Abstract
A range of prevalence of peripheral artery disease in diabetic patients has been estimated using the measurement of ankle brachial pressure index and clinical features in Asian countries. These data may be underestimates and hence underrecognized, raising questions about the numbers of patients with neuroischemic feet who are also at risk of diabetic foot ulcers. Underrecognition of these lesions may well increase the high levels of chronic wound burden resulting from peripheral artery disease as well as neuroischemic foot lesions. Improved education and training of clinical staff (nurses and family physicians) is required to combat these serious issues.
In its editorial, “The global pandemic of peripheral artery disease,” 1 The Lancet persuasively argued for better preventive strategies to curb the mortality and morbidity associated with peripheral artery disease (PAD) based on the review by Fowkes and colleagues. 2 The arguments in The Lancet 1 were clear and evidence based: the main focus was to prevent mortalities that affect the younger population, females as well as males, and those in low to middle income groups in many countries. The article also discussed morbidity: lower limb amputation is one of the unsatisfactory outcomes of morbidity. 1 The argument did not consider effects on diabetic subjects with or likely to have neuroischemic foot lesions—a feature that is reportedly increasing. 3
The prevalence of PAD in type 2 diabetic patients in most Asian countries is high,4-8 as shown in Table 1. The prevalence is wide ranging, from 12.7% (in Thailand) to 31.6% (in Pakistan), in between which lie the fairly recently reported figures for prevalence in India, China, and Taiwan. All these and other studies have used the ankle brachial systolic pressure index (ABI) as the primary sampling tool. The ABI is a well-accepted and widely available measurement, with described ranges and associations with incompressible arteries (ABI > 1.3). 9 Aside from these consideration is the awareness that PAD can be asymptomatic: this leads to underrecognized and/or late presentation. Recently, based on our survey in 2247 diabetic patients in Thailand, there are 286 PAD cases, and only 50 out of 286 PAD patients recognize any history of leg ischemia symptom, for example, intermittent claudication, rest pain, gangrene, and ulcer. 4 In other words, most PAD in diabetic patients (82.5%) are asymptomatic and consequently diagnosis would be delayed, possibly causing inappropriate treatment. These can and do lead to increased mortality and/or morbidity.
Prevalence of Peripheral Artery Disease in Diabetic Subjects in Some Asian Countries a .
Only lead authors are mentioned in the table.
Ankle Brachial Pressure Index
ABI is a measure of perfusion at the level of the foot. A portable Doppler ultrasound probe (frequency range 5-8 MHz) and sphygmomanometer cuff are used to measure systolic pressures on the arm, the ankle, and pedal circulation (posterior tibial, dorsalis pedis, and, occasionally, peroneal arteries) on both legs. The ratio of the pressures in the distal circulation to the lower value obtained from the brachial arteries yields ABI. Established ABI ranges are as follows:
≥0.9 to ≤1.3 within a normal range—exclude PAD
>1.3 excludes effects of incompressible arteries leading to false high ABI; may require additional noninvasive vascular evaluation such as toe pressure, TcPO2, or Duplex ultrasound color imaging
<0.9 indicates the presence of arterial disease and is associated with the presence of heart disease
Less than 0.5 is consistent with the presence of significant distal PAD
Some portable Doppler ultrasound machines also show blood velocity profiles that are clues to hemodynamic performance. 10
Pain in the calf muscle is a common presenting complaint of PAD; this may be masked in patients with diabetes, which could lead to underestimation of PAD and therefore its prevalence. The growing numbers of patients with some loss of sensation as well as a level of ischemia (neuroischemia) causes concern.3,11,12 Additionally, venous incompetence has been reported from a small study on diabetic subjects with no symptoms of pain as well as those with a history of foot ulcers 13 : venous incompetence is associated with lower extremity venous ulceration, all of which suggests diabetic subjects with no lower limb pain could be at risk of foot ulcers from underrecognized PAD as well as venous disease, which would have an impact on morbidity. These are data that beg the question whether those caring for diabetic foot conditions in Asia must account for neuroischemic as well as PAD in diabetic cohorts.
Arguably 50% of foot ulcers arise from ischemia or neuroischemia. 3 Treatment of ischemia is aimed at improving perfusion to the foot using interventional or conventional bypass procedures. Does improved perfusion to the foot find its way to ulcerated tissues? For healing cutaneous wounds there is a need for a functional microcirculation. 14
Tissue Microcirculation
A functional microcirculation enables the exchange of oxygen and other nutrients between capillaries and surrounding tissues. It is driven by positive pressure arteriovenous pressure gradients and regulated by external (pressure, temperature, tissue fluid pressure, intercapillary distances) as well as endogenous influences (sympathetic control, red cell viscosity, hormonal changes). Transcutaneous oxygen tension (TcPO2) measured using skin sensors are a measure of local tissue nutrition 15 : TcPO2 levels less than 30 mm Hg are associated with increasing probability of amputation 3 (see Figure 1). TcPO2 measurements are affected by capillary density 16 and are influenced by edema as well as skin thickness. 15
Comparison of measurements of pressure at the ankle, toe, and transcutaneous oxygen tension. 15
Toe blood pressure (TBP) measured using optical sensor and cuffs attached to a sphygmomanometer are more sensitive to distal tissue perfusion, as shown in Figure 2. Toe pressures and TcPO2 indicate the likelihood of wound healing on account of their sensitivity to the microcirculation, as shown in Figure 2, and should be used in preference to ABI, which are accurate to determine ankle pressures. Faglia and colleagues have estimated the variation in probability of amputation with values of TcPO2. 17
Measuring toe pressure using an optical device and cuffs.
Discussion
The aim of this report was to highlight the increased likelihood of morbidity from diabetic foot ulcers in type 2 diabetes with PAD. Increased likelihood of morbidity arises from underdiagnosed asymptomatic PAD and venous disease as well as the increase in neuroischemic lesions. For those caring for diabetic patients in Asia, this calls for further studies of the prevalence of neuroischemic feet, increased surveillance of neuroischemic patients, 12 and improved education of practitioners as well as patients/families and exercise.
Surveillance for foot conditions in diabetic subjects has been described. 12 ABI greater than 1.3 with a toe/brachial pressure less than 0.7 is associated with systemic atherosclerosis; future work using both these and TcPO2 is required to better understand the microcirculation. Ndip and Jude have described diagnosis and management of subjects with ABI in the range greater than 0.9 to less than 1.3 using medical therapy and wound care. 12
Education and training of staff are essential. Skills of measuring ABI are transferred with ease and should be encouraged at all levels of practice. In Greece, nurse training to measure ABI in order to improve education as well as the care of PAD and leg ulcer management has been reported. 18 Measurements of tissue oxygen tension and toe pressures are also easy to carry out, teach, and train. However, at present, these are better limited to hospitals with multidisciplinary teams to enable greater focus on wound care.
Education of patients and carers/family is also essential and determined by the clinician with respect to societal considerations. For example, barefoot walking practice is common in several countries in Asia; trying to overcome this social practice in order to protect and preserve feet is best done with respect to societal interests. Thailand and other Asian countries will equally benefit from improved knowledge and the steps taken in other nations to combat PAD and associated complications.
Advice on diet and exercise are commonly used by practitioners; however, there is great need to better understand the role of exercise which is necessary but what and how much to do. Watson 19 argues that though exercise is essential, the types and extents of exercise must be better understood in order to use exercise to treat patients with type 2 diabetes. Is the need for exercise exclusive to the middle- to high-income groups living in urban areas whose “Western lifestyle” is considered to be a cause of diabetes and its sequelae? Or do all ages and income groups living in rural communities need exercise. More research is required to dispense or advice in order to prevent and to better manage wounds.
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Drs Rerkasem, Kosachunhanun, Sony, and Inpankaew conducted a study in diabetic patients in Thailand, which was supported by the Health Systems Research Institute and National Research Council of Thailand. Dr Rerkasem was also supported by the National Research University Project under Thailand’s office of the Commission of Higher Education.