Polak 2016a.

Methods	Design: 6‐week prospective, double‐blind, randomised controlled study
Participants	Health condition: elderly people with pressure ulcers Sample size: Randomisation: at participant level (one ulcer per participant)§ Randomised (participants, n; ulcers, n): 60; 60 Experimental: 30; 30 Contro: 30; 30 Analysed (participants, n; ulcers, n): 49; 49 Experimental: 25; 25 Control: 24; 24 Setting, country: nursing and care centres (2 sites), Poland Inclusion criteria: stage II and III pressure ulcers (NPUAP classification) older adults (60 years or more) at high risk of pressure ulcers (< 14 points on Norton scale) pressure ulcers of more than 1 month but less than 24 months duration pressure ulcers greater than 1 cm2 but smaller than 50 cm2 pressure ulcers on the pelvic region (sacrum, coccyx, ischial tuberosity and greater trochanter of the femur) Exclusion criteria: pressure ulcers requiring surgical intervention participants with malignant, tunnelling, and necrotic wounds participants with cancer, electronic implants, osteomyelitis and metal implants around pressure ulcer participants with diabetes (HbA1c 97%), venous insufficiency, critical infection, alcoholism, and allergy to standard wound treatment Characteristics of pressure ulcer: Experimental Ulcer duration, mean (SD): 2.5 months (2) Ulcer location, (n): sacrum/coccyx (13), ischial tuberosity (8), greater trochanter (4) Ulcer stage, (n): stage II (11) and stage III (14) Control Ulcer duration, mean (SD): 2.8 months (2.7) Ulcer location, (n): sacrum/coccyx (12), ischial tuberosity (9), greater trochanter (3) Ulcer stage: stage II (11) and stage III (13) Mean age (SD): Experimental group: 80 years (9) Control group: 76 years (13) Gender: Overall: 24% male Experimental group: 24% male Control group: 25% male §It is not clearly stated whether participants or pressure ulcers were randomised but the number of pressure ulcers equals the number of participants.
Interventions	Total groups in this study: two Experimental: HVMPC groupand standard wound care Duration: 50 minutes per session; 1 session per day; 5 days a week; total 6 weeks Electrode placement: one over the ulcer and the other on healthy skin 20 cm away from the ulcer Device, manufacturer: Intelect Advanced Combo unit (Model 2771, Chattanooga Group, California USA Intensity of ES: sensory perception Frequency: 100 Hz Type of current: pulsed Polarity: cathode over the ulcer Control: sham HVMPC group and standard wound care Sham with no ES delivered Standard wound care programme for both groups Included pressure ulcer prevention measures, wound care and physical treatment advocated by interdisciplinary medical team
Outcomes	Outcomes included in this review: presented as [name of outcome in review]‐ [name of outcome in study] Proportion of pressure ulcers healed ‐ pressure ulcers healed (expressed as numbers) Complications/adverse events ‐ adverse event (expressed in descriptive format) Rate of pressure ulcer healing ‐ healing rate (expressed as percentage per week) Other outcomes not included in this review: Gilman Index Healing rate (cumulative for 6 weeks) Time point included in this review: week 6 (end of intervention) Other time point: baseline
Notes	Withdrawals, (n; reason): Experimental: 2; health deteriorated, 3; died Control: 4; health deteriorated, 2; died Funding source: no information about funding source provided Registry or published protocol: retrospectively registered at Australian New Zealand Clinical Trials Registry (identifier ANZCTR12614000207617)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: “….they were randomly allocated between the ES group (SWC plus active HVMPC) and the control group (SWC plus sham HVMPC) using a concealed process (Figure 1).” p452 Comment: insufficient detail reported
Allocation concealment (selection bias)	Low risk	Quote: “The allocation sequence was concealed by using sealed envelopes with consecutive numbers.” p452
Blinding of participants (performance bias) All outcomes	Low risk	Quote: “All patients……were blinded.” p453
Blinding of personnel (performance bias) All outcomes	High risk	Quote: “The only person engaged in the experiment who was not blinded was the principal physiotherapist, who set the devices to apply active or sham ES.” p453
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: “All ….as well as the person making weekly measurements of WSA and the statistician processing the data, were blinded.” p453
Incomplete outcome data (attrition bias) All outcomes	High risk	Comment: 11/60 (18%) dropouts
Selective reporting (reporting bias)	Low risk	Comment: all pre stated outcomes were reported
Other bias	Low risk	Comment: appears free of other bias