A short history of progression of research into seating and postural support

Pressure Mapping of a Standard Hospital Recliner and Select Cushions With Healthy Adults: A Comparative Study

PURPOSE

The aim of the study was to compare the degree of pressure created when healthy adult volunteers sat on a hospital recliner chair in various positions and on various cushions.

DESIGN

Comparative cross-sectional study.

SUBJECTS AND SETTING

Thirty-four healthy subjects were recruited from the community, an urban city in a rural area of Eastern North Carolina.

METHODS

Interface pressure measurements were taken by the investigators for each subject sitting on a standard hospital recliner under each of the following conditions: no cushion, foam cushion, nonadjustable air cushion, nonadjustable air/foam cushion, and adjustable air cushion. Subject positions, upright sitting and reclined, were randomly selected. Analyses consisted of data visualizations by investigators and univariate statistics. For each surface, mean pressure, peak pressure, and Pressure Area Index (PAI) were obtained and compared. Inferences were drawn from a repeated-measures analysis-of-covariance model.

RESULTS

Subject position was not associated with any of the measures for each surface after adjusting for other variables (average pressure P = .1094, maximum/peak pressure P = .1318, PAI P = .4336). Subject weight, the type of surface, and their interaction do impact the results (average pressure, maximum/peak pressure, and PAI, P < .0001). The foam cushion had the highest mean and average interface pressures and the lowest PAI. The nonadjustable air and air/foam cushions performed most similarly to each other, showing lowest mean and average interface pressures and the highest PAI.

CONCLUSION

Position of a hospital recliner chair in the 2 positions studied had no association with interface pressure outcomes; therefore, other methods of pressure redistribution need to be utilized by clinicians. Based on the results of this study, clinicians may need to reevaluate the type of cushion used in the acute hospital setting, as a standard foam cushion was found to increase interface pressures when compared to other cushions and a standard hospital recliner.

The Effect of a Liner on the Dispersion of Sacral Interface Pressures During Spinal Immobilization

Sacral pressure ulcers are a significant problem following spinal cord injury and are felt to be in part due to the high interface-pressures generated while strapped to the spine board. The objective of this study was to determine sacral interface-pressure and sensing area in healthy volunteers on a spine board and the effects of a gel pressure dispersion liner. Thirty-seven volunteers were placed on a pressure-sensing mat between the subject and the spine board. Measurements were carried out with and without a gel liner. Pressures and sensing area were recorded every minute for 40 minutes. The highest pressure was generated at the sacral prominence of each subject. Mean interface-pressures were higher on the spine board alone than with the gel liner (p < .0001). Overall, mean sensing area was lower on the spine board than with the gel liner (p < .0001). Standard spinal immobilization causes high sacral interface-pressures. The addition of a gel liner on the spine board decreased overall mean sacral pressures and increased mean sensing area. Generation of sacral pressure ulcers may be related to the initial interface-pressures generated while the patient is strapped to the spine board. The addition of a gel liner may reduce the incidence of sacral pressure ulcers.

Physiological measurements of tissue health; implications for clinical practice

Pressure mapping alone insufficiently describes tissue health. Comprehensive, quantitative non invasive assessment is crucial. Interface pressures (IPs) and transcutaneous blood gas levels [transcutaneous tissue oxygen (T(c) PO(2) )] were simultaneously assessed over both ischia and the sacrum to investigate the hypotheses: (i) tissue oxygenation decreases with sustained applied pressure; (ii) tissue oxygen and IP are inversely correlated in loaded soft tissues; (iii) multisite assessments are unnecessary because healthy individuals are symmetrical. Measurements were taken at 5-minute intervals for 20 minutes in both sitting and supine lying for a cohort of 20 able-bodied adults. There were no statistically significant changes over time for either variable in 96% of timepoint comparisons. Specifically, no significant differences were seen between 10 and 20 minutes in either position. These findings imply that a 10-minute assessment can reliably indicate tissue health and that tissue may adapt to applied load over time. No statistically significant correlations between T(c) PO(2) and IP were observed. However, the left and right ischia were significantly different for both variables in supine lying (P < 0.001) and for sitting IP (P < 0.010). Thus, even in this healthy cohort, postural symmetry was not observed and should not be assumed for other populations with restricted mobility. If a multisite technique cannot be used, repeated tissue health assessments must use the same anatomic location.