Donna A. Williams

Nursing Home Quality and Pressure Ulcer Prevention and Management Practices

Objectives: To measure pressure ulcer quality indicator (QI) scores and to describe the self‐reported skin integrity assessment, pressure ulcer risk assessment, and pressure ulcer prevention and treatment practices in long‐term care facilities (LTCFs).

Tissue oxygenation, perfusion, and position in patients with venous leg ulcers.

OBJECTIVES The purpose of this study was to compare the partial pressure of transcutaneous tissue oxygen (TcPO2) in persons with venous ulcers in four positions with and without inspired oxygen. METHODS TcPO2 was evaluated two times, 4 weeks apart at a chest reference and three lower extremity sites. RESULTS Lower extremity resting TcPO2 levels were lower in patients with venous ulcers than in healthy adults. Minimal changes in TcPO2 occurred with position changes when subjects breathed room air. When arterial oxygen saturation was increased using inspired oxygen, TcPO2, used as an indicator of perfusion, was lower during leg elevation, sitting, and standing compared to lying supine (p < 0.05). CONCLUSIONS Control of peripheral circulation and tissue oxygenation may be impaired in persons with venous ulcers. Leg elevation, sitting, and standing decreased wound perfusion and may not be beneficial to individuals with venous insufficiency and ulceration. Research is needed to explore relationships among tissue oxygenation, blood perfusion, compression, positioning, and venous ulcer healing.

Intact capillaries sensitive to rate, magnitude, and pattern of shear stress stimuli as assessed by hydraulic conductivity (lp)

Magnitude of abrupt changes in fluid shear stress (Delta tau) correlates with capillary hydraulic conductivity (Lp). Cultured endothelial cells differentiate between rate of change in and pattern of fluid stimulation; however, neither rate nor pattern sensitivity has been evaluated in individual capillaries. We hypothesized that Lp would be greater following abrupt compared to slow Delta tau and that magnitude of Delta tau would correlate with Lp regardless of rate. Mesenteric venular capillaries (VC, n=41) located in pithed North American leopard frogs (Rana pipiens) were cannulated either above or at in situ pressure to induce abrupt (<0.1 s) or slow (1-5 min) Delta tau. Lp was assessed always at the same pressure (30 cm H2O) using the modified Landis technique. Mean +/- SE Lp was sixfold higher (P=0.005) following abrupt (19.0 +/- 3.9 x 10(-7)) compared to slow (2.7 +/- 0.9 x 10(-7) cm/s/cm H2O) Delta tau after accounting for stimulus pattern variability. Linear relationships between Lp and Delta tau existed for both abrupt [Lp = 0.026(Delta tau)-1.6, R2=0.90, P=0.0001] and slow [Lp = 0.005(Delta tau)-0.3, R2=0.82, P=0.03] stimuli. These results suggest that frog mesenteric VC sense unique characteristics of Delta tau and respond by altering Lp.

Effect of oral hydration on skin microcirculation in healthy young and midlife and older adults

Clinically undetected underhydration lowers subcutaneous tissue oxygen, impairs healing and increases wound infection. This study examined the effect of supplemental oral hydration on noninvasive measures of skin temperature (Ts), transcutaneous skin O2 (PtcO2), and CO2 (PtcCO2), and skin blood flow (laser Doppler fluxmetry [Flux]=concentration of moving blood cells [CMBC] × Velocity) in healthy adults. Nineteen Control and 18 Test (Hydrated) subjects participated. Ad libitum fluid intake was allowed before the experiment. Sensors were placed on the chest, lower legs, and feet. Time 1 resting supine Ts, PtcO2/PtcCO2, and Flux/CMBC/Velocity were obtained. Then, the Test group ingested 500 mL of H2O. Time 2 measures were obtained 30 minutes later. Data were analyzed using ANOVA. Change in Ts, PtcO2, PtcCO2, and Velocity did not differ between groups. Flux increased more in the Test than in the Control group (p<0.01). The Flux change was explained by a CMBC increase (p<0.05). For midlife/older subjects only, the CMBC change was greater in the Test than in the Control group (p<0.01). Flux may be sufficiently sensitive to detect microvascular changes in response to supplemental oral hydration. These data also suggest that subtle levels of hypoperfusion due to underhydration may exist in community‐dwelling healthy midlife/older adults in their natural state.

A Shear Stress Component to the Modulation of Capillary Hydraulic Conductivity (Lp)

Objective: Two major factors that determine transcapillary exchange are Starling forces and hydraulic conductivity (Lp) of capillary walls. Although chemical stimuli alter Lp, the influence of mechanical stimuli has been neglected. Therefore, we tested the hypothesis that the Lp of intact capillaries would increase with the magnitude of changes in shear stress presented to each capillary.