Clinical Application of Hollow Fiber Technology

Hollow fiber technology (HFT) has the potential to allow clinical application of bioengineering principles to provide direct interstitial therapy.

The Twin Star Catheter may be configured to treat a range of clinical conditions, including:

      Wound Care
        • Compartment Syndrome
        • Brain Injury
        • Reconstructive Flaps
        • Burns
        • Surgical incisions

      Drug Delivery
        • Chemotherapeutics
        • Antibiotics
        • Pain medications
        • Regenerative growth factors

In these catheters, the hollow fiber pore size is much smaller than soft tissue cells.  This small pore size enhances tissue microcirculation by accessing interstitial spaces between cells for local or site–specific tissue drainage and infusion.

Hollow fibers are small tubes that are created with a semi–permeable material.  The material and pore size determine what can or cannot pass through the wall of the tubules. The selection of hollow fiber material is based primarily on the size of molecules to be removed or retained, as well as other physical properties.

Positioning hollow fiber catheters in tissues has been used previously for assay, using diffusion gradients (microdialysis) and hydrostatic gradients (capillary ultrafiltration probes). There is no therapeutic intention in those applications.

Drug Delivery

Compared to standard clinical catheters, hollow–fiber catheters deliver therapeutic agents (small molecules) to cells with greater and more even distribution in soft tissues. For example, hollow–fibers can deliver 10 times greater distribution of adenoviral–mediated gene transfer in rodent brains than a standard 28–gauge needle.

Central Nervous System Drug Delivery

Millions of Americans are afflicted by neurogenerative and malignant diseases affecting the central nervous system (CNS).  For many of these diseases, such as Parkinson’s, Alzheimer’s and high grade primary brain tumors, there is currently no curative therapy.  Even when effective therapeutic agents are identified, delivery into the CNS at therapeutic concentrations and sufficient distribution is presently difficult to reach clinical efficiency.

Many drugs of larger molecular size andweight are unable to pass the blood–brain barrier. Overcoming the drug–delivery obstacles to the CNS is a critical step in attaining better clinical outcomes.

Direct infusion of drugs into the brain parenchyma using convection–enhanced delivery (CED) results in the treatment of large areas of brain tissue.  CED relies on bulk flow to establish a pressure gradient over time, resulting in continuous convective flow and widespread distribution of the drug to the affected areas of the brain.

One limitation of conventional CED treatment involves the backflow of infusate along the catheter body at increased infusion rates, especially when an introducer has been used for catheter placement.

Another limitation relates to uneven distribution of infusate in tumor or injured tissue as opposed to normal brain tissue. The variability of normal brain tissues and the targeted areas of treatment creates challenges for getting the drug directly to the site.

Hollow fiber catheters improve the distribution of drugs administered directly into the central nervous system and other tissues.  Hollow fiber catheters significantly increase the surface area where the drug or fluid is delivered, at much lower pressures.

Hollow fiber reduce the risk for backflow, while creating overall higher flow rates.

Negative Pressure Wound Care Therapies

Twin Star has been developing hollow fiber catheters for use with wounds in conjunction with negative pressure wound therapy and has demonstrated a reduction of tissue swelling and improved tissue viability in pre–clinical studies.

Negative Pressure Wound Therapy (NPWT) is widely used for managing open wounds. The effects of NPWT are thought to promote wound healing through several actions including a reduction in edema, and an increase in blood flow to the wound.

Compartment Syndrome

Compartment Syndrome (CS) occurs when swelling or excess fluid increases the pressure within a confined tissue area, known as the fascial compartment. Trauma, including fractures, burns, or crush injuries, is the most frequent cause of CS. but it can also occur after vascular injury, reperfusion following ischemia, extravasation of fluid, and external compression.

Compartment Syndrome is more common in orthopedic fractures like the tibia, or the bones in the forearm.

Early diagnosis and treatment of compartment syndrome has proven difficult with present treatment modalities.

Clinical Challenges of Compartment Syndrome

The incidence of CS is highly variable, from 1 to 9 percent in tibia fractures. It is more consistently seen in defined subgroups: for example, CS has been documented to occur in up to 48 percent of patients with segmental, or multiple, tibial shaft fractures.

In recent years, the challenges of CS in injuries received during military actions has created an even greater need for improved CS treatments. Orthopedic trauma, wounds from projectiles, and especially traumatic brain injury from IEDs and other explosive weapons all may generate risks from compartment syndrome.

Current treatment for compartment syndrome usually involves an urgent surgical intervention, called fasciotomy, that relieves pressure and provides drainage. This treatment is highly invasive, with major risks from infection, nerve damage, chronic venous insufficiency, skin grafting and significant scarring.

Not doing a fasciotomy, the current standard of care, in a timely manner can result in muscular fibrosis, permanent neural dysfunction, rhabdomyolysis and consequent acute renal failure, wound infection, limb amputation and death.

There are presently no reasonable alternatives to fasciotomy when compartment syndrome is suspected, even in borderline or early cases.

Twin Star Compartment Monitoring System

Twin Star Medical’s Compartment Monitoring System (CMS), offers a system design that can both monitor pressure within the wound to provide indices of potential compartment syndrome, and reduce pressure as required by withdrawing fluid from the wound area.

Brain Injury

Brain swelling due to severe head trauma or strokes results in about 30% mortality and 30% severe disability in approximately 200,000 patients in the U.S. each year.

US annual medical costs exceed $35 billion for the care of stroke and traumatic brain injury (TBI) patients.

Traumatic brain injury is also a growing cause of long–term disability in head injuries sustained in war zones. This is becoming an issue of growing concern in modern warfare, where blast injuries are becoming common. Traumatic brain injury has been identified as the “signature injury” among those wounded in the current military engagements in Afghanistan and Iraq.

In both traumatic brain injury and stroke, brain swelling can occur and fluids accumulate within the brain space. When an injury occurs inside the skull, there is no place for swollen tissues to expand, and no tissues to absorb to drain excess fluid. This leads to an increase in the pressure, called intracranial pressure (ICP).

High ICP can cause delicate brain tissue to be crushed, or cut off vital blood flow to areas of the brain, compounding brain tissue damage.

Intracranial pressure is monitored through a catheter inserted through the skull and connected to a monitor that registers ICP.

Treatment for high ICP, may be a ventriculostomy, a procedure that drains cerebrospinal fluid (CSF) from the ventricles to bring the pressure down, or in severe cases trepanation, which removes a section of skull to provide room for swelling and drainage.

The physical and physiological factors of ICP are similar to compartment syndrome in the peripheral anatomy.