To explore the clinical efficacy of different modes of continuous negative pressure wound therapy (NPWT) on venous ulcer wounds of lower limbs, and to analyze the influencing factors.

From January 2018 to December 2019, 53 patients with venous ulcer of lower limbs who met the inclusion criteria and hospitalized in the Affiliated Hospital of Jiangnan University were recruited in this prospective randomized controlled study. According to the random number table, the patients were divided into single negative pressure therapy (SNPT) group (19 patients, 11 males and 8 females), cyclic alternating negative pressure therapy (CANPT) group (17 patients, 12 males and 5 females), and routine dressing change (RDC) group (17 patients, 10 males and 7 females), aged (47±11), (49±10), and (47±10) years respectively. After admission, patients in SNPT group were given continuous NPWT with the single negative pressure setting at -13.3 kPa, patients in CANPT group were also given continuous NPWT but with the cyclic alternating negative pressure setting from -16.0 to -10.7 kPa, while patients in RDC group were given dressing change with vaseline gauze soaked with iodophor. The wound healing rate was calculated on treatment day 7 and 14. Transcutaneous oxygen pressure (TcPO₂) around the wound was detected by TcPO₂ meter before treatment and on treatment day 7 and 14. The wound exudate/drainage fluid was collected on treatment day 1, 4, 7, 10, and 14, with the pH value measured using a pH meter, and the volume of exudate/drainage fluid recorded. Before treatment and on treatment day 7 and 14, venous blood was collected to detect the serum levels of interleukin 1β (IL-1β), IL-6, tumor necrosis factor α(TNF-α), transforming growth factor-β₁ (TGF-β₁), vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). Before treatment and on treatment day 7 and 14, wound exudates were collected for bacterial culture, and Visual Analogue Scale and Hamilton Anxiety Scale were used to evaluate the degree of wound pain and anxiety of patients respectively. The length of hospital stay and the total treatment cost were counted. Analysis of variance for repeated measurement, one-way analysis of variance, least significant difference test, Kruskal Wallis H test, Mann Whitney U test, chi-square test, Fisher′s exact probability method test, and Bonferroni correction were used to analyze the data. According to the wound healing rate on treatment day 14, the efficiency of patients were divided into two grades of significant healing with wound healing rate≥70% and non significant healing with wound healing rate<70%. According to the two categories of wound healing rate as dependent variables, the levels of TcPO₂, IL-1β, IL-6, TNF-α, TGF-β₁, VEGF, bFGF levels and bacterial detection, wound pain and anxiety before treatment, wound exudate/drainage fluid volume and pH value on treatment day 1 were taken as covariates, and binary classification multifactor logistic regression analysis was used to analyze the risk factors of significant wound healing.

(1) On treatment day 7, the wound healing rate of patients in SNPT group was (33±10) %, which was significantly higher than (24±9) % of RDC group (P<0.05). On treatment day 14, the wound healing rates of patients in SNPT group and CANPT group were (71±15)% and (66±18)%, respectively, which were significantly higher than (45±19)% of RDC group (P<0.01). (2) Compared with those of RDC group, the TcPO₂ value around the wound of patients was significantly increased in SNPT group on treatment day 14 and in CANPT group on treatment day 7 and 14 (P<0.05 or P<0.01), the pH value of wound drainage fluid of patients was significantly decreased in SNPT group on treatment day 10 and 14 and in CANPT group on treatment day 7 and 14 (P<0.05), the volume of wound drainage fluid of patients was significantly reduced in SNPT group on treatment day 10 and 14 and in CANPT group on treatment day 7, 10, and 14 (Z=-4.060, -4.954, -2.413, -4.085, -4.756, P<0.05 or P<0.01), the serum levels of IL-1β, IL-6, and TNF-α of patients were significantly decreased in SNPT group and CANPT group on treatment day 7 and 14 (P<0.01), the serum level of TGF-β₁ of patients was significantly increased in CANPT group on treatment day 14 (P<0.05), the serum levels of VEGF and bFGF were significantly increased in SNPT group and CANPT group on treatment day 14 (P<0.01), the bacteria detection proportion of wound exudate, wound pain, and anxiety scores of patients were significantly decreased in SNPT group and CANPT group on treatment day 7 and 14 (P<0.01). Compared between the negative pressure therapy two groups, except the wound pain score of patients in CANPT group was significantly lower than that in SNPT group (P<0.01) on treatment day 7, the other indicators mentioned above were similar. (3) The length of hospital stay of patients in SNPT group was similar to that in CANPT group (P>0.05), which were significantly shorter than the time in RDC group (P<0.01). The total treatment cost of patients among the three groups was similar (F=1.766, P>0.05). (4) Before treatment, the serum levels of TNF-α and bFGF, TcPO₂ around the wound, and the degree of wound pain were risk factors for significant wound healing (odds ratio=1.109, 0.950, 1.140, 2.169, 95% confidence interval=1.012-1.217, 0.912-0.988, 1.008-1.290, 1.288-3.651, P<0.05 or P<0.01).

Clinical application of continuous NPWT under single negative pressure mode and cyclic alternating negative pressure mode has a positive effect on improving the wound base and healing rate of venous ulcer of lower limbs. But cyclic alternating negative pressure mode is significantly more effective than single negative pressure mode in improving TcPO₂ around the wound, reducing wound pH value, reducing exudate volume and relieving pain. The serum levels of TNF-α and bFGF, TcPO₂ around the wound and the degree of wound pain were the risk factors that affect the wound healing significantly.

Negative-pressure wound therapy; Varicose ulcer; Wound healing; Chronic wound