Peripheral Vascular Disease Patient Clinical Trial
Official title:
Multi-spectral Imaging to Assess Wounds in Peripheral Vascular Disease Patients
Peripheral vascular disease (PVD) is a common disease of impaired blood flow resulting in
the compromised tissue perfusion of lower limbs. PAD patients can experience pain,
diminished exercise capacity, and tissue loss, with some ultimately requiring amputation.
The economic burden of PVD is significant. In the United States alone, PVD accounts for over
$20 billion in annual healthcare related costs.
The demand for the development of an effective method to characterize the viability of PVD
wounds has resulted in the emergence of several innovative techniques. Commonly used
diagnostic methods are ankle-brachial index (ABI), pulse volume recordings, duplex
ultrasonography, venous plethysmography, Transcutaneous oxygen tension (TcPO2), toe
pressures, angiography by X-ray, computed tomography, and magnetic resonance imaging.
Currently, angiography remains the diagnostic gold standard. However, many of these
techniques lack the ability to triage and adequately determine the viability of the wound.
In addition, there remains a need for effective triage technologies to help clinicians
decide whether surgical management is needed. Early determination of surgical versus
conservative management may help to improve patient functional outcomes, reduce mortality
rates, and prevent limb amputation.
Near-infrared point spectroscopy (NIRS) is a non-invasively technology with recent
applications in PVD wound assessment. To date, studies have demonstrated the validity of
NIRS technology in patients with peripheral arterial disease. NIRS measures flow,
concentration, and oxygenation of hemoglobin in arterioles, capillaries, and venules several
centimeters deep in tissue. The MSID is an evolution of existing NIRS imaging devices and
has become a portable and functional commercial device produced by KENT imaging (Calgary,
Canada). Using this new and clinically applicable NIRS technology designed for assessing
wound perfusion and oxygenation, this study seeks to adequately identify viable from
non-viable wounds and to rapidly determine indication for vascular interventions. This
technology is well-suited for use in a wound patient population as the measurements times
are short and can quickly be used at the patient bed side. As such, this project intends to
apply NIR technology to quickly assess PVD in the investigators' patient population.
Peripheral vascular disease (PVD) is a common disease of the elderly, resulting in the
compromise of blood flow to the lower limbs. As a consequence of impaired tissue perfusion,
PAD patients can experience pain, diminished exercise capacity, and tissue loss, with some
ultimately requiring amputation. Globally, lower extremity peripheral artery disease is the
third leading cause of atherosclerotic cardiovascular morbidity, affecting over 200 million
individuals worldwide. Peripheral vascular disease is becoming more prevalent with the
increase of incidence with age and a globally aging population. In 2010, it was estimated
that the number of people living with peripheral artery disease increased by 23.5% in the
last decade. The economic burden of PVD is significant. In the United States alone, PVD
accounts for over $20 billion in annual healthcare related costs. Specifically, non-healing
wounds represent a significant portion of this expenditure at more than $3 billion per year.
The demand for the development of an effective method to characterize the viability of PVD
wounds has resulted in the emergence of several innovative techniques. Commonly used
diagnostic methods are ankle-brachial index (ABI), pulse volume recordings, duplex
ultrasonography, venous plethysmography, angiography by X-ray, computed tomography, and
magnetic resonance imaging. However, many of these techniques lack the ability to triage and
adequately determine the viability of the wound. Ankle brachial index (ABI) is one of the
most common screening techniques used to establish the presence of PVD, but it lacks
sensitivity in creating sensitive and specific categorization of wounds as viable or
non-viable. ABI gives an indication of a hemodynamically significant obstruction, but does
not measure blood flow directly. Doppler ultrasound is another common method that can
measure arterial blood flow, however some groups suggest that the femoral artery blood flow
may not be an accurate hemodynamic indication of muscle ischemia. Magnetic resonance
spectroscopy is also a new technique that has been validated in its application to assess
PVD. Novel magnetic imaging sequences such as PIVOT (Perfusion, Intravascular Venous Oxygen
Saturation) combine Blood Oxygen Level Dependent (BOLD) MRI and Arterial Spin Labeling (ASL)
to comprehensively assess the tissue. Despite the strengths that many MRI techniques
promise, clinical use limitations remain due to the high costs and availability of
resources.
Peripheral vascular disease-induced lower extremity wounds have inadequate perfusion.
Currently, there are three major approaches to improve vascular perfusion to the area:
medical management, open surgery, and endovascular surgery. Medical management consists of
lifestyle modification and management of associated risk factors such as smoking, diabetes
mellitus, hyperlipidemia, hypertension, and hypercoagulability. While advances have been
made in the medical management of lower extremity ischemia-induced wounds, large arterial
revascularization remains the current standard of care. Open bypass surgery is often
employed to bypass stenotic arteries and improve perfusion to lower extremity wounds. Over
the last two decades, endovascular intervention has emerged as an additional therapy as it
is minimally invasive and may have lower associated morbidity and mortality. In addition to
improved perfusion of lower extremity wounds by medical management of surgical intervention,
local wound care is required to expedite the healing process and prevent infection.
However, there remains a need for effective triage technologies to help clinicians decide
whether surgical management is needed. This would allow for early determination of surgical
versus conservative management and inpatient versus outpatient management. If surgery is
required, patient functional outcomes are improved if it takes place earlier. As well,
inpatient management of surgical patients is extremely costly. Outpatient management of
patients with peripheral vascular wounds that do not require surgery would significantly
reduce the costs associated with surgical intervention.
Near-infrared point spectroscopy (NIRS) non-invasively measures flow, concentration, and
oxygenation of hemoglobin in arterioles, capillaries, and venules several centimeters deep
in tissue. NIRS is safe and comfortable for patients and is well-suited to measure markers
of viability in peripheral vascular disease wounds, including tissue perfusion, oxygenation
and hemoglobin. To date, studies have demonstrated the validity of NIRS technology in
patients with peripheral arterial disease. The Multi spectrum infrared device (MSID)
represents an important evolution of existing NIRS imaging devices, which were designed for
the clinical environment. The MSID has become a commercial device produced by KENT imaging
(Calgary, Canada) after several animal and clinical trials have validated its use. The MSID
is a new generation of NIR imaging devices with enhanced portability and functionality. The
MSID is able to monitor many variables, such as cytochrome oxidase as a marker of tissue
oxygen utilization, oxygen saturation, perfusion and methemoglobin as a marker of free
radical injury. The advantage of the MSID is its capacity to account for skin colour.
Melanin absorbs light and attenuates the amount of NIR light received by the camera. The
Kent imaging device has unique mathematical algorithms to account for melanin content of the
skin. In many previous studies done with NIRS technology in PVD wounds, melanin content was
not considered to be a factor as patients demographic was predominantly Caucasian. However,
in many multicultural cities where there is a wide variability in patient melanin content,
melanin corrections in NIRS imaging are very important.
Using this new and clinically applicable NIRS technology designed for PVD, this study seeks
to identify viable from non-viable wounds and to determine the severity of wound in
assessing for vascular intervention indication. This technology is well-suited for use in a
wound patient population as the measurements times are short and movement of subjects is not
an issue. As such, this project intends to apply novel technology that has the capacity to
quickly assess wounds as a complication of PVD.
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Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Treatment