Eye tracker outcomes in a randomized trial of 40 sessions of hyperbaric oxygen or sham in participants with persistent post concussive symptoms.

PURPOSE: Eye movements may offer a sensitive method to measure response to intervention in mild traumatic brain injury (mTBI). METHODS: The Brain Injury and Mechanisms of Action of Hyperbaric Oxygen for Persistent Post-Concussive Symptoms after Mild Traumatic Brain Injury Study (BIMA) randomized 71 participants to 40 sessions of hyperbaric oxygen or sham. A companion normative study (Normal) enrolled 75 participants. An eye tracking system measured left and right eye movements for saccadic and smooth pursuit. At baseline two smooth pursuit tasks, circular and horizontal ramp, and four saccadic tasks, horizontal and vertical step, reading, and memory guided-on tasks differentiated BIMA from Normal participants. The change from baseline in these tasks were measured and compared between interventions and against Normal participants at 13 weeks and six-month follow-up using the two-sample t-test. The Holm-Bonferroni procedure was used to adjust for multiple testing. RESULTS: Change from baseline in eyetracker measures for participants assigned to the hyperbaric oxygen arm did not significantly differ from those assigned to the sham arm at post-randomization time points 13 weeks and six months. Consistent shifts of BIMA participant values toward Normal values at 13 weeks and six months were observed for overall fixation duration, forward saccadic duration, and number of lines read for the reading task, number of misses on the memory guided-on task, and absolute intersaccadic interval velocity and absolute saccadic amplitude on the circular task. The distributions between Normal and BIMA participants were no longer statistically significantly different at 13 weeks and six months post enrollment for these measures. CONCLUSION: The baseline differences between BIMA and Normal suggest potential vulnerability of the smooth pursuit system and the saccadic system. During the six-month follow-up period, improvement toward Normal was seen on some measures in both the hyperbaric oxygen and sham intervention arms without difference between intervention groups. IDS: clinicaltrials.gov Identifiers NCT01611194 and NCT01925963.

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.

Eye Tracking Results in Postconcussive Syndrome Versus Normative Participants.

Purpose: Standard physical, neurologic, and neuropsychologic examinations may not detect abnormalities after mild traumatic brain injury (mTBI). An analysis of eye movements may be more sensitive to neurologic dysfunction. Methods: We performed eye tracking assessments in 71 active duty and veteran military personnel with persistent postconcussive symptoms (3 months to 5 years after mTBI) and 75 volunteers with no history of brain injury. Both eyes were sampled at 500 Hz and analyzed for various eye measurement parameters during visual tasks involving the saccadic and smooth systems. Results: No difference between mTBI and normal participants in main sequence profiles was observed. On the circular task, intersaccadic interval duration was shorter in mTBI compared with normal subjects (horizontal: Cohen's D = -0.65; vertical: Cohen's D = -0.75). For reading, absolute saccadic amplitudes (Cohen's D = -0.76) and average forward saccadic amplitudes were lower (Cohen's D = -0.61). Absolute fixation velocity was higher (Cohen's D = 1.02), and overall fixation durations (Cohen's D = 0.58), regression durations (Cohen's D = 0.49), and forward saccadic durations (Cohen's D=0.54) were longer. mTBI participants had more fixations (Cohen's D = 0.54) and regressions per line (Cohen's D = 0.70) and read fewer lines (Cohen's D = -0.38) than normal subjects. On the horizontal ramp task, mTBI participants had lower weighted smooth pursuit gains (Cohen's D = -0.55). On the horizontal step task, mTBI participants had shorter mean fixation times (Cohen's D = -0.55). Conclusions: These results suggest vulnerability of the smooth pursuit and saccadic systems in mTBI. Eye tracking shows promise as an objective, sensitive assessment of damage after mTBI. (ClinicalTrials.gov number, NCT01611194, NCT01925963.).

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.

Stimulation of Critically Ill Patients: Relationship to Sedation.

OBJECTIVES: To describe the number and type of stimulation events and the relationship of stimulation to sedation level in patients receiving mechanical ventilation. METHODS: A 4-hour direct observation was conducted in 103 patients receiving mechanical ventilation. Stimulation events and sedation level before and after the stimulation were documented. Eight categories of stimulation events were developed in a previous pilot study of 36 patients receiving mechanical ventilation. Sedation was measured continuously by using a processed electroencephalographic score (patient state index [PSI]) and intermittently by using the Richmond Agitation-Sedation Scale. RESULTS: Patients were mostly alert/mildly sedated (54.4%) at study enrollment. During the 349 hours of observation, 58.8% of the time included stimulation events. General auditory types of stimulation were most common (41.2% of observed time), followed by respiratory management and tactile family stimulation. For all events, auditory-talking, tactile-general, tactile-noxious, and tactile-highly noxious stimuli were associated with higher PSIs (all P < .001) after stimulation; other stimuli were not. Level of consciousness influenced response to stimuli, with almost all types of stimuli increasing PSI for patients more deeply sedated (PSI < 60) just before the stimuli. However, the effect of stimulation on PSI for more alert patients (PSI > 60) was small and variable. DISCUSSION: Critically ill patients receiving mechanical ventilation are subjected to various forms of auditory and tactile stimulation frequently throughout the day. All types of stimuli increased arousal in patients who were more deeply sedated. The effect of stimulation in patients who were not deeply sedated was minimal and inconsistent.

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.

Patterned feeding experience for preterm infants: study protocol for a randomized controlled trial.

BACKGROUND: Neurobehavioral disabilities occur in 5-15% of preterm infants with an estimated 50-70% of very low birth weight preterm infants experiencing later dysfunction, including cognitive, behavioral, and social delays that often persist into adulthood. Factors implicated in poor neurobehavioral and developmental outcomes are hospitalization in the neonatal intensive care unit (NICU) and inconsistent caregiving patterns. Although much underlying brain damage occurs in utero or shortly after birth, neuroprotective strategies can stop lesions from progressing, particularly when these strategies are used during the most sensitive periods of neural plasticity occurring months before term age. The purpose of this randomized trial is to test the effect of a patterned feeding experience on preterm infants' neurobehavioral organization and development, cognitive function, and clinical outcomes. METHODS: This trial uses an experimental, longitudinal, 2-group design with 120 preterm infants. Infants are enrolled within the first week of life and randomized to an experimental group receiving a patterned feeding experience from the first gavage feeding through discharge or to a control group receiving usual feeding care experience. The intervention involves a continuity of tactile experiences associated with feeding to train and build neuronal networks supportive of normal infant feeding experience. Primary outcomes are neurobehavioral organization as measured by Neurobehavioral Assessment of the Preterm Infant at 3 time points: the transition to oral feedings, NICU discharge, and 2 months corrected age. Secondary aims are cognitive function measured using the Bayley Scales of Infant and Toddler Development, Third Edition at 6 months corrected age, neurobehavioral development (sucking organization, feeding performance, and heart rate variability), and clinical outcomes (length of NICU stay and time to full oral feeding). The potential effects of demographic and biobehavioral factors (perinatal events and conditions of maternal or fetal/newborn origin and immunologic and genetic biomarkers) on the outcome variables will also be considered. DISCUSSION: Theoretically, the intervention provided at a critical time in neurologic system development and associated with a recurring event (feeding) should enhance neural connections that may be important for later development, particularly language and other cognitive and neurobehavioral organization skills. TRIAL REGISTRATION: NCT01577615 11 April 2012.

Effect of four approaches to oral feeding progression on clinical outcomes in preterm infants.

Background. The purpose of this study of preterm infants was to test the effect of four approaches to the time of transition from gavage to full oral feedings, time to discharge, and weight gain during the transition. Methods. A randomized experimental design was used with four intervention groups: early start (32 weeks' postmenstrual age)/slow progressing experience (gradually increasing oral feedings offered per day); early start/maximum experience (oral feedings offered at every feeding opportunity); late start (34 weeks' postmenstrual age)/slow progressing experience; and late start/maximum experience. Results. The analysis included 86 preterm infants. Once oral feedings were initiated, infants in the late start/maximum experience group achieved full oral feeding and were discharged to home significantly sooner than infants in either early start group. Although not significantly different, these infants also achieved these outcomes sooner than infants in the late start/slow progressing experience group. There were no differences in weight gain across groups. Conclusions. Results suggest starting oral feedings later in preterm infants may result in more rapid transition to full oral feedings and discharge although not at early postnatal ages. Provision of a more consistent approach to oral feeding may support infant neurodevelopment and reduce length of hospitalization.

Use of high frequency ultrasound to detect changes in skin integrity: An image evaluation validation procedure.

OBJECTIVES: High frequency ultrasound (HFUS) scanning may be used for prevention, detection and monitoring of pressure ulcers in patients at risk and is amenable for portable, bedside use by a variety of clinicians. Limited data are available about the criteria to determine an ideal image or measures of tissue changes representative of tissue injury. We developed and evaluated criteria for overall image quality and measures of tissue integrity. METHODS: In 40 mechanically ventilated adults in 3 ICUs, 241 HFUS sacral images were evaluated for agreement using criteria for overall image quality and tissue changes (dermal, hypodermal layer thickness and layer density). RESULTS: HFUS sacral images (N=241) were evaluated in three analyses and showed poor agreement in all three analyses using the specific criteria for global quality, however when criteria were collapsed agreement was good to substantial. Evaluator agreement for layer thickness and layer density was also good. CONCLUSIONS: A global rating is adequate for identifying good images. Agreement for measurements of layer thickness and density were also good and may be useful to identify early changes in tissue integrity leading to tissue injury. Additional data are needed concerning the association of changes in layer thickness and layer density to eventual tissue injury.

Differential eye movements in mild traumatic brain injury versus normal controls.

OBJECTIVES: Objective measures to diagnose and to monitor improvement of symptoms following mild traumatic brain injury (mTBI) are lacking. Computerized eye tracking has been advocated as a rapid, user friendly, and field-ready technique to meet this need. DESIGN: Eye-tracking data collected via a head-mounted, video-based binocular eye tracker was used to examine saccades, fixations, and smooth pursuit movement in military Service Members with postconcussive syndrome (PCS) and asymptomatic control subjects in an effort to determine if eye movement differences could be found and quantified. PARTICIPANTS: Sixty Military Service Members with PCS and 26 asymptomatic controls. OUTCOME MEASURES: The diagnosis of mTBI was confirmed by the study physiatrist's history, physical examination, and a review of any medical records. Various features of saccades, fixation and smooth pursuit eye movements were analyzed. RESULTS: Subjects with symptomatic mTBI had statistically larger position errors, smaller saccadic amplitudes, smaller predicted peak velocities, smaller peak accelerations, and longer durations. Subjects with symptomatic mTBI were also less likely to follow a target movement (less primary saccades). In general, symptomatic mTBI tracked the stepwise moving targets less accurately, revealing possible brain dysfunction. CONCLUSIONS: A reliable, standardized protocol that appears to differentiate mTBI from normals was developed for use in future research. This investigation represents a step toward objective identification of those with PCS. Future studies focused on increasing the specificity of eye movement differences in those with PCS are needed.

Effects of hyperbaric oxygen on eye tracking abnormalities in males after mild traumatic brain injury.

The effects of hyperbaric oxygen (HBO2) on eye movement abnormalities in 60 military servicemembers with at least one mild traumatic brain injury (TBI) from combat were examined in a single-center, randomized, double-blind, sham-controlled, prospective study at the Naval Medicine Operational Training Center. During the 10 wk of the study, each subject was delivered a series of 40, once a day, hyperbaric chamber compressions at a pressure of 2.0 atmospheres absolute (ATA). At each session, subjects breathed one of three preassigned oxygen fractions (10.5%, 75%, or 100%) for 1 h, resulting in an oxygen exposure equivalent to breathing either surface air, 100% oxygen at 1.5 ATA, or 100% oxygen at 2.0 ATA, respectively. Using a standardized, validated, computerized eye tracking protocol, fixation, saccades, and smooth pursuit eye movements were measured just prior to intervention and immediately postintervention. Between and within groups testing of pre- and postintervention means revealed no significant differences on eye movement abnormalities and no significant main effect for HBO2 at either 1.5 ATA or 2.0 ATA equivalent compared with the sham-control. This study demonstrated that neither 1.5 nor 2.0 ATA equivalent HBO2 had an effect on postconcussive eye movement abnormalities after mild TBI when compared with a sham-control.

Patient ventilator asynchrony in critically ill adults: frequency and types.

BACKGROUND: Patient ventilator asynchrony (PVA) occurs frequently, but little is known about the types and frequency of PVA. Asynchrony is associated with significant patient discomfort, distress and poor clinical outcomes (duration of mechanical ventilation, intensive care unit and hospital stay). METHODS: Pressure-time and flow-time waveform data were collected on 27 ICU patients using the Noninvasive Cardiac Output monitor for up to 90 min per subject and blinded waveform analysis was performed. RESULTS: PVA occurred during all phases of ventilated breaths and all modes of ventilation. The most common type of PVA was Ineffective Trigger. Ineffective trigger occurs when the patient's own breath effort will not trigger a ventilator breath. The overall frequency of asynchronous breaths in the sample was 23%, however 93% of the sample experienced at least one incident of PVA during their observation period. Seventy-seven percent of subjects experienced multiple types of PVA. CONCLUSIONS: PVA occurs frequently in a variety of types although the majority of PVA is ineffective trigger. The study uncovered previously unidentified waveforms that may indicate that there is a greater range of PVAs than previously reported. Newly described PVA, in particular, PVA combined in one breath, may signify substantial patient distress or poor physiological circumstance that clinicians should investigate.

Maternal attention and preterm infant feeding.

PURPOSE: The purpose of this study was to explore the relationships among the mother's internal working model of feeding, attentional process, feeding behaviors, and responsiveness accounting for maternal psychological distress, which may contribute to preterm infants' feeding difficulties. DESIGN AND METHODS: In this descriptive study, 21 mother-preterm infant dyads were videotaped during feeding. RESULTS: Surprisingly, the internal working model of feeding was a significant negative predictor of maternal feeding behaviors and maternal attention. All other correlations were non-significant. CONCLUSIONS: Given the early timing of the data collection, it is possible that mothers had not developed a frame of reference of their infant as a person. Research to help further understand factors and timing affecting maternal feeding behaviors is needed.

Experimental support that ocular tremor in Parkinson's disease does not originate from head movement.

INTRODUCTION: Our recent report of ocular tremor in Parkinson's disease (PD) has raised considerable controversy as to the origin of the tremor. Using an infrared based eye tracker and a magnetic head tracker, we reported that ocular tremor was recordable in PD subjects with no apparent head tremor. However, other investigators suggest that the ocular tremor may represent either transmitted appendicular tremor or subclinical head tremor inducing the vestibulo-ocular reflex (VOR). The present study aimed to further investigate the origin of ocular tremor in PD. METHODS: Eye movements were recorded in 8 PD subjects both head free, and with full head restraint by means of a head holding device and a dental impression bite plate. Head movements were recorded independently using both a high sensitivity tri-axial accelerometer and a magnetic tracking system, each synchronized to the eye tracker. RESULTS: Ocular tremor was observed in all 8 PD subjects and was not influenced by head free and head fixed conditions. Both magnetic tracking and accelerometer recordings supported that the ocular tremor was fully independent of head position. CONCLUSION: The present study findings support our initial findings that ocular tremor is a fundamental feature of PD unrelated to head movements. Although the utility of ocular tremor for diagnostic purposes requires validation, current findings in large cohorts of PD subjects suggest its potential as a reliable clinical biomarker.

Responses to noxious stimuli in sedated mechanically ventilated adults.

OBJECTIVE: To determine the effect of sedation on physiologic responses and comfort before, during and after a noxious stimulus (endotracheal tube suctioning). METHODS: The sample was a subset of a larger, longitudinal descriptive study, blood for endorphins and saliva for alpha-amylase were obtained before and after suctioning. Heart rate (HR), respiration rate (RR), oxygen saturation (SPO2), and arm and leg actigraphy were continuously recorded. RESULTS: 67 subjects from medical and surgical ICUs were primarily deeply (37%) or mildly sedated (54%) prior to suctioning. Alpha-amylase increased post suctioning (p = 0.04); endorphins did not change (p = 0.58). Neither were modified by sedation. There were no changes in HR, RR or SPO2 post suctioning. Arm (p = 0.007) and leg actigraphy (p = 0.057) changed from baseline and depended on sedation level (p = 0.0005). CONCLUSIONS: While a stress marker did increase during suctioning, only the measure of patient arm movement was significantly affected by sedation level.

Effect of alertness level and backrest elevation on skin interface pressure.

INTRODUCTION: Critically ill patients may experience reduced mobility and sensation related to various pharmacologic therapies and treatments, making this patient population especially susceptible to pressure ulcers. An alert patient may be better able to reposition in response to discomfort, therefore preventing the development of pressure ulcers. However, little is known about the effect of an individual's alertness level on skin interface pressures. This study describes the effect of alertness level and backrest elevation on skin interface pressures. MATERIALS AND METHODS: Fifty healthy participants were recruited from the Virginia Commonwealth University (Richmond, VA) population. Participants simulated each of 2 alertness levels (sedated or alert) while in 3 backrest elevations (30°, 45°, or 60°). Activity level, backrest elevation, and interface pressures were recorded continuously for 30 seconds. Random effects models were used to examine the effects of alertness level and backrest elevation on average and peak pressure. Participants had a mean age of 30 and 82% were female. RESULTS: There was a significant interaction between alertness level and angle as related to average pressure (P < 0.0001) and peak pressure (P < 0.0001). Increases in backrest elevation increased average pressure and peak pressure. Interface pressures were generally greater when participants were simulating the alert state. CONCLUSION: These findings may indicate that interface pressure is a poor indicator of patient discomfort. Higher body mass index (BMI) was associated with higher average pressure (P < 0.0001), but lower peak pressure (P < 0.0001), suggesting better pressure distribution across the patient's body area. These findings are similar to previous studies in which low BMI is associated with increased pressure ulcer risk. .