Diamond-like carbon (DLC) films were deposited on polytetrafluoroethylene (PTFE) using radio frequency (RF) plasma-enhanced chemical vapour deposition (PE-CVD). Before the DLC coating, the PTFE ...substrate was modified with a N
2 plasma pre-treatment to enhance the adhesive strength of the DLC to the substrate. The influences of the N
2 plasma pre-treatment and process pressure on the gas permeation properties of these DLC-coated PTFE samples were investigated. In the Raman spectra, the G peak position shifted to a lower wave number with increasing process pressure. With scanning electron microscopy (SEM), a network of microcracks was observed on the surface of the DLC film without N
2 plasma pre-treatment. The density of these cracks decreased with increasing process pressure. In the film subjected to a N
2 plasma pre-treatment, no cracks were observed at any process pressure. In the gas barrier test, the gas permeation decreased drastically with increasing film thickness and saturated at a thickness of 0.2
μm. The DLC-coated PTFE with the N
2 plasma pre-treatment exhibited a greater reduction in gas permeation than did the samples without pre-treatment. For both sample types, gas permeation decreased with increasing process pressure.
Aim: Downsizing of a driver for a pneumatic total artificial heart (PTAH) is one of key factors for improving the patient's QOL. However the controllability of the drive condition and the size of a ...device have a trade-off relation generally. The aim of this study is to develop a compact PTAH drive unit that can control the left and right pumps driving condition independently. Methods: The core unit of the drive unit consists of a DC servo motor, a crankshaft, a cylinder-piston, pressure regulation valves and equipped with a relief valve in the diastole phase to avoid excessive negative pressure (the size and weight: 26 x 18 x 11 cm and 3 kg). The systolic ratio (SD) is generated by the speed control of the DC servo motor. The drive system consisting of 2 core units was examined in an overflow mock circuit (Preload: 10 mmHg, Afterload: 80, 100, 120 mmHg and 20, 30, 40 mmHg in the left and right pumps). Results: The developed driver was able to regulate the SD, the HR and the pressure relief time independently in the left/right. The flow rates of the left and right pumps were 3.7-8.9 L/min and 4.1-9.5 L/min (SD: 30-50%, HR: 50-100 bpm). The driving pressures in the diastole phase were the left: -3.0- 20.0 mmHg and the right: 3.9-8.2 mmHg. Conclusions: These results indicated that the developed compact TAH drive unit had a sufficient performance and adjustability to drive PTAH pumps.
Objectives: We have been developing a mock circulation system for endurance test of ventricular assist devices that can simulate a variety of physiological circulatory conditions. In this study, we ...compared several inflow and outflow valves for generating pressure and flow waveforms of the systemic circulation on the basis of waveform analysis. Methods: The mock circulatory loop for endurance test consisted of a pulsatile pump with two closed-chambers (left ventricle and aortic compliance), a control valve (peripheral resistance) and a reservoir (left atrium). Evaluated valves (mechanical prosthetic valves, umbrella and duckbill valves) were mounted in the inlet and outlet of the left ventricle. The pump was driven at 70 bpm, and the aortic pressure (AoP) was set at the 120/80 (100) mmHg. Left ventricular pressure (LVP) and AoP were measured for 1 minute in each valve. Each waveform was evaluated by the spike component extracted with median filter processing, the vibrational component extracted with frequency analysis (FFT) and the slope of each pressure waveform calculated with differential processing. Results: Examples of obtained evaluation indices were shown as follows: the peak-to-peak of filtered LVP (spike components) and integrated values of power spectrum in spike elements by FFT (vibrational components) were 345.8 mmHg and 518.1 mmHg super(2) in mechanical valves, 218.8 mmHg and 522.1 mmHg super(2) in umbrella valves and 162.7 mmHg and 142.4 mmHg super(2) in duckbill valves, respectively. Thus, the duckbill valve showed the most favorable characteristics in which pressure waveforms were close to the nature systemic circulation. Conclusions: The endurance test circuit under development was able to generate pressure waveforms with low spike and vibrational components by using duckbill valves. It was suggested that our system has a potential to evaluate various characteristics of prosthetic valves by the simple wave pattern analysis.
Objectives: We have been developing a wearable Pneumatic Total Artificial Heart (PTAH) system with compact Wearable Pneumatic Drive (WPD) unit for bridge to transplant. This paper reports the current ...state of development including the results of the first acute animal experiment in PTAH system. Methods: The PTAH system consists of left and right diaphragm-type blood pumps and two WPD units. Two blood pumps were designed to fit anatomy, and these had housings made of polyurethane resin and stainless steel. 25mm ID and 23mm ID Bicarbon valves were mounted in the inlet and outlet ports, respectively. The sizes of the left and right pumps are 95x68x49mm and 104x74x44mm. The stroke volume of the left and right pumps are 85 and 94mL. The WPD unit consists of a brushless DC motor, a crankshaft, a cylinder-piston, non-circular gears, and air pressure regulation valves. Driving air pressure is generated by the cylinder-piston. The non-circular gears generate the fixed systolic ratio. The size and weight of the WPD unit are 20x8.5x20cm and 1.8kg, respectively. The left and right pumps were implanted in a calf weighing 98kg. Two WPD units with fixed systolic ratio of 35 and 44% were connected to left and right pumps with 2m drive lines, respectively, and fundamental performance of PTAH system was evaluated in acute animal experiment Results: The cardiac output ranged between 3.9 and 5.4L/min at the mean aortic pressures of 108-115mmHg at pump rates of 60 to 100bpm. The average electric power consumption in each WPD unit varied from 5.3 to 17.6W according to the beating rate, and the efficiency was estimated to be 2-9%. Conclusions: These results indicated that our PTAH system consisting of blood pumps and WPD units have sufficient performance for total cardiac replacement.
Aim: The purpose of this work is to develop an ultra-compact wearable pneumatic drive unit for ventricular assist device. Methods: The drive unit consists of a brushless DC motor, a crankshaft, a ...cylinder-piston, noncircular gears and air pressure regulation valves. The reciprocating motion of the cylinder-piston makes the air pressure which drives the blood pump. The noncircular gears make systolic ratio and the air pressure regulation valves regulate the maximum and minimum pressure in the cylinder-piston. The weight of the drive unit is approximately 1.7 kg. Results: The drive unit was tested in an overflow type circulation mock test using a Toyobo VAD blood pump of 70 mL of stroke volume. Pre-load and after-load were set at 10 mm Hg and 120 mm Hg, respectively. The maximum flow rate was 7 1/min at 100 bpm. The drive unit was also examined by an in vivo animal experiment. A Holstein calf weighing 80kg with the Toyobo VAD blood pump wore the drive unit on his back. The pumping rate and the systolic ratio were set at 80 bpm and 40%, respectively. The calf survived for more than 1 month in good general condition. The bypass flow was maintained 3-4 l/min. The electric power consumption of the drive unit was maintained at around 12 W. Conclusion: The performance of the ultra-compact wearable pneumatic drive unit was confirmed in vitro experiment and in vivo animal study. These results indicate that the developed drive unit has a potential to become a mechanical circulatory support system of the human heart.
