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The Symptom of Pain with Pressure Ulcers: A Review of the Literature
Pressure ulcers are areas of localized tissue damage caused by decreased oxygenation and nutrient delivery as a result of prolonged pressure over a bony prominence.1 Pressure ulcers are a relatively common problem across the spectrum of care – prevalence estimates range from 5.1% to 32%.2-4 These wounds tend to be chronic, increasing the time a patient spends in the healthcare system and costing thousands of dollars per ulcer.5 An important aspect of pressure ulcers, both for the individual and for the healthcare system concerned about quality management, is the pain and discomfort related to these wounds. Pain is a personal, subjective multidimensional phenomenon described as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”6 Although there is neither a universally accepted definition nor means of classification,7 pain is commonly considered acute or chronic. Acute pain is “pain associated with tissue damage, inflammation, or a disease process that is of relatively brief duration, regardless of its intensity.”7 Chronic pain may be defined as pain that lasts beyond the usual course of the acute disease or expected time of healing and may continue indefinitely.8 In a recent clinical update published by the International Association for the Study of Pain (IASP) based on a review by Ospina and Harstall,8 prevalence estimates of chronic pain (wound and otherwise) in four out of five studies that used the IASP definition of chronic pain ranged from 11.5% to 55.2% of the general population with a weighted mean prevalence of 35.5%.
According to Krasner,9 wound pain can be non-cyclic acute, cyclic acute, and chronic, distinguished according to the duration, intensity, and characteristics of the pain. Non-cyclic acute pain includes events that do not reoccur on a regular basis such as sharp debridement or drain removal. Cyclic acute pain involves regular pain that is short in duration and induced by activities such as dressing changes or repositioning. Chronic wound pain involves a persistent pain with or without manipulation of the wound area.9
Pain was one of seven themes identified by Langemo et al10 in their study of the lived experience with pressure ulcers. The eight participants described pain in terms of its intensity and duration; analgesic use was of concern. Because over-the-counter drugs such as acetaminophen were considered poor pain controllers, many patients took narcotics and there was worry about addiction.10 In a descriptive, qualitative study11 of five persons with pressure ulcers, participants identified three major areas of concern: physical issues, psychological issues, and social issues. Pain was a prominent physical factor (including the effects of pain on sleep and quality of life), along with exudate levels and loss of independence.
Despite concern regarding pressure ulcer prevalence and information on chronic pain in the general population, research is scarce on pain in patients with pressure ulcers. In a recent review of the pressure ulcer literature, de Laat et al12 described the effects of pain, malodor, and exudate from pressure ulcers on diagnostics and treatment. The authors cite six articles that addressed methods of pain assessment and recommendations for pain management. The Wong-Baker Facial Recognition Scale (FRS), the McGill Pain Questionnaire-Short Form (MPQ-SF), and the Visual Analogue Scale (VAS) were found to be useful in pain assessment. The de Laat review did not report prevalence or incidence rates and concluded research on pressure ulcer-related complaints is lacking.12
The symptom of pain with pressure ulcers is an emerging clinical and research issue. To more fully understand the extent of this problem and to plan a clinically sensible approach to assessment and management, a review of the literature was conducted to build on the 2003 IASP report on the occurrence of chronic pain8 and the de Laat publication.12 Specifically, the purpose of the review is to:
1. Describe how pressure ulcer pain has been measured and characterized
2. Synthesize research reports on the prevalence and incidence of pain
3. Catalogue reported factors associated with pressure ulcer pain. 
Methods
A three-step strategy was used to explore bibliographic databases that included MEDLINE, HealthSTAR, CINAHL, and seven others (see Table 1). The results of an initial search using the term decubitus ulcers were combined with keyword searches using the terms pressure ulcer, pressure sore, and bed sore. This search enabled identification of other keywords contained in the titles, abstracts, and/or index terms used to describe relevant articles. Next, all subject headings were exploded and all keywords truncated. Results for pain were combined with results for pressure ulcers and limited to English-language articles that dealt with human subjects. If an abstract met inclusion criteria (see Table 1) or no electronic abstract was available, the full article was retrieved. Articles were re-examined by a second reviewer to ensure they met inclusion criteria. Finally, the reference lists and bibliographies of retrieved papers were hand-searched to discover potentially relevant articles not identified in the electronic search. Identified titles were exported to Reference Manager Version 10 and duplicate citations eliminated. Also, because the intent of this study was to identify and appraise research focused on populations with pressure ulcers where pain was included as either a primary or secondary outcome, qualitative studies describing personal experience of pain were not included. The search methodology is further detailed in Table 1. 
Critical appraisal.
To begin the appraisal process, studies were summarized using a standard structured abstract form (see Table 2). The form was designed to capture general study information to facilitate appraisal of the sample and setting, data retrieval methods, study objectives, outcomes, and findings related to pain and pressure ulcers. Specific aspects relevant for this review, such as the setting of care, documented incidence and prevalence of pain, how pain was measured, and reports of associated factors, also were included. A synopsis was developed from the structured abstracts and presented in tabular form relevant to the study aims. Levels of evidence were not assessed because the range and type of studies would not allow for meaningful comparisons. Rather, the intent was to describe pain assessment methods and scales used.
General Result
The initial search identified 417 unique articles (see Figure 1). Of these, the 147 that met initial inclusion criteria were retrieved and abstracted. Next, a hard-copy reference check of the 147 articles was completed and six additional papers not identified in the electronic search were included for a total of 153 articles. In abstracting information from the full papers, a large proportion (104 out of 153) were excluded because they did not meet criterion (study must be experimental, quasi-experimental, or descriptive-observational). Other exclusions are outlined in Figure 1. The final set comprised 26 research studies. Of these, six (23%) were specifically focused on pressure ulcer pain prevalence; the remainder addressed other primary study purposes – eg, evaluating an intervention where pain was an outcome. 
Pressure Ulcer Pain Assessment
The final set of 26 studies13-38 featured a range of pain assessment approaches and pain assessment scales.39-44 Some studies employed more than one tool to measure pressure ulcer pain (see Table 3). More than half (17 out of 26 studies, 65%) used at least one recognized and tested pain measure. Eleven studies included one non-validated or unspecified tool to assess pressure ulcer pain. Two studies used a combination of validated and a non-validated pain measures.
Most commonly used (six studies each) were the VAS and versions of the Verbal Rating Scale (VRS). The Numeric Rating Scale (NRS) was used in four studies, the comprehensive MPQ-SF in two, and the FRS and Present Pain Intensity Scale (PPI) were used in one study each.
The affect of cognitive ability. The issue of pain assessment and mental competence was identified in two studies. In their prospective study, Dallam et al13 found that 48% of 44 responsive participants had some form of cognitive impairment based on the Mini Mental State Exam but the same pain assessment tools (VAS and FRS) were used with both the cognitively impaired and the cognitively intact portions of the study population. In a prospective, cross-sectional study, Manfredi et al14 assessed facial responses of cognitively intact and impaired participants during dressing changes. Cognitively intact participants (n = 31) were interviewed during a pressure ulcer dressing change that involved an area that extended beyond the subcutaneous line, covered an area of at least 9 cm2, and featured a moist surface. The participants were asked to identify a set of ulcer characteristics related to pain during dressing change. The facial characteristics of a group of cognitively impaired participants (n = 9) with the same ulcer characteristics were videotaped before and during a dressing change. The videotapes were viewed in random order by eight medical students and 10 nurses. The author concluded that “assuming dressing changes of ulcers reported as painful by communicative patients are also painful in non-verbal, severely demented patients, clinician observations of facial expressions and vocalizations are an accurate means of assessing the presence of pain, but not its intensity.” The issue remains as to whether non-impaired and impaired patients feel the pressure ulcer pain in the same manner and whether self-report measures are adequate or appropriate.
Assessment timing. The timing of pressure ulcer pain assessment varied across the 26 studies. The only consistent timing of the assessments involved measurement of pain related to dressing change, which occurred during or after dressing removal. Assessment times included before or after ulcer manipulation (such as dressing change, debridement, or application of a gel), randomly, and after a predetermined period of time (to establish if a product had achieved pain reduction).
Prevalence/incidence of pressure ulcer pain. Of the 26 studies under review, six (20 to 186 participants each; three studies having > 100 participants) included pressure ulcer pain prevalence estimates. No studies were found that reported the incidence of pressure ulcer pain. In the larger studies (> 100 participants), pressure ulcer pain prevalence estimates ranged between 37% and 66%.15 The smallest study (n = 20) reported a pressure ulcer pain prevalence of 100%.16 Study settings crossed the continuum of care and included tertiary hospitals, community, and palliative care settings (see Table 4). In the six studies that addressed pain prevalence, pain was assessed to document its presence and severity and, in some cases, its quality. Three studies used validated and reliable tools, two studies used tools developed by the authors, and one study used a combination of tools (see Table 4). When comparing the reported pain prevalence estimates, studies using validated tools, on average, reported higher pressure ulcer pain prevalence estimates than those using non-validated tools. The highest estimates were in two studies where the comprehensive MPQ-SF was used to assess pain. 
Pressure ulcer stage. Pressure ulcer stage was tracked in four of the six studies; classification tools included the National Pressure Ulcer Advisory Panel staging classification45; Surry 4 stage classification system46; and the Waterlow Classification of ulcers.47 In two studies, the staging classification was not identified (see Table 4).
Time of pain occurrence. Three of the six studies assessed pain at one time point (not necessarily the same point). The remaining three studies documented varying levels of pressure ulcer pain based on different timing such as dressing changes. In a cross-sectional study (n = 186), Eriksson et al19 found 12% of patients had constant pain while 54% had occasional or treatment-related pain. Szor and Bourguignon17 also found an increase in the reported level of pain with dressing change (from 84% to 88%); however, these values represent an increase of only one person reporting pain with dressing change. In a small cross-sectional study of 20 patients, Quirino et al16 reported no typical time for increased pain but noted that of the 100% of patients who reported pain, 20% had pain less than 1 hour per day and 55% experienced pain at rest.
Pain quality. Pain quality, in addition to intensity, was noted in three studies. In a cross-sectional study (n = 151), Hatcliff and Dawe18 reported approximately 30% of the pressure ulcer population had mild pain, approximately 12% had moderate pain, and approximately 7% had severe pain. In the Quirino et al study,16 all participants reported pressure ulcer pain with a mean pain intensity of 5.8 (based on the NRS). Further, using the MPQ-SF, the authors found that patients characterized pain most often as burning.16 Szor and Bourguignon17 reported that of the 28 participants who reported pressure ulcer pain, 75% rated their pain as mild, discomforting, or distressing and 18% rated their pain as horrible or excruciating.
Factors associated with pressure ulcer pain. In further analyzing the subset of six pressure ulcer pain studies, a number of factors were found to be associated with pain related to pressure ulcers (see Table 5). Stage or severity of ulcer was the most common; four of the six studies reported increased levels of pressure ulcer pain with the more severe stages of pressure ulcers.13,15,17,19 Szor and Bourguignon17 also found that participants with higher stage pressure ulcers used more word descriptors to describe their pain and that Pain Intensity Ratings were higher as ulcer staging increased.
Although pain levels were linked to dressing change, the results were equivocal, with one study reporting a slight increase in the proportion of patients reporting pain with dressing change17 and another reporting no increase.16 The relationship between age and pain intensity varied. Dallam et al13 found that maximum pain score was inversely related to age. Although Lindholm et al’s15 cross-sectional study (n = 694; 117 pressure ulcers) found persons between 80 and 89 years of age had the highest pressure ulcer pain levels, results were skewed because 86.7% of this age group were given analgesia.
Support surface use. Type of bed has been found to be associated with improvement in reported pain level. One study13 reported that patients on low-air-loss beds reported less pressure ulcer pain than persons managed with other devices. It is an interesting hypothesis but the study was not designed to make a head-to-head comparison of surfaces. Thus, conclusions about pain outcomes and surface or bed types cannot be drawn without further research.
Discussion
Evidence that pain is an important issue for persons with pressure ulcers is emerging. Of the 26 studies analyzed – where pain was reported as a primary or secondary measure – six documented pressure ulcer pain prevalence estimates, in many cases of > 50%. Although the number of studies is limited, these reports of pain severity and quality indicate that both may be under-assessed and under-managed. It is noteworthy that four studies had sizeable populations (132 to 694 participants). Pain intensity ranged from mild to excruciating16-18 and from intermittent to constant.16,19 Pressure ulcer pain was described most frequently as a sensitive, burning sensation16; the higher the pressure ulcer stage, the more descriptors used.17
Although wound pain has been assessed using numerous valid and reliable tools, 42% of the 26 studies used non-validated or unidentified measures. Commonly used measures were the VAS, NRS, VRS, and MPQ-SF. In the six studies focusing on pain with pressure ulcers, four used a generic pain assessment measure because no specific pain assessment tool has been tested for validity and reliability with this population. Two of the tools used were developed by the associated study authors. It also appears more recent studies tend to assess pain outcomes using recognized measures, increasing the confidence in the reported pain estimates.
Appropriate measures are important to allow providers to assess pressure ulcer pain and intervene with suitable pain reduction strategies. As has been concluded in studies that focus on other chronic wounds, the pain experience of persons with pressure ulcers needs to include assessment of pain intensity and quality as well as impact on daily living.48 The importance of proactive clinical assessment and management of wound pain is increasingly recognized as a quality-of-care issue – pain management clearly needs to be a minimum expectation with clinical care.
The literature provides some direction in pain assessment tool choice. Freeman et al,49 conducting a secondary analysis of a previous study,13 report that the VAS and FRS used with hospitalized elderly patients with pressure ulcers were interchangeable and it may be feasible for patients to select the type of scale they are most comfortable completing. Additionally, Roth et al50 found the MPQ-SF to be more sensitive to pressure ulcer pain than the NRS. Specifically, the MPQ-SF may be the optimal choice because it more effectively discriminated between pain experienced with Stage III and Stage IV pressure ulcers and the pain with “other” wounds. The authors found associations between severe pain and higher emotional distress. The two-step method advocated by Nemeth et al51 – ie, a quick and simple assessment for the presence of pain, followed by a more comprehensive assessment if pain is found –may be clinically sensible for the pressure ulcer population as well.
Limitations
This review was limited by several factors. Prevalence estimates of pain are based on a relatively small number of studies largely limited to hospital populations. Methodological limitations of the studies include the lack of reliable and valid measures of pain, as well as a range of poor reporting of the timing of pain assessments. This makes it difficult to synthesize findings and draw conclusions. Studies where the primary purpose was not observing pain occurrence were included; therefore, the prevalence may be underestimated. Lastly, the review was confined to adult populations and papers published in English; this may limit generalization of the findings.
Future Research and Best Practices
A number of concerns related to the assessment and management of pain require immediate research attention. First and foremost, the accurate tracking of pain as an outcome using reliable and valid measures must become both a clinical and research priority. Use of already available, generic pain measures is pragmatic but research is needed to evaluate the reliability and validity of these instruments with this wound population. Unique aspects regarding the quality of pressure ulcer pain may not be captured in the current tools. In addition, given the characteristics of persons with pressure ulcers, the measurement of pain requires further study, particularly in people with cognitive impairment. Many with pressure ulcers are unable to respond and require different pain assessment techniques.
Factors associated with pressure ulcer pain are equivocal in the research to date. Ulcer stage was consistently associated with pain in the studies cited; four of the six prevalence studies reported a positive correlation between pressure ulcer pain and ulcer stage. This challenges the often-held clinical opinion that deeper stage (Stage IV) pressure ulcers are less painful due to the increased nerve injury present with advanced pressure ulcer stages, similar to advanced burns.
Current pressure ulcer practice guidelines (eg, the Registered Nurses Association of Ontario [RNAO] document52) recommend pain assessment and management, enhanced specification about pain assessment strategies, and valid and reliable measures. Adopting a simple, valid, reliable pain assessment tool such as the VAS39 or NRS41 at an organizational or setting level may be most appropriate. With individual patients, this could be followed by a more comprehensive measure such as the MPQ-SF42 if pain is present. In this way, clinicians can enhance their understanding of pain and respond to this symptom with appropriate pharmacological and non-pharmacological approaches from the armamentarium of interventions available.
In practice, the prevalence and incidence of pain with pressure ulcers could be rigorously tracked concurrent with other types of studies (eg, interventional studies such as investigating use of special beds/surfaces as well as cohort and longitudinal cohort studies). Outcome measurement of pain will need to include comprehensive pain measures such as MPQ-SF, the VAS, or other reliable and valid pain inventories. Pain as a symptom should be carefully documented and followed; to that end, a clinically sensible, yet rigorous approach to pain assessment will serve both research quality and care purposes. Understanding the relationship of pain to ulcer stage and other factors, as well as the role of pain in pressure ulcer management, would provide valuable information for the ongoing care of persons with these wounds.
Conclusion
This review has shown that pain is an issue in persons with pressure ulcers. However, at this time it is not a primary management focus. More research is required to appreciate and measure this symptom with this population beyond hospitals and across the continuum of care. Measuring and managing pain will become even more important for effective care with an aging population at risk for pressure ulcer development.
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