Backrest Positions Research Articles

Effect of Different Backrest Positions' Degrees on Hemodynamic Stability for Mechanically Ventilated Patients

Effect of Different Backrest Positions' Degrees on Hemodynamic Stability for Mechanically Ventilated Patients

Influence of backrest angle on swallowing musculature activity and physical strain during the head lift exercise in elderly women compared with young women.

The head lift exercise (HLE) is the most common exercise for strengthening the swallowing musculature in clinical situations. This study investigated whether a change in the backrest angle of a bed influences swallowing musculature activity and physical strain during the HLE and whether it can generate an appropriate exercise load for swallowing musculature activity for older women compared with younger women. Participants were 10 elderly women and 10 young women, each of whom performed the HLE with a backrest randomly angled at 0°, 15°, 30° and 45°. The activity of the suprahyoid, infrahyoid and sternocleidomastoid muscles was assessed with electromyography. The perception of fatigue was measured with the Borg Rating of Perceived Exertion Scale. The activity of the infrahyoid and sternocleidomastoid muscles in elderly women was significantly lower when the angle of the backrest was raised to 45° vs 0°. In both groups, the Borg rating decreased significantly at the 30° and 45° backrest positions vs the 0° and 15° positions. The activity required for the suprahyoid and infrahyoid muscles in elderly women at a 30° backrest position was almost equal to the activity required by these muscles in young women at a 0° backrest position. In elderly women, it is possible that the HLE with the backrest at a 30° angle may be easier and provide a more appropriate exercise load for strengthening the swallowing muscles.

Elevation of the head during intensive care management in people with severe traumatic brain injury.

Traumatic brain injury (TBI) is a major public health problem and a fundamental cause of morbidity and mortality worldwide. The burden of TBI disproportionately affects low- and middle-income countries. Intracranial hypertension is the most frequent cause of death and disability in brain-injured people. Special interventions in the intensive care unit are required to minimise factors contributing to secondary brain injury after trauma. Therapeutic positioning of the head (different degrees of head-of-bed elevation (HBE)) has been proposed as a low cost and simple way of preventing secondary brain injury in these people. The aim of this review is to evaluate the evidence related to the clinical effects of different backrest positions of the head on important clinical outcomes or, if unavailable, relevant surrogate outcomes. To assess the clinical and physiological effects of HBE during intensive care management in people with severe TBI. We searched the following electronic databases from their inception up to March 2017: Cochrane Injuries' Specialised Register, CENTRAL, MEDLINE, Embase, three other databases and two clinical trials registers. The Cochrane Injuries' Information Specialist ran the searches. We selected all randomised controlled trials (RCTs) involving people with TBI who underwent different HBE or backrest positions. Studies may have had a parallel or cross-over design. We included adults and children over two years of age with severe TBI (Glasgow Coma Scale (GCS) less than 9). We excluded studies performed in children of less than two years of age because of their unfused skulls. We included any therapeutic HBE including supine (flat) or different degrees of head elevation with or without knee gatch or reverse Trendelenburg applied during the acute management of the TBI. Two review authors independently checked all titles and abstracts, excluding references that clearly didn't meet all selection criteria, and extracted data from selected studies on to a data extraction form specifically designed for this review. There were no cases of multiple reporting. Each review author independently evaluated risk of bias through assessing sequence generation, allocation concealment, blinding, incomplete outcome data, selective outcome reporting, and other sources of bias. We included three small studies with a cross-over design, involving a total of 20 participants (11 adults and 9 children), in this review. Our primary outcome was mortality, and there was one death by the time of follow-up 28 days after hospital admission. The trials did not measure the clinical secondary outcomes of quality of life, GCS, and disability. The included studies provided information only for the secondary outcomes intracranial pressure (ICP), cerebral perfusion pressure (CPP), and adverse effects.We were unable to pool the results as the data were either presented in different formats or no numerical data were provided. We included narrative interpretations of the available data.The overall risk of bias of the studies was unclear due to poor reporting of the methods. There was marked inconsistency across studies for the outcome of ICP and small sample sizes or wide confidence intervals for all outcomes. We therefore rated the quality of the evidence as very low for all outcomes and have not included the results of individual studies here. We do not have enough evidence to draw conclusions about the effect of HBE during intensive care management of people with TBI. The lack of consistency among studies, scarcity of data and the absence of evidence to show a correlation between physiological measurements such as ICP, CCP and clinical outcomes, mean that we are uncertain about the effects of HBE during intensive care management in people with severe TBI.Well-designed and larger trials that measure long-term clinical outcomes are needed to understand how and when different backrest positions can affect the management of severe TBI.

Biomechanics of elite recumbent handcycling: a case study

In the presented research, a kinematic and electromyographic study was performed on one world-class male elite handbiker (UCI class H3.2). Activity of 14 muscles of the upper body were measured with surface electromyography (EMG), and a motion analysis of the athlete’s movement was performed concurrently for different backrest positions, crank lengths, and crank heights at three power levels (130, 160 and 190 W). Kinematics in terms of elbow and wrist angle, muscular on-off timing, EMG amplitudes, and integrated EMG were calculated. Results showed that little changes occurred for kinematic parameters and changes in position led to a shift in muscular timing. However, no indication for immediate improvement to the athlete’s preferred original position could be observed.

Influence of Different Seating and Crank Positions on Muscular Activity in Elite Handcycling - A Case Study

Due to rising public focus scientific analysis of performance parameters is getting more and more important in paralympic sports. Several studies have been performed to investigate different design parameters of handcycles (e.g. crank length) already; however, most of those were done with able-bodied subjects, widely unfamiliar to handcycling. In this study bilateral surface electromyography (sEMG) of several muscles of the upper body and arms of an elite handcyclist (multiple medal-winner in Paralympic Games and World Championships) is performed with different crank lengths, crank positions and backrest positions at power levels of 130, 160 and 190W resulting in a total of 22 measurements. sEMG data were recorded bilaterally at a recording frequency of 1000Hz using Ag/AgCl electrodes. Concurrently the crank position was acquired with ten Vicon Bonita infrared cameras recording at 100Hz. EMG data were rectified, smoothed and normalized to crank-cycle duration (0-360 deg) for each single crank-cycle. Phases of activity for each muscle (i.e. EMG amplitude exceeds 30% of maximum amplitude) and integrated EMG (iEMG) as an indicator for net muscular e ort were calculated. Results showed that amplitude and iEMG were higher for higher power output and shorter cranks, crank and backrest position influenced several muscles but results were always similar for similar shoulder-crank-distances. It could be shown, that muscular effort is clearly influenced by the handcycle parameters investigated and that these measurements can be used to individually optimize the position in a handcycle with regard to muscular effort.

The effect of crank position and backrest inclination on shoulder load and mechanical efficiency during handcycling

Handbikes come in different models and setups, but only limited knowledge is available on the handbike-user interface. The aim of this study was to identify optimal handbike setups, assuming that in such a setup mechanical efficiency is high, while shoulder load is low. Thirteen subjects with a spinal cord injury (paraplegia) performed handcycling with different handbike setups at constant power output: four crank positions (two distances, two heights) and four backrest inclinations. The O2-consumption, kinetics, and kinematics were measured to calculate mechanical efficiency and shoulder load (glenohumeral contact force, net shoulder moments, and rotator cuff force). The analysis showed that more upright backrest positions resulted in lower shoulder load compared with the most reclined position [glenohumeral contact force (260 vs 335 N), supraspinatus (14.4% vs 18.2%), and infraspinatus force (5.4% vs 9.8%)], while there was no difference in efficiency. Except for a reduction in subscapularis force at the distant position, no differences in shoulder load or efficiency were found between crank positions. Recreational handbike users, who want to improve their physical capacity in a shoulder-friendly way, should set up their handbike with a more upright backrest position and a distant crank placement.

Effects of backrest positioning and gear ratio on nondisabled subjects' handcycling sprinting performance and kinematics

Backrest position is a significant parameter in handcycling that one must consider when seeking to optimize the user-to-chair interface. We studied the effects of backrest position on handcycle propulsion kinematics. Ten nondisabled partici pants with no handcycle propulsion experience repeated an 8 s sprint with three backrest positions (backrest angle between 45 degrees and 50 degrees to the horizontal, backrest angle between 65 degrees and 70 degrees to the horizontal, and without backrest) and three gear ratios (GRs) (GR22/21 = low, GR32/21 = medium, and GR44/21 = high). We used three-dimensional movement analysis to calculate the average maximal velocity, cycle frequency, and angle parameters for the arms and trunk. Our results showed statistically higher trunk flexion/extension (p < 0.001) and maximal velocity (p < 0.001) when a backrest was not used. Moreover, these differences were accentuated as the GR increased (GR44/21). Our results suggest that handcycle users with unimpaired upper-body and trunk function can improve handcycling performance by removing the backrest. Nevertheless, future studies on specific groups of subjects with spinal cord injury should be conducted.

Effect of Backrest Elevation on the Development of Ventilator-Associated Pneumonia

Ventilator-associated pneumonia is a common complication of mechanical ventilation. Backrest position and time spent supine are critical risk factors for aspiration, increasing the risk for pneumonia. Empirical evidence of the effect of backrest positions on the incidence of ventilator-associated pneumonia, especially during mechanical ventilation over time, is limited. To describe the relationship between backrest elevation and development of ventilator-associated pneumonia. A nonexperimental, longitudinal, descriptive design was used. The Clinical Pulmonary Infection Score was used to determine ventilator-associated pneumonia. Backrest elevation was measured continuously with a transducer system. Data were obtained from laboratory results and medical records from the start of mechanical ventilation up to 7 days. Sixty-six subjects were monitored (276 patient days). Mean backrest elevation for the entire study period was 21.7 degrees . Backrest elevations were less than 30 degrees 72% of the time and less than 10 degrees 39% of the time. The mean Clinical Pulmonary Infection Score increased but not significantly, and backrest elevation had no direct effect on mean scores. A model for predicting the Clinical Pulmonary Infection Score at day 4 included baseline score, percentage of time spent at less than 30 degrees on study day 1, and score on the Acute Physiology and Chronic Health Evaluation II, explaining 81% of the variability (F=7.31, P=.003). Subjects spent the majority of the time at backrest elevations less than 30 degrees . Only the combination of early, low backrest elevation and severity of illness affected the incidence of ventilator-associated pneumonia.

Monitoring Pulmonary Artery Pressure

cialist at UCLA Medical Center and assistant clinical professor at the UCLA School of Nursing in Los Angeles, Calif. A variety of backrest positions may be used that do not compromise the accuracy of measurements of pulmonary artery pressure. Backrest elevations of 0°, 30°, 45°, and 60° with the patient supine (back flat against bed surface) do not affect the accuracy of measurements of pulmonary artery pressure if the hemodynamic monitoring system has been properly referenced and zeroed. As the patient moves from flat to higher levels of backrest elevation, the reference level must remain horizontal to the phlebostatic axis in order for measurements of pulmonary artery pressure to remain accurate (Figure 2).

Nurses’ Accuracy in Estimating Backrest Elevation

Positioning patients is a key component of nursing care and can affect their morbidity and mortality. The Centers for Disease Control and Prevention recommend that patients receiving mechanical ventilation have the head of the bed elevated 30 degrees to 45 degrees to prevent nosocomial pneumonia. However, use of higher backrest positions for critically ill patients is not common nursing practice. Backrest elevation may be affected by the accuracy of nurses' estimates of patients' positions. To determine the difference between nurses' estimates of bed angles and measured bed angles and to describe the relationship between nurses' characteristics and the accuracy of their estimates. A convenience sample of 67 nurses attending the 1999 American Association of Critical-Care Nurses National Teaching Institute and Critical Care Exposition in New Orleans, La. Each subject provided demographic information and estimated 3 bed angles. The angles were preselected by using a random number table. Summary statistics were used and were categorized according to the demographic information provided by participants. Estimated angles were correlated with measured angles, and accuracies in estimating angles were correlated with demographic characteristics. Nurses were accurate in estimating bed angles (correlation, 0.8488). Demographic information, including sex, age, years of practice, years of critical care practice, basic education, highest educational level, and present position had no relationship to accuracy. Nurses are able to estimate backrest elevation accurately. Other explanations are needed to understand why recommendations for backrest elevation are not used in practice.

Use of backrest elevation in critical care: a pilot study

Use of lower backrest positions occurs frequently and is a factor in the development of ventilator-associated pneumonia. To determine the usual bed elevation and backrest position in a medical intensive care unit and their relationship to hemodynamic status and enteral feeding. Data were collected in a 12-bed medical respiratory intensive care unit for 2 months. A protractor was used to measure the elevation of the head of the bed. Hemodynamic status was defined by systolic, diastolic, and mean arterial blood pressure measurements retrieved from each patient's flow sheet. The sample included 347 measurements of 52 patients. Mean backrest elevation was 22.9 degrees, and 86% of patients were supine. Backrest position differed significantly (P = .005) among nursing shifts (days, evenings, nights) but not for systolic (r = -0.04, P = .49), diastolic (r = 0.01, P = .83), or mean arterial blood pressure (r = -0.01, P = .84). Backrest elevation did not differ significantly between patients who were receiving enteral feedings and patients who were not (P = .23) or between patients receiving intermittent versus continuous nutrition (P = .22). Use of higher levels of backrest elevation (> or = 30 degrees) is minimal and is not related to use of enteral feeding or to hemodynamic status. The rationale for using lower backrest positions for critically ill patients may be based on convenience, the patient's comfort, or usual patterns in the unit. However, the dangers of supine positioning and its relationship to aspiration and ventilator-associated pneumonia should not be minimized.

Effect of Backrest Position on Intracranial and Cerebral Perfusion Pressures

Prevention of secondary injury resulting from increased intracranial pressure (ICP) and the promotion of adequate cerebral blood flow are major concerns of health care professionals caring for the neurologic patient. For the past two decades studies have indicated raising the head of the bed lowers ICP. However, when perfusion pressure has been measured along with ICP, results have been conflicting. Some investigators found cerebral perfusion pressure (CPP) decreased with head elevation; others found no change. This study examined the effect of four backrest positions (flat, head elevated 30 degrees, head elevated 30 degrees with knee gatch elevated and reverse Trendelenberg) on ICP, CPP and transcranial doppler flow velocities in four subjects. Each was placed in the flat position for 15 minutes followed by 15 minutes in one of the three randomly assigned elevated backrest positions. Findings suggest backrest position should be individually assigned after analysis of the response of the ICP, CPP and blood flow velocities to that position.