2302 - Design of a Device for Supplying High Oxygen Concentration Gas to Support Breath-Hold for Radiotherapy Patients
Presenter(s)
X. Zhang, M. F. Moyers, and Y. Yuze; Shanghai Proton and Heavy Ion Center, Shanghai, China
Purpose/Objective(s): A device was conceptualized and manufactured to support breath-hold by delivering a pre-configured gas mixture at near-atmospheric pressure for patients undergoing radiotherapy. The system aims to efficiently deliver a specified high concentration of oxygen with minimal gas loss. Additionally, it can rapidly open or close the patient's breathing pathway as needed. For motion management techniques using breath-hold, the device could potentially assist with prolonging the patient's breath-hold time and enhancing the reproducibility of breath-hold, thereby increasing dose delivery accuracy and reducing treatment time.
Materials/Methods: In this study, gas from a high-pressure cylinder was depressurized using a modified positive-pressure respirator, which was adjusted to halt gas flow during breath-hold and exhalation. The gas is then heated and humidified via a warm water humidification bottle before passing through a one-way valve for patient inhalation. A high flow rate gas supply is thus made available when negative pressure is induced by the patient during inhalation. Exhaled gases are expelled into the atmosphere through another one-way valve. The gas system can be combined with a gating system such that when a gating signal is triggered, a balloon valve within the gas pathway closes preventing the patient from breathing. The balloon valve operates by rapidly switching between positive and negative pressure buffers using a pneumatic solenoid valve, enabling swift opening and closing actions. Assuming that the patient breathes only through the gas system without leakage paths, the rapid response of the balloon valve may improve the reproducibility of breath-hold maneuvers.
Results: Tests demonstrated consistent oxygen concentration. A negative pressure of 1.3 kPa was required to drive inhalation at 150 L/min, while a positive pressure of 1.5 kPa was needed for exhalation at the same flow rate. When the humidification bottle was filled with 40°C warm water, the inhaled gas maintained a relative humidity above 95% across all flow rates. Following gating signal activation, the balloon valve closed the patient's breathing pathway within 0.23 seconds.
Conclusion: The newly designed device is capable of delivering a pre-configured high-oxygen gas mixture at high flow rates to radiotherapy patients without causing discomfort. Integrated with a balloon valve, the system has the potential to improve the reproducibility of breath-hold maneuvers during extended breath-hold.