Focused Assessment with Sonography for Trauma in weightlessness: a feasibility study.
BACKGROUND
The Focused Assessment with Sonography for Trauma (FAST) examines for fluid in gravitationally dependent regions. There is no prior experience with this technique in weightlessness, such as on the International Space Station, where sonography is currently the only diagnostic imaging tool.


METHODS
A ground-based (1 g) porcine model for sonography was developed. We examined both the feasibility and the comparative performance of the FAST examination in parabolic flight. Sonographic detection and fluid behavior were evaluated in four animals during alternating weightlessness (0 g) and hypergravity (1.8 g) periods. During flight, boluses of fluid were incrementally introduced into the peritoneal cavity. Standardized sonographic windows were recorded. Postflight, the video recordings were divided into 169 20-second segments for subsequent interpretation by 12 blinded ultrasonography experts. Reviewers first decided whether a video segment was of sufficient diagnostic quality to analyze (determinate). Determinate segments were then analyzed as containing or not containing fluid. A probit regression model compared the probability of a positive fluid diagnosis to actual fluid levels (0 to 500 mL) under both 0-g and 1.8-g conditions.


RESULTS
The in-flight sonographers found real-time scanning and interpretation technically similar to that of terrestrial conditions, as long as restraint was maintained. On blinded review, 80% of the recorded ultrasound segments were considered determinate. The best sensitivity for diagnosis in 0 g was found to be from the subhepatic space, with probability of a positive fluid diagnosis ranging from 9% (no fluid) to 51% (500 mL fluid).


CONCLUSIONS
The FAST examination is technically feasible in weightlessness, and merits operational consideration for clinical contingencies in space.
Kirkpatrick
Andrew W
AW
Foothills Medical Centre, Calgary, Alberta, Canada.
Hamilton
Douglas R
DR
Nicolaou
Savvas
S
Sargsyan
Ashot E
AE
Campbell
Mark R
MR
Feiveson
Alan
A
Dulchavsky
Scott A
SA
Melton
Shannon
S
Beck
George
G
Dawson
David L
DL
D000337:Aerospace Medicine / Q000379:methods* / Q000592:standards / Q000639:trends; D000818:Animals; D004195:Disease Models, Animal; D005240:Feasibility Studies; D005260:Female; D005544:Forecasting; D018471:Hypergravity; D012044:Regression Analysis; D012212:Rheology; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D013552:Swine; D014194:Traumatology / Q000379:methods / Q000592:standards / Q000639:trends; D014463:Ultrasonography; D014893:Weightlessness; D018474:Weightlessness Simulation; D014947:Wounds and Injuries / Q000000981:diagnostic imaging*