Assessing the effects of droplet diameter on oxygen scavenging in the presence of hemoglobin via acoustic droplet vaporization

Abstract

Reducing bioavailable oxygen (O2) during reperfusion following an ischemic event can reduce cell death. O2 in whole blood (WB) is either bound by hemoglobin (measured as O2 saturation, sO2) or dissolved in plasma (measured as partial pressure of O2, pO2). 98% of O2 is bound by hemoglobin in-vivo. Acoustic droplet vaporization (ADV) scavenges dissolved O2, but its ability to scavenge hemoglobin-bound O2 is unknown. The goal of this study was to assess how varying liquid droplet diameter affects O2 scavenging from bovine WB. Anticoagulated WB was prepared for in-vitro flow phantom experiments to mimic physiological arterial blood. 0.82 μm diameter droplets were manufactured using high-shear pressure homogenization. 1.34 μm and 7.02 μm diameter droplets were manufactured using microfluidics. Droplets (5×10−4 ml/ml) were infused through an EkoSonic catheter and exposed to ultrasound. sO2 and pO2 were measured with a blood gas analyzer. A post-ADV reduction in pO2 of 5.8 ± 2.6 mmHg, 16.4 ± 4.9 mmHg, and 30.7 ± 4.5 mmHg was observed with 0.82 μm, 1.34 μm, and 7.02 μm droplets, respectively. No change in sO2 was observed with 0.82 μm and 1.34 μm droplets, but a sO2 decrease of 5.8 ± 1.5% was seen with 7.02 μm droplets.