Surface Acoustic Wave Patch for Ischemic Feet
Surface Acoustic Wave Patch for Ischemic Feet
Introduction Transcutaneous oxygen pressure (TcPO2) less than 30 mm Hg at the toe leads to local tissue hypoxia and nonhealing wounds. Studies regularly illustrate that TcPO2 values are strong predictors of healing and can accurately demonstrate altered levels when extremities have restricted blood flow. The objective of this study was to evaluate the effectiveness of surface acoustic wave (SAW) in ischemic feet on local tissue oxygenation.
Methods Ten patients, ranging from 40–75 years of age and suffering from critical limb ischemia (CLI) were selected from a vascular surgery clinic to undergo evaluation with a PainShield SAW Patch device (NanoVibronix Inc, Melville, NY). Patients were treated once with 96 Khz of SAW for 30 minutes. All patients had an ankle brachial index of < 0.4 mm Hg. Two patients (patients 1 and 8) had necrosis of at least 2 toes on the affected limb and were given the device for nightly use for 1 month.
Results Through usage of SAW there was a significant increase in all patients' saturation values. The recorded baseline in both patients with necrotic toes almost doubled and during usage there was still a measurable increase in oxygen saturation. In both of these patients the subjective pain measures dropped significantly. Pain, as assessed by the Visual Analog Scale, dropped from 9 to 2 for patient 1 and from 8 to 3 for patient 8. Patient 1 went from 5 methadone treatments per day to only 1 per day starting in week 3. Patient 8 did not change their pain medication regimen.
Conclusion Surface acoustic waves as delivered in this study had a positive effect on tissue oxygenation and saturation in ischemic feet. In lower extremities that are not surgical candidates or are either in the pre- or postsurgical environment, an SAW patch device is a good therapy in elevating the extremities' O2 saturation.
Healing of chronic wounds is dependent on many factors including type of wound, etiologies, depth, and comorbidities of the patient. According to Mustoe et al, billions of dollars are spent annually in the United States due to chronic wounds. Chronic wounds do not follow the typical hemostasis, inflammation, proliferation, and remodeling found in acute wounds. Chronic wounds typically come in a variety of etiologies, including venous ulcers, arterial ulcers, pressure ulcers, and neuropathic ulcers, which all seem very different in etiology, but may have similar difficulties healing. One reason is impaired circulation resulting in local tissue hypoxia.
Transcutaneous oxygen pressure (TcPO2) less than 30 mm Hg at the toe leads to local tissue hypoxia and nonhealing wounds. Local blood flow, affected by numerous etiologies such as impaired arterial inflow, arteriovenous pressures, capillary density, and local tissue consumption directly affect tissue partial oxygen pressures. Setacci et al stated that the most common cause of ischemic feet is atherosclerotic peripheral arterial disease, such as that which occurs secondary to diabetes mellitus. Mustoe et al also points out that diabetic ulcers are closely related to atherosclerotic large vessel conditions and chronic ischemia. Large vessel disease is not typically found in venous and pressure ulcers. Nevertheless, previous ulcerations greatly increase the possibility of reulceration due to fibrosis and decreased tissue perfusion. Moreover, other causes of ischemic feet include acute embolisms from the heart or arteries, thrombosis from procoagulative blood clots, arterial spasms, or injury from trauma and drug use. Edema in surrounding skin has also been shown to lessen TcPO2 in wounds.
According to Davies, 12% of the adult population in the United States have critical limb ischemia (CLI), defined sympotomatically as ranging from no symptoms to intermittent claudication, atypical leg pain, rest pain, ischemic ulcers, or gangrene. Beard states that about 150–200 people per 1 million progress to CLI with ischemic rest pain, ulceration, and/or gangrene. Critical limb ischemia costs approximately 200 million dollars a year in the United Kingdom. Critical limb ischemia and its sequelae have significant social and economic impacts, with 25% of patients not surviving after 1 year, amputations occurring in approximately 30% of patients, and a mortality rate of 60% at 5 years.
Ruangsetakit et al prospectively examined 50 patients living with CLI with digital gangrene or chronic ischemic ulcers to determine the values of TcPO2, which predicts ulcer healing. Transcutaneous oxygen pressure was measured in the supine position while the patient was at rest with the leg elevated at 30 degrees. The mean age of participants in this study was 68 years and the mean ankle brachial index (ABI) was 0.75. In this patient population, TcPO2 < 20 mmHg showed no improvements in ulcer healing, while patients with measurements > 40 mmHg had complete ulcer healing. Patients with a TcPO2 between 20 mm Hg and 40 mm Hg varied between no healing and complete healing, with patients having greater than 10 mm Hg decreases upon leg elevation demonstrating less healing potential. Studies regularly illustrate that TcPO2 values are strong predictors of healing and can accurately demonstrate altered levels when extremities have restricted blood flow.
Peripheral artery disease (PAD), which can eventually lead to CLI, can be treated in numerous ways. Terminal health conditions caused by CLI relate to decreased oxygen perfusion to tissues. The least invasive way to treat PAD and its symptomatology, which is completely patient dependent and supported by the literature, includes exercise training. Haas et al7 states that the most significant long-term treatment for PAD is extended exercise programs, such as walking. Nonetheless, modifying cardiovascular risk factors, surgical intervention, and pharmaceuticals can also be utilized, but with a decreased chance of success. Haas et al7 states that many clinical trials demonstrate the benefits of exercise therapy, both clinically (ie, longer walking duration before claudication) as well as chemically (ie, modified markers of ischemia in the blood and structural adaptations in the limb such as improved walking tolerance, modified inflammatory and hemostatic markers, and enhanced vasoresponsiveness), and adaptations within the limb (ie, angiogenesis, arteriogenesis, and mitochondrial synthesis) that enhance oxygen delivery and metabolic responses, potentially delaying progression of the disease, enhancing quality of life indices, and extending longevity.
Holdich et al performed a study of 10 patients with claudication monitoring TcPO2 during exercise. The authors found that TcPO2 at the beginning of claudication fell by 16% and reached 32% at the maximum distance each individual was able to walk, and the findings were easily reproducible.
Cullum et al performed a systemic review of randomized control trials examining wound care management, including compression, laser therapy, electrotherapy, and ultrasound. The wounds included leg ulcers, pressure ulcers, diabetic foot ulcers, and ischemic wounds. Ultrasound was specifically utilized in the randomized control trials for chronic wounds. The evaluation determined there was not sufficient evidence to draw conclusions about the relationship between ultrasound and chronic wound healing.
Therapeutic ultrasound operates from a range of less than 1 Mhz to 3 Mhz. Hanson et al noted that ultrasound has shown to aid in wound healing by various means in pressure ulcers and leg and foot ulcers. They noted an abstract which utilized a low-frequency ultrasound modality that was clinically effective in encouraging healing and tissue granulation within wounds via cavitation and acoustic microstreaming.
Surface acoustic wave (SAW) therapy utilizes a different acoustic wave than traditional ultrasound. While ultrasound therapy is usually a focused beam starting at the diameter of the probe that penetrates deeply with almost no energy on the surface of the skin or tissue, SAW is a very scattered beam whose energy is almost totally absorbed in the surface of the tissue. The SAW device has a maximal penetration of 4 cm, while traditional ultrasound penetrates to approximately 10 cm. Further, SAW spreads across a wide area; in the case of this device, approximately 20 cm.
Kavros and Schenck performed a case series examining the use of noncontact low-frequency (NCLF) ultrasound in the treatment of chronic foot and leg ulcerations. The study included 51 patients with numerous conditions, including limb ischemia, and found that utilizing NCLF ultrasound improved the rate of healing and closure in recalcitrant lower-extremity skin ulcerations. Moreover, Kavros et al performed a study examining NCLF ultrasound in nonhealing leg and foot ulcers with chronic CLI. In this randomized controlled trial, 35 patients received both ultrasound therapy and local wound care, while a control group received wound care without ultrasound therapy. Transcutaneous oximetry pressures in both the supine and dependent position were measured. Patients who received both ultrasound and local wound care achieved > 50% wound healing at 12 weeks compared to the control group that received only local wound care. Nevertheless, the study noted that most of the patients from both the treatment and control groups who did not successfully have 50% wound healing in the 12-week period had baseline dependent TcPO2 values < 20 mm Hg. The effectiveness of ultrasound in ischemic feet and local tissue oxygenation ranges remains a subject requiring increased study, leading to the development of this evaluation.
Abstract and Introduction
Abstract
Introduction Transcutaneous oxygen pressure (TcPO2) less than 30 mm Hg at the toe leads to local tissue hypoxia and nonhealing wounds. Studies regularly illustrate that TcPO2 values are strong predictors of healing and can accurately demonstrate altered levels when extremities have restricted blood flow. The objective of this study was to evaluate the effectiveness of surface acoustic wave (SAW) in ischemic feet on local tissue oxygenation.
Methods Ten patients, ranging from 40–75 years of age and suffering from critical limb ischemia (CLI) were selected from a vascular surgery clinic to undergo evaluation with a PainShield SAW Patch device (NanoVibronix Inc, Melville, NY). Patients were treated once with 96 Khz of SAW for 30 minutes. All patients had an ankle brachial index of < 0.4 mm Hg. Two patients (patients 1 and 8) had necrosis of at least 2 toes on the affected limb and were given the device for nightly use for 1 month.
Results Through usage of SAW there was a significant increase in all patients' saturation values. The recorded baseline in both patients with necrotic toes almost doubled and during usage there was still a measurable increase in oxygen saturation. In both of these patients the subjective pain measures dropped significantly. Pain, as assessed by the Visual Analog Scale, dropped from 9 to 2 for patient 1 and from 8 to 3 for patient 8. Patient 1 went from 5 methadone treatments per day to only 1 per day starting in week 3. Patient 8 did not change their pain medication regimen.
Conclusion Surface acoustic waves as delivered in this study had a positive effect on tissue oxygenation and saturation in ischemic feet. In lower extremities that are not surgical candidates or are either in the pre- or postsurgical environment, an SAW patch device is a good therapy in elevating the extremities' O2 saturation.
Introduction
Healing of chronic wounds is dependent on many factors including type of wound, etiologies, depth, and comorbidities of the patient. According to Mustoe et al, billions of dollars are spent annually in the United States due to chronic wounds. Chronic wounds do not follow the typical hemostasis, inflammation, proliferation, and remodeling found in acute wounds. Chronic wounds typically come in a variety of etiologies, including venous ulcers, arterial ulcers, pressure ulcers, and neuropathic ulcers, which all seem very different in etiology, but may have similar difficulties healing. One reason is impaired circulation resulting in local tissue hypoxia.
Transcutaneous oxygen pressure (TcPO2) less than 30 mm Hg at the toe leads to local tissue hypoxia and nonhealing wounds. Local blood flow, affected by numerous etiologies such as impaired arterial inflow, arteriovenous pressures, capillary density, and local tissue consumption directly affect tissue partial oxygen pressures. Setacci et al stated that the most common cause of ischemic feet is atherosclerotic peripheral arterial disease, such as that which occurs secondary to diabetes mellitus. Mustoe et al also points out that diabetic ulcers are closely related to atherosclerotic large vessel conditions and chronic ischemia. Large vessel disease is not typically found in venous and pressure ulcers. Nevertheless, previous ulcerations greatly increase the possibility of reulceration due to fibrosis and decreased tissue perfusion. Moreover, other causes of ischemic feet include acute embolisms from the heart or arteries, thrombosis from procoagulative blood clots, arterial spasms, or injury from trauma and drug use. Edema in surrounding skin has also been shown to lessen TcPO2 in wounds.
According to Davies, 12% of the adult population in the United States have critical limb ischemia (CLI), defined sympotomatically as ranging from no symptoms to intermittent claudication, atypical leg pain, rest pain, ischemic ulcers, or gangrene. Beard states that about 150–200 people per 1 million progress to CLI with ischemic rest pain, ulceration, and/or gangrene. Critical limb ischemia costs approximately 200 million dollars a year in the United Kingdom. Critical limb ischemia and its sequelae have significant social and economic impacts, with 25% of patients not surviving after 1 year, amputations occurring in approximately 30% of patients, and a mortality rate of 60% at 5 years.
Ruangsetakit et al prospectively examined 50 patients living with CLI with digital gangrene or chronic ischemic ulcers to determine the values of TcPO2, which predicts ulcer healing. Transcutaneous oxygen pressure was measured in the supine position while the patient was at rest with the leg elevated at 30 degrees. The mean age of participants in this study was 68 years and the mean ankle brachial index (ABI) was 0.75. In this patient population, TcPO2 < 20 mmHg showed no improvements in ulcer healing, while patients with measurements > 40 mmHg had complete ulcer healing. Patients with a TcPO2 between 20 mm Hg and 40 mm Hg varied between no healing and complete healing, with patients having greater than 10 mm Hg decreases upon leg elevation demonstrating less healing potential. Studies regularly illustrate that TcPO2 values are strong predictors of healing and can accurately demonstrate altered levels when extremities have restricted blood flow.
Peripheral artery disease (PAD), which can eventually lead to CLI, can be treated in numerous ways. Terminal health conditions caused by CLI relate to decreased oxygen perfusion to tissues. The least invasive way to treat PAD and its symptomatology, which is completely patient dependent and supported by the literature, includes exercise training. Haas et al7 states that the most significant long-term treatment for PAD is extended exercise programs, such as walking. Nonetheless, modifying cardiovascular risk factors, surgical intervention, and pharmaceuticals can also be utilized, but with a decreased chance of success. Haas et al7 states that many clinical trials demonstrate the benefits of exercise therapy, both clinically (ie, longer walking duration before claudication) as well as chemically (ie, modified markers of ischemia in the blood and structural adaptations in the limb such as improved walking tolerance, modified inflammatory and hemostatic markers, and enhanced vasoresponsiveness), and adaptations within the limb (ie, angiogenesis, arteriogenesis, and mitochondrial synthesis) that enhance oxygen delivery and metabolic responses, potentially delaying progression of the disease, enhancing quality of life indices, and extending longevity.
Holdich et al performed a study of 10 patients with claudication monitoring TcPO2 during exercise. The authors found that TcPO2 at the beginning of claudication fell by 16% and reached 32% at the maximum distance each individual was able to walk, and the findings were easily reproducible.
Cullum et al performed a systemic review of randomized control trials examining wound care management, including compression, laser therapy, electrotherapy, and ultrasound. The wounds included leg ulcers, pressure ulcers, diabetic foot ulcers, and ischemic wounds. Ultrasound was specifically utilized in the randomized control trials for chronic wounds. The evaluation determined there was not sufficient evidence to draw conclusions about the relationship between ultrasound and chronic wound healing.
Therapeutic ultrasound operates from a range of less than 1 Mhz to 3 Mhz. Hanson et al noted that ultrasound has shown to aid in wound healing by various means in pressure ulcers and leg and foot ulcers. They noted an abstract which utilized a low-frequency ultrasound modality that was clinically effective in encouraging healing and tissue granulation within wounds via cavitation and acoustic microstreaming.
Surface acoustic wave (SAW) therapy utilizes a different acoustic wave than traditional ultrasound. While ultrasound therapy is usually a focused beam starting at the diameter of the probe that penetrates deeply with almost no energy on the surface of the skin or tissue, SAW is a very scattered beam whose energy is almost totally absorbed in the surface of the tissue. The SAW device has a maximal penetration of 4 cm, while traditional ultrasound penetrates to approximately 10 cm. Further, SAW spreads across a wide area; in the case of this device, approximately 20 cm.
Kavros and Schenck performed a case series examining the use of noncontact low-frequency (NCLF) ultrasound in the treatment of chronic foot and leg ulcerations. The study included 51 patients with numerous conditions, including limb ischemia, and found that utilizing NCLF ultrasound improved the rate of healing and closure in recalcitrant lower-extremity skin ulcerations. Moreover, Kavros et al performed a study examining NCLF ultrasound in nonhealing leg and foot ulcers with chronic CLI. In this randomized controlled trial, 35 patients received both ultrasound therapy and local wound care, while a control group received wound care without ultrasound therapy. Transcutaneous oximetry pressures in both the supine and dependent position were measured. Patients who received both ultrasound and local wound care achieved > 50% wound healing at 12 weeks compared to the control group that received only local wound care. Nevertheless, the study noted that most of the patients from both the treatment and control groups who did not successfully have 50% wound healing in the 12-week period had baseline dependent TcPO2 values < 20 mm Hg. The effectiveness of ultrasound in ischemic feet and local tissue oxygenation ranges remains a subject requiring increased study, leading to the development of this evaluation.
