Pain and trauma in negative pressure wound therapy: a review

Abstract

Negative pressure wound therapy (NPWT) is considered an effective wound treatment, but there are a number of issues that need to be addressed for improvements to be made. This review aimed to explore the literature relating to the pain and skin trauma that may be experienced during NPWT. A literature search was carried out using the following databases: Academic Search Complete, CINAHL, PsychINFO, MEDLINE and PsyARTICLES. A total of 30 articles were reviewed. Studies reported varying levels of pain in patients undergoing NPWT, with certain treatment factors affecting the level of pain, such as the NPWT system and the dressing/filler used. Similarly, although there is much less research exploring NPWT‐related trauma, findings suggest that dressing and filler type may impact on whether trauma occurs. However, further research needs to consider the different stages of NPWT and how pain and trauma can be minimised during the whole procedure. As both pain and skin trauma impact on the patient's well‐being and on wound healing, it is essential that research further explores the factors that may affect the experience of pain and trauma, so as to inform developments in wound care.

Introduction

Negative pressure wound therapy (NPWT) is a wound treatment involving the application of sub‐atmospheric pressure to remove excessive exudate and prevent infection while changing dressings and promoting healing ^{1, 2, 3, 4}. Since its development in the 1980s, there have been a number of research studies supporting the effectiveness of NPWT in wound healing ^{5, 6, 7}. Furthermore, the treatment is considered to have economic benefits because faster healing tends to result in a reduced frequency of dressing changes and lower hospital costs ^{8, 9}.

Despite the research support for its effectiveness in wound healing, fewer studies have considered the impact of NPWT on the patient in terms of the pain that can be experienced. Wound care and dressing changes can be very painful for patients ¹⁰, and this pain can also cause patients to feel stressed or anxious, ^{11, 12} thus impacting negatively on both their physical and psychological well‐being. Such factors need to be considered in any evaluation of NPWT or other treatment.

In addition to the effects on patient's well‐being, pain has also been associated with healing time, with high levels of pain being linked to delayed healing ¹³. Stress has also been linked with healing time ¹⁴, so it is possible that painful dressing changes could prolong treatment because of both the pain and stress that patients experience, although further research is needed to confirm theories of how pain and stress during dressing change may impact on wound healing.

Recent research has begun to consider how pain can be minimised in wound care and in NPWT specifically; for example, it has been reported that dressing types can have an effect on the level of pain experienced ¹⁵. Additionally, different treatment factors may affect the level of skin trauma that occurs during treatment. With NPWT, damage to the wound bed tends to occur when new granulation tissue grows into the foam and becomes torn during dressing change; skin trauma occurs when the film dressing is removed, and this may cause bleeding, skin stripping, blistering and other damage to the skin ^{16, 17}. Such trauma not only impacts on patient's well‐being but, like pain, may also delay healing by worsening the wound bed and prolonging treatment.

Pain and trauma are important areas to consider in wound care, and research into these areas is essential for the development of improved treatment options to promote patient's well‐being and recovery. To improve NPWT, a review is needed of the pain and trauma that patients may experience, and of the different treatment factors that may influence these. As NPWT is already considered to be an effective and relatively speedy treatment compared with other options, reducing the pain and trauma during treatment could actually make it even faster and lead to greater patient satisfaction. Similarly, wound‐related costs could also be further reduced.

The aim of this review is to summarise previous research exploring pain and trauma of NPWT, and to identify the impact of different treatment factors. Consequently, this may highlight areas for further investigation.

Methods

The following databases were searched in December 2012: Academic Search Complete, CINAHL, PsychINFO, MEDLINE and PsychARTICLES, covering the period from 2001 to 2012. Keywords used in the search were as follows: [‘negative pressure wound therapy’ or ‘vacuum‐assisted closure’ or ‘topical negative therapy’] and [‘pain’ or ‘trauma’ or ‘tissue damage’ or ‘skin damage’ or ‘blister’ or ‘skin stripping’ or ‘bleeding’ or ‘in‐growth’ or ‘granulation tissue’]. Only articles that had been published in peer‐reviewed journals in the English language were included. Additionally, animal studies as well as articles that did not have an abstract or full text available were not included.

The search found 154 articles. However, many articles were broad in nature, focusing on treatment in general; therefore, articles were excluded if they did not discuss factors relating specifically to pain and/or trauma. Reference lists of identified articles were also searched. A total of 30 relevant articles were included in this review.

Review

Pain during NPWT

High levels of pain during NPWT were reported by Apostoli and Caula ¹⁸ who explored self‐reports of pain in a sample of 25 patients with cutaneous wounds who were undergoing NPWT. Patients reported significantly higher pain levels during therapy compared with their pain levels before treatment. Reported painkiller dosage was also higher during treatment, with patients having to increase their dosage to manage the pain. Levels of pain were so high in some that five patients had to take a break from treatment.

Such pain appears to be relatively common in NPWT patients. In a study of 27 patients who were undergoing NPWT for gynaecologic malignancies ¹⁹, 67% of patients reported pain during NPWT. However, this was considered to be the only complaint, other than bleeding in one patient. The study concluded that NPWT is a safe treatment; however, pain during dressing change is far from ideal. As well as causing obvious physical discomfort, pain during wound care can also have a detrimental effect on the patient's well‐being. Research has shown that pain during dressing change is also linked with stress, and patients may experience a repetitive cycle of pain, anxiety and a heightened pain perception as a result of anxiety and expectations ^{11, 12}. Furthermore, both pain and stress have been found to be associated with the length of time that a wound takes to heal ^{13, 14}, having potentially important implications for treatment outcomes and patient's well‐being. Therefore, it is essential that the experience of pain during dressing change is not overlooked.

Wound pain and wound care in general can be painful and some researchers have suggested that NPWT is no more painful than other treatments. For example, Ford‐Dunn ²⁰ presented the case of a 62‐year‐old female with a very painful open wound; although treatment was ended prematurely because of her condition worsening, the patient reported that the dressings used were no more painful than conventional dressings.

Similarly, in a randomised controlled trial comparing treatment outcomes in leg ulcer patients receiving either NPWT or standard treatment ²¹, pain levels were found to be similar in both groups during the first 5 weeks of treatment. However, those who received NPWT reported significantly less pain after the fifth week. This suggests that although NPWT may be just as painful as other wound treatments, the pain may be less prolonged and only short‐term.

Nevertheless, it is important to minimise pain as much as possible. It appears that pain during NPWT and other wound care may be considered a part of treatment that cannot be avoided. However, research into different types of NPWT and dressing has shown that pain levels can vary according to different treatment factors in NPWT, which would suggest that levels of pain can be minimised for patients undergoing NPWT.

In a systematic review of the literature into the effects of NPWT on surgical wounds, Webster et al. ²² reported that pain levels were lower in patients who received hospital‐based NPWT in comparison to patients who had commercial Vacuum‐Assisted Closure (VAC^®, KCI Medical, Kiddlington, Oxfordshire, UK), which is a specific type of NPWT. Similarly, another study of three patients who were undergoing VAC for post‐pneumonectomy bronchopleural fistula found that patients experienced acute pain despite the suction being minimal ²³. The review argued that VAC should be closely monitored for this patient group.

However, other studies have reported lower pain levels during VAC. Bollero et al. ²⁴ reported that in patients with acute traumatic leg wounds, pain was well tolerated during VAC dressing changes and that patients did not require sedation or painkillers. The only complication was severe pain in a patient with an amputated stump. Additionally, in a study comparing outcomes for Fournier's Gangrene patients, Ozturk et al. ²⁵ compared five patients who were undergoing VAC therapy with five who received standard treatment. Although there was no difference in effectiveness between the two treatments, VAC was reported to involve less pain and fewer dressing changes.

In another study involving patients with Fournier's Gangrene, Verbelen et al. ²⁶ investigated the use of a low‐vacuum NPWT system with low‐adherent contact surface in two patients. The study reported benefits of NPWT including ease of use and patient comfort. On an average, pain was reported to be low to moderate during this type of NPWT. Low‐pressure NPWT was also explored in another study of three wound patients ²⁷, which reported average pain levels to be only moderate: 4 or 5 on a scale of 0–10. Furthermore, patients reported lower pain levels as treatment progressed. These studies suggest that perceived pain can be low for patients undergoing low‐vacuum NPWT. However, both studies lacked a large sample or a control group for which to compare NPWT.

Similarly, in a study of another specific type of NPWT, the Smart Negative Pressure Wound Care System, Mölnlycke Health Care, Gothenburg, Sweden mild to moderate pain was reported in 3 of 12 patients ²⁸. This suggests that different NPWT systems can have different effects on patient pain levels. However, still a quarter of patients complained of pain. Furthermore, patients had differing wounds, including traumatic leg and ankle wounds, a diabetic/postsurgical back wound, a pressure ulcer on the ankle, venous stasis leg and ankle ulcers and a neuropathic toe wound; it is not clear which patients experienced pain and which did not, and the presence of neuropathy in at least one patient may have affected the perception of pain.

During NPWT, there are several stages that may cause patients to experience pain, including application of suction and the removal and application of dressings and films. Some researchers have looked at different dressing types used with NPWT and how these impact on the experience of pain. In a multicentre clinical investigation, gauze‐based NPWT was explored in over 152 patients ²⁹. The majority of patients had acute wounds (63 postsurgical, 12 trauma and 3 other). Other patients had chronic wounds, including venous leg ulcers (n = 4), diabetic foot ulcers (n = 15) and pressure ulcers (n = 34). A further 21 patients had a split‐thickness graft. Whilst examining wound healing, the authors also recorded patients' experiences of pain. In 80% of dressing removals, patients reported no pain. A significant reduction in pain across the process was also reported. Although six patients had reduced pain perception because of neuropathy, paraplegia or quadriplegia, the authors stated that this small number could not explain the high percentage of patients overall who reported no pain. These findings suggest that use of gauze‐based dressings in NPWT can minimise, if not eliminate, pain experienced during the procedure, although it must be acknowledged that.

The use of gauze‐based NPWT has received further support in other studies. In comparison to foam‐based NPWT, application of gauze filler has been linked with low levels of pain as well as other positive outcomes including lower costs and ease of application ^{17, 30, 31}. Tuncel et al. ⁶ reported that only 2 of 50 patients experienced severe pain during gauze‐based NPWT. This was in a sample of patients with pressure sores (n = 31), diabetic foot ulcers (n = 13), venous ulcers (n = 4) and traumas (n = 2). However, it is important to minimise the severe pain experienced by every patient.

In contrast to gauze‐based NPWT, foam‐based NPWT has been associated with trauma to the wound bed, which may cause dressing change to be more painful ¹⁶. Whilst some researchers have explored the use of alternative dressings, other researchers have investigated ways in which foam‐based NPWT can be improved. For example, Teot et al. ³² explored the use of a non adherent lipidocolloid dressing, which can be inserted between the foam and the patient's wound to prevent the growth of tissue in the foam. In a study conducted at eight hospitals in France comprising 66 patients (64% with acute wounds, mostly postoperative; 36% with chronic wounds, mostly pressure ulcers), it was reported that dressing adherence to the wound was minimal, occurring in just 12% of procedures. Before receiving NPWT, patients reported pain in 82% of procedures, and this was reported to reduce considerably as a result of the treatment. However, this study focused more on dressing adherence rather than on patients' actual experiences of pain.

Additionally, other studies have reported low pain levels with foam‐based NPWT. In a review of Avance^®, Mölnlycke Health Care, Gothenburg, Sweden NPWT, Chadwick et al. ³³ presented the case of a patient with a surgical wound who rated pain during treatment activation and deactivation as one or zero on a scale of 0–10, where 0 represented no pain at all. This patient was given foam‐based Avance NPWT and was reported to experience a high level of comfort during treatment. However, this was a case study; hence, the findings cannot be generalised.

In a slightly larger study, pain levels were explored in patients with diabetic foot ulcers and post‐amputation wounds ³⁴. The study investigated the effects of Avance foam‐based NPWT on wound depth, whilst also considering the views of patients and carers about the pain and ease of use of NPWT. Of 14 patients, 22% experienced pain during treatment activation and 17% experienced pain at treatment deactivation. During dressing change, 31% of patients experienced pain. It was concluded that pain is minimised with NPWT, although this study was a non controlled, clinical investigation and therefore not as scientifically rigorous as a randomised controlled trial. Additionally, neuropathy may have been present and could have influenced pain perception.

Although not focusing on NPWT specifically, a study by Upton and Solowiej ¹⁵ also demonstrated how dressing type can affect the level of pain experienced during dressing change. In 49 patients with chronic wounds, the authors explored differences in pain and stress levels between those who received conventional dressings (n = 39) and those who were given atraumatic dressings with Safetac technology. Physiological and psychological measures of pain and stress were taken. It was found that self‐reported pain and stress were significantly lower in those who were given atraumatic dressings as part of their care routine. Galvanic skin response was also significantly lower, and other physiological measures of heart rate, blood pressure and salivary cortisol were lower but not significant. These findings highlight the importance of dressing type and the potential impact on patients' pain levels.

In addition to the NPWT system and dressing/filler type, other factors may affect the pain experienced during NPWT, such as the creams used for example, and these should be considered in order to minimise pain. Instillation of a topical anaesthetic into the wound is one technique that has been found to reduce pain for people undergoing NPWT ³⁵, although this study involved a retrospective analysis of just five cases. Further research needs to explore the impact of other factors on the pain experienced during NPWT.

It is clear from the studies outlined in this review that pain during NPWT can vary between patients and between different treatment options. Similar findings were reported in a very different, qualitative study by Abbotts ² who explored the experiences of 12 NPWT patients through focus groups. Wound types included were abdominal surgery (n = 5), cardiac bypass surgery (n = 2), mastectomy (n = 1), toe amputation in diabetic foot (n = 1), diabetic foot ulcer (n = 1), skin graft over venous leg ulcer (n = 1) and leg degloving injury (n = 1). Although pain was identified as one of nine key themes that affected the patients' experience, patients experienced varying levels of pain, with some finding pain to be a significant problem and others not finding this to be the case.

Whilst pain may vary between patients and treatment options, it can also vary between different stages of treatment. As there are several stages in the NPWT procedure, the severity of pain may be greater at certain points. However, current research has failed to explore the pain experience during the different stages, thus telling us little about ways in which the treatment can be improved to minimise pain. It is therefore important that future research addresses this requirement.

Trauma in NPWT

In addition to pain, NPWT and other wound treatments may also cause trauma or skin damage. This may occur when tissue grows into the foam on the dressing ^{16, 17} and this tissue becomes torn during dressing change. Damage to the wound and surrounding skin can involve bleeding, blisters, skin stripping and other skin damage, leading to a higher frequency of dressing changes, a greater level of pain and a longer time taken for the wound to heal. Despite the importance of minimising trauma during NPWT and other wound care, few researchers have focused on this area.

Bleeding has been reported in some studies of NPWT, but the number of cases is small. For example, Svensson et al. ³⁶ retrospectively assessed outcomes in 33 patients who had VAC for groin infections following surgery, and reported one serious case of VAC‐associated bleeding, although this was only in one patient. Synthetic vascular graft infections treated with VAC were also at greater risk of developing infection‐related complications.

In another study, Nordmyr et al. ³⁷ followed 121 VAC‐treated arterial disease leg wounds and found bleeding associated with VAC in four patients. Similarly, in Schimp et al.'s study of 27 VAC patients with gynaecologic malignancies, ¹⁹ bleeding was reported in one patient and no other complications were reported in the remaining 26 patients.

Other studies have reported the absence of bleeding in VAC patients ^{38, 39}. However, although only small proportions of patients appear to experience bleeding, it remains a potential complication, and it is important to identify which factors make bleeding more or less likely.

Another possible complication with NPWT is the development of blisters. In a randomised controlled trial involving 51 patients, Howell et al. ⁴⁰ investigated how long it took for patients with total knee arthroplasty to achieve a dry wound through NPWT or use of sterile gauze dressing. While the number of days for a dry wound to be achieved did not differ significantly between the groups, 15 of 24 patients undergoing NPWT developed skin blisters, which resulted in the study being terminated early. Additionally, a review of five trials involving 280 patients with surgical wounds reported that one trial was stopped early because of a high level of fracture blisters occurring in those who received NPWT ²².

Despite these findings, others researchers have reported very minimal trauma in NPWT patients. For example, Verbelen et al. ²⁶ reported minimal tissue ingrowth and minimal pain with the use of low‐vacuum NPWT in patients with Fournier's Gangrene.

In Hurd et al.'s study described earlier ²⁹, outcomes were explored in patients receiving gauze‐based NPWT. Of the 152+ patients with a variety of wound types, 96% did not experience any skin damage during dressing removal. The authors reported minor damage in 3% of patients and moderate damage in just 1%. This suggests that trauma can be minimised significantly during NPWT. Pain and discomfort were also very low in this study; pain and trauma are linked because pain skin damage during wound care can result in increased pain ¹⁷; therefore, it is important to identify ways in which trauma can be minimised.

Other studies have also reported gauze‐based dressings to reduce pain and trauma compared with foam‐based dressings ¹⁷. These findings again highlight the importance of dressing type. As outlined earlier regarding the pain of NPWT, foam‐based NPWT has been linked with skin trauma and pain as a result ¹⁶, because new granulation tissue may grow into the foam. McNulty et al. ⁴¹ reported that dressing type has a significant effect on cell response after NPWT, and that wounds treated with gauze dressings showed significantly higher levels of cell death. However, studies such as that of Stansby et al. ³⁴ have reported minimal pain and trauma with foam‐based NPWT.

Teot et al.'s study showed that reduced trauma is associated with less pain ³². Patients with acute and chronic wounds were given Urgotul dressing, which was inserted between the foam and the wound to prevent the growth of tissue in the foam. Dressing adherence was minimal across the eight hospitals studied, only occurring in 12% of procedures. Pain was also reported to decrease considerably because of treatment.

However, although trauma and pain are linked, skin trauma, and also pain, may sometimes go undetected. Patients who experience neuropathy, for example, may or may not feel pain, and the absence of pain, or clinicians' lack of awareness that they actually are in pain, may mean that trauma is not attended to appropriately. Similar outcomes may occur for people with certain personality types. For example, it has been reported that ‘stoics’ report less pain than ‘catastrophisers’ ^{42, 43}. Patients who report little pain may be at greater risk of skin traumas exacerbating the wound or causing infection. Dressing types, creams and other treatment factors are important areas for investigation when exploring ways in which trauma can be reduced.

Currently, research into trauma, and treatment factors that affect trauma, is scarce. It is likely that trauma is often unreported because it has not been observed; in studies where the authors have observed skin damage, it is likely that this will be reported in the findings, and in studies where trauma has not been observed, it will not be reported on. This means that the current literature relating to trauma does not allow us to form firm conclusions. Furthermore, research studies have not focused on trauma specifically, and exploration of the factors that affect trauma is needed, with consideration of the different stages of treatment.

Conclusion

NPWT is considered to be an effective treatment in facilitating wound healing. However, as with other wound treatments, pain and skin trauma can be problematic, affecting patient's well‐being and also the healing process. As studies have shown varying levels of pain and trauma in patients undergoing NPWT, it is clear that pain and trauma can be minimised and this should be an area of priority for researchers and clinicians. Some of the factors that may affect this variation include the dressing and filler used and the NPWT system type. However, the research base is currently underdeveloped and further investigation of the impact of different treatment factors on pain and trauma needs to be carried out. Furthermore, researchers need to consider the pain and trauma experienced during the different stages of NPWT, in order to improve NPWT and its effect on the patient and on the healing of the wound.