Impact Of Postural Changes Research Articles

Noninvasive Assessment of Temporal Dynamics in Sympathetic and Parasympathetic Baroreflex Responses.

The baroreflex system is crucial for cardiovascular regulation and autonomic homeostasis. A comprehensive assessment requires understanding the simultaneous temporal dynamics of its multiple functional branches, which traditional methods often overlook. To develop and validate a noninvasive method for simultaneously assessing the temporal dynamics of sympathetic and parasympathetic baroreflexes using pulse contour analysis and the sequence method. Beat-to-beat blood pressure and ECG recordings were analyzed from 55 preoperative cardiothoracic surgery patients in the supine position and 21 subjects from the EUROBAVAR dataset in both supine and standing positions. Systolic arterial pressure (SAP), interbeat interval (IBI), cardiac output (CO), myocardial contraction (dP/dt max ), and systemic vascular resistance (SVR) were estimated using pulse contour analysis. Baroreflex sensitivity (BRS) was calculated via the sequence method and correlated with hemodynamic and heart rate variability (HRV) parameters. Parasympathetic BRS for IBI was correlated with the root mean square of successive differences of ECG RR intervals (RMSSD-HRV) at 0-beat delay. Sympathetic BRS for SVR strongly correlated with SVR, CO, and RMSSD-HRV, particularly at 3-beat delay, and was uniquely associated with SAP at 1-beat delay. Sympathetic BRS for dP/dt max correlated with dP/dt max at 1-beat delay. In contrast, BRS for CO correlated with CO and SVR at 0- and 3-beat delays. Postural changes mainly affected parasympathetically-mediated BRS for IBI and, to a lesser extent, the sympathetic vascular and myocardial branches. This method effectively captures multiple baroreflex responses and their temporal dynamics, revealing distinct autonomic mechanisms and the impact of postural changes. Further validation is warranted.

PS-C03-12: FINGER-TO-TOE PULSE WAVE VELOCITY IN RESPONSE TO SITTING POSITION

Objective: Aortic stiffness is a non-traditional risk factor for cardiovascular disease and mortality and is associated with increased central pulse pressure. It is generally measured by carotid-femoral pulse wave velocity (PWV) in a supine position. We hypothesized that, in a sitting position, the additional hydrostatic pressure exerted on the vascular wall could represent a vascular stress test. Two alternative methods can now estimate aortic stiffness and can be used conveniently in different positions: 1) brachial pulse wave analysis approach used by Mobil-O-Graph and 2) transit time approach using finger-to-toe PWV by photoplethysmography with the pOpmetre. The aim of the present study is to determine the impact of postural changes on PWV and central blood pressure estimation using these two distinct methods. Design and method: Central blood pressure and PWV were assessed in 20 healthy subjects using Mobil-O-Graph (PWV-M) and pOpmetre (PWV-pop) in three positions: supine in bed, supine in reclining chair and sitting. Central systolic blood pressure (SBP) was determined by calibration of brachial systolic and diastolic blood pressures by both methods (SBP-M and SBP-pop). Generalized estimating equations were used for analysis. Results: The PWV-M remained relatively constant and generally independent of the position (5.5 ± 1.0, 5.3 ± 1.0 and 5.5 ± 1.0 m/s). While PWV-M and PWV-pop were similar in the supine position (5.5 ± 1.0 vs 5.4 ± 1.3 m/s, P = NS), PWV-pop increased very significantly to 5.9 ± 1.5 m/s in supine in reclining chair position (P = 0.04), and to 9.2 ± 1.7 m/s in sitting position (P < 0.001). Central blood pressure estimation remained similar for SBP-M (110.2 ± 10.3 vs 106.9 ± 10.5 vs 108.8 ± 11.1 mmHg, P = NS) and for SBP-pop (107.7 ± 10.4 vs 110.3 ± 9.6 vs 109.5 ± 9.9 mmHg, P = NS). Conclusions: These results suggest that estimated PWV by brachial pulse wave analysis remains robust independent of position. However, the estimated finger-to-toe PWV by pulse transit time increases remarkably with the imposition of hydrostatic pressure on the vascular wall. We conclude that the finger-to-toe PWV may provide the opportunity to evaluated vascular wall property in a dynamic fashion using postural changes as a stress test.

0344 Use of an Adjustable Bed Base Improves Sleep Quality and Duration

Abstract Introduction The positional adjustment of a bed can potentially contribute to better sleep and alleviation of discomfort associated with a variety of medical conditions. As most studies in this area have focused on inclined sleeping for therapeutic purposes, understanding the impact of postural change on improving sleep among healthy individuals requires further research. This study compared sleep in an inclined position on an adjustable bed base to participants’ prior sleep on their original bed bases. Methods Healthy adults (61% female, ages 23-60) willing to sleep at an incline participated in an 8-week field study, using a pre-post intervention design. During the 4-week baseline period, participants used their regular bed base at home. During the 4-week intervention period, they used the Mattress Firm 600 Adjustable Base at home with head and/or feet raised (not flat). Sleep was measured objectively using SleepScore Max every night and by daily and pre-post self-report. Multilevel regression and paired t-tests were used to test for statistical significance. Results There were over 1,100 nights of tracked sleep across 26 participants. Objective sleep measurements showed many nightly improvements during the intervention compared to baseline: increased time in bed (+21 minutes, p=.003), total sleep time (+21 minutes, p=.001), and REM (+5 minutes, p=.009); less WASO, both in duration (-3 minutes, p=.046) and proportion of the night (p=.015); fewer awakenings (p=.034); and better sleep maintenance (p=.014). Improvements also were observed in 3 objective sleep quality measures: SleepScore, BodyScore, and MindScore (ps<.05).Self-report measures revealed greater comfort and enjoyment when using the adjustable base, as well as perceived improvement in a variety of outcomes, including time to fall asleep and falling asleep within a preferred amount of time, ability to sleep through the night, sleep duration, sleep quality and satisfaction, and feeling more rested in the morning (ps<.05). Conclusion Objectively-measured sleep and self-reported sleep improved in duration and quality when using the adjustable base compared to healthy adults’ original bed bases. Furthermore, qualitative and quantitative self-report results suggested that the intervention was perceived as a comfortable and enjoyable experience. Support (If Any) Mattress Firm INC

F wave in restless legs syndrome, as an electrophysiological response of clinical relief

ABSTRACT Objective The study aimed to evaluate the impact of postural changes on the F wave-related parameters and whether those changes were associated with clinical relaxation, which was achieved in restless legs syndrome patients with standing up. Methods F wave duration (FWD), compound muscle action potential duration (CMAPD), and FWD/CMAPD ratio were evaluated in supine and upward positions in 18 restless legs syndrome patients and compared with 18 age and gender-matched healthy volunteers. Results FWD/CMAPD was significantly higher for the tibial nerve at supine position (p = 0.043) but not at upright position (p = 0.206) and for ulnar nerve, both at supine (p = 0.007) and upright positions (p = 0.023) in RLS patients compared to controls. Ulnar FWD decreased significantly at the upright position in both control and RLS patients (p = 0.035, p = 0.028, respectively). CMAPD decreased only in the control group with standing up for both ulnar and tibial nerves (p = 0.048, p = 0.017, respectively). Discussion Ulnar and tibial FWD/CMAPD ratios increased in RLS patients compared to controls. However, FWD/CMAPD was not affected by the posture within the groups. Postural change seems to be a factor that decreased ulnar FWD both in RLS patients and the control group. Ulnar and tibial CMAPD reduced only in healthy controls with an upright position. Tibial and ulnar FWD/CMAPD ratios are favorable electrophysiological parameters diagnosing RLS. The tibial FWD/CMAPD ratio loses its significance only when the patient stands up, reflecting the clinical relief achieved with the postural change.

Clinical impact of repolarization changes in supine versus upright body position.

The impact of postural changes on various electrocardiography (ECG) characteristics has only been assessed in a few small studies. This large prospective trial was conducted to confirm or refute preliminary data and add important results with immediate impact on daily clinical practice. ECGs in supine and upright position from 1028 patients were analyzed. Evaluation was made according to changes in T-wave vector and direction, ST-segment deviation, heart rate, QT interval and QTc interval was performed. Findings were correlated with the medical history of patients. Positional change from supine to upright resulted in a significantly increased heart rate (8.05 ± 7.71 bpm) and a significantly increased QTc interval after Bazetts (18 ± 23.45 ms) and Fridericas (8.84 ± 17.30) formula. In the upright position significantly more T-waves turned negative (14.7%) than positive (5.7%). ST elevation was recorded in only 0.4% and ST depression in not more than 0.2% of all patients. The majority of the patients do not show significant morphological changes in their ECG by changing the body position from supine to upright. Changes of QTc time instead, are significant and the interval might be overestimated in upright. Therefore assessment of the QTc interval should strictly be done in a supine position.

Systematic Review of Postural Assessment in Individuals With Obstructive Respiratory Conditions: MEASUREMENT AND CLINICAL ASSOCIATIONS.

Changes in posture in individuals with an obstructive respiratory disease have been reported, but the extent of these deviations and their clinical significance is not well understood. This study aimed to systematically review the literature of the skeletal structural alignment in children and adults with an obstructive respiratory disease, describe the measurement techniques used, and determine the clinical relevance of any alternations. Observational cohort or cross-sectional studies of postural assessment were identified, with 2 reviewers independently assessing study quality. A total of 18 studies were included, 12 in cystic fibrosis (CF), 5 in asthma, and 1 in chronic obstructive pulmonary disease (COPD). The overall quality assessment rating was 12.6 out of 16. Increased thoracic kyphosis or scoliosis was found in both children and adults with CF. Increased shoulder protraction and elevation were evident in asthma and COPD, although changes in spinal curvature were variable. The clinical impact of postural changes was diverse, with an inconsistent influence on lung function. A mix of methods was applied for postural assessment. Skeletal structural malalignment appears to be present in some individuals with an obstructive respiratory disease, although the extent of alterations and its clinical impact is variable. Photogrammetry is used to provide a comprehensive assessment of posture in these populations.

Effects of posture on chest-wall configuration and motion during tidal breathing in normal men.

[Purpose] The purpose of this study was to clarify the impact of postural changes during tidal breathing on the configuration and motion of chest-wall in order to further breathing motion evaluation. [Subjects and Methods] Chest-wall configuration and motion in the supine, right lateral, and sitting positions were measured using optoelectronic plethysmography in 15 healthy adult men. [Results] The anteroposterior diameters of the chest wall were significantly lower in the supine position for the pulmonary and abdominal rib cages, whereas the mediolateral diameters in the lateral position were lowest for the abdominal rib cage. Regarding chest-wall motion, both craniocaudal and anteroposterior motions of the anterior surface of the pulmonary and abdominal rib cages were significantly greater in the sitting position. Regarding motion of the left lateral abdominal rib cage, lateral motion was greatest in the lateral position. [Conclusion] Chest-wall configuration and motion changed according to posture in healthy men, particularly in the pulmonary and abdominal rib cages.

The effect of postural adjustment on the thermal environment of greater snow goose goslings

This study examines how changing from a standing to a sitting posture influences the thermal environment of greater snow goose goslings (Chen caerulescens atlantica). This was investigated by estimating the standard operative temperature of four heated taxidermic mounts (3, 10, 20, and 30 d old) exposed to various wind velocities (0-5 m/s) and ground (16-23°C) and air (0-15°C) temperatures, in three orientations (head, flank, or tail toward the wind) and two postures (sitting and standing). Changes in posture influenced both conductive and convective heat exchanges. At low wind speeds, sitting on the sand reduced the standard operative temperature of goslings, while at high wind speeds sitting enhanced this temperature index. We calculated that a net thermal gain would be obtained by sitting on cold sand at air temperatures of 5, 10, and 15°C when the wind speed exceeded 3 m/s for most orientations toward the incoming wind. However, this critical wind speed would be 23% lower following a 7°C increase in ground temperature. Our study suggests that postural changes can have important consequences on goslings' thermal environment. It also stresses the importance of considering the synergistic impact of conductive and convective heat transfer processes, when studying the impact of postural changes on thermal environments.