Internal jugular vein collapsibility index associated with hypovolemia in the intensive care unit patients
© Springer-Verlag 2010
Received: 30 March 2010
Accepted: 31 May 2010
Published: 12 June 2010
To evaluate the correlation between the internal jugular vein (IJV) collapsibility index and hypovolemia in intensive care unit (ICU) patients, using point of care ultrasound imaging.
A prospective observational study was conducted in an urban tertiary care teaching hospital, in the surgical ICU. Intensivist point-of-care sonographers performed IJV ultrasound on 31 ICU patients who were diagnosed to be hypovolemic or euvolemic by their treating ICU physicians.
Hypovolemic ICU patients (16 of 31) were 50% male and 75% white with a mean age of 63 (±19) years. The variables measured between the hypovolemic and euvolemic ICU patients were the mean arterial pressure, heart rate, respiratory rate, central venous pressure (CVP). Their correlation with hypovolemia was significant (p < 0.05). The ROC curve analysis found the IJV collapsibility index ≥39% correlated best with hypovolemic ICU patient with a sensitivity of 87.5% and specificity 100%. The area under ROC curve for IJV collapsibility index was 0.938, with no significant difference to CVP with the area under ROC curve of 0.87 (p = 0.467).
IJV collapsibility index can be identified by intensivist point-of-care sonographers in the hypovolemic and euvolemic ICU patients. The presence of IJV collapsibility index greater than 39% may be associated with hypovolemia in ICU patients.
Assessment of intravascular volume status and hypovolemia can be challenging at times, especially when relying on physical examination and physiologic data in ICU patients [1, 2, 4]. Bedside echocardiography can estimate central venous pressure (CVP) based on evaluation of the inferior vena cava (IVC) distention and respiratory variation [4, 6]. This can sometimes be limited by equipment availability, ultrasound expertise and the inability to view the IVC [4, 6]. The current standard for measuring the right-sided filling pressures and CVP requires an invasive central venous catheter, which can delay intravascular resuscitation and be associated with possible iatrogenic complications .
Point of care ultrasound imaging technique of the IJV has been proposed for the evaluation of the CVP [3, 5]. Lipton  describes estimating CVP by identifying the ultrasound pattern of the jugular venous pulsation. Keller et al.  discussed the correlation of IJV aspect ratio (height/width) to estimate a CVP of 8 mmHg in spontaneously breathing patients. The measurement of end-expiratory IJV diameter in spontaneously breathing supine patient has shown high correlation with CVP . In this study, we evaluated ICU patients who were euvolemic, hypovolemic, spontaneously breathing or on mechanical ventilation and with or without vasopressor support.
We hypothesize that point of care ultrasound imaging of IJV collapsibility index would be associated and correlate with hypovolemia in ICU patients.
This prospective, observational study was performed in the surgical ICU of an urban tertiary care teaching hospital. The study was approved by the Institutional Review Boards of Henry Ford Hospital and informed consent was obtained from all persons or their next of kin prior to their inclusion in the study. Convenience samples of 31 patients were included in the study. Recruitment was based on the presenting symptoms that led the treating ICU physicians to decide if the patient’s volume status was hypovolemic or euvolemic. This diagnosis and criteria used for volume assessment was based on objective data and the clinical assessment by the treating ICU physician, as heart rate, blood pressure, respiratory rate, as well as invasive monitoring with CVP measurements. The diagnosis and assessment of the treating ICU physician was considered the reference. All enrolled patients had their right or left IJV scanned and measured by one of two intensivist point-of-care sonographers experienced in point-of-care ultrasound. The intensivist point-of-care sonographers were not involved in the medical management of these ICU patients, but were not blinded to the volume status of the patients studied. Inclusion criteria included age of 18 years or older, admission to the surgical ICU and volume assessment determined as hypovolemia or euvolemia by the treating ICU physician. Exclusion criteria were inability to image IJV secondary to a cervical collar, surgical dressing or inability for the patient to be properly positioned. The IJV with a central venous catheter was not examined rather the opposite side was evaluated if no contraindications. No patients were excluded once enrolled and measurements were completed.
Protocol for measurement of internal jugular venous (IJV) collapsibility index
1. Position patient at 30° head elevation, as standard of care for mechanically ventilated patients, ensuring overall comfort
2. Rotate the head slightly <30° to expose right or left IJV
3. Place transducer transversely across the patient neck, the area lateral to the level of the cricoid cartilage
4. IJV vessel identification was done by identifying 2 vessels lateral to the trachea and IJV is identified by compressibility, color flow or pulse wave Doppler
5. Applying minimum pressure, enough to obtain adequate ultrasound image of the right/left IJV
6. Rotate the transducer clockwise or counter-clockwise to obtain the most circular cross-sectional image of the IJV
7. Store the image of the patient’s complete respiratory cycle
8. Measure the AP diameter during maximum and minimum distention during a respiratory cycle. On occasion, M mode was used to determine max and min AP diameter
9. Calculate IJV collapsibility index = [(Max diameter − Min diameter)/(Max diameter)] × 100%
Primary data analysis used included Chi-squared analysis for binary variables and nonparametric Mann–Whitney test for continuous variables. p value < 0.05 was considered statistically significant. Logistic regression model adjusted for the association of the predicted variables in hypovolemia. ROC curve was done for those variables with statistically significant association with hypovolemia.
Baseline characteristics of euvolemic and hypovolemic patients
Hypovolemic (n = 16)
Euvolemic (n = 15)
Heart rate (beats/min)
Resp rate (breaths/min)
Mechanical ventilation with PEEP
IJV collapsibility index
The hypovolemic patients were 50% male and 75% white. The baseline physiologic variables of the hypovolemic group were as follows: mean blood pressure 77 (±32) mmHg, heart rate 99 (±19) beats per minute, and respiratory rate 23 (±7) breaths per minute, and temperature 37.3°C (±0.8). Significant variables between the hypovolemic and euvolemic patients were the mean arterial pressure, heart rate, respiratory rate, CVP, and IJV collapsibility index (Table 2).
Variables associated with hypovolemic patients
OR (95% CI)
Heart rate (beats/min)
Resp. rate (breaths/min)
IJV Collapsibility Index
Subset analysis of the five mechanically ventilated hypovolemic patients showed a mean IJV collapsibility index of 52.9% compared to the one euvolemic mechanically ventilated patient with an IJV collapsibility index of 21% (p = 0.31). All mechanically ventilated patients were on PEEP.
Point-of-care ultrasound can identify the IJV collapsibility index, which can aid in determining the volume status in ICU patients. The IJV collapsibility index can be applied to most ICU patients including those with mechanical ventilation on PEEP or vasopressor support, which were not included in previous studies [1, 2].
On daily clinical rounds, intensivists depend on multiple adjunct physiologic and invasive monitoring parameters to aid in determining the volume status of the ICU patient. IJV collapsibility index can be used as an adjunct to physiologic parameter such as higher heart rate, higher respiratory rate, and lower systolic blood pressure and lower CVP found in hypovolemic patients.
The measurement process of IJV collapsibility index can be readily accessible, feasible, reproducible, and found to be equivalent in both right and left IJV and in males and females. The training involved requires being able to perform point-of-care ultrasound examination and identify the IJV, then the limited technical expertise of measuring the AP diameter during maximal and minimal distention and calculating the collapsibility index.
Our study was designed to determine the correlation between clinical volume status and IJV collapsibility index. This study was not designed to replace invasive monitoring in ICU patients, rather to determine if the IJV collapsibility index is a promising adjunct to our current objective parameters including invasive CVP monitoring, given the limitation and time required in obtaining central venous access.
The study had some limitations. It was an observational analysis done at a single institution. There was potential selection bias on the limited convenient sample enrolled. All patients enrolled had no recent formal echocardiography prior to identify tricuspid stenosis or regurgitation or any other cardiac disorder that may lead to a falsely elevated central venous pressures. There was no gold standard technique to determine if the patient was hypovolemic or euvolemic as a pulmonary artery catheter, to measure pressures and cardiac output. Instead the volume status was determined by the treating ICU physician, using subjective and objective data including CVP, blood pressure, heart rate, urine output, radiographs in determining the ICU patient to be euvolemic or hypovolemic. Another limitation, the intensivist point-of-care sonographers performing the study were not blinded to the volume status of the patient, which can lead to bias in measurements.
Whether the presence of mechanical ventilation, PEEP, and patient effort of respiration has any effect on the IJV collapsibility index is unknown, but the mean results showed the same trend in IJV collapsibility index in mechanically ventilated patients compared to those who were spontaneously breathing.
Larger studies are needed to verify these results. Future studies may also consider a more standardized method for volume assessment to be used as a gold standard, in addition to the clinical assessment of the treating ICU physician. As an adjunct to invasive CVP monitoring, future studies will be needed to determine the utility of the IJV collapsibility index in the setting of early aggressive fluid resuscitation.
IJV collapsibility index can be identified via point-of-care ultrasound in the hypovolemic and euvolemic ICU patients. The presence of IJV collapsibility index greater than 39% may be associated with hypovolemic ICU patients with or without mechanical ventilation.
Conflict of interest
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