Patient's pain feedback using negative pressure wound therapy with foam and gauze

Abstract

Wounds can be caused by different mechanisms and have a significant morbidity and mortality. Negative pressure wound therapy (NPWT) is one of the most successful treatment modalities for wound healing. We have been using both foam and gauze‐based NPWT. During application of NPWT, we noticed that the patient's pain was of varying intensity depending on the filler used. The aim of our work was to compare the level of pain and feedback before, during the treatment and at the dressing change after treatment with NPWT with two different fillers. For this study, we compared a pool of 13 gauze‐treated patients with a pool of 18 foam‐treated patients regarding the level of pain and feedback before, during the treatment and at the dressing change after treatment with NPWT. They were all post‐traumatic patients with loss of tissue up to the muscular band. The patients were asked to respond to a questionnaire interviewed by the same physician to assess the level of pain using VNS (verbal numerical scale). We observed similar difference of means before and during the treatment with NPWT with gauze and foam. Regarding the pain at the dressing change, the mean of the scores for the foam was 6·5 while for the gauze was 4·15. In this case, we noticed the most significant difference between means from the scores given: 2·35 which was a statistically significant difference between the two groups (P = 0·046). The finding of this study confirms less pain at the dressing change after treatment with gauze‐based NPWT. In our opinion, this finding is related to the more adhesive property of the foam probably because of the ingrowth of the granulation tissue in the micropores present on the foam. Considering this statement, we recommend the foam for neuropathic and paraplegic patients and the gauze for patients with bone and tendon exposition wounds, patients that do not tolerate NPWT with foam and low compliant patient particularly paediatric and old‐age patients. We remind that the performance of this study was not sponsored by any company.

INTRODUCTION

Wounds can be caused by different mechanisms and can evolve from acute to chronic with a significant morbidity and mortality. Nowadays there are many treatment modalities for wound healing. Negative pressure wound therapy (NPWT) is one of the most successful and recent data from the literature confirms this statement 1, 2, 3, 4.

NPWT uses a pump and an appropriate dressing system and applies a sub‐atmospheric pressure on the wound bed. It is useful to speed up the healing process by stimulating the formation of granulation tissue through the removal of fluids and contaminants, to increase the mechanical stimulation of cells and to promote tissue perfusion and wound contraction.

Initial studies about NPWT were published in the Russian medical literature in the 1980s 5, 6, 7, 8, 9, followed by Argenta and Morykwas published their clinical experience using the NPWT with the foam, in 1989 (10). Later in 2007, Smith and Nephew introduced the gauze as a medium to transfer the negative pressure.

In the Department of Plastic Reconstructive and Aesthetic Surgery at the University Hospital San Giovanni Battista of Turin, so far, two different fillers in order to transfer negative pressure on the wound are used: the foam (VAC KCI, San Antonio, TX) introduced by Argenta and Morykwas in 1997 and the gauze (V1STA/RENASYS™ SMITH&NEPHEW, London, UK) available since 2007. The optimal pressure range to obtain a good clinical result for the foam is between 80 and −125 mmHg (11) and for the gauze is between −40 and −80 mmHg (12).

During application of NPWT, we noticed that the patient's pain was of varying intensity depending on the filler used. Wounds are painful and the application of anything into a painful wound causes pain but more, removal unquestionably will exacerbate it (13). Some patients undergoing NPWT will experience considerable pain, whereas others will feel none (e.g. neuropathic or paraplegic patients) (14). The consequences of pain include activation of the stress response and the potential impeding of normal wound healing (15). It is important to consider wound‐related pain control holistically from local wound bed factors and dressing selection to patient‐centred concerns and the treatment of the wound cause (16).

We searched data in the literature regarding pain associated with the application of NPWT. Although our research, we realized that there were no data about the patient's feedback on the level of pain before, during and at the dressing change after treatment with NPWT with two different fillers. So, we decided, to get completed by the patients admitted to our department a questionnaire reporting the level of pain before, during and at the dressing change after treatment with NPWT with two different fillers in order to gain knowledge.

Seven to fifteen days after treatment with NPWT with gauze and foam, 31 Caucasian patients were asked to respond to this questionnaire, interviewed by the same physician.

The aim of this study was to compare the level of pain before, during and at the dressing change after treatment with NPWT with two different fillers.

MATERIALS AND METHODS

A comparative study was carried out to evaluate the level of pain and feedback before, during the treatment and at the dressing change after treatment with NPWT with two different fillers. The study was conducted in the Department of Plastic Reconstructive and Aesthetic Surgery at the University Hospital San Giovanni Battista of Turin during the period from May 2008 to September 2010.

The NPWT consists of applying a negative pressure to the wound in order to allow the drainage of liquids and microorganisms. In this way, we have oedema reduced, an improved circulation and consequently the increase of the granulation tissue formation. In addition, there is also a reduction of bacterial load. Actually, we can now use two different fillers to transfer the negative pressure to the wound bed: the polyurethane or polyvinyl alcohol foam (VAC KCI) and a polihexamethylene biguanide pre‐impregnated gauze (PHMB) with saline (V1STA/RENASYS™ SMITH&NEPHEW), placed on the bottom of the wound, fixed with an adhesive coating. In both methods, a transparent adhesive is used to fix dressing around the drain to complete the seal in accordance with the manufacturer's guidelines 11, 12. Dressing was changed once every 3 days. The optimal pressure range to obtain a good clinical result for the foam is between 80 and −125 mmHg (11) and for the gauze is between −40 and −80 mmHg (12).

The VAC. Therapy System promotes wound healing through the use of topical negative pressure therapy (NPWT). The system consists of a console ‘VAC Therapy Unit', a kit for dressing change ‘VAC Therapy Dressing’, containers and accessories such as the transparent adhesive. For the treatment with the VAC Therapy (VAC KCI) we always used a 400–600 mm pore diameter polyurethane foam (VAC® Dressing Pack) to transfer the negative pressure of 125 mmHg continuously. A transparent adhesive was used to secure the dressing around the drain. Dressing was changed once every 3 days.

The treatment with V1STA/RENASYS™ uses a PHMB with saline, placed on the bottom of the wound. This method needs a negative pressure of 80 mmHg transferred by a drain according to the Chariker–Jeter method. We always used this level of pressure continuously. This system consists of a console, a kit of dressing change, a container and accessories. A transparent adhesive is used to secure the dressing around the drain. The dressing was changed every 2–3 days.

After the Ethics Committee approval of our hospital and the signature of the informed consensus paper, 31 Caucasian patients were asked to respond to a questionnaire, interviewed by the same physician, reporting the level of pain before, during and at the dressing change after treatment with NPWT with two different fillers (Table 1). The physician was blinded to the type of filler used to apply the negative pressure. Only the corresponding author of this article was aware of the filler used. The division of the questionnaires was made by him dividing them according to the filler used.

Table 1.

Patient's baseline characteristics (n = 31)

Patients treated with NPWT with gauze	Patients treated with NPWT with foam
n = 13 (4 males and 9 females)	n = 18 (10 males and 8 females)
Mean age (years): 62·7 years	Mean age (years): 62·6 years
Average time of treatment: 20·7 days	Average time of treatment: 27·8 days
Wound type: Trauma (100%)	Wound type: (Trauma 100%)
Mean of wound areas (cm2): 184	Mean of wound areas (cm2): 161
Principle comorbidities (%):	Principle comorbidities (%):
– Hypertension: 38%	– Hypertension: 33%
– Peripheral vascular disease: 20	– Peripheral vascular disease: 16
Wounds location (%):	Wounds location:
– 10 lower extremities (77%)	– 17 lower extremities (94·4%)
– 1 abdominal region (7·7%)	– 1 abdominal region (5·6%)
– 1 scalp region (7·7%)
– 1 breast region (7·7%)

NPWT, negative pressure wound therapy.

For this study, we compared a pool of 13 gauze‐treated patients with a pool of 18 foam‐treated patients after passing the following inclusion/exclusion criteria. Inclusion criteria: acute post‐traumatic (car/motorcycle accident or surgical complication) wounds up to the muscular band, age range 18–80, wound size from 30 cm². Exclusion criteria: chronic wounds, diabetes and pregnancy.

We usually used NPWT with gauze in the treatment of irregular and round edges surface wounds compromised with subcutaneous fistulas and NPWT with foam for the treatment of flat wounds, deep wounds with a great loss of substance and hyperexudating wounds.

The questionnaire to assess the level of pain was prepared using VNS (verbal numerical scale). The VNS is a simple rating scale of pain. It is linear and easily understood by the patient who simply chooses a number between 0 and 10 to represent the level of pain (Figure 1). In the questionnaire the following details were noted: personal data, location of the lesion, duration of treatment, pre‐treatment pain, pain during treatment, pain at the dressing change (Figure 2).

Figure 1.

VNS scale.

Figure 2.

Questionnaire for the assessment of pain during treatment with NPWT with gauze or foam.

Seven to fifteen days after the treatment with NPWT with gauze and foam 31 patients were asked to respond to this questionnaire interviewed by the same physician (Table 1). Of these, 18 patients were treated with foam (10 males and 8 females, mean age: 62·6 years, average time of treatment: 27·8 days) and 13 with gauze (4 males and 9 females, mean age: 62·7 years, average time of treatment: 20·7 days). They were all post‐traumatic patients with loss of tissue up to the muscular band. In the 18 patients treated with foam, 17 wounds were located at the lower extremities and one at the abdominal region. In 13 patients treated with gauze 10 wounds were located at the lower extremities, one at the abdominal region, one at the scalp and one located at the right breast. The mean of the wound areas for the patients treated with the foam was 161 cm², median 57 and standard deviation 204, while for the gauze the mean was 184 cm², median 96 and standard deviation 208. From these 31 patients, 4 patients were treated with both the fillers according to the evolution of the wound and patient compliance. In three of them we had to change from gauze to foam and in one from foam to gauze (Table 2).

Table 2.

Patients treated with both the fillers (gauze and foam)

Patient	Sex	Age	Wound area (cm2)	Wound location	Filler change	Time of treatment days)	Difference in the scores for the pain before treatment with NPWT	Difference in the scores for the pain during treatment with NPWT	Difference in the scores for the pain at the dressing change
1	M	71	700	Lower extremity	From gauze to foam	Gauze: 4	Gauze: 3	Gauze: 3	Gauze: 5
						Foam: 15	Foam: 3	Foam: 4	Foam: 7
2	F	36	30	Lower extremity	From gauze to foam	Gauze: 50	Gauze: 2	Gauze: 2	Gauze: 4
						Foam: 45	Foam: 2	Foam: 4	Foam: 7
3	F	82	35	Abdominal region	From gauze to foam	Gauze: 36	Gauze: 1	Gauze: 1	Gauze: 1
						Foam: 65	Foam: 1	Foam: 2	Foam: 3
4	F	63	500	Lower extremity	From foam to gauze	Foam: 15	Foam: 8	Foam: 6	Foam: 10
						Gauze: 50	Gauze: 7	Gauze: 5	Gauze: 5

NPWT, negative pressure wound therapy.

For the statistical analysis, we evaluated the variables considered in the data forms and were performed descriptive analysis: mean, median, standard deviation, range, minimum and maximum value. It was also performed the t‐test to evaluate statistical significance.

RESULTS

After analysing the data of the completed questionnaires, we calculated the mean scores of pain before treatment, of pain during treatment and of pain at dressing change. The mean of the scores assigned to the foam for the pain before treatment was 5·89, range 8, median 6·5, min 1, max 9, standard deviation 2·76, while for the gauze the mean of the scores was 4·62, range 9, median 5, min 1, max 10, standard deviation 2·87. In this case, we observed similar means with a difference of means 1·27 (Figure 3). Regarding the pain during the treatment, the mean of scores for the foam was 4·3, range 8, median 4, min 1, max 9, standard deviation 2·56, while for the gauze the mean of scores was 3·3, range 7, median 3, min 1, max 8, standard deviation 2·21. In this case too, we observed a similar trend of the means and the differences between the means was 1 (Figure 4). Regarding the pain at the dressing change, the mean of the scores for the foam was 6·5 range 9, median 7·5, min 1, max 10, standard deviation 3·36, while for the gauze the mean was 4·15, range 7, median 5, min 1, max 8, standard deviation 2·64 (Figure 5). We noticed the most significant difference between means from the scores given at dressing change: 2·35, so we decided to perform the Student's t‐test with the following result: t = 2·089 with 29 degrees of freedom (P = 0·046). The difference between the average values of the two groups is greater than would be expected by chance, there is a statistically significant difference between groups (P = 0·046) (Figure 6).

Figure 3.

The mean of the scores assigned for the pain before treatment with gauze and foam.

Figure 4.

The mean of the scores assigned for the pain during treatment with gauze and foam.

Figure 5.

The mean of the scores assigned for the pain at dressing change during treatment with gauze and foam.

Figure 6.

Normal probability plot: cumulative frequency‐residual value representing the pain at the dressing change. (mean scores given for the foam vs mean scores given for the gauze.)

DISCUSSION

The aim of our work was to compare the level of pain and feedback before, during the treatment and at the dressing change after treatment with NPWT with two different fillers. We carried out a judgmental sampling and tried to select two pools of patients with similar characteristics (Table 1).

NPWT is successfully used in managing and accelerating wound healing. This is also supported by the medical literature 1, 2, 3, 4. Initial studies about NPWT were published in the Russian medical literature in the 1980s 5, 6, 7, 8, 9. Meanwhile, in 1989 Argenta and Morykwas published their clinical experience using the NPWT with the foam (10). Later in 2007, Smith and Nephew introduced the gauze as a medium to transfer the negative pressure.

In our department, two types of fillers are used as a medium to transfer the negative pressure to the wound bed, the gauze and the foam. During application of NPWT, we noticed that the patient's pain was of varying intensity depending on the filler used. Literature lacks of data about the level of pain and feedback of the patient before, during and at the dressing change after treatment with NPWT with two different fillers. In order to acquire knowledge, we decided to take a survey by interviewing the patients admitted to our department and treated with NPWT with gauze and foam.

Wounds are painful and therefore patients will avoid or will not permit treatments that result in pain. In NPWT, this can manifest itself as manipulation of the pump parameters patients disruption of the dressing and other non compliant acts. The application of anything into a painful wound causes pain but more, removal unquestionably will exacerbate it (13).

Pain is a very personal experience; some patients undergoing NPWT will experience considerable pain, whereas others will feel none (e.g. neuropathic or paraplegic patients) (14). That is why we selected only post‐traumatic (car/motorcycle accident or surgical complication) wounds up to the muscular band and excluded chronic and diabetic wounds, in order to obtain, as possible, objective data without bias. The disadvantage of this choice was that the number of patients after passing inclusion/exclusion criteria was not so high.

After analysing the data from the filled in questionnaires, the most important thing we noticed regarding the feedback of the patient was that at the dressing change the gauze showed to be less painful. These data were statistically significant (P = 0·046). In the four patients where we used both filler, the first patient was suffering from combined tibia and fibula fracture with exposed plate. In this case, we needed a more rapid growth of the granulation tissue, so we changed from gauze to foam. The second patient had a very extensive lesion area, 700 cm². It was not possible to apply the negative pressure with gauze to such extensive area, so we had to change to foam. The third patient presented an exposed abdominal mesh. In this case too, we needed a more rapid growth of granulation tissue, so we changed from gauze to foam. In the fourth patient, the characteristics of the wound had changed after the treatment with the foam: persisted an undermined area, so we changed from foam to gauze. The data obtained from these four patients treated with both fillers confirmed the previous data, less pain at gauze dressing change. In this case, we think that these data are more objective because they are derived from the same patient treated with both filler (Table 2).

In our opinion, according to this finding, less pain at gauze dressing change is related to the more adhesive property of the foam probably as a result of the ingrowth of the granulation tissue in the micropores present on the foam. The foam due to micropores present on it permits the ingrowth of the granulation tissue in the micropores, while the gauze due to its dense lines and the spiral pattern does not permit this ingrowth of the granulation tissue. This statement was also supported by the experimental studies obtained from the literature which state that there are anatomical differences between the two fillers (17). Borquist et al. (17) showed that wound bed tissue grows into foam but not into gauze and that a greater force ratio is needed to remove foam than to remove gauze from the wound. This is in agreement with clinical observations that foam forms a strong mechanical bond with the wound bed tissue, and upon removal, the wound bed may be disrupted, pieces of the foam may remain in the wound, and that patients regularly experience pain (18). Gauze offers less thick granulation tissue without ingrowth into the wound filler, which may make dressing changes less painful compared with the foam with less scarring and thereby less contraction upon healing. More force is needed to remove foam than gauze and there is greater ingrowth into foam. This may explain the clinical observations that the wound bed is disrupted and the patient experiences pain during dressing changes after treatment with foam (17).

Campbell et al. (4) have described ingrowth of granulation tissue into foam. This study shows that the wound bed tissue extended approximately 400 µm into the foam after 3 days of therapy. Morykwas et al. (19) found that granulation tissue grew approximately 1000 µm into foam after 4 days of continuous NPWT at −125 mmHg. This study found no such ingrowth into gauze, which corresponds with clinical observations that gauze is easier to remove and does not disrupt the wound bed or cause patient pain during dressing changes.

In 152 patients, a multicentre trail was carried out by Hurd et al. (14) to evaluate pain associated with gauze dressing changes as part of NPWT reported minimal pain during therapy and dressing changes. It was reported that pain was absent in 80% of dressing changes. A principle reason for this may be that no damage to the granulating surface was observed in the majority of dressing changes.

The findings of this study suggest that the patients treated with NPWT with gauze have less pain at dressing change compared with the patients treated with NPWT with foam.

In conclusion, after considering these statements and the results from this study, we recommend the foam for neuropathic and paraplegic patients and the gauze for patients with bone and tendon exposition wounds, patients who do not tolerate NPWT with foam and low compliant patient particularly paediatric and old‐age patients.

ACKNOWLEDGEMENT

None of the authors disclose any financial and personal relationships with other people or organisations that could influence this work.