Inflow Cannula Pressure Sensor for Autonomous Dynamic Ventricular Assist Device Control

Background: Through significant technological improvement and shortage of donor organs, ventricular assist devices (VAD) have become an important part of end-stage heart failure treatment. However, VADs are still associated with adverse effects, such as congestion or ventricular wall collapse. These adverse effects are the result of the inability of current generation VADs to dynamically adapt the pumping power to the real time perfusion needs of the human body.

Various control schemes based on a multitude of signals have been developed to overcome this limitation. Of these, the left ventricular pressure, especially the end-diastolic pressure (EDP), has been highly promising. However, there is currently no commercial solution available, which is capable of reliably and continuously measuring this pressure.

Method: Tube shaped testing platforms (TP), mimicking the inflow cannula of a VAD, have been developed and produced for long-term implantation. Each TP contains six fully integrated sensor capsules (SC) based on previous work.

The blood contacting inner side of the titanium tube is fully coated with a smooth, 20-µm-thick Parylene-C layer with six seamlessly integrated pressure transmitting diaphragms. A commercial pressure sensor is enclosed in silicone oil behind each diaphragm, enabling independent pressure acquisition at six different locations inside the TP.

A TP was implanted as a parallel circuit to the thoracic aorta in a sheep model during an acute animal trial. The pressure data acquired by each TP sensor (TPS) was compared with a catheter-tip mounted reference sensor (RS) placed near the sensors in the bloodstream. The TPS was calibrated with respect to offset and linear scaling post-experimentally.

Results: Over the course of the trial, blood pressure in the range from 40 to 85 mm Hg was recorded at a rate of 200 Hz. The pressure recorded by the six TPS is in excellent agreement with the RS, maintaining a pressure difference (TPS-RS) of less than ±1 mm Hg for most data points. Only in the upper half of the pressure increase from EDP to systolic pressure a difference of up to +5 mm Hg is observed. Measured peak pressure and EDP was compared with the RS, resulting in a difference of +0.11 ±0.42 mm Hg and -0.14 ±0.55 mm Hg (n = 880–920) respectively.

Conclusion: The produced TPS demonstrated excellent ability to fully resolve the pressure wave and to accurately and precisely measure the EDP, encouraging the integration of sensors in VAD inflow cannula.

Publication History

Article published online:
03 February 2022