Roy C. Ziegelstein, MD

The use of hand‐carried ultrasound by nonspecialists is increasing. Of particular interest to hospitalists is bedside ultrasound assessment of the inferior vena cava (IVC), which more accurately estimates left atrial pressure than does assessment of jugular venous pressure by physical examination.[1] Invasively measured central venous pressure (CVP) also correlates closely with estimates from IVC imaging.[1, 2, 3, 4] Although quick, accurate bedside determination of CVP may have broad potential applications in hospital medicine,[5, 6, 7, 8] of particular interest to patients and their advocates is whether hospitalists are sufficiently skilled to perform this procedure. Lucas et al. found that 8 hospitalists trained to perform 6 cardiac assessments by hand‐carried ultrasound could identify an enlarged IVC with moderate accuracy (sensitivity 56%, specificity 86%).[9] To our knowledge, no other study has examined whether hospitalists can readily develop the skills to accurately assess the IVC by ultrasound. We therefore studied whether the skills needed to acquire and interpret IVC images by ultrasound could be acquired by hospitalists after a brief training program.

METHODS

RESULTS

From among 18 hospitalist volunteers, the 10 board‐certified hospitalists who could attend 1 of the scheduled training sessions were enrolled and completed the study. Hospitalists' demographic information and performance are summarized in Table 1. Hospitalists completed the initial online curriculum in an average of 18.37 minutes. After the in‐person training session, 8 of 10 hospitalists acquired adequate IVC images on all 5 volunteer subjects. One hospitalist obtained adequate images in 4 of 5 patients. Another hospitalist only obtained adequate images in 3 of 5 patients; a hepatic vein and the abdominal aorta were erroneously measured instead of the IVC in 1 subject each. This hospitalist later performed supervised IVC imaging on 7 additional hospital inpatients and was the only hospitalist to request additional direct supervision by the research echocardiography technician. All hospitalists were able to accurately quantify the IVC collapsibility index and estimate the CVP from all 10 prerecorded cases showing still images and video clips of the IVC. Based on IVC images, 1 of the 5 volunteers used in testing each day had a very elevated CVP, and the other 4 had CVPs ranging from low to normal. The volunteer's average BMI was overweight at 27.4, with a range from 15.4 to 37.1.

At 7.40.7 weeks (range, 6.98.6 weeks) follow‐up, 9 of 10 hospitalists obtained adequate IVC images in all 5 volunteer subjects and interpreted them correctly for estimating CVP. The hospitalist who performed most poorly at the initial assessment acquired adequate images and interpreted them correctly in 4 of 5 patients at follow‐up. Overall, hospitalists' visual assessment of IVC collapsibility index agreed with the quantitative collapsibility index calculation in 180 of 198 (91%) of the interpretable encounters. By the time of the follow‐up assessment, hospitalists had performed IVC imaging on 3.93.0 additional hospital inpatients (range, 011 inpatients). Lack of time assigned to the clinical service was the main barrier limiting further IVC imaging during that interval. Hospitalists also identified time constraints and need for secure yet accessible device storage as other barriers.

None of the hospitalists had previous experience imaging the IVC, and prior to training they rated their average confidence to acquire an IVC image and interpret it by the hand‐carried ultrasound device at 3 (3, 4) and 3 (3, 4), respectively. After the initial training session, 9 of 10 hospitalists believed they had received adequate online and in‐person training and were confident in their ability to acquire and interpret IVC images. After all training sessions the hospitalists on average rated their confidence statistically significantly better for acquiring and interpreting IVC images at 2 (1, 2) (P=0.005) and 2 (1, 2) (P=0.004), respectively compared to baseline.

DISCUSSION

This study shows that after a relatively brief training intervention, hospitalists can develop and over a short term retain important skills in the acquisition and interpretation of IVC images to estimate CVP. Estimating CVP is key to the care of many patients, but cannot be done accurately by most physicians.[10] Although our study has a number of limitations, the ability to estimate CVP acquired after only a brief training intervention could have important effects on patient care. Given that a dilated IVC with reduced respiratory collapsibility was found to be a statistically significant predictor of 30‐day readmission for heart failure,¹¹ key clinical outcomes to measure in future work include whether IVC ultrasound assessment can help guide diuresis, limit complications, and ultimately reduce rehospitalizations for heart failure, the most expensive diagnosis for Medicare.[12]

Because hand‐carried ultrasound is a point‐of‐care diagnostic tool, we also examined the ability of hospitalists to visually approximate the IVC collapsibility index. Hospitalists' qualitative performance (IVC collapsibility judged correctly 91% of the time without performing formal measurements) is consistent with studies involving emergency medicine physicians and suggests that CVP may be rapidly and accurately estimated in most instances.[13] There may be, however, value to formally measuring the IVC maximum diameter, because it may be inaccurately visually estimated due to changes in scale when the imaging depth is adjusted. Accurately measuring the IVC maximum diameter is important because a maximum diameter of more than 2.0 cm is evidence of an elevated right atrial pressure (82% sensitivity and 84% specificity for predicting right atrial pressure of 10 mm Hg or above) and an elevated pulmonary capillary wedge pressure (75% sensitivity and 83% specificity for pulmonary capillary wedge pressure of 15 mm Hg or more).[14]

Limitations

Our findings should be interpreted cautiously given the relatively small number of hospitalists and subjects used for hand‐carried ultrasound imaging. Although our direct observations of hospitalist performance in IVC imaging were based on objective measurements performed and interpreted accurately, we did not record the images, which would have allowed separate analyses of inter‐rater reliability measures. The majority of volunteer subjects were chronically ill, but they were nonetheless stable outpatients and may have been easier to position and image relative to acutely ill inpatients. Hospitalist self‐selected participation may introduce a bias favoring hospitalists interested in learning hand‐carried ultrasound skills; however, nearly half of the hospitalist group volunteered and enrollments in the study were based only on their availability for the previously scheduled study dates.

IMPLICATIONS FOR TRAINING

Our study, especially the assessment of the hospitalists' ability to retain their skills, adds to what is known about training hospitalists in hand‐carried ultrasound and may help inform deliberations among hospitalists as to whether to join other professional societies in defining specialty‐specific bedside ultrasound indications and training protocols.[9, 15] As individuals acquire new skills at variable rates, training cannot be defined by the number of procedures performed, but rather by the need to provide objective evidence of acquired procedural skills. Thus, going forward there is also a need to develop and validate tools for assessment of competence in IVC imaging skills.

The use of hand‐carried ultrasound by nonspecialists is increasing. Of particular interest to hospitalists is bedside ultrasound assessment of the inferior vena cava (IVC), which more accurately estimates left atrial pressure than does assessment of jugular venous pressure by physical examination.[1] Invasively measured central venous pressure (CVP) also correlates closely with estimates from IVC imaging.[1, 2, 3, 4] Although quick, accurate bedside determination of CVP may have broad potential applications in hospital medicine,[5, 6, 7, 8] of particular interest to patients and their advocates is whether hospitalists are sufficiently skilled to perform this procedure. Lucas et al. found that 8 hospitalists trained to perform 6 cardiac assessments by hand‐carried ultrasound could identify an enlarged IVC with moderate accuracy (sensitivity 56%, specificity 86%).[9] To our knowledge, no other study has examined whether hospitalists can readily develop the skills to accurately assess the IVC by ultrasound. We therefore studied whether the skills needed to acquire and interpret IVC images by ultrasound could be acquired by hospitalists after a brief training program.

METHODS

RESULTS

From among 18 hospitalist volunteers, the 10 board‐certified hospitalists who could attend 1 of the scheduled training sessions were enrolled and completed the study. Hospitalists' demographic information and performance are summarized in Table 1. Hospitalists completed the initial online curriculum in an average of 18.37 minutes. After the in‐person training session, 8 of 10 hospitalists acquired adequate IVC images on all 5 volunteer subjects. One hospitalist obtained adequate images in 4 of 5 patients. Another hospitalist only obtained adequate images in 3 of 5 patients; a hepatic vein and the abdominal aorta were erroneously measured instead of the IVC in 1 subject each. This hospitalist later performed supervised IVC imaging on 7 additional hospital inpatients and was the only hospitalist to request additional direct supervision by the research echocardiography technician. All hospitalists were able to accurately quantify the IVC collapsibility index and estimate the CVP from all 10 prerecorded cases showing still images and video clips of the IVC. Based on IVC images, 1 of the 5 volunteers used in testing each day had a very elevated CVP, and the other 4 had CVPs ranging from low to normal. The volunteer's average BMI was overweight at 27.4, with a range from 15.4 to 37.1.

At 7.40.7 weeks (range, 6.98.6 weeks) follow‐up, 9 of 10 hospitalists obtained adequate IVC images in all 5 volunteer subjects and interpreted them correctly for estimating CVP. The hospitalist who performed most poorly at the initial assessment acquired adequate images and interpreted them correctly in 4 of 5 patients at follow‐up. Overall, hospitalists' visual assessment of IVC collapsibility index agreed with the quantitative collapsibility index calculation in 180 of 198 (91%) of the interpretable encounters. By the time of the follow‐up assessment, hospitalists had performed IVC imaging on 3.93.0 additional hospital inpatients (range, 011 inpatients). Lack of time assigned to the clinical service was the main barrier limiting further IVC imaging during that interval. Hospitalists also identified time constraints and need for secure yet accessible device storage as other barriers.

None of the hospitalists had previous experience imaging the IVC, and prior to training they rated their average confidence to acquire an IVC image and interpret it by the hand‐carried ultrasound device at 3 (3, 4) and 3 (3, 4), respectively. After the initial training session, 9 of 10 hospitalists believed they had received adequate online and in‐person training and were confident in their ability to acquire and interpret IVC images. After all training sessions the hospitalists on average rated their confidence statistically significantly better for acquiring and interpreting IVC images at 2 (1, 2) (P=0.005) and 2 (1, 2) (P=0.004), respectively compared to baseline.

DISCUSSION

This study shows that after a relatively brief training intervention, hospitalists can develop and over a short term retain important skills in the acquisition and interpretation of IVC images to estimate CVP. Estimating CVP is key to the care of many patients, but cannot be done accurately by most physicians.[10] Although our study has a number of limitations, the ability to estimate CVP acquired after only a brief training intervention could have important effects on patient care. Given that a dilated IVC with reduced respiratory collapsibility was found to be a statistically significant predictor of 30‐day readmission for heart failure,¹¹ key clinical outcomes to measure in future work include whether IVC ultrasound assessment can help guide diuresis, limit complications, and ultimately reduce rehospitalizations for heart failure, the most expensive diagnosis for Medicare.[12]

Because hand‐carried ultrasound is a point‐of‐care diagnostic tool, we also examined the ability of hospitalists to visually approximate the IVC collapsibility index. Hospitalists' qualitative performance (IVC collapsibility judged correctly 91% of the time without performing formal measurements) is consistent with studies involving emergency medicine physicians and suggests that CVP may be rapidly and accurately estimated in most instances.[13] There may be, however, value to formally measuring the IVC maximum diameter, because it may be inaccurately visually estimated due to changes in scale when the imaging depth is adjusted. Accurately measuring the IVC maximum diameter is important because a maximum diameter of more than 2.0 cm is evidence of an elevated right atrial pressure (82% sensitivity and 84% specificity for predicting right atrial pressure of 10 mm Hg or above) and an elevated pulmonary capillary wedge pressure (75% sensitivity and 83% specificity for pulmonary capillary wedge pressure of 15 mm Hg or more).[14]

Limitations

Our findings should be interpreted cautiously given the relatively small number of hospitalists and subjects used for hand‐carried ultrasound imaging. Although our direct observations of hospitalist performance in IVC imaging were based on objective measurements performed and interpreted accurately, we did not record the images, which would have allowed separate analyses of inter‐rater reliability measures. The majority of volunteer subjects were chronically ill, but they were nonetheless stable outpatients and may have been easier to position and image relative to acutely ill inpatients. Hospitalist self‐selected participation may introduce a bias favoring hospitalists interested in learning hand‐carried ultrasound skills; however, nearly half of the hospitalist group volunteered and enrollments in the study were based only on their availability for the previously scheduled study dates.

IMPLICATIONS FOR TRAINING

Our study, especially the assessment of the hospitalists' ability to retain their skills, adds to what is known about training hospitalists in hand‐carried ultrasound and may help inform deliberations among hospitalists as to whether to join other professional societies in defining specialty‐specific bedside ultrasound indications and training protocols.[9, 15] As individuals acquire new skills at variable rates, training cannot be defined by the number of procedures performed, but rather by the need to provide objective evidence of acquired procedural skills. Thus, going forward there is also a need to develop and validate tools for assessment of competence in IVC imaging skills.

The use of hand‐carried ultrasound by nonspecialists is increasing. Of particular interest to hospitalists is bedside ultrasound assessment of the inferior vena cava (IVC), which more accurately estimates left atrial pressure than does assessment of jugular venous pressure by physical examination.[1] Invasively measured central venous pressure (CVP) also correlates closely with estimates from IVC imaging.[1, 2, 3, 4] Although quick, accurate bedside determination of CVP may have broad potential applications in hospital medicine,[5, 6, 7, 8] of particular interest to patients and their advocates is whether hospitalists are sufficiently skilled to perform this procedure. Lucas et al. found that 8 hospitalists trained to perform 6 cardiac assessments by hand‐carried ultrasound could identify an enlarged IVC with moderate accuracy (sensitivity 56%, specificity 86%).[9] To our knowledge, no other study has examined whether hospitalists can readily develop the skills to accurately assess the IVC by ultrasound. We therefore studied whether the skills needed to acquire and interpret IVC images by ultrasound could be acquired by hospitalists after a brief training program.

METHODS

RESULTS

From among 18 hospitalist volunteers, the 10 board‐certified hospitalists who could attend 1 of the scheduled training sessions were enrolled and completed the study. Hospitalists' demographic information and performance are summarized in Table 1. Hospitalists completed the initial online curriculum in an average of 18.37 minutes. After the in‐person training session, 8 of 10 hospitalists acquired adequate IVC images on all 5 volunteer subjects. One hospitalist obtained adequate images in 4 of 5 patients. Another hospitalist only obtained adequate images in 3 of 5 patients; a hepatic vein and the abdominal aorta were erroneously measured instead of the IVC in 1 subject each. This hospitalist later performed supervised IVC imaging on 7 additional hospital inpatients and was the only hospitalist to request additional direct supervision by the research echocardiography technician. All hospitalists were able to accurately quantify the IVC collapsibility index and estimate the CVP from all 10 prerecorded cases showing still images and video clips of the IVC. Based on IVC images, 1 of the 5 volunteers used in testing each day had a very elevated CVP, and the other 4 had CVPs ranging from low to normal. The volunteer's average BMI was overweight at 27.4, with a range from 15.4 to 37.1.

At 7.40.7 weeks (range, 6.98.6 weeks) follow‐up, 9 of 10 hospitalists obtained adequate IVC images in all 5 volunteer subjects and interpreted them correctly for estimating CVP. The hospitalist who performed most poorly at the initial assessment acquired adequate images and interpreted them correctly in 4 of 5 patients at follow‐up. Overall, hospitalists' visual assessment of IVC collapsibility index agreed with the quantitative collapsibility index calculation in 180 of 198 (91%) of the interpretable encounters. By the time of the follow‐up assessment, hospitalists had performed IVC imaging on 3.93.0 additional hospital inpatients (range, 011 inpatients). Lack of time assigned to the clinical service was the main barrier limiting further IVC imaging during that interval. Hospitalists also identified time constraints and need for secure yet accessible device storage as other barriers.

None of the hospitalists had previous experience imaging the IVC, and prior to training they rated their average confidence to acquire an IVC image and interpret it by the hand‐carried ultrasound device at 3 (3, 4) and 3 (3, 4), respectively. After the initial training session, 9 of 10 hospitalists believed they had received adequate online and in‐person training and were confident in their ability to acquire and interpret IVC images. After all training sessions the hospitalists on average rated their confidence statistically significantly better for acquiring and interpreting IVC images at 2 (1, 2) (P=0.005) and 2 (1, 2) (P=0.004), respectively compared to baseline.

DISCUSSION

This study shows that after a relatively brief training intervention, hospitalists can develop and over a short term retain important skills in the acquisition and interpretation of IVC images to estimate CVP. Estimating CVP is key to the care of many patients, but cannot be done accurately by most physicians.[10] Although our study has a number of limitations, the ability to estimate CVP acquired after only a brief training intervention could have important effects on patient care. Given that a dilated IVC with reduced respiratory collapsibility was found to be a statistically significant predictor of 30‐day readmission for heart failure,¹¹ key clinical outcomes to measure in future work include whether IVC ultrasound assessment can help guide diuresis, limit complications, and ultimately reduce rehospitalizations for heart failure, the most expensive diagnosis for Medicare.[12]

Because hand‐carried ultrasound is a point‐of‐care diagnostic tool, we also examined the ability of hospitalists to visually approximate the IVC collapsibility index. Hospitalists' qualitative performance (IVC collapsibility judged correctly 91% of the time without performing formal measurements) is consistent with studies involving emergency medicine physicians and suggests that CVP may be rapidly and accurately estimated in most instances.[13] There may be, however, value to formally measuring the IVC maximum diameter, because it may be inaccurately visually estimated due to changes in scale when the imaging depth is adjusted. Accurately measuring the IVC maximum diameter is important because a maximum diameter of more than 2.0 cm is evidence of an elevated right atrial pressure (82% sensitivity and 84% specificity for predicting right atrial pressure of 10 mm Hg or above) and an elevated pulmonary capillary wedge pressure (75% sensitivity and 83% specificity for pulmonary capillary wedge pressure of 15 mm Hg or more).[14]

Limitations

Our findings should be interpreted cautiously given the relatively small number of hospitalists and subjects used for hand‐carried ultrasound imaging. Although our direct observations of hospitalist performance in IVC imaging were based on objective measurements performed and interpreted accurately, we did not record the images, which would have allowed separate analyses of inter‐rater reliability measures. The majority of volunteer subjects were chronically ill, but they were nonetheless stable outpatients and may have been easier to position and image relative to acutely ill inpatients. Hospitalist self‐selected participation may introduce a bias favoring hospitalists interested in learning hand‐carried ultrasound skills; however, nearly half of the hospitalist group volunteered and enrollments in the study were based only on their availability for the previously scheduled study dates.

IMPLICATIONS FOR TRAINING

Our study, especially the assessment of the hospitalists' ability to retain their skills, adds to what is known about training hospitalists in hand‐carried ultrasound and may help inform deliberations among hospitalists as to whether to join other professional societies in defining specialty‐specific bedside ultrasound indications and training protocols.[9, 15] As individuals acquire new skills at variable rates, training cannot be defined by the number of procedures performed, but rather by the need to provide objective evidence of acquired procedural skills. Thus, going forward there is also a need to develop and validate tools for assessment of competence in IVC imaging skills.