Abstract
Objectives:
To measure buttock pressure during toilet seating in persons with spinal cord injury (SCI).
Design:
A case series study.
Setting:
Kibikogen Rehabilitation Center for Employment Injuries.
Methods:
The study included 41 persons with SCI. Buttock pressure was measured during toilet seating, with or without a toilet seat cushion (foam cushion, gel cushion, air cushion) on the toilet seat.
Results:
The subjects were classified into three groups according to the site of the maximum pressure [greater trochanter (GT) region, ischial tuberosities (IT), and sacral region (SR)] recorded on the pressure map of the non-cushioned toilet seat, into the GT, IT and SR groups, respectively. All three types of cushions altered the buttock pressure distribution during no-cushion toilet seating. In the GT group, all three cushions significantly reduced the peak pressure in the GT area, compared to the control (no-cushion). The foam cushion significantly increased the peak pressure in the IT area (Pisch) in the GT group, relative to the control. However, the foam cushion significantly increased while the gel cushion significantly reduced Pisch, relative to the control. In SR group, the air cushion significantly reduced the peak pressure in the SR, relative to the control.
Conclusion:
We recommend the use of the gel cushion for the IT group and the air cushion in GT and SR group to reduce buttock pressure during toilet seating in persons with SCI.
Keywords: Toileting, Rehabilitation, Pressure ulcer
Introduction
Despite the technological advances in prevention measures, pressure ulcers are currently the most common complication in individuals with spinal cord injury (SCI).1 Serious skin breakdown in these subjects occurs most frequently over the ischial tuberosities (IT).2 Development of serious tissue breakdown at this point is caused by prolonged sitting. Patients with SCI using the wheelchair are advised to use cushions and to undertake pressure relief movements.
Persons with SCI spend a relatively long time in the toilet due to bladder and bowel dysfunction. Coggrave et al.3 investigated the management of neurogenic bowel dysfunction in outpatients with SCI of any level or density, aged 18 years or more, over a period of at least 1 year.3 They reported that bowel management required more than 30 min in 36% of their subjects3 and concluded that the defecation process in these individuals entails prolonged toilet seating. In this regard, individuals with complete SCI need more time for defecation3 and are at higher risk for the development of pressure ulcer than those with incomplete lesions. In our daily clinical practice, we encounter persons with SCI who sit directly on the toilet seat without any pressure relief cushion. To our knowledge, there is little or no information on buttock pressure during toilet seating and its impact on pressure ulcers. This issue is clinically important since it is clinically known that the majority of patients with SCI do not perform pressure relief movements during toilet seating to prevent potential the development of pressure ulcers.
Good prevention depends on identifying individuals at risk for developing pressure ulcer. While the etiology of pressure ulcer is multifactorial, including direct pressure, friction, shearing, incontinence, nutrition and immobility,4 contact pressure on the body parts plays a key role in the development of these ulcers.2
Several studies have examined buttock pressure in wheel-chaired persons with SCI.2,5,6 However, to our knowledge, no study has investigated buttock pressure during toilet seating in patients with SCI. Various types of cushions for wheelchairs are commercially available. These are designed to provide protection against skin breakdown. Furthermore, various methods of pressure relief are practiced, including push-ups while seated in a wheelchair.2 In contrast, there is only little information on the strategies that can prevent pressure ulcers during bowel program. By measuring buttock pressure and its distribution during toilet seating in patients with SCI, the present study was designed to determine the benefits of various types of toilet seat cushions (air cushion, floatation pad or gel cushion, and urethane cushion or foam cushion) on buttock pressure in patients with SCI.
This is the first study in a series to be conducted in the future aimed at determining the impact of prolonged toilet seating on pressure ulcer formation in individuals with SCI and measures to prevent such complication.
Materials and methods
Subjects
The study included 41 persons with SCI who completed the rehabilitation program at our hospital and were in a clinically stable state. Only subjects with the following criteria were included: (1) capable of independent use of the toilet for defecation, (2) classified with ASIA Impairment Scale A7. Patients with ASIA Impairment Scale B, C and D injury were excluded to rule out possible influence of leg muscles strength and sensory feedback on buttock pressure and distribution, (3) free from pressure ulceration, heterotopic ossification and limitation of range of motion of the hip, knee and ankle joints, which could influence buttock pressure. The subject’s characteristics are presented in Table 1. Among the subjects, 38 had traumatic SCI while the remaining three had congenital SCI (spina bifida). The mean age was 39.8 ± 15.2 years (±SD, range, 14–73). The experimental protocol was approved by the Research Ethics Committee of our institution and all subjects signed the informed consent form presented before the study.
Table 1.
Clinical features of the 41 study participants.
| Cause of SCI | |
|---|---|
| Traumatic | 38 |
| Congenital (Spina bifida) | 3 |
| Age at examination (years) | 39.8 ± 15.2 |
| Sex | |
| Males | 29 |
| Females | 12 |
| Height (cm) | 165 ± 8.4 |
| Weight (kg) | 57 ± 11.2 |
| Level of SCI | C8-L1 |
| ASIA Impairment scale | A |
Data are Mean ± SD or number of subjects.
Measurement of buttock pressure
Buttock pressure was recorded by the Tekscan pressure measurement system (Big-Mat 2000, a flexible sensor mat with a 2064-cell (43 × 48) matrix (Nitta Co., Japan). Each cell can measure force per one square centimeter. The sensor seat was connected to a personal computer. We measured buttock pressure in all 41 individuals with SCI while seated in own wheelchair using the ROHO High Profile type (Permobill Co., Ltd., Japan) air cushion. Buttock pressure was also measured during toilet seating under four conditions, using: (1) no cushion, (2) commercially available toilet foam cushion (Fig. 1, left), (3) toilet gel cushion (Fig. 1, center), and (4) toilet air cushion (Fig. 1, right). The ROHO wheelchair cushion is constructed of rubber cells and commonly used by patients with SCI at the rehabilitation center in Japan based on the high-pressure distribution efficiency.
Figure 1.
Toilets with adjustable seat heights and three types of commercially available pressure-distributing toilet cushions used in the present study.
The toilet seat used in this study was the “U” shape type made of resin material. The outer diameter of the toilet seat was 38 × 43 cm and the inner diameter was 20 × 30 cm. The toilet foam cushion was the hard urethane foam “Yawaraka Benza” type (TOTO Co. Inc., Japan), with an outside diameter of 36 × 40 cm and inside diameter of 17 × 28 cm. The gel cushion was the “Action pad” (ACTION JAPAN INC., Japan). It consisted of the left and right parts, which were placed separately on the seat. The toilet air cushion was from ROHO Co. (ROHO type) containing 36 rubber cells. The outer 18 cells were taller while the inner 18 cells were lower. The amount of air in the ROHO wheelchair cushion and ROHO toilet cushion was adjusted to atmospheric pressure as follows. The cushions were prepared on a hard examination table by over-inflating all cells, and then the valve was opened for a few minutes until equalization of the internal cushion pressure with the external air pressure. The valve was then closed. At this point, optimal reduction in interface pressure at the ITs was obtained.5
The toilet used in this study was of the sitting type with adjustable height “ADL EXERCISE DEVICE” (SAKAI Medical. Co., Japan) (Fig. 1). In this study, toilet seating was defined as follows; (1) complete contact between the plantar aspect of the feet with the floor, (2) knee and ankle joints angles at 90 degrees, (3) sitting without support in a comfortable position, (4) straddling of three fists width, (5) hands on the lap while the subject was seated. This toilet is often used for toilet training at our hospital.
Following the calibration procedure, buttock pressure measurement commenced one minute later after seating to reduce the effect of creep characteristics (deformation). The duration of recording was set up to be more than three minutes and calibration was performed before each measurement to reduce measurement errors. All signals were digitized and the measured data were subsequently analyzed offline. We calculated the maximum pressure recorded on the entire pressure map (Pmax) and peak maximum pressure in the IT area (Pisch), greater trochanter (Ptroch) and sacral region (Psac), using a custom-designed software developed in our laboratories6. The mean values of the right and left sides were recorded separately for the IT and greater trochanters. We also measured the distance between the points at which the highest buttock pressures were recorded over bilateral ITs while seated (distance between the left and right ITs).
Statistical analysis
All data were expressed as Mean ± SD. The paired Student’s t-test was used for comparison of the maximum buttock pressure recorded on the toilet seat without cushion and that of the wheelchair. Analysis of variance (ANOVA) was used for comparison of the four conditions (toilet seat cushion type). When ANOVA showed significant differences (P < 0.05), Scheffé’s test was used to determine the differences between two sitting conditions. A P value <0.05 denoted the presence of a significant difference within and between the two groups. All statistical analyses were performed using SPSS (version 12.0, SPSS Inc., Chicago, IL).
Results
In all 41 subjects, Pmax was significantly higher on the toilet seat without cushion (344 ± 127 mmHg) than on wheelchair with air cushion (249 ± 93 mmHg) (P < 0.001). We divided our subjects into three groups according to the site of the maximum pressure recorded on the entire pressure map while toilet seated without cushion, including the greater trochanter group (GT group: n = 23, 20 males, 3 females), IT group (n = 8, 3 males, 5 females), and sacral region (SR) group (n = 10, 6 males, 4 females). There were no significant differences in Pmax while toilet seated without cushion among the three groups, though there was a trend for a higher pressure in the GT group.
The buttock pressure distribution varied according to the toilet cushion type. In the GT group, Ptroch values with the foam, gel and air cushions were significantly lower than that without cushion (P < 0.001, Fig. 2(a)). On the other hand, Psac values with the three cushions were not different compared with that without cushion. Interestingly, Pisch value was significantly higher with the foam cushion than without cushion (P < 0.001), gel cushion (P < 0.001) and air cushion (P < 0.001) (Fig. 2(a)). These results suggest a shift in the buttock support area from the great trochanter to the IT with the foam toilet seat cushion in the seated subjects.
Figure 2.
Buttock pressure in the three groups with and without the cushions. Data are Mean ± SD. (a) Greater trochanter (GT) group: *P < 0.001, compared to Pisch without cushion, †P < 0.001, compared to Pisch with gel cushion, ‡P < 0.001, compared to Pisch with air cushion, §P < 0.001, compared to Ptroch without cushion, ||P < 0.05, compared to Ptroch with foam cushion, ¶P < 0.001, compared to Ptroch without cushion, **P < 0.001, compared to Ptroch without cushion. (b) IT group: *P < 0.05, compared to Pisch without cushion, (c) Sacral region (SR) group: *P < 0.01, compared to Pisch without cushion, †P < 0.01, compared to Pisch with gel cushion, ‡P < 0.01, compared to Pisch with air cushion, §P < 0.001, compared to Psac without cushion. Pisch; peak maximum pressure in the IT area, Ptroch; peak maximum pressure in the greater trochanter area, Psac; peak maximum pressure in sacral region.
Further analysis of data of the IT group showed that Pisch with gel cushion was significantly lower than that without cushion (P < 0.05) (Fig. 2(b)). In contrast, the Ptroch and the Psac groups showed no significant differences between without cushion and each of the three cushion types.
For the SR group, Psac was significantly lower during toilet seating with the air cushion, compared to without cushion (P < 0.001, Fig. 2(c)). There were no significant differences between Ptroch without cushion and each of the three cushion types. Interestingly, Pisch was significantly higher with the foam cushion than without cushion (P < 0.01), gel cushion (P < 0.01) and air cushion (P < 0.01), similar to the GT group.
Figure 3 shows the distance between the left and right ITs in the IT, GT and SR groups. The distance was significantly shorter in the GT group than the IT group (P < 0.05) and SR group (P < 0.05). Finally, there were no significant difference in body mass index (BMI) among the three groups.
Figure 3.
The inter-ITs distance in the three study groups. Data are Mean ± SD.*P < 0.05
Discussion
Our study is the first to measure the level of buttock pressure and its distribution in toilet seated persons with SCI. The following are the main findings of our study.
For the whole group of 41 subjects, toilet seating without cushion was associated with significantly higher Pmax (344 ± 127 mmHg), compared with wheelchair seating with air cushion (249 ± 93 mmHg).
While seated on the toilet without a cushion, the site of maximum pressure on the entire pressure map showed three different buttock pressure distribution patterns, including the GT, IT and SR.
In the GT group, the use of any of the three types of cushions significantly reduced Ptroch level during toilet seating. On the other hand, the use of the foam cushion significantly increased Pisch compared to no cushion.
In the IT group, the use of the gel cushion significantly reduced Pisch compared with the control (no cushion).
In the SR group, the use of the air cushion was associated with a significant reduction in Psac compared with no cushion.
Analysis of data of all 41 subjects showed a significantly higher Pmax during toilet seating without a cushion, compared with that during sitting on the wheelchair with air cushion, amounting to about 1.4 times that of the wheelchair. These findings suggest that toilet seating increases the risk of pressure ulcer in SCI patients with motor and sensory disturbances, compared with wheelchair seating.
Previous studies found that the highest seating interface pressure in SCI was recorded at the IT2,8,9. Interestingly, the results of the present study showed that the maximum pressure in the non-cushion toilet seating varied widely and was located on the GT in 23 subjects, on the ITs in 8 subjects and SR in 10 subjects. The shape of the toilet seat and the anatomic distance between bilateral ITs are the two main factors that determine the difference in buttock pressure distribution between wheelchair and toilet seat. The distance between the left and right Its (inter-ITs space) in the GT group was significantly shorter than those of the IT and SR groups. In the present study, the subjects were seated comfortably on the toilet seat, but the buttocks of the subjects of the GT group protruded through the toilet cushion/seat into the toilet bowel due to the shorter inter-Its distance, compared with the other two groups. In other words, subjects of the GT group achieved buttock support through the greater trochanter structures. In this regard, there were no significant differences in the inter-IT distance between the IT and SR groups. All study subjects had received/practiced manually anal digit stimulation and/or digit bowel evacuation in the past. Those subjects who insert their fingers into the anus from between the thighs might sit back on the toilet seat and are classified as the SR group. On the other hand, those who insert their fingers into the anus from the back might sit more forward than the SR group and are classified as the IT group.
The results of the present study showed that the air cushion was the most effective in reducing buttock pressure while the SCI subjects of the GT and SR groups were seated on the toilet. On the other hand, for subjects of the IT group, the gel cushion was effective in reducing pressure during toilet seating. Recently, Lustig et al.10 assessed buttock pressure in one healthy female during toilet seating, with and without toilet air cushion. The result of their pressure mapping study also demonstrated that the air cushion reduced peak interface pressure and had a pressure redistribution capacity, which provide protection of the local tissues near the ITs. Considered together, our results and those of the above study suggest that before selecting a cushion for the toilet seat, it is important to determine the type of pressure distribution (i.e. GT group, IT group and SR group). When buttock pressure measurement is not feasible, a simple assessment of the maximum buttock pressure points during toilet seating is to insert the examiner hands between the buttocks and the seat/cushion.
In the present study, the use of the foam cushion on the toilet seat significantly increased Pisch in the GT and IT groups. This finding suggests that the buttocks were less likely to protrude through the cushion/seat into the toilet bowel cavity with the use icushion is of moderate hardness and does not stretch into the toilet like the gel or air cushion. Second, the internal diameter of the foam cushion is narrower than the toilet seat. Third, the seat for the toilet used in our laboratory is designed with slight inclination. Considered together, we advise SCI patients with pressure ulcers or are at risk of development of such complication to avoid the use of foam cushions.
Study limitation
One limitation of this study was the lack of information on the soft tissue volume present in the buttocks area. This is important since the pressure distribution on the toilet seat is influenced not only by the inter-ITs distance but also by the amount of soft tissue in the buttocks. When comparing two SCI persons with the same inter-IT distance, the buttocks are more likely to sag into the toilet bowl cavity in those subjects with buttocks containing small amount of soft tissue. Despite the above limitations, the results of this study highlight the importance of understanding the differences in buttock pressure magnitude and distribution, between the toilet seat and wheelchair in persons with SCI.
Conclusion
We have demonstrated in the present study that the use of a cushion interface changes the level and distribution of buttock pressure during toilet seating in subjects with SCI. The three types of toilet seat cushions tested in the study showed variable pressure relief effect, with the gel cushion being most beneficial for the IT group and the air cushion for the GT and SR groups in persons with SCI.
Disclaimer statements
Contributors None.
Conflicts of interest Authors have no conflict of interests to declare.
Acknowledgements
We thank Dr. Faiq G. Issa (Word-Medex Pty Ltd, Sydney Australia, www.word-medex.com.au) for the careful reading and editing of the manuscript.
Funding Statement
None.
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