Supine Body Research Articles

Numerical Modeling of Venous Outflow from the Cranial Cavity in the Supine Body Position

The hemodynamic relevance of differently located stenoses of the internal jugular veins remains undetermined. It particularly concerns nozzle-like strictures in the upper parts of these veins and stenotic jugular valves located at the end of these veins. This study was aimed at understanding flow disturbances caused by such stenoses. The computational fluid dynamics software Flowsquare+ was used. We constructed 3-dimensional models of the venous outflow, comprising two alternative routes: the tube representing the internal jugular vein and an irregular network representing the vertebral veins. At the beginning of the tube representing the internal jugular vein, differently shaped and sized short strictures representing nozzle-like strictures were built in. At the end of this tube, differently shaped membranes representing the jugular valve were built in. With the use of computational fluid dynamics modeling, we studied how these two obstacles influenced the outflow. We found that the most relevant outflow disturbances were evoked by the nozzle-like strictures in the upper part of the internal jugular vein that were small, long, or asymmetrically positioned. Very tight stenotic valves and septum-like malformed valve were equally hemodynamically relevant. These findings suggest that both upper and lower strictures of the internal jugular vein can be of clinical significance.

Evaluating Intraocular Pressure Alterations during Large Muscle Group Isometric Exercises with Varying Head and Body Positions.

Performing physical exercise affects intraocular pressure, and its elevation and fluctuations are the main risk factors for glaucoma development or progression. The aim of this study was to examine the acute alterations in intraocular pressure (IOP) during four unweighted isometric exercises and to determine whether the different head and body positions taken during exercise additionally affect IOP. Twelve healthy volunteers between the ages of 25 and 33 performed four isometric exercises: wall sit in neutral head and body position, elbow plank in prone head and body position, reverse plank in supine head and body position for 1 min, and right-side plank in lateral head and body position for 30 s. Intraocular pressure was measured by applanation portable tonometry, before performing the exercise, immediately after exercise completion, and after five minutes of rest. A significant acute increase in intraocular pressure was found as a response to the performance of the elbow plank (p < 0.01), the reverse plank (p < 0.001), and the right-side plank (p < 0.001). The wall sit exercise did not reveal a statistically significant IOP elevation (p = 0.232). Different head and body positions had no significant additional influence on IOP (F (3,33) = 0.611; p = 0.613), even though the alteration in IOP was found to be greater in exercises with a lower head and body position. Our data revealed that IOP elevation seems to be affected by the performance of the elbow plank, the reverse plank, and the right-side plank; and not by the wall sit exercise. More different isometric exercises should be examined to find ones that are safe to perform for glaucoma patients.

CT‐based 3D reconstruction and basic anatomical analysis of the 3D anatomy of the air sac system in domestic birds

AbstractThe complex anatomy of the avian respiratory system makes it necessary to broaden our knowledge using modern imaging and reconstructional possibilities. The visualization of these structures can be used for clinical situations, in research or as teaching aids in veterinary education. For this we generated 3D models from diagnostic imaging data (computed tomography [CT] scans) of birds. We describe in detail a repeatable method of animal preparation for scanning, data handling and image analysis. CT scans with varying slice thickness and resolution were obtained in prone and supine body positions to analyse air sac morphology and volume changes relative to posture or sexual dimorphism in birds. The resulting data were prepared and analysed using a reconstructional software (3D Slicer) based on manual and semi‐automatic labelling and subsequent 3D models of the air sac system were created. The terminology employed has been referenced from the Nomina Anatomica Avium, Second Ed.

Dynamic changes in lung water density and volume following supine body positioning.

Measure the changes in relative lung water density (rLWD), lung volume, and total lung water content as a function of time after supine body positioning. An efficient ultrashort-TE pulse sequence with a yarnball k-space trajectory was used to measure water density-weighted lung images for 25 min following supine body positioning (free breathing, 74-s acquisitions, 3D images at functional residual capacity, 18 time points) in 9 healthy volunteers. Global and regional (10 chest-to-back positions) rLWD, lung volume, and total lung water volume were measured in all subjects at all time points. Volume changes were validated with a nitrogen washout study in 3 participants. Global rLWD increased significantly (p = 0.001) from 31.8 ± 5.5% to 34.8 ± 6.8%, while lung volumes decreased significantly (p < 0.001) from 2390 ± 620 mL to 2130 ± 630 mL over the same 25-min interval. Total lung water volume decreased slightly from 730 ± 125 mL to 706 ± 126 mL (p = 0.028). There was a significant chest-to-back gradient in rLWD (20.7 ± 4.6% to 39.9 ± 6.1%) at all time points with absolute increases of 1.8 ± 1.2% at the chest and 5.4 ± 1.9% at the back. Nitrogen washout studies yielded a similar reduction in lung volume (12.5 ± 0.9%) and time course following supine positioning. Lung volumes during tidal breathing decrease significantly over tens of minutes following supine body positioning, with corresponding increases in lung water density (9.2 ± 4.4% relative increase). The total volume of lung water is slightly reduced over this interval (3.3 ± 4.0% relative change). Evaluation of rLWD should take time after supine positioning, and more generally, all sources of lung volume changes should be taken into consideration to avoid significant bias.

#4657 COMPARISON OF TWO BIOIMPEDANCE SPECTROSCOPY DEVICES: A PRACTICAL STEP FORWARD ON THE WAY TO DAILY BIOIMPEDANCE MEASUREMENTS FOR DIALYSIS PATIENTS

Abstract Background and Aims Bioimpedance spectroscopy (BIS) is a non-invasive diagnostic tool to assess volume status and body composition through the measurement of voltage drops in alternating currents and subsequent extrapolation of extracellular (R0), intracellular (Ri), and total body (RInf) resistances. Currently available devices mostly rely on disposable electrodes and require supine body position. Here we tested whether a new, more versatile BIS device with reusable electrodes matches an established system in various setups, aiming to enable daily BIS-measurements in the near future. Method Two BIS devices (“Cella” and the “Body Composition Monitor” [BCM]) were compared both with four resistance testboxes (circuit boards with resistors and capacitors simulating different body conditions) and in 40 healthy volunteers. In-vivo comparisons included supine hand-to-foot (HF) reference measurements with adhesive disposable electrodes and hand-to-hand (HH) measurements with adhesive disposable and prototype reusable electrode sets (Figure 1). Results Analyses of testboxes were reproducible in both devices (intra-device coefficients of variation &amp;lt;1%). Mean differences from testbox components were similar and small for R0 (2-3 Ohm) but not for Ri, where Cella was off by 101 Ohm compared to the BCM's 29 Ohm in a testbox designed with a deliberately low R0/Ri ratio. In-vivo, HF measurements with disposable electrodes differed significantly between both devices (p &amp;lt; 0.001). Prototype reusable HH electrodes exhibited a bias towards larger resistances than HF measurements (R0: 738.36 Ohm vs. 643.09 Ohm; Ri: 1508.18 Ohm vs. 1257.17 Ohm; RInf 500.03 vs. 423.81 Ohm, respectively) and the HH/HF ratio varied between 1.0-1.4 (R0 and RInf) and 0.9-1.6 (Ri). Conclusion While the Cella BIS device was shown to produce results with comparable consistency to the BCM in-vivo, the latter measured more accurately under testbox conditions. Accuracy of in-vivo measurements could not be determined for lack of gold-standard measurements. Implementation of HH reusable electrodes will require per-patient calibration against HF measurements due to the large inter-patient fluctuations in the HH/HF ratio. We recommend further longitudinal analyses of intra-patient HH/HF ratios to investigate long-term variabilities.

The Implementation of Neurophysiological Pre-Trainin Protocols to Improve Performance, R.O.M and Decrease Pain- A Case Study

Post-Activation Performance Enhancement (PAPE) is one of many strategies employed to improve athletic performance, modulate pain and improve range of motion (ROM). This neurophysiological pre-training protocol involves physiological mechanisms such as Autogenetic Inhibition, Reciprocal Inhibition (AI &amp; RI), and Post-Activation Potentiation (PAP). A male powerlifter with 20 years of lifting experience presented a primary complaint of right-sided hip pain when attempting to produce leg drive in a competition Bench Press position. The pain was described as a debilitating 9/10 deep hip pain associated with immediate weakness/loss of hip and leg muscle contraction and abandonment of the attempt. The pain was reproducible and exacerbated by hip extension, internal rotation, and abduction, with limited end-range ROM on hip extension. Due to increased pain upon extension, internal rotation, and abduction, a gluteus medius dysfunction and abduction/extension intolerance were differentially diagnosed. Using the PAPE principles, a treatment strategy was designed. In the competition Bench Press, hip extension is recruited to assist with the transmission of Ground Reaction Force (GRF) from the feet, and lower limbs, also to assist with lumbar spine extension optimisation by which an axial skeletal arch is established. Due to the position of the supine body on the bench press board, the femurs are abducted to enable a person to lie supine with the feet on the floor. When under load, the athlete actively extends the hip, with concurrent femoral abduction. This is a high-performance technique. Prior to setting up on the bench press, the participant was instructed to perform six total sets of seated adduction maximum isometric holds against a foam roller between the knees for 10-20 seconds. After the first six rounds of seated adductor isometric holds, the participant reported 0/10 pain on the subsequent warm-up sets. Full ROM was also reported. The participant proceeded to perform a 220kg 1RM Bench Press with the necessary ROM, leg drive, and no pain. The exercise prescription in this study specifically utilised the mechanisms associated with PAPE, PAP, and RI. The aim of this intervention was to activate the adductor musculature to provide hip extension and inhibit abduction activity. The pre-activation sets of maximal isometric adductor holds were specifically designed to elicit a Reciprocal Inhibition of the hip abductors. This provided a neurophysiological window for the subject to reenter hip extension and obtain the optimal Bench Press setup for performance. Further research focussing on neurophysiological rehabilitative strategies should be conducted. This case study provides a great insight into the possibilities and warrants further investigation around the protocols and mechanisms examined above.

Off-Vertical Body Orientation Delays the Perceived Onset of Visual Motion

The integration of vestibular, visual and body cues is a fundamental process in the perception of self-motion and is commonly experienced in an upright posture. However, when the body is tilted in an off-vertical orientation these signals are no longer aligned relative to the influence of gravity. In this study, the perceived timing of visual motion was examined in the presence of sensory conflict introduced by manipulating the orientation of the body, generating a mismatch between body and vestibular cues due to gravity and creating an ambiguous vestibular signal of either head tilt or translation. In a series of temporal-order judgment tasks, participants reported the perceived onset of a visual scene simulating rotation around the yaw axis presented in virtual reality with a paired auditory tone while in an upright, supine and side-recumbent body position. The results revealed that the perceived onset of visual motion was further delayed from zero (i.e., true simultaneity between visual onset and a reference auditory tone) by approximately an additional 30ms when viewed in a supine or side-recumbent orientation compared to an upright posture. There were also no significant differences in the timing estimates of the visual motion between all the non-upright orientations. This indicates that the perceived timing of visual motion is negatively impacted by the presence of conflict in the vestibular and body signals due to the direction of gravity and body orientation, even when the mismatch is not in the direct plane of the axis of rotation.

International multispecialty consensus on how to image, define, and grade ultrasound imaging features of first metatarsophalangeal joint osteoarthritis, a Delphi consensus study

ObjectiveTo reach consensus concerning which ultrasound imaging features should be assessed and graded, and what ultrasound imaging procedure should be performed when examining osteoarthritic change in the first metatarsophalangeal joint. DesignAn online Delphi study was conducted over four iterative rounds with 16 expert health professionals. Items were scored from 0 to 100 (0 ​= ​not at all important; 100 ​= ​extremely important). Consensus was defined based upon an item receiving a median score of ≥70% acceptance. Items receiving median score of ≤50% were rejected. Items considered ambiguous (median score 51%–69% of acceptance) were assessed in an additional round. A final round determined the content validity of items through calculation of the content validity ratio and content validity index. ResultsSixteen items were deemed essential, which included osteophytes graded dichotomously, cartilage damage graded continuously, synovitis and joint space narrowing graded on a semiquantitative scale. The panel deemed essential that the first metatarsophalangeal joint start in a neutral position, then move through range of motion for both dorsal and plantar scanning, orientating the probe in longitudinal and in transverse, whilst using first metatarsal head and proximal phalanx as anatomical landmarks. A supine body position was only deemed essential for a dorsal scan and a neutral foot/ankle position was only rated essential for a plantar scan. The content validity index of the 16 essential items was 0.19. ConclusionThe consensus exercise has identified the essential components the ultrasound imaging acquisition procedure should encompass when examining first metatarsophalangeal joint osteoarthritis.

Falling Stories: Cinematic Naturalism and Disability in Frank Norris’ and Stephen Crane's City Sketches

Falling Stories: Cinematic Naturalism and Disability in Frank Norris’ and Stephen Crane's City Sketches

Changes in the upper airway volume after orthognathic surgery: three-dimensional measurements in a supine body position

The objectives of this study were to analyse the changes in airway cross-sectional areas and volumes due to surgical movements of the jaws and to identify any possible correlation with the direction of the movements. Fifty-seven participants, aged 18–28 years (mean 20.8 years) at surgery, were followed up for 12 months postoperatively. Pre- and postoperative measurements of the facial region obtained from computed tomography in a supine position were analysed according to the surgical movements and changes in the upper airways. Intra-rater reliability was assessed. Comparisons and correlations of jaw movements, changes in airway volume, and body mass index (BMI) were made. The cohort showed a significant change between the pre- and postoperative measurements for areas associated with the anterior nasal spine (P = 0.013), posterior nasal spine (P = 0.049), uvula (P = 0.006), and epiglottis (P = 0.046). Additionally, a correlation was found between the airway volume change and the change in mandible position (correlation coefficient 0.324, P = 0.014). All participants were non-smokers, and no correlation was observed between BMI and the upper airway volume. Changes in the upper airway can be expected following surgical movements of the jaws. A correlation was shown between a sagittal direction of the movements and the changes in the airways. Patients with obstructive sleep apnoea who are indicated for surgical movements of the jaws are expected to benefit from orthognathic surgery.

International multispecialty consensus on how to image, define, and grade ultrasound imaging features of first metatarsophalangeal joint osteoarthritis: A Delphi consensus study

The objective of this research was to adopt a Delphi study design to reach consensus concerning which ultrasound imaging features should be assessed and graded, and what ultrasound imaging procedure should be performed when examining osteoarthritic change in the first metatarsophalangeal joint. An online Delphi study was conducted over four iterative rounds with 16 expert health professionals. Items were scored from 0-100 (0 = not at all important; 100 = extremely important). Consensus was defined based upon items receiving ≥70% of acceptance [1]. Items receiving ≤50% were rejected. Items considered ambiguous (median 51% - 69% of acceptance) were assessed in an additional round [2]. A final round determined the content validity of items through calculation of the content validity ratio and content validity index [3]. Sixteen items were deemed essential and seven items non-essential. Items deemed essential to assess included osteophytes graded dichotomously, cartilage damage graded continuously, synovitis and joint space narrowing graded on a semiquantitative scale. The panel deemed essential that the first metatarsophalangeal joint start in its neutral position then move through range of motion during scanning for both dorsal and plantar scan, orientating the probe in longitudinal and in transverse aspects, whilst using first metatarsal head and proximal phalanx as anatomical landmarks. A supine body position was only deemed essential for a dorsal scan and a neutral foot/ankle position was only rated essential for a plantar scan. The content validity index of the essential items was 0.19. The consensus exercise has identified essential components the ultrasound imaging acquisition procedure should encompass when examining first metatarsophalangeal joint osteoarthritis. The outcomes of the Delphi study will inform future studies into the methodological development of an ultrasound imaging atlas to grade the degree of osteoarthritic change in the first metatarsophalangeal joint.

Prone positioning may increase lung overdistension in COVID-19-induced ARDS

Real-time effects of changing body position and positive end-expiratory pressure (PEEP) on regional lung overdistension and collapse in individual patients remain largely unknown and not timely monitored. The aim of this study was to individualize PEEP in supine and prone body positions seeking to reduce lung collapse and overdistension in mechanically ventilated patients with coronavirus disease (COVID-19)-induced acute respiratory distress syndrome (ARDS). We hypothesized that prone positioning with bedside titrated PEEP would provide attenuation of both overdistension and collapse. In this prospective observational study, patients with COVID-19-induced ARDS under mechanical ventilation were included. We used electrical impedance tomography (EIT) with decremental PEEP titration algorithm (PEEPEIT-titration), which provides information on regional lung overdistension and collapse, along with global respiratory system compliance, to individualize PEEP and body position. PEEPEIT-titration in supine position followed by PEEPEIT-titration in prone position were performed. Immediately before each PEEPEIT-titration, the same lung recruitment maneuver was performed: 2 min of PEEP 24 cmH2O and driving pressure of 15 cmH2O. Forty-two PEEPEIT-titration were performed in ten patients (21 pairs supine and prone positions). We have found larger % of overdistension along the PEEP titration in prone than supine position (P = 0.042). A larger % of collapse along the PEEP titration was found in supine than prone position (P = 0.037). A smaller respiratory system compliance was found in prone than supine position (P < 0.0005). In patients with COVID-19-induced ARDS, prone body position, when compared with supine body position, decreased lung collapse at low PEEP levels, but increased lung overdistension at PEEP levels greater than 10 cm H2O.Trial registration number: NCT04460859.

Acute Effects of 160-Degree V-Shape Whole-Body Periodic Acceleration (WBPA) on Blood Pressure and Cardiovascular Hemodynamics

Whole-Body Periodic Acceleration (WBPA) has been reported to induce endothelial nitric oxide and cause vasodilation. However, the effects of WBPA on blood pressure and cardiovascular hemodynamics are still unclear and controversial. The objective of this study was to determine whether a single session of 160-degree V-shape Whole-Body Periodic Acceleration (WBPA-V-160), i.e., periodic motion of the supine body headward to footward, improved blood pressure and cardiovascular parameters. A pre-evaluation and post-evaluation of blood pressure and cardiovascular hemodynamics via DynaPulse Noninvasive and Quantitative Hemodynamic Profile Analysis were performed after a single 30 min trial of WBPA-V-160 with a moving distance, headward to footward, of 2 mm, at a constant frequency of 4 Hz. Systolic BP, diastolic BP, heart rate, end systolic pressure, end diastolic pressure, mean arterial BP, and pulse pressure at post-evaluation were significantly lower than at pre-evaluation after WBPA-V-160, whereas systemic vascular compliance and brachial artery distensibility at post-evaluation were significantly higher than at pre-evaluation. The WBPA-V-160, performed for 30 min, did improve blood pressure and cardiovascular hemodynamics by lowing the BP parameters and enhancing systemic vascular compliance.

Computed tomography venography description of the normal anatomy of the canine hindlimb venous system.

This study was performed to provide a description of the normal anatomy of the canine hindlimb veins using helical CT images. The studies of 30 dogs that underwent CT venography with a 64-slice helical CT scanner were retrospectively reviewed. The dogs were positioned in a head-first prone or head-first supine body position. A topogram CT scan was performed from the pelvic limbs cranial to the iliac wings to the tips of the paws. Bolus-tracking software was used for the dual-phase angiogram, and contrast medium was administered in a cephalic vein. The venous phase was scanned after a delay time of a few seconds after the arterial phase in a caudocranial direction. Three-dimensional images were generated using maximum intensity projections and volume rendering technique. Representative images of three of the 30 dogs were selected and anatomic structures labelled.

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West African Dwarf (WAD) goats are important source of animal protein, ubiquitous in rural Nigerian households and undergo necessary surgical procedures. Induction of general anaesthesia in goats is associated with resultant severe systemic side effects due to position-induced stress. This study investigated cardiopulmonary and stress responses of WAD goats to three sedatives in different body positioning. Six adult WAD bucks, weighing 11&plusmn;2.0 kg were randomly selected for three separate experiments using of xylazine (0.05 mg/kg), acepromazine (0.2 mg/kg) or midazolam (0.3 mg/kg) intramuscularly in five clinical trials lasting five days each. Goats were restrained in standing (control), Right Lateral (RL), Left Lateral (LL), supine and prone positions. Venous blood (5 ml) via jugular venipuncture was collected before and after each sedation to determine selected stress biomarkers [blood glucose (mg/dL), plasma cortisol (mmol/L) and lactate dehydrogenase LDH (U/L)]. Heart Rate-HR (beats/min), Respiratory Rate-RR (breaths/min), Mean Arterial Pressure-MAP (mmHg), Oxygen-haemoglobin Saturation-SpO2 (%) and Rectal Temperature -RT (&deg;C) were measured at intervals of 10 min for 1 h. Bucks were rested for 14 days in between clinical trials. Data were analysed using descriptive statistics and ANOVA at p&lt;0.05. In LL, supine and prone body positions, peak blood glucose levels and plasma cortisol, respectively were significantly increased with xylazine, acepromazine and midazolam compared to control. Plasma levels of LDH were significantly decreased compared to control for the RL, LL, supine and prone positions with xylazine and acepromazine sedation. Acepromazine and Midazolam had highest HR with supine position. Xylazine sedation resulted in severe hypotension and hyperglycaemia with LL and supine body positions whereas acepromazine and midazolam sedation resulted in mild hypotension and increased heart rate with LL and prone body positions. The LL and prone positioning should be used cautiously in caprine sedation. Acepromazine and midazolam were found to be safer alternatives to xylazine. Key words: Body positioning, cardiopulmonary stress responses, sedation, West African Dwarf goats.

Maternal sleep behaviours preceding fetal heart rate events on cardiotocography.

In Australia, a significant proportion of stillbirths remain unexplained. Recent research has highlighted nocturnal maternal behaviours as potentially modifiable contributors. This study determined whether sleep-related behaviours including sleep position and sleep-disordered breathing adversely affect fetuses overnight, in both uncomplicated pregnancies and those at increased risk due to hypertensive disorders or fetal growth restriction (FGR). All participants underwent polysomnography with time-synchronized fetal heart rate (FHR) monitoring (cardiotocography - CTG) in late pregnancy. CTGs were analysed for abnormal FHR events, including decelerations and reduced variability, by two blinded observers and exported into the sleep study to temporally align FHR events with sleep behaviours. For each FHR event, 10 control epochs with normal FHR were randomly selected for the same participant. Conditional logistic regression assessed the relationships between FHR events and sleep behaviours. From 116 participants, 52 had a total of 129 FHR events overnight; namely prolonged decelerations and prolonged periods of reduced variability. Significantly more FHR events were observed in women with FGR and/or a hypertensive disorder compared with uncomplicated pregnancies (P=0.006). FHR events were twice as likely to be preceded by a change in body position within the previous 5min, compared with control epochs (P=0.007), particularly in hypertensive pregnancies both with and without FGR. Overall, FHR events were not temporally related to supine body position, respiratory events or snoring. Our results indicate that most fetuses tolerate sleep-related stressors, but further research is needed to identify the interplay of maternal and fetal conditions putting the fetus at risk overnight. KEY POINTS: Maternal sleep behaviours including supine position and sleep-disordered breathing are potential contributors to stillbirth but much of this work is based on self-reported data. Using time-synchronized polysomnography and cardiotocography, we found that nocturnal fetal heart rate decelerations were more likely to be preceded by a change in body position compared with epochs containing normal fetal heart rate, particularly in hypertensive pregnancies with or without fetal growth restriction. There was no temporal relationship between maternal sleeping position, snoring or apnoeic events and an abnormal fetal heart rate overnight. We conclude that most fetuses can tolerate sleep-related stressors with no evidence of fetal heart rate changes indicating compromised wellbeing. Further work needs to identify how sleep behaviours contribute to stillbirth risk and how these intersect with underlying maternal and fetal conditions.

Validation of models of venous outflow from the cranial cavity in the supine and upright body positions

Validation of models of venous outflow from the cranial cavity in the supine and upright body positions

A supine body posture reduces the error-related negativity: A test of a dissonance theory prediction.

A supine body posture reduces the error-related negativity: A test of a dissonance theory prediction.

The influence of gravity on respiratory kinematics during phonation measured by dynamic magnetic resonance imaging

Respiratory kinematics are important for the regulation of voice production. Dynamic MRI is an excellent tool to study respiratory motion providing high-resolution cross-sectional images. Unfortunately, in clinical MRI systems images can only be acquired in a horizontal subject position, which does not take into account gravitational effects on the respiratory apparatus. To study the effect of body posture on respiratory kinematics during phonation, 8 singers were examined both in an open-configuration MRI with a rotatable gantry and a conventional horizontal MRI system. During dynamic MRI the subjects sang sustained tones at different pitches in both supine and upright body positions. Sagittal images of the respiratory system were obtained at 1–3 images per second, from which 6 anatomically defined distances were extracted to characterize its movements in the anterior, medium and posterior section of the diaphragm as well as the rip cage (diameter at the height of the 3rd and 5th rip) and the anterior–posterior position of the diaphragm cupola. Regardless of body position, singers maintained their general principles of respiratory kinematics with combined diaphragm and thorax muscle activation for breath support. This was achieved by expanding their chest an additional 20% during inspiration when singing in the supine position but not for sole breathing. The diaphragm was cranially displaced in supine position for both singing and breathing and its motion range increased. These results facilitate a more realistic extrapolation of research data obtained in a supine position.

A left lateral body position increases pulmonary vein stress in healthy humans.

Pulmonary vein (PV) stretch is proarrhythmic for atrial fibrillation (AF). AF patients often report that a left lateral (LL) body position can trigger arrhythmia symptoms. Because the PV myocardium is thought to trigger AF, we hypothesized that the LL compared to the supine body position increases PV wall stress. Functional cardiac magnetic resonance imaging was performed in supine and LL recumbent body position in awake condition in healthy human volunteers (n = 20). Following a change from supine to LL position, the heart moved in an anterior‐LL direction in the thorax. The right superior PV diameter was increased by 19% (24.6 ± 3.1 vs. 20.7 ± 3.2 mm, p = 0.009) and left atrial (LA) volume was larger by 17% (61.7[15.4] vs. 51.0[17.8] ml, p = 0.015) in LL than supine position, respectively. The passive LA conduit fraction (normalized difference between maximum and pre‐contraction LA volume) increased by 25% in LL compared to supine position (19.6 ± 9.0 vs. 15.7 ± 7.6%, respectively, p = 0.016). Local wall stress in the PV regions increased in LL compared to supine position (overall mean: 1.01 ± 0.12 vs. 1.10 ± 0.10 arb. unit, LL vs. supine, position effect p = 0.041), whereas this was not the case in the LA walls (overall mean: 1.18 ± 0.31 vs. 1.21 ± 0.21 arb. unit, LL vs. supine, position effect p = 0.381). In conclusion, a left lateral body position increases PV myocardial stress during the atrial relaxation phase of healthy volunteers. These results have implications for the mechanisms of posture‐triggered AF.