Effect of diluent fluid viscosity on acoustic droplet vaporization-mediated dissolved oxygen scavenging

Abstract

Acoustic droplet vaporization (ADV) can be used to scavenge dissolved oxygen and reduce the partial pressure of oxygen (pO2) in a fluid containing perfluoropentane droplets. The impact of the diluent fluid’s viscosity on ADV-mediated pO2 reduction was investigated. Polyvinylpyrrolidone (PVP) was dissolved in saline to modify the solution’s viscosity. The diluent fluid viscosity (η) and surface tension (γ) were measured. Droplets were manufactured using amalgamation and differential centrifugation to yield diameters between 1-6 μm. Droplets were diluted to 6.5x106 droplets/mL in saline (γ = 68 mN/m, η = 0.7 cP), 3 mg/mL PVP solution (γ = 65 mN/m, η = 1.2 cP), or 15 mg/mL PVP solution (γ = 65 mN/m, η = 4 cP). The viscosities of the 3 mg/mL and 15 mg/mL PVP solutions mimicked those of plasma and whole blood, respectively. Droplet solutions were exposed to ultrasound (5 MHz, 4.25 MPa peak negative pressure in situ, 10 cycles) in a 37°C in vitro flow system. The initial pO2 in the fluids was 113±2 mmHg, similar to human arterial pO2. After ultrasound exposure, the pO2 in saline, 3 mg/mL PVP, and 15 mg/mL PVP solutions were reduced by 39.9±0.8 mmHg, 31.9±0.7 mmHg, and 16.0±0.4 mmHg, respectively. These studies indicated that ADV-mediated pO2 reduction increased with decreasing viscosity.