Performance Assessment of a Humidity Measurement System and Its Use to Evaluate Moisture Characteristics of Wheelchair Cushions at the User-Seat Interface.

Little is known about the changes in moisture that occur at the body-seat interface during sitting. However, as increased moisture can add to the risk of skin damage, we have developed an array of MEMS (Micro-Electro-Mechanical System) humidity sensors to measure at this interface. Sensors were first evaluated against traceable standards, followed by use in a cross-over field test (n = 11; 20 min duration) using different wheelchair cushions (foam and gel). Relative humidity (RH) was measured at the left mid-thigh, right mid-thigh and coccyx. Sensors were shown to be unaffected by loading and showed highly reliable responses to measured changes in humidity, varying little from the traceable standard (<5%). Field-test data, smoothed through a moving average filter, revealed significant differences between the three chosen locations and between the gel and foam cushions. Maximum RH was attained in less than five minutes regardless of cushion material (foam or gel). Importantly, RH does not appear to distribute uniformly over the body-seat interface; suggesting multiple sensor positions would appear essential for effectively monitoring moisture in this interface. Material properties of the cushions appear to have a significant effect on RH characteristics (profile) at the body-seat interface, but not necessarily the time to peak moisture.

Wearing American Football helmets increases cervicocephalic kinaesthetic awareness in "elite" American Football players but not controls.

BACKGROUND: While there have been investigations into the reduced neck injury rate of wearing protective helmets, there is little information on its effects on normal kinaesthetic neck function. This study aims to quantify the kinaesthetic and movement effects of the American football helmet. METHODS: Fifteen British Collegiate American football players (mean age 22.2, SD 1.9; BMI kg.m(2) 26.3, SD 3.7) were age and size matched to 11 non-American football playing university students (mean age 22.5, SD 3.6; BMI 24.3, SD 3.3 kg.m(2)). Both groups had their active cervical range of motion and head repositioning accuracy measured during neck flexion/extension using a modified cervical range of motion device and a similarly modified football helmet. RESULTS: Wearing helmets significantly reduced active cervical range of motion in extension in both groups (P = 0.007 and P = 0.001 Controls and American Footballers respectively). While both groups had similar repositioning when not wearing a helmet (flexion P = 0.99; extension P = 0.52), when wearing helmets, American football players appeared to be more accurate in relation to cervical kinaesthetic repositioning (ANOVA: P = 0.077: flexion effect size =0.84; extension effect size =0.38). CONCLUSIONS: Wearing American football helmets significantly reduces the active cervical range of motion in extension, along with a change in the neutral head position. American footballers have a greater accuracy in repositioning their head from flexion (potentially enhanced proprioception) when wearing a helmet. This finding might allow development of a simple objective test to help discern presence of minor concussive or cervical musculoskeletal injury on or off the field.

Microenvironment temperature prediction between body and seat interface using autoregressive data-driven model.

There is a need to develop a greater understanding of temperature at the skin-seat interface during prolonged seating from the perspectives of both industrial design (comfort/discomfort) and medical care (skin ulcer formation). Here we test the concept of predicting temperature at the seat surface and skin interface during prolonged sitting (such as required from wheelchair users). As caregivers are usually busy, such a method would give them warning ahead of a problem. This paper describes a data-driven model capable of predicting thermal changes and thus having the potential to provide an early warning (15- to 25-min ahead prediction) of an impending temperature that may increase the risk for potential skin damages for those subject to enforced sitting and who have little or no sensory feedback from this area. Initially, the oscillations of the original signal are suppressed using the reconstruction strategy of empirical mode decomposition (EMD). Consequentially, the autoregressive data-driven model can be used to predict future thermal trends based on a shorter period of acquisition, which reduces the possibility of introducing human errors and artefacts associated with longer duration "enforced" sitting by volunteers. In this study, the method had a maximum predictive error of <0.4 °C when used to predict the temperature at the seat and skin interface 15 min ahead, but required 45 min data prior to give this accuracy. Although the 45 min front loading of data appears large (in proportion to the 15 min prediction), a relative strength derives from the fact that the same algorithm could be used on the other 4 sitting datasets created by the same individual, suggesting that the period of 45 min required to train the algorithm is transferable to other data from the same individual. This approach might be developed (along with incorporation of other measures such as movement and humidity) into a system that can give caregivers prior warning to help avoid exacerbating the skin disorders of patients who suffer from low body insensitivity and disability requiring them to be immobile in seats for prolonged periods.

Settling down time following initial sitting and its relationship with comfort and discomfort.

This study examined the subjective rating of wheelchair comfort and discomfort (numerical rating scale questionnaire) and the duration of objective in-chair movement reduction "settling down time" following initial contact with the seating surface. Healthy young subjects (n = 22) sat for 5 min on contoured foam or wood cushion surfaces fitted to otherwise identical wheelchairs. Force sensing resistors attached to each quadrant of the sitting interface measured the relative movements of the subjects over time. A significant correlation was found between settling down time (SDT) and reported leg/feet discomfort (p = 0.003; correlation co-efficient = 0.44); and a significant negative correlation was found between SDT and overall comfort (p = 0.015; correlation co-efficient = -0.36). When comparing cushion surfaces: SDT was significantly longer (p < 0.0001) for subjects sitting on wood (5.8 s) compared to contoured foam (3.9 s); Leg/feet discomfort was significant higher (p = 0.007) for subjects sitting on wood (1.1 out of 10) compared to contoured foam (0.3 out of 10); Overall discomfort was significant higher (p = 0.009) for subjects sitting on wood (1.3 out of 10) compared to contoured foam (0.5 out of 10); Comfort was significantly lower (p = 0.001) for subjects sitting on wood (6.5 out of 10) compared to contoured foam (8.3 out of 10); Support was significantly lower (p = 0.001) for subjects sitting on wood (6.4 out of 10) compared to contoured foam (8 out of 10). The results of this study suggest that the shape and firmness of the surface at the buttock-wheelchair interface can affect a subject's SDT following initial contact with the seat as well as their perception of comfort and discomfort. In addition, there appears to be a relationship between longer SDT's and increased discomfort ratings, and shorter SDT's and increased comfort ratings. Therefore, testing for SDT's may be useful in the indirect objective assessment of wheelchair cushions and possibly other types of seating surfaces with design differences that aim to improve comfort and minimize discomfort.

Studying thermal characteristics of seating materials by recording temperature from 3 positions at the seat-subject interface.

AIM OF THE STUDY: To determine whether 3 fixed positions of seat-subject interface temperature measurement offer more information than a single point of measurement. MATERIALS AND METHODS: Temperature data was simultaneously acquired (sampling frequency 1 Hz/sensor) from each of three sensor positions (right & left mid-thigh and coccyx), from the subject-seat interface. The data was acquired whilst subjects (6 males, 5 females: 21-40 yrs: BMI 19.3-26.4) sat for 20 min on each of three types of seat material (foam, gel mould and solid wood). Data collection was performed at the same time of day for each subject: ambient temperature between 21.1 and 21.2 °C, ambient relative humidity 50.9%. RESULTS: Analysis of data from the sensors, post mathematical smoothing, for each subject (n = 11; ANOVA, followed by post-hoc t-tests) revealed each of the measurement positions to have a significantly different recorded temperature (p < 0.01). However, profile of temperature change at the same measurement position using the same seating material during the 20 min sitting period, was highly correlated (r > 0.99) between subjects, a consistent finding across all 11 subjects regardless of seat material selected. CONCLUSION: Use of 3 positions of measurement (3 sensors) appears necessary when performing detailed studies of temperature change at the seat-subject interface. The high level of comparability of results between subjects supports potential of this method to resolve quantitative components of qualitative measurements, e.g., thermal comfort.

The patient: a novel source of error in clinical temperature measurement using infrared aural thermometry.

INTRODUCTION: The vital signs are an important component of patient assessment. With respect to body temperature; there has been a move away from mercury-in-glass thermometers toward the relatively inexpensive, safer to use infrared tympanic, auricular, or ear thermometer. Although already in widespread use, the reliability of these devices has increasingly been called into question. Few studies, however, have considered that the problem might reside outside the device itself. OBJECTIVE: To investigate the correlation between left ear temperature and right ear temperature using an infrared tympanic thermometer (ITT). DESIGN: A prospective, single-blind trail with randomized assignment of the first ear to be assessed. SETTING/LOCATION: Welsh Institute of Chiropractic (WIOC), University of Glamorgan. SUBJECTS: One hundred and thirty two (132) asymptomatic subjects who were opportunistically sampled on entry into the WIOC. None of the subjects had any neurologic deficit, or any known underlying pathologic problems. All were students at the University of Glamorgan (age range, 18-48 years). A smaller sample of the same cohort was used on a separate occasion to compare ITTs from 2 different manufacturers using the same protocol. INTERVENTION: Measurement of ear (ear canal/tympanic) temperature bilaterally using an ITT. OUTCOME MEASURES: Bilateral asymmetry in ear canal temperature. Analysis consisted of nonparametric statistical tests, using Spearman's correlation for comparison and the Wilcoxon matched pairs test for differences. RESULTS: In 132 subjects who completed the main study, although a degree of correlation was found, the relationship did not extrapolate through zero. At temperatures more than 0.4 degrees C above or below 36.7 degrees C, there was a significant difference in temperature in the left compared with the right ear. Additionally, the left ear tended to register a lower temperature than the right ear at temperatures below 36.7 degrees C, whereas the left ear tended to read a higher temperature than the right ear above 36.7 degrees C. CONCLUSIONS: The authors suggest that clinicians consider measuring both ears, and take the greater of the readings to be a more accurate reflection of the patient's core temperature. The difference may perhaps even be related to the person's health. This change in methodology should increase the reliability of the measurement and go some way toward restoring confidence in the use of ITT devices.