Flow-controlled Ventilation During Percutaneous CT-guided Liver Tumor Ablation

Tumors in the liver can be treated using percutaneous ablation. At the Amsterdam UMC, this procedure is often performed under CT guidance by an interventional radiologist. The available ablation techniques include thermal ablation (microwave ablation (MWA) and radiofrequency ablation (RFA)) and non-thermal ablation (irreversible electroporation (IRE)). Thermal ablation is performed under general anesthesia or deep sedation, whereas non-thermal ablation is always performed under general anesthesia.

Flow-controlled ventilation (FCV) is a ventilation technique in which increased diaphragm stability is observed due to a continuous flow during both inspiration and expiration. This contrasts with volume- or pressure-controlled ventilation, where active inspiration is followed by passive expiration through an increase in pressure or flow, leading to greater diaphragm movement during the ventilation cycle. With volume- or pressure-controlled ventilation, diaphragm position fluctuates between inspiration and expiration, requiring temporary pauses in ventilation (apnea; allowing the diaphragm to become motionless) during ablation needle positioning.

During volume- or pressure-controlled ventilation and the associated apnea periods, increased formation of atelectasis is often observed. This results in changes in diaphragm position during and after each apnea, which can complicate accurate needle placement. With FCV, apnea is not necessary-the continuous flow results in minimal diaphragm excursion and can be maintained throughout the entire procedure without interruption.

Both ventilation modes are currently used during CT-guided percutaneous ablation of liver and pancreatic tumors. However, the choice of ventilation technique presently lies with the attending anesthesiologist. In practice, some anesthesiologists prefer volume- or pressure-controlled ventilation, as these are traditionally the most commonly used modes. Others opt for FCV due to its minimal effect on diaphragm excursion and its potentially beneficial effects on atelectasis formation and intraprocedural image quality.

Given the subdiaphragmatic location of both organs and the presence of critical surrounding structures that must be preserved during the procedure, interventional radiologists find FCV particularly advantageous. Moreover, continuous ventilation without apnea is preferred by anesthesiologists, as it avoids periods of reduced oxygenation.

FCV is an already approved ventilation technique at Amsterdam UMC and is used during percutaneous ablations, surgeries performed by ENT and pulmonary specialists, and in the intensive care unit for critically ill patients. Through this study, the investigators aim to evaluate the use of FCV as a ventilation technique during CT-guided percutaneous ablations of liver tumors and to compare it with volume- or pressure-controlled ventilation.