High-Frequency Ultrasound: Description of Sacral Tissue Characteristics in Healthy Adults.

OBJECTIVES: The purpose of this study was to describe selected sacral tissue characteristics in a convenience sample of healthy volunteer subjects. DESIGN: Descriptive. SAMPLE AND SETTING: Fifty healthy volunteers in a clinical learning center in a school of nursing. METHODS: Sacral scans were obtained using a 20-MHz ultrasound scanning system in 3 positions: prone and 60° and 90° side-lying from the back. The images were analyzed by software in the ultrasound program using quantitative parameters of dermal thickness and density (dermal median intensity and derived number of low-echogenic pixels to total pixels [LEP:TP] ratio). RESULTS: In general, average values were as follows: dermal thickness between 2.32 and 2.65 mm; median pixel intensity between 102 and 112; and the LEP:TP ratio between 0.39 and 0.56. There were significant differences in sacral tissue characteristics between measures of thickness and dermal density (median intensity and LEP:TP ratio) by subject side-lying position (60° and 90°) versus prone position, with all P values less than .0001. CONCLUSIONS: Overall, the ranges were consistent across measures of thickness and dermal density except for systematic differences between side-lying and prone positions. When comparing thickness, median intensity, or LEP:TP ratio, it is important to report subject position. To best recognize tissue inflammation indicative of pressure injuries before surface changes are seen, it is useful to understand healthy high-frequency ultrasound sacral tissue characteristics. It is anticipated that quantitative assessment of dermal thickness, density, and LEP:TP ratio could help identify individuals with incipient pressure injury.

Utility of high-frequency ultrasound: moving beyond the surface to detect changes in skin integrity.

Ultrasound imaging is a versatile modality frequently used in clinical medicine, most likely due to its low cost, low risk to patients, and the ability to provide images in real time. Ultrasound used typically in clinical settings has frequencies between 2 and 12 MHz. Lower frequencies produce greater resolution but are limited in depth penetration; higher frequencies produce greater resolution, but depth of penetration is limited. High-frequency ultrasound (HFUS) shows promise for detection of certain changes in the skin and this has implications for early detection of changes associated with pressure ulcer formation and wound healing. The purpose of this article was to provide an overview of where HFUS has been used with the skin and provide some discussion on its utility with detecting skin changes related to pressure.

OR Time and Sacral Pressure Injuries in Critically Ill Surgical Patients.

Critically ill patients are at risk for developing pressure injuries during operative and other invasive procedures. The purpose of this secondary analysis was to explore the relationship of OR time to sacral pressure injuries in critically ill patients using high frequency ultrasound as a method of assessment. The 41 participants examined in this study had both time in the OR and up to eight days of pressure injury data. The multivariable model containing OR bed time, body mass index, and Braden Scale score produced the best prediction of pressure injury (area under the curve = 0.859). A higher body mass index (P = .09), shorter OR bed time (P = .01), and lower Braden Scale score (P = .05) were associated with a greater chance of pressure injury. These results suggest that use of high frequency ultrasound may identify tissue changes before observable skin changes, leading to earlier pressure injury prevention strategies.

Lack of Association of High Backrest With Sacral Tissue Changes in Adults Receiving Mechanical Ventilation.

BACKGROUND: Although higher backrest elevation may be a theoretical risk for integrity of sacral tissues, few data support use of high backrest elevation. OBJECTIVE: To describe the effect of backrest elevation on the integrity of sacral tissue in critically ill adults receiving mechanical ventilation. METHODS: Patients from 3 critical care units (surgical trauma, medical respiratory, and neuroscience) who were expected to have mechanical ventilation for at least 24 hours were intubated and mechanical ventilation was started. Participants were enrolled in the study within 24 hours of intubation. Backrest elevation was continuously measured by using mechanical system- based accelerometers. Integrity of sacral tissue was evaluated by using high-frequency sonography. RESULTS: Data for 84 patients who had measurements of both backrest elevation and skin integrity were available for analysis. General linear models indicated no significant difference among the proportions of time spent at less than 20° (P values: .57 the first 24 hours, .17 the first 48 hours, .81 the first 72 hours), 20° to 30° (P values: .25 the first 24 hours, .08 the first 48 hours, .25 the first 72 hours), or greater than 30° (P values: .62 the first 24 hours, .28 the first 48 hours, .68 the first 72 hours) among participants with no injury, no change in injury, improvement in injury, or injury that worsened. CONCLUSIONS: Level of backrest elevation is not associated with changes in tissue integrity. Body positioning in critically ill patients receiving mechanical ventilation may not be as important or as effective as once thought.

High-Frequency Ultrasound: Obtaining Optimal Images and the Effect of Image Artifacts on Image Quality.

Objective: High-frequency ultrasound (HFUS) images are being researched for use in the prevention, detection, and monitoring of pressure injuries in patients at risk. This seminal longitudinal study in mechanically ventilated adults describes image quality, the incidence of image artifacts, and their effect on image quality in critically ill subjects. Approach: Mechanically ventilated subjects from three adult intensive care units were enrolled, and multiple sacral images from each subject were obtained daily. Using a subset of best image per patient per day, artifacts were grouped, and their effect on image quality was statistically evaluated. Results: Of a total of 1761 images collected from 137 subjects, 8% were rated as poor. In the subset, 70% had good quality ratings. Four groups of artifacts were identified as follows: "bubbles," "texture problems," "layer nondifferentiation," and "reduced area for evaluation." Artifacts from at least one group were found in 83% of images. Bubbles were most frequently seen, but artifacts with adverse effect on image quality were "layer nondifferentiation," "texture problems," and "reduced area for evaluation." Innovation: HFUS image evaluation is still in the development phase with respect to tissue injury use. Artifacts are generally omnipresent. Quickly recognizing artifacts that most significantly affect image quality during scanning will result in higher quality images for research and clinical applications. Conclusion: Good quality images were achievable in study units; although frequent artifacts were present in images, in general, they did not interfere with evaluation. Artifacts related to "layer nondifferentiation" was the greatest predictor of poor image quality, prompting operators to immediately rescan the area.

High frequency ultrasound sacral images in the critically ill: Tissue characteristics versus visual evaluation.

PURPOSE: High frequency ultrasound (HFUS) systems may identify tissue injury. We compared HFUS tissue characteristics (dermal thickness and dermal density) with visual image examination. METHODS: Longitudinal study in critically ill mechanically ventilated adults, from three ICUs (Surgical Trauma, Medical Respiratory, Neuroscience) enrolled within 24hours of airway intubation. Sacral HFUS images were obtained daily for up to seven days. Expert evaluation of the best image per day was completed and compared to HFUS generated tissue characteristics (dermal thickness and dermal density). RESULTS: Of the113 subjects with 1614 comparisons analysed, 73.2% to 84% were normal, and 6.3% to 11.8% of the comparisons had injury present but no change was noted in the injury observed. There were no significant differences in one-day comparisons among type of injury and mean dermal thickness (p=0.6645) or dermal median intensity (adjusted p=0.06-0.17). All other day-to-day comparisons were similarly non-significant. CONCLUSIONS: We found no association among dermal density, dermal thickness and visual examination of changes in sacral HFUS images for any day-to-day comparison. The use of sacral HFUS as a screening tool for the development of tissue injury is in its infancy. Additional comparative studies should be conducted to identify its future clinical usefulness.

Tissue interface pressure and skin integrity in critically ill, mechanically ventilated patients.

OBJECTIVE: To describe tissue interface pressure, time spent above critical pressure levels and the effect on skin integrity at seven anatomical locations. DESIGN, SETTING, PATIENTS: Descriptive, longitudinal study in critically ill mechanically ventilated adults, from Surgical Trauma ICU-STICU; Medical Respiratory ICU-MRICU; Neuroscience ICU-NSICU in a Mid-Atlantic urban university medical centre. Subjects were enroled in the study within 24hours of intubation. MEASUREMENTS: Tissue interface pressure was measured continuously using the XSENSOR pressure mapping system (XSENSOR Technology Corporation, Calgary, Canada). Skin integrity was observed at all sites, twice daily, using the National Pressure Ulcer Advisory Panel staging system, for the first seven ICU days and at day 10 and 14. RESULTS: Of the 132 subjects, 90.9% had no observed changes in skin integrity. Maximum interface pressure was above 32mmHg virtually 100% of the time for the sacrum, left and right trochanter. At the 45mmHg level, the left and right trochanter had the greatest amount of time above this level (greater than 95% of the time), followed by the sacrum, left and right scapula, and the left and right heels. Similarly, at levels above 60mmHg, the same site order applied. For those six subjects with sacral skin integrity changes, maximum pressures were greater than 32mmHg 100% of the time. Four of the six sacral changes were associated with greater amounts of time above both 45mmHg and 60mmHg than the entire sample. CONCLUSIONS: Maximum tissue interface pressure was above critical levels for the majority of the documented periods, especially in the sacrum, although few changes in skin integrity were documented. Time spent above critical levels for mean pressures were considerably less compared to maximum pressures. Maximum pressures may have reflected pressure spikes, but the large amount of time above the critical pressure levels remains substantial.

Backrest Elevation and Tissue Interface Pressure by Anatomical Location During Mechanical Ventilation.

BACKGROUND: Backrest elevations less than 30° are recommended to reduce pressure ulcers, but positions greater than 30° are recommended during mechanical ventilation to reduce risk for ventilator-associated pneumonia. Interface pressure may vary with level of backrest elevation and anatomical location (eg, sacrum, heels). OBJECTIVE: To describe backrest elevation and anatomical location and intensity of skin pressure across the body in patients receiving mechanical ventilation. METHODS: In a longitudinal study, patients from 3 adult intensive care units in a single institution receiving mechanical ventilation were enrolled within 24 hours of intubation from February 2010 through May 2012. Backrest elevation (by inclinometer) and pressure (by a pressure-mapping system) were measured continuously for 72 hours. Mean tissue interface pressure was determined for 7 anatomical areas: left and right scapula, left and right trochanter, sacrum, and left and right heel. RESULTS: Data on 133 patients were analyzed. For each 1° increase in backrest elevation, mean interface pressure decreased 0.09 to 0.42 mm Hg. For each unit increase in body mass index, mean trochanter pressure increased 0.22 to 0.24 mm Hg. Knee angle (lower extremity bent at the knee) and mobility were time-varying covariates in models of the relationship between backrest elevation and tissue interface pressure. CONCLUSIONS: Individual factors such as patient movement and body mass index may be important elements related to risk for pressure ulcers and ventilator-associated pneumonia, and a more nuanced approach in which positioning decisions are tailored to optimize outcomes for individual patients appears warranted.

Effects of position and operator on high-frequency ultrasound scan quality.

OBJECTIVES: High-frequency ultrasound may evaluate those at risk for pressure ulcers. Images may be obtained by clinicians with limited training. The prone position is recommended for obtaining sacral scans but may not be feasible in the critically ill. This study investigated image quality using multiple operators and a variety of patient positions. RESEARCH METHODOLOGY: Sacral scans were performed in three randomised positions in 50 volunteers by three different investigators using a 20 MHz ultrasound system. General linear models and ANOVA random effects models were used to examine the effects of operator and position on image quality rating, and measures of dermal thickness and dermal density. RESULTS: The best scan for each position and operator was used for analysis (n=447 images). Image rating varied by operator (p=0.0004), although mean ratings were 3.5 or above for all operators. Dermal thickness was less for the prone position than in 90° or 60° side-lying positions (p=0.0137, p=0.0003). Dermal density was lower for the prone position than for the 90° or 60° positions (p<0.0001 for both). CONCLUSIONS: These data show that overall scan quality was acceptable in all positions with all operators. However, differences were found between side-lying positions and the prone for dermal thickness and dermal density measures.

Predictors of agitation in critically ill adults.

BACKGROUND: Agitation in critically ill adults is a frequent complication of hospitalization and results in multiple adverse outcomes. Potential causes of agitation are numerous; however, data on factors predictive of agitation are limited. OBJECTIVES: To identify predictors of agitation by examining demographic and clinical characteristics of critically ill patients. METHODS: A medical record review was performed. Documentation of agitation was indicated by scores on the Richmond Agitation-Sedation Scale or the use of an agitation keyword. Records of 200 patients from 1 medical and 1 surgical intensive care unit were used for the study. Risk factors were determined for 2 points in time: admission to the intensive care unit and within 24 hours before the first episode of agitation. Data on baseline demographics, preadmission risk factors, and clinical data were collected and were evaluated by using logistic multivariable regression to determine predictors of agitation. RESULTS: Predictors of agitation on admission to intensive care were history of use of illicit substances, height, respiratory and central nervous system subscores on the Sequential Organ Failure Assessment, and use of restraints. Predictors of agitation within 24 hours before the onset of agitation were history of psychiatric diagnosis, height, score on the Sequential Organ Failure Assessment, ratio of Pao2 to fraction of inspired oxygen less than 200, serum pH, percentage of hours with restraints, percentage of hours of mechanical ventilation, pain, and presence of genitourinary catheters. CONCLUSIONS: Predictors of agitation on admission and within 24 hours before the onset of agitation were primarily clinical variables.

Agitation onset, frequency, and associated temporal factors in critically ill adults.

BACKGROUND: Agitation is a frequent complication in critically ill adults, can result in life-threatening events for patients or care providers, and extends the hospital length of stay, thereby increasing hospital costs. OBJECTIVES: To describe the incidence, onset, and temporal factors related to agitation in critically ill adults. METHODS: Data were collected for the first 5 days of stay of all adult patients consecutively admitted to a medical respiratory intensive care unit and a surgical trauma intensive care unit during a 2-month period. Agitation was documented by using scores on the Richmond Agitation-Sedation Scale or notation of agitation in the medical record. The hour was used as the documentation epoch, and data were summarized by hour, 4-hour block, and day for each patient. RESULTS: Data were collected on 200 patients, 100 from each unit. Among the sample, 118 (59%) were agitated at some time during the 5 days. The overall agitation rate was 7.8% of the total hourly time. Mean onset of agitation was 11.6 hours from time of admission to the unit. Of the 118 patients who were agitated at some time, 102 (86%) had agitation on day 1. Compared with patients in the surgical trauma unit, patients in the medical respiratory unit had significantly more hours of agitation the first day and first hour of admission and significantly earlier onset of agitation. CONCLUSIONS: Agitation was present in more than one-half of the patients in the sample, typically developed on the first day, and involved consecutive days.