Estimating the accuracy of optic nerve sheath diameter measurement using a pocket-sized, handheld ultrasound on a simulation model.
BACKGROUND
Ultrasound measurement of optic nerve sheath diameter (ONSD) appears to be a promising, rapid, non-invasive bedside tool for identification of elevated intra-cranial pressure. With improvements in ultrasound technology, machines are becoming smaller; however, it is unclear if these ultra-portable handheld units have the resolution to make these measurements precisely. In this study, we estimate the accuracy of ONSD measurement in a pocket-sized ultrasound unit.


METHODS
Utilizing a locally developed, previously validated model of the eye, ONSD was measured by two expert observers, three times with two machines and on five models with different optic nerve sheath sizes. A pocket ultrasound (Vscan, GE Healthcare) and a standard portable ultrasound (M-Turbo, SonoSite) were used to measure the models. Data was analyzed by Bland-Altman plot and intra-class correlation coefficient (ICC).


RESULTS
The ICC between raters for the SonoSite was 0.878, and for the Vscan was 0.826. The between-machine agreement ICC was 0.752. Bland-Altman agreement analysis between the two ultrasound methods showed an even spread across the range of sheath sizes, and that the Vscan tended to read on average 0.33 mm higher than the SonoSite for each measurement, with a standard deviation of 0.65 mm.


CONCLUSIONS
Accurate ONSD measurement may be possible utilizing pocket-sized, handheld ultrasound devices despite their small screen size, lower resolution, and lower probe frequencies. Further study in human subjects is warranted for all newer handheld ultrasound models as they become available on the market.
Undergraduate Medical Education, University of Manitoba, Winnipeg, MB, Canada.
Garrett G R J
GG
Johnson
Departments of Surgery, University of Manitoba, GF439, 820 Sherbrook Street, Winnipeg, MB, R3A 1R9, Canada.|Clinician Investigator Program, University of Manitoba, Winnipeg, MB, Canada.
Frederick A
FA
Zeiler
Department of Internal Medicine, Section of Critical Care, University of Manitoba, Winnipeg, MB, Canada.
Bertram
B
Unger
Pediatrics and Child Health, University of Manitoba, Winnipeg, MB, Canada.
Gregory
G
Hansen
Department of Critical Care, Keck Medical School, USC, Los Angeles, CA, USA.
Dimitrios
D
Karakitsos
Departments of Surgery, University of Manitoba, GF439, 820 Sherbrook Street, Winnipeg, MB, R3A 1R9, Canada. gillmanlm@yahoo.ca.
Lawrence M
http://orcid.org/0000-0003-2429-9740
LM
Gillman
Handheld ultrasound; Intra-cranial pressure; Optic nerve sheath diameter; Point-of-care ultrasound; Ultrasound