The main objectives of this study were to evaluate pressure mapping in multiple sclerosis, Friedreich's ataxia and spinal cord injury, identifying possible differences between them, and determine the existence of relationship between the results of pressure mapping and those of the functional tests that are most widely used in rehabilitation. Once the results were analyzed, only the PMEAN variable provided sufficiently different values between the three pathologies. Therefore, this variable was the only one capable of differentiating between the three subgroups of the sample. In addition, this variable shows that the behavior of sedentary people who are diagnosed with multiple sclerosis and spinal cord injury was significantly different from that of people diagnosed with Friedreich's ataxia. Furthermore, it was observed that the highest number of relationships occurred between pressure mapping and functional tests in the multiple sclerosis group.
The values obtained by pressure mapping in this study differ from those previously obtained in other investigations, such as that of Berthold et al.(32),we obtained lower values in PMEAN and higher in PMAX. On the other hand, those authors stated that the PMEANvalue should not exceed the clinically accepted limit of 32 mmHg, and that a PMAX of 200 mmHg is too high. This shows that the three populations of our study are above the reference values in both variables.
The reviewed literature shows that PMEAN and PMAXare the ones that provide more information about the distribution of pressure in sitting. Crawford et al.(33) and Stinson et al.(34)only analyzed the values of PMEAN and PMAX, since these show the most significant differences between severely disabled people with pathologies such as multiple sclerosis, spinal cord injury and stroke. However, this is not in line with the results obtained in this study, since PMEAN and A also showed statistically significant and clinically more sensitive results than the functional tests used in the multiple sclerosis and Friedreich's ataxia subgroups. Despite this, and in accordance with the literature published to date, PMEANis the key variable. Consequently, it should be interpreted as a fundamental parameter for the design and evaluation of specific treatments for people with these pathologies.
With respect to the protocol used to record pressure mapping, it consisted in 8 minutes of adaptation and 2 minutes of recording. This distribution of times is based on previous studies(20,33),which postulated that, before recording the data, the subject must spend some time on the device in order to adapt to it, verifying that the ideal duration is 8 minutes, and that the 2-minute duration of the test means that reliable information is obtained, especially with people in wheelchairs with multiple sclerosis(33).
Regarding the functional tests, relevant differences were found in the test results by pathology and in comparison with other authors. In LRT, the normal value is 17 centimeters(21). In this test, values below the normal range were obtained in the group with multiple sclerosis and spinal cord injury, which is far from the results obtained by Freeman et al.(22) and Choe et al.(24)in people with Friedreich’s ataxia, which were within the normal ranges (no background was found in the scientific literature for these results in people with this pathology).
In FRT, the normal value in the age range of 41-69 years is between 35.1-38.1 centimeters(23).Similarly, values below normal were obtained in people with multiple sclerosis and spinal cord injury, which is far from the results of the studies of Frzovic et et al.(35) andKizony et al.(36). In people with Friedreich's ataxia, a value was achieved within the normal ranges (no background in the scientific literature was found). In FST, the total score was 56 points(29). The data obtained in the multiple sclerosis and spinal injury groups were also below the values reported by previous studies(37,38).Finally, in TCT, the total score was 100 points(39). The data obtained in the multiple sclerosis and spinal injury groups were below the data collected in previous studies(40,41). From the results obtained in the literature review of the functional tests, it is clear that the authors studied people with the same pathologies, although probably with a lower degree of disability and severity in the development of the characteristic symptomatology of these diseases.
In BBS, our populations obtained ratings between 5.5 and 15.5 points. These scores are lower than the average scores obtained byDowns et al.(26), Eftekharsadat et al.(42)(in people with multiple sclerosis) and Santos de Olivera et al.(43)(in patients with spinocerebellar ataxia).However, our results are similar to those of such studies in people with spinal cord injury. It is evident that our sample obtained lower values due to the fact that they were populations that cannot walk or stand. This condition significantly affects the score on that scale.
As expected in PPAS, a validated test for persons with cerebral palsy(27), our results in the pathologies studied cannot be compared with those of other authors, as there are no previous studies available in the literature. The study populations achieved better values in postural quality quantification than the standards for this tool.
In FIST, our data show that sedentary control was lower compared to the populations of multiple sclerosis(38)and non-ambulatory individuals with spinal cord injury(37).In TCT, this behavior was also observed(40,41). These results suggest that our population is severely affected.
Finally, the differences between the functional tests and pressure mapping, there were few but very strong correlations. In the three subgroups studied, the correlations between the pressure mapping variables and the functional tests were more numerous, especially in the multiple sclerosis group. Similarly, the functional measures recorded in the same starting position (sitting) were more strongly related to the recordings of pressure mapping in sitting. It is worth highlighting the behavior of A in LRT and FRT, which demonstrates that when the subject's contact area in pressure mapping is lower, the scores in LRT and FRT are higher, whereas PMEANincreases when the LRT and FRT scores are higher. These correlations found make clear reference to the fact that the construct evaluated by pressure mapping is the state of the postural trunk control.
The main limitation of this work was the small sample size, which was due to the fact that they were people with a serious disability and dependence in the same care center. Likewise, the novelty of the subject and the wide possibilities for future research in this field must be recognized to contribute to the development of the assistance services, which directly affects the improvement of the quality of life of people with serious disabilities and dependence. That is, the approach of specific physiotherapy protocols should be pursued taking into account the status of people with multiple sclerosis, Friedreich's ataxia and spinal cord injury.
In addition, the study of pressures in sitting should be addressed with the use of cushions and at different angles of inclination of the back of the wheelchair to determine whether these modifications significantly reduce the pressure and if this correlates with a lower appearance of ulcers.