A prospective assessment of sacral pressures in healthy volunteers seated upright and reclined with legs elevated in a recliner.

Prolonged, unrelieved pressure is a major risk factor for pressure ulceration, and interface tissue pressures have been shown to be very high when a person is sitting. Using convenience sampling methods, 23 healthy participants (four men, 19 women, mean age 45 years, body mass index [BMI] range 20-45) participated in a prospective pilot study to evaluate the effect of BMI and two commonly used seating positions in standard hospital reclining chairs on tissue (especially sacral) interface pressures. Measurements were obtained when volunteers were seated upright with plantar surfaces of feet touching the floor (Position 1) and reclining with legs resting on an elevated surface (Position 2). Measurements were obtained for 6 minutes using a thin, flexible force sensing array 430-mm x 430-mm seat mat. Average pressure, maximum pressure, and the number of sensors reading >60 mm Hg and >80 mm Hg were used for analysis across the total surface and at the sacrum. Participants were categorized by BMI (category 1: 20-22, category 2: 23-28, category 3: 29+; no participants had a BMI <20). Leg elevation reduced average pressure across the total surface (from 42.9 mm Hg to 40.0 mm Hg, P = 0.015) and the number of sensors reading >60 mm Hg at the sacrum (from 31.4 to 27.1, P = 0.047). BMI and position were significantly correlated with the number of sensors reading >80 mm Hg (P = 0.008) and average pressure (P = 0.031). Pairwise comparisons showed significant differences existed between BMI categories 1 (average delta: -3.63, indicating down position is better) and 3 (average delta: 4.67, indicating up position is better) for the difference in number of sensors above 80 mm Hg (P = 0.030). Research is needed to further explore the relationship between BMI and tissue pressure, but the results of this study suggest that for patients with a BMI >29, elevating the heels/reclining the chair significantly reduces sacral tissue interface pressure. Further research specific to pressure relief in the sitting position is needed, as neither position examined in this study was found to reduce interface pressures to generally considered safe levels for reduced-mobility patients.