservoir

[0094] 8. Inflation valves

[0095] 9. Conduits

[0096] 10. Circuitry controlling inflation valves

[0097] 11. Conduits

[0098] 12. Infrared sensor acquires input of tissue infrared emission.

[0099] 13. Inflation Air Cells (in Compression Cuff)

[0100] 14. Inflatable double walled plastic chamber at foot

[0101] 15. Optionally selected blood flow sensor at the proximal end of the limb

[0102] 16. inner shells of the Inflatable double walled plastic chamber

[0103] 17. outer shell of said double walled chamber (14)

[0104] 18. the valve (18) for inflation of said double walled chamber (14)

[0105] 19. Pressure modulation port of the double walled chamber (14)

[0106] 20. Optional blood flow sensor (preferably for PPG signal), to be mounted selectively at the wound tissue region, where negative pressure is applied

[0107] 21. represents distal end of the limb or hand (or other optionally selected body-part), where the negative pressure is applied

[0108] 22. closable component of the chamber (14), provisioned for mounting and holding the limb for negative pressure therapy

[0109] 23. That region of the closable component (22) where inner shell (16) and outer shell (17) are sealed/integrated together.

[0110] FIG. 1 depicts a simplified overall design of the sequential compression system, including the apparatus for negative pressure therapy. The system compresses a limb at specific time intervals during the cardiac cycle as determined by inputs to the system. By blood flow sensors, namely sensor (1) for actuating EKG signal (1) or sensor (2) for actuating PPG signal, inputs to the system are selected from at least in one form, namely the EKG or photo plethysmograph (PPG) waveform. EKG or PPG leads are attached to the body to supply the heart's pulsatile signal. At the distal end of the limb where the blood flow increase is desired, a PPG monitor [not seen in the figure} is attached to detect pulsatile blood flow in the underlying tissue. Based on the cardiac blood-flow response in the form of PPG waveform inputs, at the distal limb the computing system with the controller module for the system (4), supported with the provisioned database (5) therein activates and regulates the inflatable components to provide optimal pulse cycle pressure modulation and negative pressure therapy. A series of inflatable air cells (13) are wrapped around the limb. Inflation of air cells occurs from fluid filling the cell through fluid traversing from the Air Reservoir (7) through Conduits (9) through the Inflation Valves (8) through Conduits (11) into the Air Cells (13); Fluid releases from the Air Cells (or compression cuff) (13) through conduits to Deflation Valves (not depicted). Fluid is generated by an air compressor (10) to maintain fluid under high pressure in the Reservoir (7).

[0111] One important component of the present system for pulse cycle pressure modulation and negative pressure therapy is at least one sensor (1, or 2 or 15 or 20), which provides feedback necessary to deliver higher quality treatment. Said blood flow sensor may be selected from at least one of the following factors: [0112] a. Vibrations: a vibration sensor can be used to sense the start of the movement of the blood. This may not be the actual blood flow. [0113] b. Indwelling pressure sensor catheter: there are catheters which can be put into major vascular structures close to the site of treatment which will sense the actual pressure and the feedback from those pressure can help to guide the adjustment in the cuff pressure. [0114] c. Wave form at selected point: the heart pumps the blood in the classic waveform, the waveform as Normal Pulses, is critical to mimic physiological functioning. Various points on the waveform if enhanced may have different effect on the ultimate microcirculation of the treatment part. A sensor programmed pickup of the waveform and start compressions based on the waveform or the compressions based on the position of the waveform as predicted by the structure of the previous waveform. Once the change in the pressure has been applied, the waveform changes in a predictable manner. This can be used to further modify and fine-tune the end waveform will have the physiological effect for an individual patient. [0115] d. EKG signal: the electrical activity of the heart travels faster than the actual blood and with current sensors can be picked up from different parts of the body including the extremities, chest or a combination of multiple points. [0116] e. Doppler flow: can detect the actual flow of blood under the sensor and alteration of the actual flow by the changes in the pressure can be used to further modify the pressure to a desired goal.

[0117] Smart materials are designed materials that have one or more properties that can be significantly changed in a controlled fashion by external stimuli, such as stress, temperature, moisture, pH, electric or magnetic fields. As the field of smart materials develops, materials are available which can stiffen with the passage of electric current. As the electric current can be passed very rapidly with the current electronic circuitry the speed and the options to mimic the pulse wave accurately is significantly enhanced. The use of such material leads to significant approximation to the natural state of pulse. This effect can be used to enhance the treatment potential of the invention.

[0118] Tourniquet using the invention to provide compression of the limb between the venous pressure and arterial pressure will engorge the veins without blocking/diminishing the arterial flow. The venous engorgement can be used for either placement of vascular cannulas or for blood draws. The venous engorgement applied over a long time can be used for enhancing the vein for fistula formation for dialysis.

[0119] There is a significant problem of syncope whenever high gravitational forces are applied to the human body. The blood starts pooling in the dependent portion of the body causing severe circulatory irregularities and can lead to stroke or syncope. This device can be connected to the thighs and arms to prevent excessive or diminished flow to the center of body in case of significant gravitational forces.

[0120] The Inflation System is comprised of the individual components: Air Compressor (6), Air Reservoir (7), Inflation valves (8), Conduits (9), Circuitry controlling inflation valves (10), Conduits (11), Inflation Air Cells (13), and can be replaced with other mechanisms that actuate compression onto the limb in a sequential manner. These include: [0121] 1) Nanotechnology of material which stiffens with electrical current or fluid or any other activator where the material would surround the limb to be compressed, have appropriate conduits to an actuator, and have the capability to compress at local areas along the entirety of the limb or area to be compressed. [0122] 2) Using the Inflation System of any fluid other than air that can compress the limb.

[0123] An alternative embodiment may also combine a sub-atmospheric pressure reservoir and vacuum pump, together with suitable valves and valve actuators with the Inflation System elements already described. By combining these elements, extremely rapid inflation-deflation cycles may be achieved by venting the inflation air cells to the low-pressure reservoir, rather than to the ambient atmosphere. Additionally, the sub-atmospheric pressure reservoir may be used in combination with vacuum wound healing dressings to provide wound treatment that overcomes the deficiencies inherent in prior art vacuum wound dressing systems.

[0124] One of the preferred embodiment of the present system of the invention, as indicated in FIG. 1 includes the apparatus responsible for creating negative pressure, particularly directly at the tissues of distal limb portion, leading towards increased arterial blood flow and improved venous return. FIGS. 2 duly illustrate the said inflatable double walled chamber (14) for actuating negative pressure therapy. The most important component for negative pressure therapy is the inflatable double walled plastic chamber (14), to be mounted at the distal limp section, namely at the foot or below knee or around palm/below elbow etc. of the patient. Preferably said double walled chamber (14) comprises of two mutually stretchable or inflatable shells (16) and (17), both made of polymeric sheets. Once air or another suitably selected fluid is filled between two inflatable shells, inner shells (16) and outer shell (17) of said double walled chamber (14), using the valve (18) for inflation, it provides stiffness for outer shell (17) and will not allow collapse or bulging of said chamber (14) during treatment using positive or negative pressure.

[0125] In one of the embodiments of the present system of the invention, firstly the end portion of the patient's limb, usually leg or hand (21), is preferably mounted with a blood flow sensor (20) at the distal end of the limb placed within the double walled inflatable chamber (14). The distal end of said limb or hand (21) is inserted within the cavity of said double walled chamber (14) through the closable component (22) of said chamber (14), wherein said component (22) is provisioned for mounting and holding the limb for negative pressure therapy. Said closable component (22) of the chamber (14) is relatively rigid in comparison to the walls (16) and (17), wherein the inner surface of said component (22), which comes in direct contact with the skin of the limb or hand or any other region of body-part, comprises of a layer or lining of silicon sealant. Said silicon sealant or any other optionally selected material therein, provided with the surface of said closable component (22) is actually capable of creating a vacuum-based sealing with skin of the limb/hand or body-part of the patient, which is very much comfortable to the patient. The closable component (22) of chamber (14) actually integrates the inner shell (16) and outer shell (17) at its edges (23) and therefore it is comparatively more firm in structure. Said chamber opening end (22) of chamber (14) is so constructed that it comprises of padding of silicon sealant (23) for surrounding and sealing the limb (21), wherein said padding of silicon sealing is capable of preventing air leakage at the interface of limb (21) and the chamber opening end (22) during negative or positive pressure change within the inflated said chamber (14). Once the said chamber (14) is effectively mounted at distal region of the patient's limb and duly inflated, it is ready to respond to the controller modules (4) in real time to the signal inputs of patient's cardiac cycle, as recorded by the computing system therein and its database (5). Based on the real time signal inputs of patient's cardiac cycle, the air or fluid pressure is decreased or released through the pressure modulation port (19), directly connected to the suction pump used conduit.

[0126] It is pertinent to mention herein that the construction and dimension of said inflatable chamber (14) of the present system of the invention may optionally comprise of single wall and wherein said wall of the inflatable chamber (14) may support the creation of negative pressure around the limb portion (21), enclosed within the cavity of the said inflatable chamber (14). Principle behind selection of the shape, dimension and construction of the said chamber (14), particularly for a person skilled in the art, is that the inner cavity of said chamber (14) should effectively support air or fluid pressure variation therein and therefore creation of negative pressure directly on the tissues of distal region of the limb, enclosed within the said cavity, mainly in real time response to the signal inputs recorded for real time signal inputs of patient's cardiac cycle.

[0127] In view of the preferred embodiment of the system for negative pressure therapy of the present invention, it is important to analyse the impaired blood circulation system in a patient with edema or wound on his limb. Such analysis will help in understanding the present method of the invention involving the system for pulse cycle pressure modulation and negative pressure therapy.

[0128] It is a well-known fact that the circulatory system of a mammal includes the arterial blood flow system, venous return system, lymphatic system and capillary system. Any imbalance among the flow of blood, lymph or other fluid may be a reason for edema in a limb or impaired blood flow. It is the regular practice to apply cuff assisted compression devices for increasing the blood flow in the arterial blood flow system. However, due to said compression of limb the blood/fluid pressure within venous return system, lymphatic system and capillary systems may get adversely affected, which may lead to further irregularity in the circulatory system. As the blood starts flowing from the arterial system to the capillary system and further on to the venous system, it starts leaking fluid, which has to be reabsorbed back by the venous system.

[0129] The tissue pressure which forces the fluid from tissue into the blood vessel starts rising when there is injury to the tissue. Pressure applied from outside the limb to increase tissue pressure to decrease edema has been used in the form of pressure bandage. Since it applies pressure in both systolic and diastolic phase of the blood flow it decreases the swelling but it also decreases the microcirculation flow. Since it prevents flow of plasma from coming out of blood vessel during the systolic phase, it compromises the nutrients and oxygen delivery to the inflamed tissue leading to additional ischemic injury and thus delays healing.

[0130] Pressures within the capillary system varies along the course of the capillary from its arterial to its venous end, as blood flows through the capillary, where various influences impact on intracapillary fluid flow. As fluid flows through the capillary, its pulsatility gets progressively more blunted. By the time fluid reaches the distal part of the capillary, the venous side, pulsatility is significantly diminished. The entire system of capillary flow, into and out of the surrounding interstitium and soft tissues, creates a system which is critical to provide nutrition to those tissues. This system is described in the Starling-Landis theory of fluid flow through capillaries. The pressure within the capillary system also varies with time as the pulse wave advances. As the pulse wave passes through the capillary from the arterial side to the venous side, the fluid moves out of the arterial end during the peak of the arterial pressure and moves back into the capillary at its far end, the venous end, where the intracapillary pressure is lower.

[0131] Lymphatic flow decreases with externally applied continuous pressure as continuous pressure collapses the collecting system and does not allow the lymphatic system to fill. In contrast cardio synchronized externally applied limb pressure allows the lymphatic system to fill and thus enhance its flow. Similar principles apply to the venous system, although the one-way valves in the venous system are less and are only in larger vessels.

[0132] Synchronized compression will move the fluid sequentially through the lymphatic system as it has multiple connected chambers with one-way valves. Whereas continuous pressure does not allow lymphatics to fill, application of intermittent pressure to a limb will fill lymphatics repeatedly and the next cycle of pressure will push the collected fluid in the lymphatic chamber out to the next lymphatic chamber, thus enhancing lymphatic flow. The increased flow of fluid through the lymphatic system provides the much-needed nutrition and oxygen to maintain optimal health of the lymphatic system. This has a potential role in antiaging therapies.

[0133] Inflammation causes exuding of protein-rich fluid from the capillary micro circulation. As part of the inflammatory process leaking blood vessels enable fluid to move out of capillaries into the interstitium. By selectively enhancing pressure at the wound site, the instant device in consideration can help push interstitial fluid back into the microcirculation. This has the potential of reducing edema at the site of the injury.

[0134] Therefore, with regard to highlighting important advantages of the present invention, one exemplary case-analysis relating the limitations of the conventional treatment of Edema is described:

[0135] The edema of the wound is a very difficult problem to treat. There are several factors which determine the blood flow to the skin and various tissues. Some of the major such factors include: [0136] a. Tissue pressure; [0137] b. Tissue oncotic pressure; [0138] c. Blood pressure; [0139] d. Blood oncotic pressure; [0140] e. Venous pressure; [0141] f. Arterial pressure, and [0142] g. Colloidal pressure. [0143] h. Capillary wall permeability.

[0144] Solution using the instant invention:

[0145] Current treatments for edema utilize applying a bandage throughout the pulse cycle. The pressure is increased for both arterial and venous side or the trough and the peak of the pulse wave. The pressure counteracts the pulse pressure, causing decrease in the flow of interstitial fluid, which compromises the provision of nutrients to the tissue, with resultant poor perfusion and risk of infection and ulcer formation.

[0146] Cardio synchronized compression at the tissue site: If we selectively apply the pressure at the tissue site only in phase with the cardiac cycle, it will allow the interstitial fluid to be pushed back into capillaries when the limb is compressed. If we use cardio-synchronized compressions to increase the tissue pressure fluid will be pushed back into the venous system where it will be drained, and thus removed from the tissue. This will decrease the tissue pressure, leading to increase blood flow and interstitial fluid flow during the arterial phase, providing better nutrients and oxygenation to the tissue.

[0147] Working mechanism of APET therapy and VFET therapy in wound healing are as under:

[0148] As per the present invention in an exemplary scenario, the principle of pressure therapy towards treating an edema of the wound is as under: [0149] Principle of pressure: positive pressure and negative pressure [0150] APET Therapy: positive pressure at thigh and negative pressure at wound site, during systole; and [0151] VFET Therapy: positive pressure at foot during diastole. [0152] Indications for both pressures: Wound healing and Edema/inflammation treatment respectively

[0153] 1. Arterial Pulse Enhancement Technology (APET): The arterial pulse can be enhanced in two ways: [0154] a. Positive pressure proximal to the tissue to enhance the diastolic phase of the pulse pressure for the pulse wave passing beneath the tissue. e.g. Cuff on thigh for increasing blood flow to the leg. the classic APET technology. or PP-APET (positive pressure-arterial pulse enhancement technology); and

[0155] b. Negative pressure at the site of the tissue, during the systolic phase, to bring more blood to the tissue area. NP-APET or Negative pressure arterial pulse enhancement technology. This can be applied by placing a negative pressure device around the wound during the systolic phase of the pulse flow. This will increase the tissue perfusion and interstitial fluid flow during the systolic phase of the pulse.

[0156] 2. Venous Flow Enhancement Technology (VFET): Venous flow can be enhanced by applying cardio synchronised positive pressure during the diastolic phase of the pulse. External Pressure which correlate with tissue pressure rises and pushes the fluid back inside the venous system. Tissue pressure enhancement during the diastolic phase moves the fluid from the interstitial tissue into the venous system, decreasing the edema. The VFET can be used for two indications:

[0157] a. To enhance the venous drainage

[0158] b. to enhance the lymphatic drainage

[0159] VFET should not be used in uncontrolled infected tissue due to risk of spreading the infection to blood or causing septicemia.

[0160] FIG. 3 explains an illustrative scenario of treating a patient with impaired blood flow and suffering from edema of distal wound; wherein various waveform inputs are comparatively analysed and accordingly the apparatus of present invention and its controller module is calibrated towards pulse cycle pressure modulation and negative pressure therapy, particularly to mimic and enhance the natural arterial blood flow or venous return towards healing the said impaired blood flow complications and/or the distal wound. EKG or PPG leads are attached to the body to supply the heart's pulsatile signal, the EKG or PPG. At the distal end of the limb where the blood flow increase is desired, a PPG monitor is attached to detect pulsatile blood flow in the underlying tissue. Based on the cardiac blood-flow response in the form of EKG waveform inputs or PPG waveform inputs, the computing system with the controller module for the system (4), supported with the provisioned database (5) therein activates and regulates the inflatable components towards pulse cycle pressure modulation and negative pressure therapy.

[0161] From the elaborate graphical representation of FIG. 3, the effect of applying the pressure therapy using the apparatus of present invention, particularly involving the APET and VFET principles of pressure therapy of the present invention as explained hereinabove, is comprehensively understood. By applying the positive pressure through compression-cuff (12) at the limb during systole, the arterial blood flow gets increased, which is indicated by the enhanced waveform signal (i.e. by PP-APE Arterial Enhanced Pulse). Said arterial blood flow further increases by applying negative pressure at the wound site during systole through the Inflatable double walled plastic chamber (14), preferably simultaneously with the said cuff-compression at (12), as shown by waveform signal of NP-APE Arterial Enhanced Pulse. When positive pressure is applied at tissue site of leg, the venous flow also gets enhanced, as indicated in comparative manner by both the venous waveform signals, namely Baseline Venous Flow and the VFET Enhanced Baseline Venous flow.

[0162] While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than of limitation and that changes may be made within the purview of the appended claims without departing from the true scope and spirit of the invention in its broader aspects. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention. The inventors further require that the scope accorded the claims be in accordance with the broadest possible construction available under the law as it exists on the date of filing hereof (and of the application from which this application obtains priority, if any) and that no narrowing of the scope of the appended claims be allowed due to subsequent changes in the law, as such a narrowing would constitute an ex post facto adjudication, and a taking without due process or just compensation.