Ischaemic or borderline-perfusion wounds

• All three ischaemic wounds healed completely, with no further wound-edge necrosis and no reported pain during therapy (p.2–3).
• SPP values were low (Case 1: 25; Case 2: 30; Case 3: 20 mmHg) yet outcomes were good (p.2, Table 1).
• Duration of LPN was 21–28 days (median 24 days), similar to NPWT durations reported for non-ischaemic wounds (p.3).
• Two patients (Cases 1 and 3) had a split-thickness skin graft after good granulation; Case 2 healed by wound contraction after LPN was stopped (p.2).
• Authors caution the 50 mmHg setting may not suit all ischaemic wounds — patients with even lower SPP may still develop necrosis, so close observation is required (p.4).

CAT: OCEBM 4 · Three patients in a single arm cannot support the comparative claim that 50 mmHg is safer than 125 mmHg, and that is exactly the claim this paper is used for. GRADE starts Low for observational data and is downgraded twice for extreme imprecision and for very serious risk of bias: no control arm, no blinding, outcomes judged clinically by the treating surgeons, and a hypothesis that was formed before the cases and confirmed by them. Very low is the floor and there is nothing to raise it. What is actually here, with every denominator: 3 of 3 patients healed completely; 0 of 3 developed further wound-edge necrosis; 0 of 3 reported pain during therapy. Skin perfusion pressures were 25, 30 and 20 mmHg, all below the 40 mmHg cut-off the unit uses (sensitivity 72 per cent, specificity 88 per cent). Ulcer sizes were 50 x 25, 50 x 22 and 60 x 18 mm. Therapy ran 28, 23 and 21 days. Two of 3 were closed with a split-thickness skin graft and 1 of 3 healed by contraction 14 days after therapy stopped. Arithmetic that does not reconcile: the paper states 'the median duration of LPN was 24 days'. The median of 21, 23 and 28 is 23. Twenty-four is the mean. The paper mislabels its only summary statistic, and 24 days is the number the wiki and the downstream protocol have carried. The rationale is borrowed, not demonstrated: the physiological premise — that 125 mmHg raises tissue pressure enough to occlude capillaries at an ischaemic wound edge — is taken from the Kairinos work this wiki holds, and no tissue pressure, perfusion or oximetry was measured in any of these three patients at any point. The authors concede the limit themselves: 50 mmHg 'may not suit all ischaemic wounds', patients with lower SPP may still necrose, and close observation is required.

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• In all three configurations tissue pressure increased proportionately to applied suction (p < 0.0005); no negative pressures were ever recorded (p.1, p.4).
• Circumferential dressings produced significantly larger pressure increments than noncircumferential (p < 0.0005) or cavity (p < 0.0005) groups; the latter two did not differ (p = 0.269) (p.1, p.5).
• Over 48 h the raised pressure fell significantly (circumferential p = 0.04; noncircumferential p < 0.0005), but only 3 of 10 wounds dropped below their pre-dressing baseline; soonest was 24 h (p.1, p.7).
• In 2 of 10 wounds (both circumferential) tissue pressure rose further over time, and 3 of 10 stayed ≥10 mmHg above baseline at 48 h (p.7).
• Because normal capillary perfusion pressure is only 10–35 mmHg, the authors argue a sustained ≥10 mmHg rise could occlude capillaries in tissue with already-compromised perfusion (p.7).

CAT: OCEBM 5 (mechanistic reasoning) / GRADE NOT APPLICABLE — the outcome is interstitial pressure in mmHg, a surrogate, and no patient-important effect estimate exists for GRADE to act on. The JBI Critical Appraisal Checklist for Quasi-Experimental (non-randomised experimental) Studies is applied in its place. · GRADE does not apply and assigning it a certainty level would be a category error. There is no comparator, no clinical event, no risk, no ratio and no confidence interval anywhere in this paper. Its outcome is a pressure transducer reading. GRADE grades certainty in an estimate of an effect on an outcome that matters to a patient; this study produces none, so the correct answer is a reasoned refusal, and the previous entry of 'OCEBM 3 / GRADE Low, start low cohort, +1 large effect' was wrong on every element. The finding, with its denominators: tissue pressure rose proportionately to applied suction in all three dressing configurations, and a negative (hypobaric) tissue pressure was never recorded in any of the 15 tests. Circumferential dressings raised pressure more than non-circumferential (p less than 0.0005) and more than cavity dressings (p less than 0.0005); the latter two did not differ (p = 0.269). Over 48 hours at −125 mmHg the raised pressure declined significantly (circumferential beta = −0.21, p = 0.04; non-circumferential p less than 0.0005) but only 3 of 10 wounds fell below their own baseline, the soonest at 24 hours, 2 of 10 rose further, and 3 of 10 remained at least 10 mmHg above baseline at 48 hours. Because normal capillary perfusion pressure is 10 to 35 mmHg, a sustained 10 mmHg rise is mechanistically sufficient to occlude capillaries in tissue that is already marginal. Two qualifications the paper's own text supplies and the abstract does not. First, the abstract prints p less than 0.0005 for all three groups while the results print p less than 0.005 for the non-circumferential and cavity groups. Second, one of the five cavity wounds, a septic spinal dehiscence, showed no significant rise at all (p = 0.51), so the claim holds at group level in 3 of 3 configurations but at wound level in 4 of 5 cavity wounds.

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• Circumferential NPWT reduced hand perfusion by a mean 40 ± 11.5% at −400 mmHg and 17 ± 8.9% at −125 mmHg (both p < 0.0005); no hand showed increased perfusion (p.1, p.4).
• The perfusion drop was significantly greater at −400 than −125 mmHg (p < 0.015) (p.1, p.4).
• Noncircumferential NPWT lowered TcPO2 in all 12 legs: 7.35 ± 7.4 mmHg at −400 mmHg and 5.10 ± 7.4 mmHg at −125 mmHg (both p < 0.0005); the −400 vs −125 difference was not significant (p = 0.07) (p.1, p.4).
• Tissue oxygen after suction-off remained significantly below the pre-suction baseline (p = 0.02 and 0.03) (p.5).
• The authors propose laser Doppler misreads compression: as vessels narrow, blood velocity spikes (equation of continuity) so Doppler "perfusion units" rise even while true perfusion falls, reconciling the conflicting literature (p.6, p.7, p.8).

CAT: Same dataset as chapters 6 and 7 of the Kairinos 2011 UCT thesis — see the rationale. OCEBM 5 (mechanistic experiment on healthy volunteers). RoB 2 applied to the randomised -400 against -125 mmHg comparison, giving SOME CONCERNS to HIGH; the suction-versus-control contrast is appraised on its own terms as a paired physiological experiment. GRADE is not applicable — the outcomes are radioactivity counts and transcutaneous oxygen tension in intact healthy skin, which are surrogates for nothing that has been validated against a wound outcome. · First, the double-counting warning, because it matters more than the GRADE. This is the same dataset as chapters 6 and 7 of kairinos 2011 uct thesis npwt pressure perfusion. Same volunteers, same hands, same legs, same numbers. A motivation or a review that cites the thesis alongside this paper as though they were two sources is counting ten volunteers twice. The two are not interchangeable even as a single source: the thesis prints p less than 0.005 where this paper's abstract prints p less than 0.0005, and the thesis gives the -125 mmHg oximetry reduction as 5.0 mmHg (SD 4.67) where the abstract gives 5.10 plus or minus 7.4. GRADE is refused for a stated reason: the outcome is a surrogate, and not a validated one. Gamma-camera counts under a foam sandwich on an intact healthy hand, and transcutaneous oxygen tension on the shin of a seated volunteer, are physiological quantities measured over minutes. No healing, granulation, infection, graft take or amputation outcome exists here, and no study has established that a 17% fall in hand counts predicts anything about a wound. Rating certainty in an effect on a surrogate that has never been linked to a patient outcome would give the number a standing it has not earned. The findings themselves are internally consistent and point one way. Circumferential NPWT reduced perfusion by 40 plus or minus 11.5 percent at -400 mmHg and 17 plus or minus 8.9 percent at -125 mmHg, with no hand showing an increase and the blinded nuclear medicine reporter calling 19 of 20 scans asymmetric. Transcutaneous oxygen fell in ALL 12 LEGS, and stayed below the pre-suction mean after the suction was switched off. Consistency across two independent modalities, in every single subject, is the strength of this paper. Its weakness is that the stated precision is not supported, and the details are in the appraisal field below: three different p-values are printed for one comparison, and two of the three group means do not reproduce from the paper's own tables.

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• Recommendation 2 (100% agreement): manual palpation of the dorsalis pedis and posterior tibial arteries is the first step in vascular assessment. Recommendation 3 states that ABPI may be falsely elevated in people with diabetes — medial calcification producing falsely elevated readings — which is why palpation, toe pressures and TcPO₂ are given alongside it.
• PEDIS perfusion grading, adapted (Table 4) — the numbers most useful to a motivation:
• Grade 1, no PAD: palpable dorsalis pedis and posterior tibial pulses, or ABPI 0.9–1.3, or toe-brachial index >0.6 or toe pressure 55 mmHg, or TcPO₂ >40 mmHg.
• Grade 2, PAD without critical limb ischaemia: intermittent claudication, or ABPI <0.9 with ankle pressure >50 mmHg, or TBI <0.6 with systolic toe pressure >30 mmHg, or TcPO₂ 30–60 mmHg.
• Grade 3, critical limb ischaemia: no palpable pulses, with the corresponding pressure thresholds (systolic toe pressure and TcPO₂ <30 mmHg).
• Revascularisation should always be considered whenever a major amputation is contemplated, and in patients with persistent ischaemic rest pain.
• Annual foot screening for all patients with diabetes, covering peripheral arterial disease, loss of protective sensation, prior amputation, prior or active ulceration, visual or mobility disability, callus with sensory loss, and deformity with sensory loss; risk stratified with a 60-second screening tool.
• Infection is diagnosed on clinical signs and symptoms, not on microbiology alone. All deep wounds should be probed to bone with a blunt sterile metal instrument.
• Sharp debridement should be performed by experienced practitioners — podiatrist or specialised nurse — with specialist training. Six other debridement modalities are listed as alternatives where that is unavailable.
• Off-loading is treated as central to both prevention and healing, with total contact casting the reference standard.
• Frames the case for the multidisciplinary team by quoting IWGDF: a strategy of prevention, education, multidisciplinary ulcer treatment and close monitoring can reduce amputation rates by 49–85%.

AGREE II: Recommended with modifications — Scope 67% · Stakeholders 50% · Rigour 27% · Clarity 78% · Applicability 63% · Independence 17%

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• Four core mechanisms of action underpin every indication: (1) reduces tissue oedema; (2) increases granulation tissue formation; (3) increased perfusion as a secondary/later effect; (4) with instillation and dwell time can reduce wound contamination.
• Vascular surgery: high-level evidence supports NPWT for infected vessels and prosthetic vascular grafts — strong recommendation for high-risk surgical patients with a fully exposed, infected prosthetic vascular graft, together with debridement and appropriate antibiotics; continuous suction at lower levels (-50 to -100 mmHg) recommended to avoid bleeding.
• Traumatic/surgical wounds: NPWT is first-line for preoperative wound-bed preparation post-debridement, typically 7-10 days before definitive surgery; strong for open fractures that cannot be closed primarily (used between debridement and reconstruction); caution when tendon/bone exposed; do not use if underlying arterial impairment is not addressed (red).
• Diabetic foot ulcers: first-line post-surgical treatment for DFU once ischaemia is excluded (University of Texas Grade A2/A3); consider for chronic DFU not progressing after 4 weeks; contraindicated where ischaemia is due to concomitant peripheral arterial disease (red).
• Sternal dehiscence: NPWT is the method of choice for post-sternotomy mediastinitis (strong); caution in the haemodynamically unstable patient; the open sternum with exposed vulnerable structures is not an indication (red).
• Abdominal / dehisced abdominal wounds: strong for the open abdomen and for dehisced wounds with intact abdominal wall; NPWT with instillation (NPWTi-d) is effective in reducing infection in the infected open/dehisced abdomen (moderate); do not use if size/severity does not merit it.
• Skin grafts, burns, venous ulcers, pressure injuries, enterocutaneous fistulae: NPWT endorsed for wound-bed optimisation before grafting and intra-operative graft stabilisation; acute burn indications supported but not a substitute for grafting; venous ulcers only if <30% area reduction in 4 weeks and ABPI 0.8-1.2 (contraindicated if ABPI <0.6); NPIAP stage 3/4 pressure injuries until surgical closure (moderate); ECF in selected collapsible/low-output cases only, never in unexplored fistulae.
• Closed incisional NPWT (ciNPT): recommended to decrease wound complications, dehiscence, haematoma/seroma and surgical site infection (strong).
• Contraindications listed: clotting disorders, active non-capillary bleeding post-debridement, exposed organs/vasculature/anastomoses, eschar or dry necrosis, neoplastic tissue, untreated osteomyelitis, non-enteric and unexplored fistulae.

AGREE II: Recommended with modifications — Scope 67% · Stakeholders 56% · Rigour 23% · Clarity 67% · Applicability 46% · Independence 25%

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