title: Development of an Optical Detector of Thrombus Formation on the Pivot Bearing of a Rotary Blood Pump.
abstract: Continuous optical monitoring of thrombus formation in extracorporeal mechanical circulatory support (EMCS) devices will contribute to safe, long-term EMCS. A clinically applicable optical detector must be able to distinguish among the optical characteristics of oxygen saturation (SaO2 ), hematocrit (Hct), and thrombus formation. In vitro studies of spectral changes at wavelengths from 400 to 900 nm associated with SaO2 , Hct, and thrombus formed around the top pivot bearing of a Gyro C1E3 pump were conducted. Fresh porcine blood anticoagulated with sodium citrate was circulated in a mock circuit using the pump. The SaO2 , Hct, and anticoagulation activity were altered using an oxygenator, autologous plasma, and calcium chlorite injection, respectively. Light from a xenon lamp was guided by an incident fiber perpendicularly fixed on the top bearing. This light was scattered by blood pooled between the male and female pivots. The detection fiber was perpendicularly fixed against the incident fiber, and the side-scattered light was detected and guided to a spectrophotometer. As a result, light at two different wavelengths, 420 and 810 nm, was identified as suitable for thrombus detection because it was negligibly influenced by SaO2 and was able to detect the optical characteristics of fibrin. The light at these two wavelengths responded more quickly to thrombus formation than the inlet or outlet pressure, and flow rate change. The optical changes showed the changes in Hct around the top pivot bearing, which is caused by the reduction in density of fibrin-trapped red blood cells (RBCs) due to the RBCs being swept away by the surrounding blood flow. The proposed method was also able to detect fibrin production by extracting subtle differences in the optical characteristics between the Hct and thrombus formation.
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan. sakota.ao@aist.go.jp.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sakota
authors.affiliation: Department of Cardiovascular Surgery, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Tatsuki
authors.initials: T
authors.lastname: Fujiwara
authors.affiliation: Department of Advanced Surgical Technology Research and Development, Graduate School of Medical and Dental Science, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Ouchi
authors.affiliation: Senko Medical Instrument Mfg. Co., Ltd., Saitama, Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Kuwana
authors.affiliation: Optoquest Co., Ltd., Saitama, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamazaki
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Maruyama
mesh_terms: D000818:Animals; D004867:Equipment Design; D005112:Extracorporeal Circulation / Q000009:adverse effects* / Q000295:instrumentation; D005336:Fiber Optic Technology / Q000295:instrumentation*; D006400:Hematocrit; D006439:Hemodynamics; D013552:Swine; D013927:Thrombosis / Q000175:diagnosis* / Q000209:etiology*
keywords: Mechanical circulatory support; Pivot bearing; Rotary blood pump; Thrombus; Visible and near-infrared light spectroscopy