Effect Of Postural Changes Research Articles

Effect of Postural Changes on Cardiorespiratory Coordination in Humans

In this study we assessed the effect of body postural changes from the supine (Sup) to the upright (Up) position on the magnitude and phase of respiratory sinus arrhythmia (RSA) and the phase-locking between the heart rhythm and respiration. In eight healthy human subjects, electrocardiograms (ECG) and respiratory signals were recorded. The magnitude and phase of RSA were evaluated by selective averaging of R-R interval changes from multiple respiratory cycles over the respiratory phase. For the assessment of cardiorespiratory coordination, we analyzed the phase-locking between heart rate, computed from R-R intervals of ECG, and respiratory rate, computed from intervals of inspiratory onsets of respiration, using Hilbert transform. A significant decrease in the magnitude of RSA and percentage and duration of phase-locking between heart rate and respiratory rate was observed during Up as compared to Sup. Further, there was a significant increase in the phase of RSA during Up as compared to Sup. In conclusion, measures of RSA and interaction between cardiac and respiratory rhythms are affected by body posture in humans.

Effect of Postural Changes on Cardiorespiratory Coordination in Humans

Effect of Postural Changes on Cardiorespiratory Coordination in Humans

Assessment of macro‐ and microcirculation in contemporary critical limb ischemia

A paucity of data exists regarding manifestations of macro- and microcirculation in contemporary critical limb ischemia (CLI). The aim of this study was (1) to evaluate the differences in foot circulation based on angiographic findings, (2) to clarify the relationship between macro- and microcirculation, and (3) to investigate the effects of postural changes on micro as well as macrocirculation between the supine position to the dependent position. A total of 40 critically ischemic limbs in 29 patients were included in this study. Noninvasive evaluation of macrocirculation, based on the ankle brachial index (ABI) and ankle pressure, and microcirculation, using skin perfusion pressure (SPP), was performed in both the supine and dependent positions. There was no significant difference in macro- and microcirculations between any angiographical involvements. In the supine position, dorsal SPP correlated significantly with ABI (P = 0.021, r = 0.363) and ankle-pressure (P = 0.001, r = 0.495), whereas plantar SPP failed to correlate with ABI (P = 0.198, r = 0.208) or ankle-pressure (P = 0.185, r = 0.214). In the dependent position, however, SPP showed no significant correlation with ABI and ankle pressure. Postural change from the supine to dependent position yielded a significant increase in SPP (dorsal: 37.2 ± 16.2 to 77.9 ± 17.7 mm Hg, P < 0.001; plantar: 33.6 ± 17.3 to 75.7 ± 18.3 mm Hg, P < 0.001) as well as ABI and ankle-pressure (ABI: 0.70 ± 0.35 to 0.78 ± 0.42, P = 0.003; ankle-pressure; 108 ± 61 to 111 ± 60 mm Hg, P = 0.038). The effect of postural change on SPP showed no difference between patients with and without any clinical and angiographical complications. Of microcirculation assessed, only dorsal SPP correlated significantly with macrocirculation in the supine position. Furthermore, postural change from the supine to dependent position produced a dramatic improvement in microcirculation due to the effects of gravity.

Reflecting on posture

Cardiovascular parameters are most often assessed at rest, and in many cases in the supine position. This generally facilitates measurement procedures and obviates the need to account for external and usually complex confounding factors, other than those related to the inherent physiology being investigated. Although the supine resting position may be relevant for some part of circadian living, a large part of human activity is characterized by locomotion and the upright posture. Physiological adaptations to locomotion are studied under controlled conditions and at varying degrees of exercise. However, although primary measures of basic physiological quantities (e.g. stroke volume) can be obtained with some level of confidence at rest in supine position, it becomes extremely difficult to measure them during exercise, and so they are generally derived from other measurable quantities, with the associated errors. Notwithstanding this, the large body of work done so far on the physiological response to exercise has been extremely beneficial in elucidating both underlying and adaptive mechanisms for the function of the circulatory system. On the other hand, assessment of the changes occurring in cardiovascular variables when shifting from supine to standing is the procedure most commonly adopted to explore the response of cardiovascular control mechanisms to gravitational challenges, both when investigating physiological adaptations to the upright posture in healthy individuals and when assessing alterations in cardiovascular regulation in patients with a variety of diseases.

Quantitative cardiovascular magnetic resonance in pregnant women: cross-sectional analysis of physiological parameters throughout pregnancy and the impact of the supine position.

BackgroundThere are physiological reasons for the effects of positioning on hemodynamic variables and cardiac dimensions related to altered intra-abdominal and intra-thoracic pressures. This problem is especially evident in pregnant women due to the additional aorto-caval compression by the enlarged uterus. The purpose of this study was to investigate the effect of postural changes on cardiac dimensions and function during mid and late pregnancy using cardiovascular magnetic resonance (CMR).MethodsHealthy non-pregnant women, pregnant women at 20th week of gestation and at 32nd week of gestation without history of cardiac disease were recruited to the study and underwent CMR in supine and left lateral positions. Cardiac hemodynamic parameters and dimensions were measured and compared between both positions.ResultsFive non-pregnant women, 6 healthy pregnant women at mid pregnancy and 8 healthy pregnant women at late pregnancy were enrolled in the study. In the group of non-pregnant women left ventricular (LV) cardiac output (CO) significantly decreased by 9% (p = 0.043) and right ventricular (RV) end-diastolic volume (EDV) significantly increased by 5% (p = 0.043) from the supine to the left lateral position. During mid pregnancy LV ejection fraction (EF), stroke volume (SV), left atrium lateral diameter and left atrial supero-inferior diameter increased significantly from the supine position to the left lateral position: 8%, 27%, 5% and 11%, respectively (p < 0.05). RV EDV, SV and right atrium supero-inferior diameter significantly increased from the supine to the left lateral position: 25%, 31% and 13% (p < 0.05), respectively. During late pregnancy a significant increment of LV EF, EDV, SV and CO was observed in the left lateral position: 11%, 21%, 35% and 24% (p < 0.05), respectively. Left atrial diameters were significantly larger in the left lateral position compared to the supine position (p < 0.05). RV CO was significantly increased in the left lateral position compared to the supine position (p < 0.05).ConclusionsDuring pregnancy positional changes affect significantly cardiac hemodynamic parameters and dimensions. Pregnant women who need serial studies by CMR should be imaged in a consistent position. From as early as 20 weeks the left lateral position should be preferred on the supine position because it positively affects venous return, SV and CO.

Effect of Posture Change on the Geometric Features of the Healthy Carotid Bifurcation

Segmented cross-sectional MRI images were used to construct 3-D virtual models of the carotid bifurcation in ten healthy volunteers. Geometric features, such as bifurcation angle, internal carotid artery (ICA) angle, planarity angle, asymmetry angle, tortuosity, curvature, bifurcation area ratio, ICA/common carotid artery (CCA), external carotid artery (ECA)/CCA, and ECA/ICA diameter ratios, were calculated for both carotids in two head postures: 1) the supine neutral position; and 2) the prone sleeping position with head rotation to the right ( ∼ 80°). The results obtained have shown that head rotation causes 1) significant variations in bifurcation angle [32% mean increase for the right carotid (RC) and 21% mean decrease for the left carotid (LC)] and internal carotid artery angle (97% mean increase for the RC, 43% mean decrease for the LC); 2) a slight increase in planarity and asymmetry angles for both RC and LC; 3) minor and variable curvature changes for the CCA and for the branches; 4) slight tortuosity changes for the braches but not for the CCA; and 5) unsubstantial alterations in area and diameter ratios (percentage changes %). The significant geometric changes observed in most subjects with head posture may also cause significant changes in bifurcation hemodynamics and warrant future investigation of the hemodynamic parameters related to the development of atherosclerotic disease such as low oscillating wall shear stress and particle residence times.

Postural constraints on movement variability.

Movements are inherently variable. When we move to a particular point in space, a cloud of final limb positions is observed around the target. Previously we noted that patterns of variability at the end of movement to a circular target were not circular, but instead reflected patterns of limb stiffness-in directions where limb stiffness was high, variability in end position was low, and vice versa. Here we examine the determinants of variability at movement end in more detail. To do this, we have subjects move the handle of a robotic device from different starting positions into a circular target. We use position servocontrolled displacements of the robot's handle to measure limb stiffness at the end of movement and we also record patterns of end position variability. To examine the effect of change in posture on movement variability, we use a visual motor transformation in which we change the limb configuration and also the actual movement target, while holding constant the visual display. We find that, regardless of movement direction, patterns of variability at the end of movement vary systematically with limb configuration and are also related to patterns of limb stiffness, which are likewise configuration dependent. The result suggests that postural configuration determines the base level of movement variability, on top of which control mechanisms can act to further alter variability.

When and How to Investigate the Patient with Headache

The common complaint of headache usually has a benign cause, most often a primary headache syndrome. The history and neurologic and general physical examinations usually permit a definitive diagnosis. When in doubt, diagnostic testing is indicated. Certain historical and examination findings increase the likelihood of a secondary headache disorder and the need for diagnostic testing. These include (1) recent head or neck injury; (2) a new, worse, worsening, or abrupt onset headache; (3) headache brought on by Valsalva maneuver or cough; (4) headache brought on by exertion; (5) headache associated with sexual activity; (6) pregnancy; (7) headache in the patient over the age of ~50; (8) neurologic findings and/or symptoms; (9) systemic signs and/or symptoms; (10) secondary risk factors, such as cancer or human immunodeficiency virus (HIV) infection. Less worrisome are headaches that wake the patient from sleep at night, always occur on the same side, or show a prominent effect of change in posture on the patient's pain. Diagnostic studies include neuroimaging, cerebrospinal fluid (CSF) examination, and blood tests, which are selected depending on the patient's history and findings. For most patients, the diagnostic test of choice is a magnetic resonance imaging (MRI) brain scan. Computed tomography (CT) of the brain is usually obtained in the setting of trauma or the abrupt onset of headache. CSF examination is useful in diagnosing subarachnoid bleeding, infection, and high and low CSF pressure syndromes.

Posture systematically alters ear-canal reflectance and DPOAE properties

Several studies have demonstrated that the auditory system is sensitive to changes in posture, presumably through changes in intracranial pressure (ICP) that in turn alter the intracochlear pressure, which affects the stiffness of the middle-ear system. This observation has led to efforts to develop an ear-canal based noninvasive diagnostic measure for monitoring ICP, which is currently monitored invasively via access through the skull or spine. Here, we demonstrate the effects of postural changes, and presumably ICP changes, on distortion product otoacoustic emissions (DPOAE) magnitude, DPOAE angle, and power reflectance. Measurements were made on 12 normal-hearing subjects in two postural positions: upright at 90° and tilted at −45° to the horizontal. Measurements on each subject were repeated five times across five separate measurement sessions. All three measures showed significant changes (p<0.001) between upright and tilted for frequencies between 500 and 2000Hz, and DPOAE angle changes were significant at all measured frequencies (500–4000Hz). Intra-subject variability, assessed via standard deviations for each subject’s multiple measurements, were generally smaller in the upright position relative to the tilted position.

Effect of posture change and alternation, on efficiency, blood lactate concentration and muscle activity during uphill cycling.

Effect of posture change and alternation, on efficiency, blood lactate concentration and muscle activity during uphill cycling.

Dynamic Bulging of Intervertebral Discs in the Degenerative Lumbar Spine

The effect of postural change on degenerative lumbar discs was quantified using novel kinematic magnetic resonance imaging (kMRI). The purpose is to describe the bulging of degenerative intervertebral lumbar discs in vivo subjected to different postural loads using a novel kMRI. Symptomatic lumbar disc degeneration is a leading cause of pain and disability throughout the world. Over 70% of US citizens will experience a debilitating episode of low back pain. Earlier reports of degenerative disc changes are cadaver studies or are performed with recumbent MRI that eliminates the functional effects of gravity and muscle power. Little data are available on the behavior of degenerative intervertebral discs in vivo under physiologic loads. A total of 513 patients obtained kMRI. Disc bulging beyond the intervertebral space was quantified during upright neutral, flexion, and extension imaging. The degree of intervertebral disc degeneration was correlated using the Pfirrmann Classification. Moderately degenerated intervertebral discs (grade III and IV) demonstrated greater bulging than mildly degenerated discs (grade II). Severely degenerated discs (grade V) also showed a trend toward greater bulging, but this was not significant. Grade I discs at all levels moved posteriorly in flexion and anteriorly in extension when compared to neutral posture. However, mild to severe (grade II-V) degenerative discs behaved differently in response to postural loads. Extension resulted in significant posterior bulging, while flexion did not demonstrate obvious anterior derangement. Disc bulging increases with the severity of disc degeneration. Grade I discs demonstrate the expected sagittal migration in response to postural load. However, more degenerative discs behave less predictably, and spine extension may result in significant posterior disc bulging. Degenerative changes in the intervertebral disc significantly affect the kinematic patterns under postural load in vivo. kMRI is a useful tool to quantify the kinematic behavior of degenerative intervertertebral discs.

Effects of postural changes and removal of vestibular inputs on blood flow to and from the hindlimb of conscious felines

Considerable data show that the vestibular system contributes to blood pressure regulation. Prior studies reported that lesions that eliminate inputs from the inner ears attenuate the vasoconstriction that ordinarily occurs in the hindlimbs of conscious cats during head-up rotations. These data led to the hypothesis that labyrinthine-deficient animals would experience considerable lower body blood pooling during head-up postural alterations. The present study tested this hypothesis by comparing blood flow though the femoral artery and vein of conscious cats during 20-60 degrees head-up tilts from the prone position before and after removal of vestibular inputs. In vestibular-intact animals, venous return from the hindlimb dropped considerably at the onset of head-up tilts and, at 5 s after the initiation of 60 degrees rotations, was 66% lower than when the animals were prone. However, after the animals were maintained in the head-up position for another 15 s, venous return was just 33% lower than before the tilt commenced. At the same time point, arterial inflow to the limb had decreased 32% from baseline, such that the decrease in blood flow out of the limb due to the force of gravity was precisely matched by a reduction in blood reaching the limb. After vestibular lesions, the decline in femoral artery blood flow that ordinarily occurs during head-up tilts was attenuated, such that more blood flowed into the leg. Contrary to expectations, in most animals, venous return was facilitated, such that no more blood accumulated in the hindlimb than when labyrinthine signals were present. These data show that peripheral blood pooling is unlikely to account for the fluctuations in blood pressure that can occur during postural changes of animals lacking inputs from the inner ear. Instead, alterations in total peripheral resistance following vestibular dysfunction could affect the regulation of blood pressure.

Obesity effect on perceived postural stress during static posture maintenance tasks

Postural stresses related to manual work tasks may be significantly affected by the bodily condition of workers. One such condition is obesity, which is characterised by excess fat mass in the body. This study empirically examined the obesity effect on postural stress during static posture maintenance tasks. In total, 20 obese and 20 non-obese participants performed static box-holding for a set of 84 working postures defined based on the Ovako Working Posture Analysing System. The participants reported postural stresses using the rated perceived exertion scale. Obesity was found to significantly increase postural stress across the 84 working postures and, also, amplify the effects of postural changes on postural stress. The study findings suggest that ergonomic workplace/job design for obese workers would be a challenge requiring a proactive approach and creativity in problem solving. In addition, the use of ergonomic knowledge in design would be more critical when targeting obese than non-obese workers. The study findings are relevant to ergonomic workplace/job design for obese workers.

Effects of postural changes on arterial to venous blood flow in the dependent limbs of conscious cats

It is routinely assumed that the force of gravity can cause blood pooling in the dependent limbs, as venous return from the body region is reduced. However, the effects of postural alterations on blood flow to and from the limbs have not been directly compared or quantified. In the present study, blood flow in the femoral artery and vein of conscious cats were measured using transit‐time ultrasound technology as the animals were rotated head‐up by amplitudes up to 60°. 60° head‐up rotations produced significant (ANOVA, p&lt;0.05) decreases in venous blood flow beginning ≈3 sec following tilt onset, which became maximal at ≈5 sec, with an alteration of 55‐65% from pre‐tilt values. As the animals were maintained head‐up, venous blood flow began to increase, and was 18‐29% lower than pre‐tilt values by 40 sec following rotation initiation. This recovery of venous flow was accompanied by a 17‐34% decrease in arterial blood flow that peaked ≈9 sec after tilt onset. These data confirm that venous return from the dependent limb is greatly attenuated during postural alterations, and the magnitude may be larger than expected. However, the largest perturbation in venous return is transient, and this combined with accompanying decreases in arterial blood flow limits peripheral pooling.

The Effect of Postural Changes on Intracardiac Filling Pressures

Introduction: Patients with congestive heart failure (CHF) tend to resist lying in the left lateral decubitus position. We hypothesized that cardiac filling pressures (FP) from implanted devices could provide hemodynamic explanations for these observations. Methods: Seven subjects with implantable hemodynamic monitoring (IHM) devices were enrolled. The IHM acquired heart rate (HR) and FP data that consisted of RV systolic and diastolic pressures (RVSP, RVDP), as well as the estimated PA diastolic pressure (ePAD).

Effect of Postural Variations on Carbon Monoxide Diffusing Capacity in Healthy Subjects and Patients with Chronic Obstructive Pulmonary Disease

Background: The scientific literature does not supply enough information about the effects of postural changes on diffusing lung capacity for carbon monoxide (DL_CO) in patients with chronic obstructive pulmonary disease (COPD), in particular regarding the prone position. Objectives: We evaluated posture-related changes in DL_CO in healthy subjects and in COPD patients in order to especially assess how prone posture affects gas exchange. Methods: In this cross-sectional study, DL_CO was measured in 10 healthy subjects and 30 COPD patients in standing, seated, supine and prone positions. Results: In healthy individuals, DL_CO tended to improve from the upright to the supine position (21.42 ± 2.90 and 26.07 ± 5.11 ml/min/mm Hg, respectively); in the same group, changing the position from upright to prone also caused significant improvements in DL_CO (absolute value, 21.42 ± 2.90 vs. 24.80 ± 4.39 ml/min/mm Hg, p < 0.05, or percent of predicted, 78.58 ± 11.12 vs. 91.44 ± 13.23, p < 0.05) and in DL_CO proportional to alveolar volume (DL_CO/VA; 4.52 ± 0.57 vs. 5.66 ± 1.48 ml/min/mm Hg/l, p < 0.05). No significant differences in DL_CO have been observed in COPD patients from the standing to the prone position. Multivariate linear regression models showed that the posture-related changes in DL_CO, DL_CO expressed as percent of predicted and in DL_CO/VA are directly correlated with the transition from upright/sitting to supine/prone. Conclusions: In healthy subjects, the effect of postural changes on DL_CO could be explained by a more homogeneous perfusion, whereas the lack of variations in COPD patients could be attributed to the increased rigidity of lung capillaries, which could represent an early sensitive marker of damage of the alveolar capillary interface in these patients.

Postural changes during showering affect the entry of water into the ear canal

The aim of the study is to demonstrate the effect of postural changes in keeping the ears dry during showering. A prospective, randomized, single blinded trial. Tertiary otolaryngological unit. Forty adult volunteers were recruited and randomly allocated to have a shower either with a head down or a head up posture. Presence of fluorescein in the deeper ear canal. Ninety-three per cent of ears in the head down group had no fluorescein and 95% of ears in the head up group showed the presence of fluorescein, indicating presence of water in the deeper ear canals. When a head down position was assumed during showering, water did not enter the deeper part of the ear canal in 93% of ears.

Interface Pressure and Stiffness of Various Elastic Stockings during Posture Changes and Exercise

The importance of measuring interface pressure and stiffness to characterize the elastic properties of materials has been stressed with regard to elastic stockings and elastic bandages. The objective of this study was to compare the pressure profiles of nine different elastic stockings and to quantify the effects of posture changes and exercise on compression. Using a pressure transducer (Air Pack Type Analyzer), the interface pressure associated with nine different elastic stockings was measured at level B1 during supine resting, standing, and exercise. The elastic stockings examined could be divided into two categories according to extensibility: short stretch (< 105% extensibility) and long stretch (> 105% extensibility). Short-stretch stockings include thick round-knitted stockings, firm round-knitted stockings, and flat-knitted stockings. Short-stretch stockings showed a higher peak working pressure and a larger pressure amplitude during exercise than long-stretch stockings. Short-stretch stockings can be expected to have more pronounced benefits for augmenting muscle pumping in the same way as short-stretch bandages. In selecting suitable elastic stockings for patients, the stiffness should be taken into account in addition to interface pressure.

Effect of Postural Change on Nasal Airway and Autonomic Nervous System Established by Rhinomanometry and Heart Rate Variability Analysis

Clinically, nasal obstruction is experienced frequently in the supine position, and the nasal autonomic nervous system (ANS) may be involved in the mechanism. The central ANS functions at maintaining cardiovascular hemodynamics. However, during postural change, the corresponding changes of the central ANS may simultaneously change the nasal airway as well. In this study, the relationships between nasal ANS and central ANS were explored using rhinomanometry (RMM) and heart rate variability (HRV) analysis between postural changes. Twelve healthy volunteers aged between 19 and 39 years and without a history of allergic rhinitis or significant nasal anatomic obstruction were enrolled for the study. The nasal airway was measured using RMM in a sitting position and then in a supine position; the electrocardiography was simultaneously recorded. In supine position, the total nasal airflow significantly decreased and the airway resistance significantly increased (p<0.05, Wilcoxon signed-rank test). The ratio of low frequency power to high frequency (HF) power of HRV that represents sympathetic modulation significantly decreased in the supine position (p<0.05, Wilcoxon signed-rank test). However, the HF that represents parasympathetic activity did not show significant change with postural change. The correlations of heartbeat interval with total inspiratory airflow and total inspiratory resistance were significant also (p<0.01, Pearson's correlation). The central ANS activities significantly correlated with changes to the nasal airway during postural change. The central ANS, especially the sympathetic nervous system, may play a role in controlling nasal airway during postural change.

The Relation between the Changes of Postural Achievement, Lower Limb Muscle Activities, and Balance Stability in Three Different Deep-squatting Postures

Deep squatting places a burden on the lower limb muscles and influences postural balance. We attempted to determine the effects of postural changes on the rectus femoris, tibialis anterior, gastrocnemius, soleus, and extensor digitorum brevis muscles during squatting in 8 healthy male subjects. Three squatting conditions were involved: full squatting (FS), tiptoe squatting (TT), and tiptoe squatting on a 15 degrees slope (TTS), performed randomly and recorded in a period of 4 min for each task. The influence of the squatting condition on electromyography and vertical ground reaction force parameters was examined in order to observe the effect of postural alteration on muscle activity and balance control. The results showed that the change of squatting posture from FS to TT decreased the activity of the rectus femoris and tibialis anterior muscles. FS has been suspected as a main cause of musculoskeletal complaint during prolonged squatting. In contrast, as the heel was lifted, the extensor digitorum brevis muscle increased to 39% of maximum activation. On the other hand, sway analysis at TT showed balance instability regarding the large area occupation of the center of pressure displacement. The presence of a 15 degrees slope significantly reduced the muscular load. This simple study suggests that the inclusion of a sloping surface in daily activities that requires a squatting posture would be an effective means to reduce muscular load.