Study design and population
This study used a randomized controlled, non-blinded, parallel comparison design and adhered to CONSORT guidelines. (UMIN-CTR trial registration number: UMIN000017716). For participant allocation, a permuted block (4 persons/block) randomization method was used to ensure balanced assignments. A computer-generated list of random numbers was used. The allocation ratio was 1:1. The research assistant generated the random allocation sequence, enrolled participants, and assigned participants to interventions. The study was conducted from August to November 2015 at a nursing home in Kanazawa City, Japan.
Participants were nursing home residents with chronic leg edema. Chronic edema was defined as subcutaneous tissue swelling that continued for ≥3 months based on a previous study.19 Inclusion criteria were nursing home residents aged ≥65 years and those who spent more time sitting than standing or lying during the day. Exclusion criteria were residents diagnosed with aneurysm or thrombosis, those who were not diagnosed with chronic leg edema, those who were otherwise considered unsuitable by a physician or nurse, or those who could not provide consent.
Pitting depth is classified into the following: 0 to 4: 0 = 0 mm; 1+ = 0 – 1.9 mm; 2+ = 2 – 3.9 mm; 3+ = 4 – 5.9 mm; and 4+ = ≥6 mm depending on the physical examination method.20 Participants classified as having chronic leg edema were those with pitting depth of ≥1+ severe edema on at least one site of their legs.
Intervention
The intervention group underwent vibration therapy for 2 weeks. The size of the vibration device (Rela feel, Global-Micronics Co., Ltd. Kashiwa, Japan) was 616 × 182 × 114 mm (length × width × height). The frequency and horizontal vibration acceleration were set at 47 Hz and 1.78 m/s2, respectively, as per the permissible range for the minimum health and safety requirements.21 Previous studies reported that this device can be safely used for elderly individuals.22 The vibrator was placed under the legs with cushions between them (Figure 1). Vibrations were performed three times: morning (06:00–09:30), day (12:30–14:30), night (18:00–21:00), and each vibration was performed for 15 min. During the morning and daytime vibration therapy sessions, participants were either sitting or lying down depending on their lifestyle. At night, patients were lying down. The control group received no intervention, including leg vibration or elevation.
Outcome measurements
The primary outcome was pitting score. Secondary outcomes were leg volume and subcutaneous echo-free space grade (SEF) evaluated using ultrasound (US) images. We evaluated all measurement items before and after intervention period.
Pitting scores were calculated using the pitting test results. The pitting test was performed as described in a previous study.23 The investigator applied an even amount of pressure on the measuring site with the right thumb for 10 s. All measurements were provided by one researcher, and the intra-rater reliability (1, 1) of the pressure was 0.923. Measurements were taken at 22 sites in the right and left lower extremities. Pitting depths were converted to pitting scores: pitting 0, 0 point; pitting 1+, 1 point; pitting 2+, 2 points; pitting 3+, 3 points; and pitting 4+, 4 points. The points were added to obtain a total score for each leg.
The leg volume was determined using the following formula to calculate the truncated cone volume.24 V = V1 + V2, V1 = 1/3πh (r1r1+r1r2+r2r2), and V2 = 1/3πh (r2r2+r2r3+r3r3), where V1 represents the volume of the ankle to distal leg; V2 represents the volume of the distal to proximal leg; r1 is the ankle radius, r2 is the distal leg radius, and r3 is the proximal leg radius; and h is the leg length (one-third of the length of the lateral ankle to the fibular head apex).
SEF is a qualitative analysis method to analyze US images. The principal researcher obtained all US images at 10 sites on the right and left lower extremities. The dorsalis pedis was a short-axis image, whereas the remainder was long-axis images. A US console (Noblus, Hitachi Aloka Medical, Ltd., Mitaka, Japan) and linear transducer (L64, frequency range: 5–18 MHz) with identical settings were used: gain, 15; dynamic range, 70 dB; and focus point, 0.5 cm. SEF was classified into the SEF in five grades: 0, 1, 2-type A, 2-type B, and 2-type C using a modified method described by Suehiro et al.25 (Figure 2). Leg images were classified by the principal researcher and another researcher with experienced in analyzing US images of leg edema. SEF values were converted to SEF scores: grade 0, 0 point; grade 1, 1 point; grade 2-type A, 2 points; grade 2-type B, 3 points; and grade 2-type C, 4 points. The points were added to achieve the total score for each leg.
Data for participants’ characteristics included age, sex, present illness, ADLs,26 body mass index (BMI), total serum protein level, serum albumin level, and medication use. The time spent walking, sitting, and lying down was recorded. In addition, the principal researcher measured participants’ triceps skinfold, arm circumference, and arm muscle circumference and performed a Stemmer’s test. This test was performed by pinching and lifting a skinfold at the base of the second toe. If the skin can be pinched and lifted, the Stemmer’s sign is negative, whereas if it cannot be pinched and lifted, the sign is positive. A positive Stemmer’s sign means the patient has subcutaneous tissue fibrosis.27
Analysis
Mann–Whitney U tests were used to compare differences in age, height, weight, and BMI between the intervention and control groups. Fisher’s exact tests were used to compare differences in other characteristics between the two groups. The total number of legs of the participants were used to assess the pitting score, leg volume, and SEF. Edema severity at baseline and leg volume changes were analyzed for the intervention and control groups using Mann–Whitney U tests. Differences in pitting and SEF scores at pre- and post-intervention in each group were analyzed using the Mann–Whitney U test. Values are shown as median (interquartile range [IQR]). To determine if chronic leg edema was controlled, participants were divided into edema-controlled and edema uncontrolled groups. Controlled edema indicated a lower or similar total pitting score at post- than at pre-intervention. Uncontrolled edema indicated that the total pitting score at post-intervention was higher than at post-intervention. Chi-square tests were used to assess the association between the intervention and edema control groups. P < 0.05 was considered significant. All analyses were performed using the Statistical Package for the Social Sciences version 19 (IBM-SPSS, Inc. Chicago, IL, USA).
Ethical considerations
The present study was conducted in accordance with the Helsinki declaration and was approved by the ethical review board at Kanazawa University (approval number: 599-1). This study was implemented after obtaining the participants’ and their families’ written informed consent. All measurements and intervention sessions were performed by two registered nurses to ensure participants’ safety. Moreover, participants’ vital signs were evaluated at pre- and post-vibration every day (the intervention group) to its effects on the circulatory systems.