In this article, a novel cryotherapy approach using a uniform, controlled, and consistent in vivo application of liquid nitrogen (LN2) spray as a Metered Cryospray™ (MCS) process is described. Although MCS may be used for many potential clinical applications, this paper focuses on the development that led to the controlled and consistent delivery of radial LN2 cryogen spray in order to generate a uniform circumferential effect and how the amount of MCS can be adapted to specifically ablate targeted diseases within a patient’s lumen such as an airway or esophagus.

Spray cryotherapy using liquid nitrogen (LN) is a general surgical tool used to ablate benign or malignant lesions. Adequate egress of the gaseous nitrogen (N) generated during this process must be provided for safe use when LN is used within the body rather than topically. When delivered to either the gastrointestinal tract (requiring active venting via a suction tube) or body cavities open to room barometric pressure (such as lung airways) allowing for passive venting, the N gas generated from the boiling process must be evacuated. This work will examine the egress of N during procedures requiring passive venting from human airways undergoing liquid nitrogen spray cryotherapy. Venting characteristics for safe N egress will be presented and discussed based on analytical modeling using fluid mechanics simulations and experimental studies of N venting with laboratory and porcine models.

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