Cross-sectional Area Of Internal Jugular Vein Research Articles

Daily use of veno-constrictive thigh cuffs during 30 days of strict 6° head-down tilt bedrest to reverse the headward fluid shift

Introduction: Chronic exposure to weightlessness induces a persistent headward fluid shift, which may contribute to the development of Spaceflight Associated Neuro-ocular Syndrome (SANS). Strict 6° head-down tilt bedrest (HDTBR) is a spaceflight analog that induces a headward fluid shift and development of SANS findings, enabling the evaluation of potential countermeasures. Lower body exercise can induce a sustained post-exercise hyperemia thereby shifting blood away from the central circulation. In addition, veno-constrictive thigh cuffs (VTC) can sequester blood volume in the legs. The purpose of this study was to determine whether 6 hours of daily VTC use following cycling exercise (Ex+VTC) could reverse the headward fluid shift during 30 days of strict 6° HDTBR. We hypothesized that Ex+VTC would sequester fluid in the legs leading to increased thigh circumference and reduced stroke volume (SV), cardiac output (CO), internal jugular vein (IJV) cross-sectional area (CSA) and pressure, and intraocular pressure (IOP). Methods: Participants were randomly assigned to a Control (n=12, 6 female) or Ex+VTC (n=12, 4 female) group and completed baseline data collection (BDC) in the seated and supine posture followed by 30 days of strict 6° HDTBR. The Ex+VTC group completed a maximal exercise test on a cycle ergometer in 6° HDT posture during BDC to establish work rates during HDTBR. The Ex+VTC group performed 10 minutes of light cycle exercise, cycled for 45 minutes at 45% of their max wattage, and then donned VTC to ~50 mmHg for 6 hours on 6 of 7 days per week during HDTBR. Data were collected before exercise and 30 minutes and 6 hours after exercise and donning VTCs on days 3, 17, and 29 of HDTBR. Controls were studied at similar time points. Days were nested within the models. Mixed models were used to determine differences between groups in the change in thigh circumference measured using a flexible tape measure, bilateral IOP measured using tonometry, CO measured using the inert gas rebreathe technique (Innocor), and ultrasound of bilateral IJV CSA and pressure from before to 30 min and 6 hours after use of the countermeasure. Left and right IJV and IOP data were nested within each participant. Results: The Ex+VTC group completed all exercise sessions followed by 6 hours of VTC use. Compared to Control, thigh circumference was greater after 30 minutes (+1.3 vs. -0.2 cm, p<0.001) and 6 hours of VTC use (+2.5 cm vs. -0.1 cm in controls, p<0.001). SV (-38 vs. 2 ml, p<0.001) and CO (-1.5 vs. 0.3 L/min, p<0.001) were reduced at 30 minutes and 6 hours of VTC use (SV: -30 vs. 5 ml, p<0.001; CO: -1.1 vs. 0.6 L/min, p<0.001) compared to Control. IJV CSA and pressure were reduced at 30 minutes (CSA, p<0.001; pressure, p=0.001) and 6 hours of VTC use (CSA, p<0.001; pressure, p=0.007). IOP was not different compared to Control. Conclusions:Use of VTC for 6 hours after 45 minutes of exercise successfully sequestered fluid in the legs, leading to a reduction in central blood volume, IJV CSA, and IJV pressure. Thus, an Ex+VTC countermeasure resulted in a partial fluid shift reversal. This research was supported by the NASA Human Research Program. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effect of passive leg raising on the cross-sectional area of the right internal jugular vein in patients with obesity: a randomised controlled trial protocol

BackgroundVenous access in patients with obesity presents significant challenges. The success of central venous catheterisation largely depends on the cross-sectional area (CSA) of the internal jugular vein (IJV). While techniques...

Jugular venous flow dynamics during acute weightlessness.

During spaceflight, fluids shift headward, causing internal jugular vein (IJV) distension and altered hemodynamics, including stasis and retrograde flow, that may increase the risk of thrombosis. This study's purpose was to determine the effects of acute exposure to weightlessness (0-G) on IJV dimensions and flow dynamics. We used two-dimensional (2-D) ultrasound to measure IJV cross-sectional area (CSA) and Doppler ultrasound to characterize venous blood flow patterns in the right and left IJV in 13 healthy participants (6 females) while 1) seated and supine on the ground, 2) supine during 0-G parabolic flight, and 3) supine during level flight (at 1-G). On Earth, in 1-G, moving from seated to supine posture increased CSA in both left (+62 [95% CI: +42 to 81] mm2, P < 0.0001) and right (+86 [95% CI: +58 to 113] mm2, P < 0.00012) IJV. Entry into 0-G further increased IJV CSA in both left (+27 [95% CI: +5 to 48] mm2, P = 0.02) and right (+30 [95% CI: +0.3 to 61] mm2, P = 0.02) relative to supine in 1-G. We observed stagnant flow in the left IJV of one participant during 0-G parabolic flight that remained during level flight but was not present during any imaging during preflight measures in the seated or supine postures; normal venous flow patterns were observed in the right IJV during all conditions in all participants. Alterations to cerebral outflow dynamics in the left IJV can occur during acute exposure to weightlessness and thus, may increase the risk of venous thrombosis during any duration of spaceflight.NEW & NOTEWORTHY The absence of hydrostatic pressure gradients in the vascular system and loss of tissue weight during weightlessness results in altered flow dynamics in the left internal jugular vein in some astronauts that may contribute to an increased risk of thromboembolism during spaceflight. Here, we report that the internal jugular veins distend bilaterally in healthy participants and that flow stasis can occur in the left internal jugular vein during acute weightlessness produced by parabolic flight.

Systematic review of the use of ultrasound for venous assessment and venous thrombosis screening in spaceflight

The validity of venous ultrasound (V-US) for the diagnosis of deep vein thrombosis (DVT) during spaceflight is unknown and difficult to establish in diagnostic accuracy and diagnostic management studies in this context. We performed a systematic review of the use of V-US in the upper-body venous system in spaceflight to identify microgravity-related changes and the effect of venous interventions to reverse them, and to assess appropriateness of spaceflight V-US with terrestrial standards. An appropriateness tool was developed following expert panel discussions and review of terrestrial diagnostic studies, including criteria relevant to crew experience, in-flight equipment, assessment sites, ultrasound modalities, and DVT diagnosis. Microgravity-related findings reported as an increase in internal jugular vein (IJV) cross-sectional area and pressure were associated with reduced, stagnant, and retrograde flow. Changes were on average responsive to venous interventions using lower body negative pressure, Bracelets, Valsalva and Mueller manoeuvres, and contralateral IJV compression. In comparison with terrestrial standards, spaceflight V-US did not meet all appropriateness criteria. In DVT studies (n = 3), a single thrombosis was reported and only ultrasound modality criterion met the standards. In the other studies (n = 15), all the criteria were appropriate except crew experience criterion, which was appropriate in only four studies. Future practice and research should account for microgravity-related changes, evaluate individual effect of venous interventions, and adopt Earth-based V-US standards.

Computational Fluid Dynamic Simulation of the Cerebral Venous System in Multiple Sclerosis and Control Patients: Are Hemodynamic Variances Evident in Multiple Sclerosis?

An investigation was performed to determine the relevant hemodynamic parameters which could help assess vascular pathology in human diseases. Using these parameters, this study aims to assess if there are any hemodynamic differences in the cerebral veins of multiple sclerosis (MS) patients and controls which could impact the etiology of MS. 40 MS participants and 20 controls were recruited for this study. Magnetic resonance imaging (MRI) was performed to enable 3D geometries of the anatomy and the blood flow rates at the boundaries to be computed. Computational fluid dynamics (CFD) models were created for each participant and simulated using patient-specific boundary conditions. The pressure drop and vascular resistance did not significantly differ between the groups. The internal jugular vein (IJV) cross-sectional area was larger in the MS group (Right IJV: p = 0.04, Left IJV: p = 0.02) and the straight sinus (ST) flow rate was higher in MS across all ages (p = 0.005) compared to controls. Vascular resistance was shown to indicate regions in the cerebral veins which could correspond to increased venous pressure. Conclusion & Significance: This study shows that the pressure and vascular resistance of the cerebral veins are unlikely to be directly related to the etiology of MS. The finding of higher ST flow could correspond to increased inflammation in the deep venous system. Resistance as a measure of vascular pathology shows promise and could be useful to holistically investigate blood flow hemodynamics in a variety of other diseases of the circulatory system.

Correlation of Internal Jugular Vein Collapsibility With Central Venous Pressure in Patients With Liver Cirrhosis.

We aimed to compare internal jugular vein and inferior vena cava ultrasonography as predictors of central venous pressure in cirrhotic patients. We performed ultrasound assessments of the internal jugular vein (IJV) and the inferior vena cava and then invasively measured central venous pressure (CVP). We then compared their correlation with CVP and performed area under the receiver operating characteristic curves to determine which had best sensitivity and specificity. IJV cross-sectional area collapsibility index at 30° correlated better with CVP ( r = -0.56, P < 0.001), and an IJV AP-CI at 30° ≤ 24.8% was better at predicting a CVP ≥8 mm Hg, with 100% sensitivity and 97.1% specificity. Thus, IJV point-of-care ultrasound might be superior than inferior vena cava point-of-care ultrasound as a predictor of CVP in cirrhotic patients.

Impact of rigid cervical collars on the vital signs and cervical vasculature: Should we be on the alert for anything?

ObjectiveIn this study, it was aimed to reveal the effect of RCC application on vital signs and physiology of the neck vascular structures. MethodsThe study was designed as a prospective interventional study on 11 volunteers. The factors that would affect the hemodynamics of the volunteers were standardized before the measurements. The vital signs before and after RCC were measured and under the guidance of ultrasonography (USG), internal jugular vein cross-sectional area (CSA), diameter of the common carotid artery (CCAD), peak systolic velocity (PSV). end-diastolic velocity (EDV), time-averaged maximum velocity (TAMAX), Pulsatility Index, Resistivity Index, time averaged mean velocity (TAMEAN), Volume Flow (FV) measurements were made and compared with each other. ResultsAmong 11 volunteers, the study included 5 women (45.5%). 10 min of RCC application was associated with a reduction of the heart rate by 7.9 bpm (95% CI 4.84–10.98) (pre-collar 74.73 + −8.84, post-collar 66.82 + −9.05, p < 0.001). A corresponding 7.18 mmHg (95% CI 2.11–12.25) decrease in systolic blood pressure (pre-collar mean 115.82 mmHg + −12.55, post-collar mean 108.64 mmHg + −11.46, p = 0.01) and 108.55 mL/min reduction of mean common carotid artery blood volume (95% CI 22.28–194.82) (pre-collar 590.14 mL/min + −194.63, post-collar 481.59 mL/min + −279.36, p = 0.019) were noted. Internal jugular vein CSA has decreased for 0.17 cm2 (95% CI 0.05–0.29) (pre-collar CSA 0.53 + −0.29, post-collar CSA 0.36 + −0.17, p = 0.012). ConclusionIn healthy volunteers, RCC application lasting for ten minutes may reduce systolic blood pressure and heart rate, while decreasing blood volume in both the common carotid artery and the internal jugular vein. It has also been noted that the collapse is larger in the internal jugular vein than in the common carotid artery following the pressure applied by RCC.

The effect of different pressures of pneumoperitoneum on the dimensions of internal jugular vein – A prospective double-blind, randomised study

During laparoscopic surgeries, pneumoperitoneum increases intraabdominal pressure (IAP) which can increase the central venous pressure (CVP), and significant haemodynamic changes. In this study, we evaluated the effect of two different pressures of pneumoperitoneum, standard (13-15 mmHg), and low (6-8 mmHg) on the cross-sectional area (CSA) of the internal jugular vein (IJV) using ultrasonography, haemodynamic changes and duration of surgery. Surgeon's comfort and feasibility of performing laparoscopic surgeries with low pressure pneumoperitoneum was also studied. This prospective, double-blind, randomised study included 148 patients of American Society of Anesthesiologists physical status class I and II undergoing laparoscopic surgeries. They were allocated into two groups: group S (standard) (number (n) = 73) had the IAP maintained between 13-15 mmHg; group L (low) had an IAP of 6-8 mmHg (n = 75). CSA of right IJV was measured before induction of anaesthesia (T1), 5 min after intubation (T2), 5 min after pneumoperitoneum (T3), before desufflation (T4) and 5 min prior to extubation (T5). Chi-square test, and Student's paired and unpaired t test were used for statistical analysis. The increase in IJV CSA at T3 when compared to T2 was statistically significant in both the groups (P < 0.001). On desufflation, the change in IJV CSA showed significant decrease in T5 value than T4 value in both the groups (P < 0.001). However, the percentage change in the IJV CSA was more in group S (35.4%) than group L (21.2%). CSA of IJV increased significantly even with lower IAP of 6-8 mmHg. Laparoscopic surgery can be performed conveniently even at low IAP.

Bedside ultrasound to assess acute central venous pressure change during treatment of decompensated heart failure.

Accurate volume status assessment is crucial for the treatment of acute decompensated heart failure (ADHF). Volume status assessment by physical exam is often inaccurate, necessitating invasive measurement with right heart catheterization (RHC), which carries safety, pragmatic (scheduling, holding anticoagulants, etc.), and financial burdens. Therefore, a reliable, non-invasive, cost-effective alternative is desired. Previously, we developed an ultrasound (US) based technique to measure internal jugular vein (IJV) compliance during RHC which was used for single time point central venous pressure (CVP) predictions. We now aim to apply this technique to track acute changes in CVP during diuresis for ADHF in patients with an in-dwelling pulmonary artery catheter (PAC). We used an observational, prospective study design and recruited 15 patients from the cardiac critical unit (CCU) being treated for ADHF (systolic or diastolic) with intravenous (IV) diuretics with/without inotropic agents who underwent Swan- Ganz catheter/PAC insertion for continuous CVP monitoring. 13 of 15 patients received milrinone infusions. US images of the IJV were obtained at end-expiration and during the strain phase of Valsalva at multiple 2-3 hours intervals. Change in IJV cross-sectional area (CSA) (ImageJ) was used as a measure of IJV compliance. Patients unable to perform the Valsalva maneuver were excluded. Calculated percentage change (%Δ) in CSA of IJV was plotted against CVP. An inverse relationship was observed between CVP and %Δ in CSA of IJV. The data was fit with a polynomial regression curve (R2=0.36, root mean square error=3.19). Fivefold cross-validation showed a stable model for predicting CVP based on CSA (R2=0.31, root mean square error=3.18). Serial portable US assessment of IJV compliance can act as a surrogate measure of CVP and, therefore, can provide reliable information on acute hemodynamic changes in ADHF.

Cerebrovascular Effects of Lower Body Negative Pressure at 3T MRI: Implications for Long‐Duration Space Travel

Optic disc edema develops in most astronauts during long-duration spaceflight. It is hypothesized to result from weightlessness-induced venous congestion of the head and neck and is an unresolved health risk of space travel. Determine if short-term application of lower body negative pressure (LBNP) could reduce internal jugular vein (IJV) expansion associated with the supine posture without negatively impacting cerebral perfusion or causing IJV flow stasis. Prospective. Nine healthy volunteers (six women). 3T/cine two-dimensional phase-contrast gradient echo; pseudo-continuous arterial spin labeling single-shot gradient echo echo-planar. The study was performed with two sequential conditions in randomized order: supine posture and supine posture with 25 mmHg LBNP (LBNP25 ). LBNP was achieved by enclosing the lower extremities in a semi-airtight acrylic chamber connected to a vacuum. Heart rate, bulk cerebrovasculature flow, IJV cross-sectional area, fractional IJV outflow relative to arterial inflow, and cerebral perfusion were assessed in each condition. Paired t-tests were used to compare measurement means across conditions. Significance was defined as P < 0.05. LBNP25 significantly increased heart rate from 64 ± 9 to 71 ± 8 beats per minute and significantly decreased IJV cross-sectional area, IJV outflow fraction, cerebral arterial flow rate, and cerebral arterial stroke volume from 1.28 ± 0.64 to 0.56 ± 0.31 cm2 , 0.75 ± 0.20 to 0.66 ± 0.28, 780 ± 154 to 708 ± 137 mL/min and 12.2 ± 2.8 to 9.7 ± 1.7mL/cycle, respectively. During LBNP25 , there was no significant change in gray or white matter cerebral perfusion (P=0.26 and P=0.24 respectively) and IJV absolute mean peak flow velocity remained ≥4cm/sec in all subjects. Short-term application of LBNP25 reduced IJV expansion without decreasing cerebral perfusion or inducing IJV flow stasis. 1 TECHNICAL EFFICACY STAGE: 1.

Effect of a neck collar on brain turgor: a potential role in preventing concussions?

BackgroundMild internal jugular vein (IJV) compression, aimed at increasing intracranial fluid volume to prevent motion of the brain relative to the skull, has reduced brain injury markers in athletes suffering...

Bedside ultrasound assessments of jugular venous compliance to track central venous pressure change during the treatment of decompensated heart failure

Abstract Background Accurate volume status assessment is crucial for the treatment of acute decompensated heart failure (ADHF). Volume status assessment by physical exam is inaccurate, necessitating invasive measurement with right heart catheterization (RHC), which carries safety, pragmatic (scheduling, holding anticoagulants, etc) and financial burdens. Therefore, a reliable, non-invasive, cost-effective alternative is desired. Previously, we developed an ultrasound (US) based technique to measure internal jugular vein (IJV) compliance during RHC which was used for single time point central venous pressure (CVP) predictions. We now aim to apply this technique to track acute changes in CVP during diuresis for ADHF in patients with an in-dwelling pulmonary artery catheter. Purpose The objective of our study was to devise a rapid, portable and reliable alternative to RHC to track acute volume changes during treatment of ADHF. Methods We used an observational, prospective study design and recruited 15 patients from the CCU between 7/19–12/19 being treated for ADHF (systolic or diastolic) with IV diuretics +/−inotropic agents who underwent PA catheter insertion for continuous CVP monitoring. 13 of 15 patients received milrinone infusions. US images of the IJV were obtained at end expiration and during the strain phase of Valsalva at multiple 2–3 hr intervals. Change in IJV cross sectional area (ImageJ) was used as a measure of IJV compliance. Patients unable to perform the Valsalva maneuver and on mechanical circulatory support were excluded. Results Calculated % change in CSA of IJV was plotted against CVP. An inverse relationship was observed between CVP and % change in CSA of IJV. The data was fit with an inverse exponential regression shown in Figure 1 (R2=0.36, root mean square error = 3.19). Fivefold cross validation showed a stable model for predicting CVP based CSA (R2=0.34, root mean square error = 3.26) Conclusion Serial portable US assessment of IJV compliance can act a surrogate measure of CVP and,therefore, can provide reliable information on acute hemodynamic changes in ADHF. Funding Acknowledgement Type of funding source: None

Central venous pressure estimation from ultrasound assessment of the jugular venous pulse.

ObjectivesAcquiring central venous pressure (CVP), an important clinical parameter, requires an invasive procedure, which poses risk to patients. The aim of the study was to develop a non-invasive methodology for determining mean-CVP from ultrasound assessment of the jugular venous pulse.MethodsIn thirty-four adult patients (age = 60 ± 12 years; 10 males), CVP was measured using a central venous catheter, with internal jugular vein (IJV) cross-sectional area (CSA) variation along the cardiac beat acquired using ultrasound. The resultant CVP and IJV-CSA signals were synchronized with electrocardiogram (ECG) signals acquired from the patients. Autocorrelation signals were derived from the IJV-CSA signals using algorithms in R (open-source statistical software). The correlation r-values for successive lag intervals were extracted and used to build a linear regression model in which mean-CVP was the response variable and the lagging autocorrelation r-values and mean IJV-CSA, were the predictor variables. The optimum model was identified using the minimum AIC value and validated using 10-fold cross-validation.ResultsWhile the CVP and IJV-CSA signals were poorly correlated (mean r = -0.018, SD = 0.357) due to the IJV-CSA signal lagging behind the CVP signal, their autocorrelation counterparts were highly positively correlated (mean r = 0.725, SD = 0.215). Using the lagging autocorrelation r-values as predictors, mean-CVP was predicted with reasonable accuracy (r2 = 0.612), with a mean-absolute-error of 1.455 cmH2O, which rose to 2.436 cmH2O when cross-validation was performed.ConclusionsMean-CVP can be estimated non-invasively by using the lagged autocorrelation r-values of the IJV-CSA signal. This new methodology may have considerable potential as a clinical monitoring and diagnostic tool.

Associations Between Doppler Internal Jugular Vein Blood Flow and Transverse Sinus Stasis Detected by Magnetic Resonance Imaging.

This study aimed to compare the estimated internal jugular vein (IJV) volume flow with Doppler ultrasound in patients with slow flow in the transverse sinuses and normal transverse sinuses on brain magnetic resonance imaging (MRI). Eighty patients between the ages of 18 and 80 years who did not have any signs of sinus vein thrombosis on brain MRI were included. On MRI, cases with hyperintensity due to a signal void loss in the transverse sinuses in coronal fluid attenuation inversion recovery sequences were included in the slow-flow group. The presence of sinus thrombosis was excluded with other MRI pulse sequences and clinical findings. The participants were divided into 2 groups as having normal and slow flow according to MRI findings. Then bilateral IJV volume flow measurements were made by Doppler ultrasound. Bilateral volume flow was estimated by time-averaged blood flow velocities sampled in the center of the IJV, and IJV cross-sectional areas were measured. We defined the dominant IJV as the one having the higher estimated volume flow of the 2 sides. Total estimated IJV blood flow was lower (P < .001) in patients with slow flow on MRI (546 mL/min) compared to those without (768 mL/min). A similar finding was seen for the nondominant IJV. In a receiver operating characteristic analysis, the cutoff value for the total estimated IJV volume flow was determined to be 590 mL/min, and the cutoff value for nondominant estimated IJV volume flow was determined to be 202 mL/min to distinguish between the groups. Low estimated volume blood flow in the IJV is associated with MRI evidence of stasis in the ipsilateral transverse sinus.

Venous and Arterial Responses to Partial Gravity.

Introduction: Chronic exposure to the weightlessness-induced cephalad fluid shift is hypothesized to be a primary contributor to the development of spaceflight-associated neuro-ocular syndrome (SANS) and may be associated with an increased risk of venous thrombosis in the jugular vein. This study characterized the relationship between gravitational level (Gz-level) and acute vascular changes.Methods: Internal jugular vein (IJV) cross-sectional area, inferior vena cava (IVC) diameter, and common carotid artery (CCA) flow were measured using ultrasound in nine subjects (5F, 4M) while seated when exposed to 1.00-Gz, 0.75-Gz, 0.50-Gz, and 0.25-Gz during parabolic flight and while supine before flight (0-G analog). Additionally, IJV flow patterns were characterized.Results: IJV cross-sectional area progressively increased from 12 (95% CI: 9–16) mm2 during 1.00-Gz seated to 24 (13–35), 34 (21–46), 68 (40–97), and 103 (75–131) mm2 during 0.75-Gz, 0.50-Gz, and 0.25-Gz seated and 1.00-Gz supine, respectively. Also, IJV flow pattern shifted from the continuous forward flow observed during 1.00-Gz and 0.75-Gz seated to pulsatile flow during 0.50-Gz seated, 0.25-Gz seated, and 1.00-Gz supine. In contrast, we were unable to detect differences in IVC diameter measured during 1.00-G seated and any level of partial gravity or during 1.00-Gz supine. CCA blood flow during 1.00-G seated was significantly less than 0.75-Gz and 1.00-Gz supine but differences were not detected at partial gravity levels 0.50-Gz and 0.25-Gz.Conclusions: Acute exposure to decreasing Gz-levels is associated with an expansion of the IJV and flow patterns that become similar to those observed in supine subjects and in astronauts during spaceflight. These data suggest that Gz-levels greater than 0.50-Gz may be required to reduce the weightlessness-induced headward fluid shift that may contribute to the risks of SANS and venous thrombosis during spaceflight.

Effect of different manoeuvres on internal jugular vein cross-sectional area in obese and normal-weight patients.

Effect of different manoeuvres on internal jugular vein cross-sectional area in obese and normal-weight patients.

Assessment of Jugular Venous Blood Flow Stasis and Thrombosis During Spaceflight

Exposure to a weightless environment during spaceflight results in a chronic headward blood and tissue fluid shift compared with the upright posture on Earth, with unknown consequences to cerebral venous outflow. To assess internal jugular vein (IJV) flow and morphology during spaceflight and to investigate if lower body negative pressure is associated with reversing the headward fluid shift experienced during spaceflight. This prospective cohort study included 11 International Space Station crew members participating in long-duration spaceflight missions . Internal jugular vein measurements from before launch and approximately 40 days after landing were acquired in 3 positions: seated, supine, and 15° head-down tilt. In-flight IJV measurements were acquired at approximately 50 days and 150 days into spaceflight during normal spaceflight conditions as well as during use of lower body negative pressure. Data were analyzed in June 2019. Posture changes on Earth, spaceflight, and lower body negative pressure. Ultrasonographic assessments of IJV cross-sectional area, pressure, blood flow, and thrombus formation. The 11 healthy crew members included in the study (mean [SD] age, 46.9 [6.3] years, 9 [82%] men) spent a mean (SD) of 210 (76) days in space. Mean IJV area increased from 9.8 (95% CI, -1.2 to 20.7) mm2 in the preflight seated position to 70.3 (95% CI, 59.3-81.2) mm2 during spaceflight (P < .001). Mean IJV pressure increased from the preflight seated position measurement of 5.1 (95% CI, 2.5-7.8) mm Hg to 21.1 (95% CI, 18.5-23.7) mm Hg during spaceflight (P < .001). Furthermore, stagnant or reverse flow in the IJV was observed in 6 crew members (55%) on approximate flight day 50. Notably, 1 crew member was found to have an occlusive IJV thrombus, and a potential partial IJV thrombus was identified in another crew member retrospectively. Lower body negative pressure was associated with improved blood flow in 10 of 17 sessions (59%) during spaceflight. This cohort study found stagnant and retrograde blood flow associated with spaceflight in the IJVs of astronauts and IJV thrombosis in at least 1 astronaut, a newly discovered risk associated with spaceflight. Lower body negative pressure may be a promising countermeasure to enhance venous blood flow in the upper body during spaceflight.

Comparison of the effect of different degrees of passive leg raising on the internal jugular vein cross-sectional area in patients before thoracic surgery

BackgroundThis study investigated the effect of different degrees of passive leg raising (PLR) on the internal jugular vein (IJV) cross-sectional area (CSA) and on the success rate of IJV cannulation in patients waiting for thoracic surgery, to analyze whether body mass index (BMI), gender, age, fasting time and preoperative rehydration have any impact on changes in the IJV CSA.MethodsEighty-two patients scheduled for selective thoracic surgery were enrolled in this study. Patients were randomly assigned based on a computer-generated randomization sequence into 3 groups: 0, 30, and 50 degrees (n = 32, 25, and 25 patients, respectively). The right IJV CSA in the sequence of 0-degree (supine position), 30-degree and 50-degree PLR positions was recorded in all patients using an ultrasound probe. The relationship of BMI, gender, age, fasting time and preoperative rehydration to the IJV CSA was analyzed. Then, each patient was returned to a supine position. After waiting for at least 5 min, patients were placed in a PLR position at 0, 30, or 50 degrees, and then IJV cannulation was performed without ultrasound guidance. The success rate of IJV catheterization at different PLR angles was compared.ResultsThe average CSA of the right IJV in the supine position, 30-degree PLR position and 50-degree PLR position was 1.39 ± 0.63 cm2, 1.65 ± 0.73 cm2, and 1.68 ± 0.71 cm2, respectively. These results showed gradual increases in the IJV CSA of 18.5% (30-degree PLR) and 20.2% (50-degree PLR) when compared to that in the supine position (P = 0.045 and 0.025, respectively). However, only fasting time had a significant impact on the increase in the right IJV CSA at different PLR angles (P = 0.026). Other factors, such as BMI, gender, age and preoperative rehydration, had no significant effects. The success rates of IJV catheterization at angles of 0, 30 and 50 degrees were 84.3, 88 and 92%, respectively; however, there were no significant differences among the three groups (P = 0.674).ConclusionsPLR increases the CSA of the right IJV, especially for patients with long fasting times before thoracic surgery. The effect of the 30-degree PLR position is similar to that of the 50-degree PLR position. However, the success rate of right IJV catheterization was not enhanced in this study using landmark-guided puncture, even though the CSA of the right IJV was increased.Trial registrationClinical trial registration number: ChiCTR1800015051. Date of registration: March 2018.

Investigating the time-lapsed effects of rigid cervical collars on the dimensions of the internal jugular vein.

Protocol advocates the use of rigid cervical collars (RCCs) in head trauma patients as they are at risk of concomitant cervical spine injury. Literature has shown RCCs to be a potential cause of venous outflow obstruction, changing internal jugular vein (IJV) cross-sectional area (CSA), and raising intracranial pressure (ICP). This study aims to investigate the effects of applying a RCC, for a period of four hours, on the dimensions of the IJV, in healthy participants. Seventeen participants (nine male, eight female) took part in this study. Circumference and CSAs of the IJV were measured bilaterally by a single observer using a GE LOGIQ e ultrasound system. Measurements were taken pre-RCC application, immediately after, every hour over four hours, and five minutes postcollar removal. The CSA of the IJV was 8.3 ±6.0 mm2 pre-RCC application. The CSA of the IJV doubled (18.92 ±10.55 mm2 ) after four hours and decreased back to 9.36 ±6.8 mm2 five minutes postcollar removal. The circumference of the IJV was 17.29 ±6.03 mm pre-RCC application, increasing to 20.34 ±5.59 mm by the end of the fourth hour and returning to 16.14 ±5.16 mm five minutes postcollar removal. Related-samples Friedman's ANOVA test showed statistically significant differences for both left and right CSAs and circumferences of the IJV measured across the four hours (P-value<0.05). Ultrasound assessment of CSA of the IJV may correlate with changes in ICP. Further studies may provide insight into the effects of collar design, and guide future trauma protocol to minimize intracranial pressure fluctuations. Clin. Anat. 32:196-200, 2019. © 2018 Wiley Periodicals, Inc.

Effect of positive end-expiratory pressure on the cross-sectional area of the internal jugular vein and anatomic relationship between the internal jugular vein and the carotid artery in general anaesthesia of laryngeal mask airway

Objective: To investigate the effect of positive end-expiratory pressure(PEEP) on the cross-sectional area (CSA) of the internal jugular vein (IJV) and anatomic relationship between the IJV and the common carotid artery (CCA) in general anaesthesia of laryngeal mask airway(LMA). Methods: Sixty American Society of Anesthesiologists (ASA) Ⅰ or Ⅱ grade patients undergoing elective operation received general anaesthesia using LMA from May to November 2017, aged 20-65, were included in this study and randomly divided into 4 groups: group P0 (PEEP: 0 cmH(2)O), group P5 (PEEP: 5 cmH(2)O), group P10 (PEEP: 10 cmH(2)O), group P15 (PEEP: 15 cmH(2)O). Following the induction of anesthesia, LMA was inserted, and mechanical ventilation was started while the right cervical vessels was imaged by ultrasonography after applying 4 different PEEPs in random order. Measurements were made after 1 min in each PEEP. The CSA, transverse diameter (TD), anteroposterior diameters (AD) of the IJV and the diameter, overlap distance and overlap index of CCA was measured. The arterial blood pressure, heart rate, and vasoactive drugs used were also recorded. Results: The CSA of group P0, P10 and P15 was (1.36±0.55), (1.80±0.54), (2.02±0.58) cm(2). The TD was (1.31±0.33), (1.61±0.49), (1.74±0.53) cm. The AD was (1.12±0.20), (1.33±0.30), (1.46±0.32) cm. Compared to group P0, the CSA, TD and AD of IJV in group P10 and P15 were significantly increased (P0/P10: t=7.81, 3.81, 4.30, all P<0.01; P0/P15: t=11.68, 5.40, 6.96, all P<0.01). There was no significant difference in the AD and TD of IJV between group P10 and P15 (all P>0.05), while the CSA of group P15 was bigger than that of group P10 (t=2.17, P<0.05). The overlap distance of group P0, P10 and P15 was (0.51±0.12), (0.62±0.16), (0.66±0.15) cm. The overlap index was (76.80±20.03)%, (91.10±26.13)%, (96.21±25.36)%. Compared to group P0, the overlap distance and overlap index in group P10 and P15 were significantly increased (P0/P10: t=4.49, 3.41, both P<0.01; P0/P15: t=5.91, 4.63, both P<0.01). There was no significant changes in the overlap distance and overlap index between group P10 and P15 (all P>0.05). The MAP of group P15 was lower than that of group P10 [(73.35±9.73 )vs (67.58±12.58) mmHg, t=2.745, P<0.05]. No patients were given atropine or norepinephrine. Conclusions: The application of PEEP effectively increases the CSA of IJV in general anaesthesia of LMA. At the same time, it also lead to higher overlap index between the IJV and CCA.Ten cmH(2)O PEEP provides the best balance between the increase of CSA and the stability of haemodynamics.