Ultrasound Evaluation of Sinus Fluid Levels in Swine During Microgravity Conditions

Abstract

Acute rhinosinusitis is a common problem that could occur in space secondary to absence of gravity-dependent drainage or odontogenic or external sources of infection. The purpose of this study was to determine the efficacy of ultrasound to determine sinus fluid distribution levels in swine and to assess the accuracy of ultrasound in the animal during normal and microgravity conditions. Anesthetized swine had a catheter placed through a frontal bone window to allow aliquots of a viscous solution to be injected at 1 G (N = 4) or during brief microgravity parabolic flights (N = 4). Ultrasound examinations were performed with a high frequency probe during baseline and fluid-induced conditions. There was a consistent air-fluid level interface seen on ultrasound examination with the injection of 1 ml of fluid during 1-G conditions. Microgravity conditions caused the rapid (< 10 s) dissolution of the air-fluid level associated with dispersion of the fluid to the walIs of the sinus cavity in a uniform fashion. The air-fluid interface was recreated with return to 1 G. Ultrasound is a reliable diagnostic test for assessing fluid levels; these experiments demonstrate the technique can be used during microgravity conditions with attention to altered fluid behavior in the absence of gravity.