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Biomedical subjects

Mary Jo Geyer

Publications and source records attributed to Mary Jo Geyer.

7 recordsLinked to original sources
PubMed2005

A comparison of changes in rhythms of sacral skin blood flow in response to heating and indentation.

OBJECTIVE: To differentiate blood flow control mechanisms associated with indentation from those associated with heating and to discern heat-induced and pressure-induced changes by comparing the effect of externally applied stress on skin blood flow (SBF) to the response to externally applied heat. DESIGN: Repeated-measures design. SETTING: A university research laboratory. PARTICIPANTS: Ten healthy, young adults (5 men, 5 women; mean age +/- standard deviation, 30.0+/-3.1y). Intervention Incremental heat (35 degrees -45 degrees C, 1 degrees step/min) and pressure (0-60 mmHg, 5 mmHg step/3 min) on the sacrum using a computer-controlled indenter. Sessions for heat and pressure protocols were separated by 7+/-2 days. MAIN OUTCOME MEASURES: We used a Laserflo Blood Perfusion Monitor 2 and Softip pencil probe to measure capillary blood perfusion and wavelet analysis to decompose the blood flow signal. The power spectrum was divided into 5 ranges corresponding to metabolic, neurogenic, myogenic, respiratory, and cardiac control mechanisms. The average relative (ie, normalized) power in each frequency range was computed to determine of the relative contribution of each control mechanism. RESULTS: Power in the myogenic frequency range was higher after incremental pressure and lower after incremental heating, whereas power in the metabolic frequency range was lower after incremental pressure and higher after incremental heating ( P <.01). Mean blood flow decreased as pressure increased from 0 to 15 mmHg; mean blood flow increased as pressure increased from 15 to 60 mmHg. CONCLUSIONS: SBF, as recorded by the laser Doppler, suggests that there may be a myogenic control mechanism mediating blood flow after incremental tissue loads and that a metabolic control mechanism may mediate blood flow after heat application to the tissue. The study of local blood flow control mechanisms and their response to pathomechanical perturbations may be possible using wavelet analysis of blood flow oscillations. More research is needed to establish the clinical utility of these findings in the development of support surfaces intended to reduce the risk of developing pressure ulcers.

Adult↗
PubMed2005

Using support surfaces to manage tissue integrity.

PURPOSE: To provide the clinician with an overview of support surfaces used to manage tissue integrity as well as a review of how pressure ulcers develop. TARGET AUDIENCE: This continuing education activity is intended for physicians and nurses with an interest in understanding how available support surfaces can impact the development and treatment of pressure ulcers. OBJECTIVES: After reading the article and taking the test, the participant should be able to:

Air↗
PubMed2005

Analysis of week-to-week variability in skin blood flow measurements using wavelet transforms.

The study of skin blood flow responses is confounded by temporal variability in blood flow measurements. Spectral analysis has been shown useful in isolating the effects of distinct control mechanisms on various stimuli in the microcirculatory system. However, the sensitivity of spectral analysis to temporal blood blow variability has not been reported. This study was designed to assess week-to-week variability in blood flow measurements using wavelet-based spectrum analysis. Ten healthy, young subjects (mean age+/-SD, 30.0+/-3.1 years) were recruited into the study. Incremental heating (35-45 degrees C, 1 degrees step min-1) was applied on the skin over the sacrum once per week for three consecutive weeks. Wavelet analysis was used to decompose the laser Doppler blood flow signal into frequency bands determined to be associated with endothelial nitric oxide (0.008-0.02 Hz), neurogenic (0.02-0.05 Hz), myogenic (0.05-0.15 Hz), respiratory (0.15-0.4 Hz), and cardiac (0.4-2.0 Hz) control mechanisms. The results showed that coefficients of variation for the power in each frequency band at baseline are smaller than the coefficients of variation of blood flow at baseline or at maximal blood flow ratio (P<0.05). Myogenic and respiratory frequency bands showed the highest coefficients of variation among the five frequency bands. An increase in power in the endothelial nitric oxide frequency band and a decrease in power in the myogenic frequency band of the maximal blood flow response were reproduced in three consecutive weeks. Our study suggests that wavelet analysis is an effective method to overcome temporal variability in skin blood flow measurements.

Adult↗
PubMed2004

Quantifying fibrosis in venous disease: mechanical properties of lipodermatosclerotic and healthy tissue.

OBJECTIVES: To quantify the mechanical properties of medioposterior bulk calf tissue in patients with lipodermatosclerotic venous-insufficient tissue and individuals with apparently healthy tissue using a novel ultrasound indentometry method, and to identify parameters with the potential for quantifying fibrosis in subsequent studies. DESIGN: 2-group, quasi-experimental design SETTING: Soft Tissue Mechanics Laboratory, University of Pittsburgh, Pittsburgh, PA PARTICIPANTS: 9 healthy and 9 venous-insufficient individuals aged 35 to 85 years INTERVENTIONS: Ultrasound indentometry and computed tomography (CT) of calf tissue MAIN OUTCOME MEASURES: Between group differences and associations among quasi-linear viscoelastic (QLV) tissue parameters and CT descriptors MAIN RESULTS: Established the accuracy, validity, and reliability of the QLV model and ultrasound indentometry method. Demonstrated a range of significant differences between the groups (P <.020 to P <.004) for selected QLV parameters. Also found significant correlations between CT measures of fibrosis and dermal thickness and QLV elastic measures (P <.034 to P <.005). CONCLUSION: Attempts to quantify fibrosis in lipodermatosclerosis have included histologic exams, palpation/pitting, durometer readings, and imaging techniques, but these efforts have failed to produce a clinically practical, noninvasive method. A novel ultrasound indentometry method was used to acquire in vivo data from which tissue parameters were derived. These data support the further development of ultrasound indentometry as a method to quantify fibrosis in venous disease.

Adult↗
PubMed2003

Wheelchair seating: a state of the science report.

Regardless of the field, agenda-setting processes are integral to establishing research and development priorities. Beginning in 1998, the National Institute on Disability and Rehabilitation Research mandated that each newly funded Rehabilitation Engineering and Research Center (RERC) hold a state-of-the-science consensus forum during the third year of its 5-year funding cycle. NIDRR's aim in formalizing this agenda-setting process was to facilitate the formulation of future research and development priorities for each respective RERC. In February 2001, the RERC on Wheeled Mobility, University of Pittsburgh, conducted one of the first such forums. The scope encompassed both current scientific knowledge and clinical issues. In preparation, expert interviews were carried out to establish the focus for the forum. Because a stakeholder forum on wheelchair technology had recently been held, opinion favored wheelchair seating as the focus and included the following core areas: seating for use in wheelchair transportation, seated postural control, seating discomfort, and tissue integrity management. The aim of this report is to present a summary of the workshop outcomes, describe the process, and increase awareness of this agenda-setting process in order to enhance future participation in a process that critically influences the field of wheeled mobility.

Persons with Disabilities↗
PubMedDate not supplied

Using wavelet analysis to characterize the thermoregulatory mechanisms of sacral skin blood flow.

Pressure-induced skin blood flow responses measured via laser Doppler flowmetry are commonly reported in the time domain. The usefulness of spectral analysis in examining blood flow control mechanisms has been demonstrated, but traditional Fourier analysis does not provide sufficient resolution to reveal characteristic low frequencies. Time-frequency (wavelet) analysis was performed on 10 subjects' sacral skin blood flow responses to heating (45 degrees C) with improved resolution. Five frequency bands were identified (0.008-0.02 Hz, 0.02-0.05 Hz, 0.05-0.15 Hz, 0.15-0.4 Hz, and 0.4-2.0 Hz) corresponding to metabolic, neurogenic, myogenic, respiratory, or cardiac origins. Significant differences were observed in the mean normalized power of the metabolic (p < 0.01) and myogenic frequency bands (p < 0.01) between preheating and maximal heating and preheating and postheating periods. Power increased for the metabolic frequency and decreased for the myogenic frequency. Wavelet analysis successfully characterized thermoregulatory control mechanisms by revealing the contributions of the physiological rhythms embedded in the blood flow signal.

Adult↗