Influence of Peripheral Neuropathy and Microangiopathy on Skin Hydration in the Feet of Patients With Diabetes Mellitus

Sik Namgoong, MD, PhD; Jong-Phil Yang, MD; Seung-Kyu Han, MD, PhD; Ye-Na Lee, MSc, RN, CWCN; Eun Sang Dhong, MD, PhD

Disclosures

Wounds. 2019;31(7):173-178. 

In This Article

Materials and Methods

Materials

The medical records of 361 patients with diabetes mellitus who were treated at the Diabetic Wound Center of Korea University Guro Hospital (Seoul, South Korea) between June 2012 and May 2015 were reviewed. Patients who met the following criteria were included in the study: (1) data of the Semmes-Weinstein monofilament test as well as electromyography (EMG) and nerve conduction velocity (NCV) of both motor and sensory fibers; (b) transcutaneous oximetry (TcpO2) findings; (c) corneometry findings; and (d) medical history of diabetes > 5 years. Patients who had wound infections or cellulitis while undergoing the tests were excluded.

Overall, 266 patients (200 men, 66 women) with a mean age of 63.0 ± 2.9 years (range, 30–91 years) met the inclusion criteria (Table 1). Among those 266 patients, 228 (85.7%) had ulcers. The degree of xerosis was graded as severe, moderate, or acceptable. Severe was defined as having corneometry values < 21 arbitrary units (a.u.; n = 88), moderate as having corneometry values of 21 a.u. to 30 a.u. (n = 156), and acceptable as having corneometry values > 30 a.u. (n = 22).

The degree of diabetic neuropathy was graded as severe, moderate, or acceptable. Severe was defined as having monofilament test values < 7, with positive neuropathy findings on the EMG/NCV test (n = 26). Moderate was defined as having monofilament test values < 7, with negative neuropathy findings on the EMG/NCV tests; or monofilament test values ≥ 7, with positive neuropathy findings on the EMG/NCV tests (n = 157). Acceptable was defined as having monofilament test values ≥ 7, with negative neuropathy findings on the EMG/NCV tests (n = 83).

The degree of microcirculation was graded as severe, moderate, or acceptable. Severe was defined as having a TcpO2 value < 21 mm Hg (n = 52), whereas moderate had TcpO2 values of 21 mm Hg to 40 mm Hg (n = 103) and acceptable had values > 40 mm Hg (n = 111).

Measurement of Skin Hydration

Skin hydration was evaluated objectively using a corneometry device (Elasticity & Moisture Sensor; Bomtech Electronics Co Ltd, Seoul, Korea).

Hydration of the stratum corneum was measured on the dorsum of the foot at the most proximal point adjacent to the ulcer (Figure 1); patients with ulcers were placed in supine position for measurement. Skin hydration was always measured on the dorsum of the foot in an area directly opposite the lesion, even if the ulcer was present on the plantar aspect. In cases without an ulcer, hydration was measured at the tarsometatarsal level with the patient in a supine position. All patients were asked to refrain from washing with soap, using detergents, or applying cosmetics 24 hours prior to the test in order to eliminate the effect of these substances on skin moisture. All measurements were taken under standard climate conditions (25 ± 1°C; 50% ± 5% relative humidity) by a trained, experienced investigator (Y-N Lee) after a calibration check was performed. The mean value of 3 recordings at each site was used as the data, and all 3 recordings were completed at 1 visit (Figure 2).

Figure 1.

Patient position and sites tested during corneometry and transcutaneous oximetry (TcPO2) measurement. (A) The position of the patients during corneometry and TcPO2 measurement and the specific site for TcPO2 measurement; and (B) specific site for corneometry.

Figure 2.

The 3 subgroups of skin hydration: (A) poor hydration (4 arbitrary units [a.u.]), (B) moderate hydration (23 a.u.), and (C) acceptable hydration (42 a.u.).

Measurement of Neuropathy

The assessment of peripheral neuropathy included evaluation of quantitative sensory testing using the 5.07/10-g monofilament test and the EMG/NCV test.

For the Semmes-Weinstein monofilament test, each filament was applied perpendicular to the skin surface with enough force so that it buckles. Testing was performed at 10 different sites on each foot as recommended.[13,14] The EMG/NCV values of both sensory and motor fibers also were recorded by a physiatrist in the Department of Rehabilitation at Korea University Guro Hospital. Motor NCV tests were performed in the median, ulnar, peroneal, and tibial nerves, and F waves were recorded for each nerve. Sensory NCV tests were performed in the median, ulnar, and sural nerves. H reflex studies also were performed. Needle EMG was carried out in 3 muscles: vastus lateralis, tibialis anterior, and gastrocnemius medialis. Based on the suggestions from the Diabetes Control and Complications Trial, the following criteria were included as the diagnostic criteria for diabetic neuropathy:[15,16] amplitude of the sural nerve was < 5 μV; amplitude of the median sensory nerve was < 10 μV; amplitude of the peroneal motor nerve was < 1 mV; latency was > 6 ms, or conduction velocity was < 40 m/s; the F wave latency was absent or > 55 ms; the H reflex was absent; and fibrillations were observed in the lower extremity muscles.

Measurement of TcpO2

To evaluate microcirculation of the feet, TcpO2 was measured using a PF 5040 TcpO2 (PeriFlux System 5040; Perimed AB, Stockholm, Sweden) paired with the PeriSoft program (PeriSoft for Windows 2.50; Perimed AB). Measurement of TcpO2 was performed at the same site as that at which corneometry was performed (Figure 1) by the fourth study author (Y-N Lee).[17] The TcpO2 levels were recorded at 43°C after a 20-minute equilibration period.

Ethical Considerations

The study protocol was approved by the institutional review board of Korea University Guro Hospital (Approval No. KUGH 15092–001). This study was performed in accordance with the Declaration of Helsinki.

Statistical Analyses

All data were expressed as mean ± standard deviation. Statistical comparisons were performed using the linear-by-linear association trend test and Pearson's chi-square test. A P value < .05 was considered statistically significant. Statistical analysis was performed using SAS 9.3 statistical software (SAS Institute, Cary, NC).

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