MAGNETIC PUMP FOR AUGMENTING FLUID CIRCULATION IN A BODY USING IABP

A host of factors, including illness, can lead to abnormalities in the human body fluid functions. A temporary (or in some cases, even permanent) augmentation is therefore required to maintain the requisite level of fluidic body functions, via external circulatory support devices.

Specifically in the case of the blood circulation system, the problem becomes more complex, as
(i) Cyclic frequency is high (80 to 200 bpm),
(ii) Augmentation needs to be in synchronization with actual beat to be effective, and
(iii) Augmentation needs to act within a few milliseconds of a trigger signal to stay in synchronization.

Most mechanical displacement-based pumps cannot operate at such high frequencies with effective response time unless the motion is periodic.
As a result, existing ventricular assistance devices and intra-aortic balloon pumps, make use of pressurized pneumatic systems to trigger an augmentation event with quick response time. Such systems, however, suffer from having to use inconvenient and elaborate external apparatus. These consist of a pneumatic reservoir and pump circuit, which acts as the prime mover to push Helium into a balloon-based augmentation device, that is placed suitably in the body to provide timely augmentation to the blood flow. The systems are hence bulky, difficult to move and need special care when the patient needs to be transported. That a simple function such as augmentation through a pressurized helium gas shall require such excessive paraphernalia support which is bulky is odd. It is necessitated because of lack of a simple electro mechanical system which can provide a quick response augmentation with low inertia when triggered.

To enable convenient portability, there is a need for a more compact and portable system for circulation of blood in the body, which enables augmentation in quick response time without the need of excessive paraphernalia like pneumatic reservoirs and pumps. This necessitates development of a low inertia, high throughput, compact and quick response system to provide augmentation, so that more practical portability can be afforded.

The present paper covers the development of a compact, low inertia, high-throughput electromagnetic pump with quick response time so that Helium can be directly pumped into the catheter for timely augmentation. The target here is to afford a much more compact, lightweight, and efficient augmentation system for delivering synchronized augmentation at same or better rate than the elaborate pneumatic systems. This shall also make the devices portable and improve quality of life for the end user.

The proposed magnetic pump is a pressure augmentation device that leverages a novel, low-inertia, and quick response time pump design, based on electromagnetic actuation. It represents a significant step in providing trigger-based augmentation of fluid flow in the body, with specific applications to cardiac cycle, at much lower form factor and cost. Alternate working fluids that can be extracted directly from surrounding air (to negate the need for a special fluid reservoir) can also be explored and exploited during development of the product.

Introduction

There are several important fluidic functions that are vital for our survival. These include circulation of blood in the body, breathing air through the lungs, and food ingestion and excretion.

However, due to abnormalities developed during illness or other factors, such functions may get compromised and the patient may need temporary or permanent augmentation of some form to maintain a requisite level of fluidic body functions. This is achieved through a mechanical circulatory assistance or a support device.

The aim of the invention is to enable a compact and mobile method for enabling body fluid augmentation in tandem with a trigger with low response time, and with least possibility of contamination, so that mobility and independence of patient can be improved.

Intra-AORTIC Balloon Pumps: Managing Blood Circulation

Augmenting blood circulation systems needs correct timing and trigger with respect to heartbeat rate for effective augmentation. In certain scenarios, wrong timing of the augmentation trigger can turn out to be out of phase with the augmentation need of the cyclic process and may result in a counterproductive scenario. These include irreparable damage, and even a fatal outcome.

Such augmentation systems, therefore, require an instantaneous trigger to response time to remain in tandem with the heart rhythm. Existing sophisticated systems may perform real-time Electrocardiogram (ECG), blood pressure monitoring, and trigger augmentation event. They leverage elaborate pneumatic systems that use a working gas/air controlled by solenoids to avoid inertial delays caused by typical mechanical systems.

The Intra-Aortic Balloon Pump (IABP) can reduce the workload on the heart, allowing it to pump more blood. A catheter connected to the device, is placed inside the aorta, and the balloon on the end of the catheter inflates and deflates with the rhythm of the heart. As the blood exits from the Aorta, its pressure is further augmented by timing the expansion of the balloon to occur in tandem. This creates increased perforation of blood through the system as the volume displaced by the expanding balloon, pushes more blood down the aorta.

Existing intra-aortic augmentation devices leverage pneumatic circuits and reservoirs with a pneumatic pump, to provide instantaneous energy on release of a solenoid valve to trigger Helium-based balloon augmentation in an artery. Such a device, while delivering a low response time, is often bulky and costly.

Again, patients in an augmented state may need to be transported to alternate facilities, wherein the process becomes cumbersome due to the need to tag along a heavy device with all subsystems. This can have a severely restrictive impact on overall mobility, a critical factor under certain conditions.

Further, some patients need lifelong augmentation and need the device to move along with them. Scaling down the augmentation device to something that can easily be carried in a “carry -on“ bag or backpack shall serve a large purpose in improving mobility and quality of life of such patients.

The Magnetic Pump Alternative

Current devices use a pressurized air chamber to provide low inertia, high response energy to displace the Helium gas across a membrane. This requires elaborate air pumps and reservoirs and an elaborate pneumatic circuit and control system. All of this is still triggered by a Solenoid valve which works on electromagnetic principle.

The magnetic pump alternative plans to use multiple electromagnetic components to directly displace the Helium gas across the membrane. A similar trigger time, as required for triggering the solenoids electromagnetic components of legacy products, can thus achieve direct actuation of the membrane to push the Helium in to the catheter for augmentation.

The aspect ratio of such a chamber which contains a membrane with Helium gas on one side and the electromagnetic components on the other side shall be such that with small displacements of, say about 1 to 2 mm , a large volumetric displacement and pressure augmentation can be achieved . This is possible by making the chamber of very large cross section (for volumetric gain) but very low thickness. Thus, the complete pneumatic circuit with pump and reservoirs, which were hitherto used, gets eliminated and affords us a very small package of the device.

Variability of displaced volume and/or pressure created can be managed by having an expansion chamber that operates on a pressure switch and prevents spike of pressure within the catheter and prevents its inadvertent rupture due to high pressure. The resultant device can easily fit within the backpack or a Carry-on bag and affords more convenient portability of the device.

The innovation also affords significant inventory carrying cost reduction by 60% to 70%.

In future developments of the device, we can also negate the need for a helium reservoir by sourcing the working gas in the catheter form air directly. This may use the ambient air or part of it for enabling augmentation in the catheter.

Conclusion

Intra Aortal Augmentation is critical for treatment of cardiogenic shock and vital to their survival. The current bulky systems do meet this requirement adequately. They however are bulky and cause hindrance to mobility of the patient. The cost, availability and bulk of the equipment are a hindrance to its penetration to the masses where such occurrences persist and support available is minimal.

The innovation not only makes the device more portable, and mobility enabled, it also reduces the Inventory carrying costs by more than 60% to 70%, thus making the device more accessible and having deeper penetration into developing markets.

To gain and maintain market leadership in such cutting edge and lifesaving technology product, it is important that innovations continue to make the product more affordable as well as versatile in utility. This innovation helps achieve both these objectives and shall allow the first mover to stay in lead of the market.

The innovation of use of magnetic pump is thus a significant step in providing trigger-based augmentation of fluid flow in the body using IABP, with specific applications to cardiac cycle, at much lower form factor and cost. Also reduced weight and easier to transport allows long term therapy patients to carry it in a small bag with them.

References

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Author

Darshan BT

Program Manager, Diagnostics at L&T Technology Services