Efficacy of Hydromechanical Therapy in Nonhealing, Chronic Wounds as a Cost- and Clinically Effective Wound Care Modality

Chronic wounds present serious medical and surgical challenges due to a significant degree of recalcitrance to standard, more expensive wound care treatments. Multiple systemic and cellular factors could be involved, such as arterial insufficiency, venous insufficiency, radiation fibrosis, nutritional deficiency, bacterial colonization, and biofilm. Nonhealing chronic wounds negatively affect the quality of life of patients and cost the United States health care system more than $25 billion per year.¹

Bacterial colonization and biofilm are disruptive to the normal healing pathways; yet they are ineffectively managed with antibiotics, antiseptics, and/or serial sharp debridement.² Polymicrobial colonization of chronic wounds contributes to multispecies biofilm formation on wound surfaces with concurrent disruption of collagen synthesis, alteration of matrix metalloproteases, and inhibition of neutrophil and macrophage functions.³ Bacteria produce numerous healing inhibitors such as proteases, enzymes, and toxins, lower local wound tissue oxygen levels, and deplete nutrients necessary for healing.⁴ Furthermore, wound surface factors, such as foreign bodies and necrotic tissue, only serve as a milieu that promotes bacterial growth, further delaying or preventing normal healing through overstimulation of metalloproteases. Consequently, wounds remain in an unregulated state of inflammation without granulation, epithelialization, or wound contraction.^5,6

Pressurized irrigation is frequently used in surgical field cleansing. Within the field of wound care, this methodology has garnered some attention. However, it is often overlooked despite its ability to achieve mechanical debridement by noninvasively dislodging harmful nonviable tissue while also disrupting and reducing wound surface bacterial burden in nonhealing wounds. This type of pressurized irrigation has been an appropriate treatment for all contaminated or infected surgical wounds and necrotizing soft-tissue infections. It is posited that pressurized irrigation breaks the recurring cycle of inflammation in chronic wounds, allowing them to progress to a subsequent normal wound-healing pathway.^7,8 Frequent pressurized irrigation, often pulsed, provides gentle and selective hydromechanical debridement that facilitates the removal of surface bacteria and devitalized tissue while promoting the generation of healthy granulating tissue.⁹

Furthermore, cyclical mechanical stimulation with low-frequency impact may lead to improved wound healing.¹⁰ In a clinical, commonly acute, setting, pressurized irrigation is utilized as pulsed lavage to remove foreign bodies and devitalized tissues. This ability to selectively debride exudative tissue using hydromechanical forces while preserving and stimulating wound surface regeneration may provide a unique modality with synergistically beneficial healing effects in chronic wounds.

Pressurized irrigation is also inexpensive and can be accomplished in any wound treatment setting. Additionally, tap water is no more prone to risks of infection than sterile irrigation solution,¹¹ this modality can be easily and frequently carried out in the patient’s home. Often, patients with complex chronic wounds are not ideal surgical candidates because of age, comorbidities, and malnutrition. Hydromechanical irrigation represents a tremendous cost-saving opportunity in caring for patients with chronic wounds compared with other wound healing products and modalities that are expensive and high resource-demanding, such as negative pressure wound therapy (NPWT), hyperbaric oxygen therapy, and biologic dressings.

Despite the potential advantages, wound care providers typically utilize more expensive modalities and approaches. Previously, the current authors presented a case of a difficult nonhealing wound in which NPWT failed, but the wound showed improvement after hydromechanical therapy using home tap water.¹² In this article, the authors present clinical cases of nonhealing, chronic wounds managed using hydromechanical therapy with either normal saline or tap water. The aim was to demonstrate that this inexpensive and readily available modality can significantly enhance the healing of complex, nonhealing wounds.

Daily treatment of chronic wounds was performed in the outpatient, inpatient, subacute, and home care settings using hydromechanical power with either 3 L irrigation with 0.9% normal saline at 15 psi or with tap water averaging 10 psi to 20 psi. Many of these patients were not ideal surgical candidates and/or had wounds in which other modalities failed. Representative patients were selected from the authors’ practices (PM and LG). Patients provided informed consent.

Case 1

A 67-year-old male who was ambulatory, had peripheral vascular disease and type 1 diabetes, and was on an insulin pump presented with a large, chronic plantar foot wound (6.5 cm × 10 cm) (Figure 1A). The wound had been unsuccessfully treated with  NPWT for 3 months with no progress. There was significant plantar tendon and metatarsal head exposure, with wounds tracking dorsally and proximally-medially through the skin. Home tap water irrigation was instituted with only wet-to-moist dressing changes daily. No antibiotic was required. The wound quickly showed significant improvement, with good granulation tissue formation in less than 2 months (Figure 1B); the wound was subsequently covered with a split-thickness skin graft (2.5 cm × 7 cm). The wound completely healed over the course of 5 months (Figure 1C), with no recurrence seen at the 15-month follow-up visit (Figure 1D).

Case 2

A 62-year-old female with end-stage multiple sclerosis presented with a chronic stage IV sacral pressure ulcer (3.5 cm × 6.8 cm) and with complaints of increased pain, exudate, and malodor (Figure 2A). The wound had been slowly deteriorating for more than 1 year. Wound cultures revealed methicillin-resistant Staphylococcus aureus (MRSA). Despite adequate pressure relief and nutritional support, previous use of topical enzyme, autolytic debriding agents with intravenous antibiotics, and advanced wound care dressings had failed. The patient, in a subacute nursing facility, was started on daily pulsed irrigation using 3 L (0.0625%)of sodium hypochlorite solution per treatment for 2 weeks, and then transitioned to daily 3 L of 0.9% normal saline irrigation. In 2 weeks, treatment was associated with improved wound pain, decreased exudate, and decreased malodor. Hydromechanical power was later delivered 5 times weekly in a home care setting. Healthy granulation tissue covering the exposed sacral bone developed by 4 weeks, and a significant reduction in wound size was seen at 3 months (Figure 2B). The wound was subsequently healed by secondary intention in 7 months (Figure 2C).

Case 3

A 70-year-old female with hypertension and uterine cancer presented with a postoperative abdominal surgical wound (4.0 cm × 8.5 cm) after a robotic-assisted laparoscopic hysterectomy (Figure 3A). The subacute surgical wound dehiscence and infection were initially managed with surgical debridement, NPWT, and intravenous antibiotics. Negative pressure wound therapy was discontinued after 8 days due to increased pain and a malodorous exudate. Hydromechanical power using 3 L of 0.9% normal saline was delivered daily, initially in a subacute nursing facility and later in a home care setting. Treatment was augmented with daily hydrogel dressing changes. Within 4 days, healthy granulation tissue was noted (Figure 3B). In 2 weeks, the wound had significantly improved (Figure 3C) and completely healed by 5 months (Figure 3D).

Case 4

A 49-year-old male with a C7 spinal cord injury presented with a chronic stage IV sacral pressure ulcer (3.5 cm × 7.0 cm) (Figure 4A) that had worsened in the 2 months before presentation. Wound cultures revealed MRSA, and previous nonsurgical management with advanced silver dressings with alternating pressure relief mattresses, nutritional support, and intravenous antibiotics failed. Hydromechanical power using 3 L of 0.9% normal saline was delivered daily at home with daily hydrogel dressing changes. The patient was continued on a pressure relief mattress with nutritional support. The wound significantly improved by 4 weeks (Figure 4B) and completely healed by secondary intention after 6 months (Figure 4C).

Case 5

A 78-year-old female who was nonambulatory and had peripheral vascular disease, type 2 diabetes, and a recent cerebrovascular accident presented with a chronic stage IV ischial pressure ulcer (4.0 cm × 8.1 cm) (Figure 5A). Wound cultures revealed MRSA, and previous nonsurgical management with 3 months of NPWT, intravenous antibiotics, and alternating pressure relief mattress had failed. The patient, in a subacute nursing facility, was started on daily pulsed irrigation using 3 L of 0.0625% sodium hypochlorite solution for 2 weeks and transitioned to daily 3 L of warmed 0.9% normal saline irrigation and daily hydrogel dressings. The wound showed significant improvement in appearance by 2 weeks (Figure 5B) and healed by secondary intention after 6 months (Figure 5C).

Case 6

A 69-year-old female with type 2 diabetes and Hodgkin lymphoma presented with a chronic, large posterior neck wound (10.5 cm × 15 cm) after surgical removal of spinal fixation hardware due to an MRSA surgical site infection (Figure 6A). Negative pressure wound therapy during the preceding 12 months had failed. The patient received intermittent long-term antibiotics via a peripherally inserted central catheter line. In a subacute setting, pulsed irrigation was delivered daily using 3 L of 0.9% normal saline in addition to daily hydrogel dressing changes. Treatment was subsequently provided 5 times weekly in a home care setting. The wound had significantly improved by 4 weeks (Figure 6B) and healed by secondary intention by 5 months (Figure 6C).

This case series reports difficult-to-heal chronic wounds that improved significantly and eventually healed after unsuccessful attempts with more mainstream modalities. The current results highlight the use of hydromechanical therapy in wound care, further substantiating the previous case report by the authors of this present study.¹² Hydromechanical therapy has been a mainstay and is a readily available, easily executable methodology for wound healing. It enables a relatively gentle debridement of devitalized tissue and cleanses the surface of the wound to make it conducive to healing. It also provides a moist healing environment that facilitates tissue regeneration. According to literature from 2015,⁹ hydromechanical therapy is also believed to enhance such regeneration with mechanical forces on wounds through continuous and repetitive physical impact. Generic hydromechanical therapy can be a convenient, affordable modality for patients in an outpatient setting. If adopted appropriately, this could have a positive impact on health care costs and antibiotic stewardship to control bacterial resistance, which is a major contributor in chronic wound care.

A significantly greater hydraulic pressure than the adhesive force between the wound and the contaminants must be applied to remove small particles and bacteria. The removal efficiency is proportional to the pressure applied to the wound surface.¹³ Pulsed lavage irrigation commonly utilizes a low pressure (range, 4–15 psi), powered pump irrigator to deliver more effective pressurized irrigation, compared with gravity flow (1 psi), bulb syringe (4 psi) or 30 cc syringe, and 18-gauge needle (8 psi).^14,15 Currently, mechanical pressurized irrigation is recommended for dirty or heavily contaminated traumatic wounds in the emergency department or, when combined with surgical debridement, to treat patients with infected wounds in the operating room.^4,16-18 Bacteria, particulate matter, necrotic tissue, and exudate are retained on the wound surface through adhesive forces with varying degrees of strength. Pressurized fluid disrupts bacterial adherence through fluid dynamic forces. It is rather effective in removing loose debris, foreign bodies, and pathogens, leading to better healing of chronic wounds.^19,20

Rodeheaver et al¹⁴ demonstrated an 84.8% bacterial decrease in bacterial contamination of experimental wounds using a pulsed lavage system at a pressure of 15 psi. Using pressures as high as 40 psi, the bacterial load was significantly decreased by 86.9% in 9 patients with contaminated or infected acute wounds.²¹ Mote and Malay²² reported a near 70% absence of any bacteria identified on the immediate postlavage wound culture among 73 debridements in 55 patients. The Agency for Health Care Policy and Research recommended that irrigation pressure ranging from 4 psi to 15 psi were sufficient to remove surface pathogens and debris without causing adverse effects.²⁴ A consensus in the literature shows that irrigation pressure greater than 8 psi effectively removes debris and bacteria and prevents clinical infection.^11,16,21,25 Although the ability of wound cleansing enhances as irrigation pressure increases, the benefit of high pressure must be weighed against its related adverse effects. Irrigation pressures of 50 psi to 70 psi have been shown to adversely affect tissue through tissue destruction and inhibition of fracture healing in in vitro and animal models,^26-28 and thus are associated with increased susceptibility to infection.^16,29 However, despite some common beliefs, even with pressures as high as 90 psi, there is no evidence that bacteria and foreign bodies on the wound surface are disseminated and injected into soft-tissue wounds.^29-32

Isotonic sterile saline irrigation fluid, which is readily available and cost-effective, is the most common wound irrigation solution and has not been shown to inhibit normal healing processes, damage tissues, or cause allergic reactions.³³ Various solutions such as sterile water, distilled water, and tap water are suggested.³⁴ There is no significant difference in clinical infection rates in acute wounds¹¹,^35,36 or in chronic wounds³⁷ that were cleansed with either tap water or normal saline. A general tap water faucet provides a pressurized water flow, at about 20 psi to 45 psi. Although the water pressure may vary in different areas or buildings, residential water pressures are generally greater than 10 psi.³⁶ Even at lower water pressures, some showerheads can increase the fluid dynamic forces by more efficiently channeling water. Therefore, water flow can often be adjusted to keep the pressure at an acceptable range (15–20 psi). The pressurized stream, tolerable to patients, is a good indicator of a feasible pressure to avoid host tissue damage (overdebridement). Although tap water can be easily utilized in a patient’s home, pulse lavage is widely available in a facility setting, primarily hospitals, and via specialized delivery devices such as wound irrigation bags in long-term care facilities.³⁸ Despite its potential benefits to wounds, this technology is commonly used in an operating room with limited application in routine wound care. However, given its efficacy, pressurized irrigation (such as that delivered through inexpensive commercially available portable saline-based pulse irrigators or a home shower device using tap water) can help change the paradigm in wound care by cleansing wounds through hydromechanical debridement and effectively removing debris, reducing bacterial counts, and promoting granulation tissue formation. Finally, when it comes to the tonicity of the irrigation fluid, the current authors recommend that a minimal amount be left on the wound posttreatment in case of water irrigation to avoid contact surface cellular swelling due to its hypotonic nature.

Biofilm is a relatively new concept in the field of chronic wound treatment. Biofilms are complex microbial communities embedded in an extracellular polymeric substance secreted by each biofilm bacteria, protecting neutrophils, antibodies, and antibiotic attacks in the host environment.³⁹ In addition, the bacteria release proteases capable of degrading human growth factors and tissue proteins that are integral to the healing process, leading to a chronic inflammatory state.⁴⁰ In the presence of delayed wound healing, biofilm formation should be considered foremost.⁴¹ Almost all device-related infections and 65% of all chronic infections treated by physicians are caused by bacteria growing in biofilms.⁴² Reports by the National Institutes of Health⁴³ estimates that 85% of all human infectious diseases involve biofilms.The bacteria are usually attached to the wound surface via the wound bed, suture, or an implanted medical device facilitating biofilm formation. Current research suggests that mechanical debridement is the best way to remove biofilm.¹³ Although the residual pathogens can reconstitute the biofilm, they are more vulnerable to host immunity and antibiotics.⁴⁴ Furthermore, biofilm can reconstitute itself within 1 to 2 days; therefore, any effort to disrupt it requires treatment in repetitive short intervals, at least daily, until the wounds are healed. To the authors’ knowledge, almost none of the popular chronic wound care modalities involve any mechanical disruption of biofilms.

In general, wound treatment commences with adequate debridement and maintains a physiologically moist wound environment for precursor cells and growth factors to survive.⁴⁵ Adequate debridement is critical to eventual healing—too little or ineffective debridement results in the persistence of biofilm remnants and thus a continual hostile healing environment. Overly aggressive debridement, as in nonselective sharp surgical debridement, invariably leads to the destruction of healthy tissue and an unnecessarily wider wound. Hydromechanical debridement, however, offers a debridement force, often gauged by the patient’s pain tolerance, just enough to dislodge the nonvitalized tissue and its associated biofilm without significant damage to the healthy surrounding tissue. In addition, it offers a moist wound environment that prevents dehydration of healing granulation tissue to minimize crust formation around the wound margins and facilitates eventual cell migration, leading to faster closure rates.^46,47

Wound treatment with water, such as hydrotherapy or whirlpool, has long been used as a component of wound care. Pulsed lavage, first studied at Walter Reed Medical Center more than 3 decades ago, has long been appreciated for reducing bacterial content through irrigating wounds with a pressured solution.¹⁹ Curiously, comparing the rate of granulation tissue formation between pulsed lavage and whirlpool treatment, Haynes et al⁴⁶ reported the rate of granulation tissue formation was significantly higher in those receiving pulsed lavage. These results suggest that administering adequately strong pressure is beneficial to the healing process. Separately, Svedman⁴⁷ observed that granulation tissue in chronic leg ulcers appeared more rapidly following pulsed irrigation than with the conventional saline wet dressings, partly due to the efficient removal of wound exudates using the irrigation technique. Interestingly, using a laser Doppler flowmeter, Svedman⁴⁷ noted increased blood flow in leg ulcers managed with irrigation. This additional finding may suggest further stimulating effects of mechanical impact on the progression of those wounds.

Fluid irrigation, whether pulsed or continuous, exerts percussive forces upon the wound surface. Although mechanical forces (eg, suction and vibration) cause wound tissues to undergo heightened granulation and vascularization, thus leading to faster healing, direct evidence of percussive forces impacting wounds has been lacking until recently. Irion et al⁴⁸ utilized a rat model to show that in wounds impacted with a percussive piston delivering a constant low pressure, the low-frequency mechanical force would heal 50% faster than in a control animal. Through extensive research on NPWT device mechanisms, it has been established that mechanical forces act on cells in wound tissue through compression, stretching, and shearing, therefore modifying the spatial configuration of their inner cytoskeleton networks.¹⁰ Subsequently, this leads to increased proliferation and migration of those cells, giving rise to enhanced healing. One can infer that pressurized irrigation may also improve wound healing by delivering such mechanically impactful actions. Therefore, the current authors believe the kinetic energy delivered through hydromechanical therapy, in addition to biofilm disruption, also impacts tissue at the cellular level leading to regenerative responses. Consequently, higher kinetic energy in the volume of irrigation and speed at which it is delivered (felt and tolerated by patients as pressure) can be expected to translate into more clinical tissue healing. The present authors anticipate that additional research will further validate this hypothesis and decipher its underlying molecular and cellular mechanisms.

In several of the current authors’ patients, the wounds had been previously and unsuccessfully treated with NPWT for extended periods. It is well established that NPWT improves healing through mechanical forces that promote tissue regeneration. It is widely used in chronic wounds following wound debridement and is typically changed every 2 to 3 days. Although there is some evidence of decreased bacterial counts with NPWT, biofilms in chronic wounds often persist and demonstrate resistance to the otherwise positive healing effects of the negative pressure. This further underscores the importance of how fluid irrigation acts on wounds by simultaneous mechanical stimulation of healing tissue and continuous disruption of the biofilm.

Finally, the cost savings of using hydromechanical therapy to manage difficult wounds is significantly lower, considering its simplicity and wide availability. A generic hydroirrigator available for purchase at many stores costs on average $37, and the fluid used can be saline or simply water from a shower faucet.¹² Compared with NPWT, the plethora of supplies required for debridement and antibiotics utilized, hydromechanical therapy is significantly more affordable and accessible. The vastly lower costs, ease of application, efficacy through continued disruption and removal of biofilm, and healing achieved through sustained stimulation of wound beds ensure⁴⁸ its usage as frequently as clinically necessary. Additionally, hydromechanical debridement utilizes minimal ancillary resources and requires minimal training to administer, further lowering costs. With the current cost-conscious state of health care and its ever-expanding and increasingly expensive array of wound treatment modalities,¹ this traditional, inexpensive, convenient, yet effective treatment using hydromechanical forces certainly deserves renewed attention.

This case series had several limitations. Some may posit that the wounds would have healed without implementation of hydromechanical therapy. As shown in this study, prior therapeutic modalities had not achieved notable healing; however, the authors believe the addition of this therapy proved to be beneficial in healing these wounds. Distinct takeoff and subsequent continued improvements since the commencement of hydromechanical therapy were noted by the senior authors. While the authors acknowledge that a case series is not as impactful in the literature,  a randomized controlled study in the realm of a diverse expanse of chronic wounds of numerous clinical and demographical variables would be difficult.

The current clinical results demonstrate the underutilized potential of hydromechanical therapy and its effect in managing difficult-to-heal and nonhealing chronic wounds. When used appropriately, this technique has the potential to improve clinical outcomes, patient quality of life, and health care costs. Its ease of application, accessibility, and convenience make hydromechanical therapy an important modality to consider in chronic wound care.

Authors: Haley DesJardins, MD¹; Sydney Char, MD¹; Patrick Marasco, MD²; Yung-Chang Hsu, MD³; and Lifei Guo, MD, PhD, FACS⁴

Affiliations: ¹Tufts University School of Medicine, Boston, MA; ²Lawrence General Hospital, Lawrence, MA; ³China Medical University Hospital, Taichung, Taiwan; ⁴Lahey Hospital and Medical Center Burlington, Burlington, MA

Correspondence: Lifei Guo, MD, PhD, FACS, Lahey Hospital and Medical Center Burlington, Plastic Surgery, 41 Mall Road, Burlington, MA 01805; lifei.guo@lahey.org

Disclosure: The authors disclose no financial or other conflicts of interest.