Burn depth assessment by dual-wavelength light emitting diodes-excited photoacoustic imaging in rats.

Accurate burn depth assessment is crucial to determine treatment plans for burn patients. We have previously proposed a method for performing burn depth assessments based on photoacoustic (PA) imaging, and we have demonstrated the validity of this method, which allows the successful detection of PA signals originating from the blood under the bloodless burned tissue, using rat burn models. Based on these findings, we started a clinical study in which we faced two technical issues: (1) When the burn depth was shallow, PA signals due to skin contamination and/or melanin in the epidermis (surface signals) could not be distinguished from PA signals originating from the blood in the dermis; (2) the size of the system was too large. To solve these issues, we propose a burn depth diagnosis based on dual-wavelength light emitting diodes (LEDs)-excited PA imaging. The use of LEDs rendered the system compact compared to the previous one that used a conventional solid-state laser. We replicated human burned skin by applying a titrated synthetic melanin solution onto the wound surface in albino rat burn models and measured their burn depths by PA excitation at 690 and 850 nm, where melanin and haemoglobin show greatly different absorption coefficients. As a result, the surface signals were eliminated by subtracting the PA signals at 690 nm from those at 850 nm. The resultant estimated burn depths were strongly correlated with the histological assessment results. The validity of the proposed method was also examined using a burn model of rats with real melanin.

Antithrombogenicity of the Gyro permanently implantable pump with the RPM dynamic suspension system for the impeller.

In 1995, a group at Baylor College of Medicine started to develop the NEDO biventricular assist device (BVAD) using two Gyro permanently implantable (PI) centrifugal pumps. This pump consists of a sealless pump housing and an impeller supported with a double pivot bearing. In May 2001, an RPM dynamic suspension system (RPM-DS) for the impeller was developed to improve durability and antithrombogenicity without a complex magnetic suspension system. From March 2000 to March 2002, eight BVAD bovine experimental studies were performed for more than 1 month. Two pumps were implanted in two cases without the RPM-DS (group A) and in six cases with the RPM-DS (group B). In group A, the survival period was 45 and 50 days. The primary reason for termination was an increase in the requiring power, which was related to deposition of white thrombus on the bottom bearing. In group B, the survival period was 37, 48, 51, 60, 80, and 90 days. The reasons for termination were not related to thrombus formation. No thrombus was observed in the pumps except for one right pump. In that experiment, the thrombus formation may have occurred when that pump had a low flow rate at a level of 1 L/min for 6 hr. These studies demonstrate the apparent antithrombogenic effect of RPM-DS. The NEDO BVAD is ready to move into a 3-month preclinical system evaluation.

Physiological adaptation to a nonpulsatile biventricular assist system.

Physiological adaptation of the recipient to a nonpulsatile biventricular assist system (NPBVAS) is not well understood. The aim of this study is to evaluate the physiological adaptation of experimental animals after NPBVAS implantation. Since May 2001, four long-term NPBVAS implant experiments in calves were performed. The blood gas and hemodynamic data were analyzed retrospectively. An additional prospective experiment was performed to confirm retrospective findings. All calves (n = 5) lived longer than 5 weeks without complication. In retrospective analysis, there was not a correlation between the O2 content and total blood flow in the pulmonary artery during the 1st postoperative week, but they began to correlate within the 2nd postoperative week. Then, there was a strong correlation after the 3rd postoperative week (r = 0.753). In the prospective experiment, O2 content related to total pulmonary flow after 2 weeks (r = 0.732) was the same as in the retrospective study. Most of the hemodynamic parameters studied became normalized after 14 days. In addition, easier controllability of the blood pumps was demonstrated after the 2nd postoperative week in all five experiments. Experimental results suggested that the native healthy heart accepted NPBVAS by reducing its cardiac output in 2 weeks. In addition, complicated control of the BPVAS was not necessary after 2 weeks of implantation. These results demonstrate the possibility of physiological adaptation to the NPBVAS being established within 2 postoperative weeks.