How a Breath Can Steer the Needle: Ventilation Strategies That Freeze the Liver for Tumor Ablation

Every breath a patient takes moves the liver by several millimeters, and for interventional radiologists threading needles into liver tumors under general anesthesia, those millimeters can be the difference between a complete cure and an incomplete treatment. A new study from Oslo University Hospital, published in CVIR Oncology, has for the first time systematically compared five different ventilation strategies within the same group of patients to quantify exactly how much each one moves the liver. The results offer a practical roadmap for anesthesiologists and radiologists who must balance the competing demands of respiratory safety and surgical precision during thermal ablation of liver tumors, a minimally invasive alternative to surgical resection for colorectal cancer liver metastases.

The clinical stakes are considerable. Thermal ablation, whether by radiofrequency or microwave energy, destroys tumor tissue by heating it through an applicator placed percutaneously into the lesion. Precise placement of that applicator is vital to achieve sufficient ablation margins around the tumor and to avoid injuring healthy structures nearby. Ventilation-induced organ movement complicates this task in several ways: for stereotactic puncture techniques, control of respiratory motion strongly influences accuracy, and for software that confirms ablation completeness by fusing pre- and post-ablation images, respiratory movement can render co-registration between image sets genuinely challenging. When the target shifts several millimeters with each breath, even sophisticated navigation systems struggle to guarantee that the entire tumor and a safety halo around it have been treated.

Historically, the preferred technique for stabilizing the liver has been one-lung ventilation, in which a double-lumen tube allows the right lung to be deliberately deflated while the left lung is ventilated. With the right lung collapsed, the liver loses much of the mechanical push from the diaphragm on that side, and the acoustic window for tumors near the top of the liver also improves. But this strategy is far from benign. It is profoundly non-physiological: the ventilated lung may suffer injury from high end-inspiratory volumes, oxidative stress, and increased perfusion, while the deflated lung is exposed to atelectasis-related ischemia-reperfusion injury and re-expansion damage when it is finally reinflated. The larger dimensions of the double-lumen tube increase the risk of laryngeal injury, and patient factors such as cardiopulmonary comorbidity, obesity, and advanced age can reduce tolerance of one-lung ventilation altogether, sometimes forcing the team to abandon the technique mid-procedure because of hypoxia or hemodynamic instability.

An increasingly popular alternative is high-frequency jet ventilation, or HFJV, which delivers very small pulses of gas at extremely high rates, in this study at the manufacturer’s default setting of 600 breaths per minute. Because each pulse is tiny, the diaphragm barely moves, and the liver stays nearly still. HFJV has been shown in previous work to provide minimal ventilation-induced liver movement and is now widely used for image-guided ablation. It is not, however, a universal solution. It requires specialized equipment and expertise that are not available everywhere, it can cause carbon dioxide retention during prolonged procedures, and it carries a risk of barotrauma if air cannot escape adequately. Patients with chronic obstructive pulmonary disease, obesity, or recent pneumothorax may be unsuitable candidates. One refinement, so-called double-jet ventilation, adds a normal-frequency jet component to improve carbon dioxide removal, but the researchers suspected this might come at the cost of increased liver movement.

To settle these questions, the Norwegian team conducted a single-center, non-randomized observational crossover study as a predefined substudy of the New Comet trial, a randomized controlled trial comparing surgical resection with thermal ablation of colorectal cancer liver metastases. Twenty patients scheduled for ablation between November 2022 and April 2024 each received all five ventilation modes in a predefined sequence, meaning every patient served as their own control. The modes were standard ventilation at 6 milliliters per kilogram of ideal body weight; a gentler low-tidal-volume, high-frequency strategy at 4 milliliters per kilogram delivered through a conventional endotracheal tube and ventilator; one-lung ventilation with right lung deflation; and high-frequency jet ventilation with and without the additional normal-frequency jet component. Anesthesia was maintained with target-controlled propofol and remifentanil infusions, with depth of anesthesia monitored by bispectral index, and rocuronium was given to facilitate intubation. The team aimed to keep arterial carbon dioxide below 8 kilopascals and oxygen saturation above 90 percent, with an adverse incident protocol ready if those targets were missed.

Measuring liver motion required careful technique. An experienced radiologist used ultrasound to record the cranio-caudal displacement of the inferior liver margin in both lobes: the left lobe was imaged in a sagittal plane in the epigastrium, while the right lobe was imaged through a parasagittal subcostal window as close as possible to the anterior axillary line. For each ventilation mode, the distance between the most cranial and most caudal positions of the inferior margin was measured across at least two respiratory cycles, with the transducer held in the same position throughout. The order of ventilation modes was not disclosed to the radiologist, although complete blinding proved impossible because jet ventilation produces characteristic noise and torso movement. In total, 200 measurements were collected, ten per patient, and the reliability of the method was verified by having two additional blinded radiologists independently analyze recorded ultrasound videos, with interobserver agreement assessed using intraclass correlation coefficients and Bland-Altman analysis against a predefined clinically acceptable variability of 2 millimeters or less.

The numbers were striking. Standard ventilation produced the greatest movement, with the left inferior liver margin traveling 5.8 millimeters and the right margin 7.3 millimeters during a respiratory cycle. The gentle low-tidal-volume, high-frequency strategy cut this to 4.0 millimeters on the left and 4.6 millimeters on the right, a meaningful reduction achieved with equipment available in any operating room. High-frequency jet ventilation was the clear winner, holding movement to just 1.2 millimeters on the left and a remarkable 0.5 millimeters on the right. Right-sided one-lung ventilation performed nearly as well for the right lobe, limiting movement of the right margin to 1.6 millimeters, though it offered far less benefit on the left, where the persistently ventilated left lung kept pushing the liver. Double-jet ventilation fell between HFJV and the conventional modes, confirming that adding the normal-frequency jet component to improve carbon dioxide removal does indeed increase liver movement on both sides.

Statistical analysis using linear mixed-effects models with a random intercept for each subject confirmed that these differences were robust. After log transformation of the movement data and Bonferroni correction for multiple testing, standard ventilation produced significantly greater movement than each of the other four methods on both sides, with all comparisons reaching significance except one-lung ventilation versus double-jet ventilation on the left side. Applying the predefined 2-millimeter clinical tolerance, only one-lung ventilation remained within that threshold of HFJV on the right side, while both double-jet ventilation and one-lung ventilation fell within tolerance on the left. Notably, gender, body mass index, and ideal body weight showed no statistically significant association with liver movement, and there was even a tendency toward less movement in the higher BMI group. Interobserver reliability was good, with 93.3 percent of paired video measurements within the 2-millimeter tolerance, and no intraoperative complications were registered during the study.

The authors are candid about the limitations. The sample of twenty patients was small, though the crossover design increased precision by allowing within-patient comparisons. The ventilation modes were applied in a fixed order, so order and carry-over effects cannot be excluded despite a standardized one-minute stabilization period, and neuromuscular blockade was not standardized, meaning residual rocuronium effect may have influenced diaphragmatic tone in later modes. The measurements were taken under short, controlled conditions rather than during prolonged ablation with a single strategy, and jet ventilation was delivered through the tracheal lumen of a double-lumen tube rather than a standard endotracheal tube, which the team chose deliberately to avoid the laryngeal risk of additional tube changes. Jet ventilation settings also vary across the literature, with many centers using lower frequencies of around 200 to 250 breaths per minute to limit hypercarbia over long procedures, potentially at the cost of more movement.

Even so, the practical message is clear and likely to influence practice well beyond Oslo. No single ventilation mode is universally optimal, and the choice should be individualized according to tumor location, patient comorbidities, and local expertise. High-frequency jet ventilation remains the preferred option when available and feasible, with one-lung ventilation as a strong alternative for selected right-sided tumors, particularly those in the hepatic dome where the deflated lung also improves the ultrasound window. For patients in whom advanced techniques are too risky or simply unavailable, gentle ventilation combined with timed breath holds offers a pragmatic middle path that meaningfully reduces motion compared with standard ventilation. The authors suggest that future research should explore whether more aggressive gentle ventilation strategies can further reduce movement safely over longer periods, and whether simple decision tools can be developed to guide ventilation strategy by incorporating tumor location, comorbidity, and the availability of advanced equipment. In a field where millimeters determine margins, knowing exactly what each breath costs is a powerful new piece of information.

Subject of Research: The effect of ventilation methods on liver movement during general anesthesia for thermal ablation of liver tumors

Article Title: The effect of ventilation methods on liver movement during general anesthesia for thermal ablation of liver tumors

Article References: The effect of ventilation methods on liver movement during general anesthesia for thermal ablation of liver tumors. (n.d.). https://doi.org/10.1007/s44343-026-00065-z

Image Credits: AI Generated

DOI: 10.1007/s44343-026-00065-z

Keywords: thermal ablation, liver tumors, high-frequency jet ventilation, one-lung ventilation, gentle ventilation, liver movement, anesthesia, interventional radiology, colorectal liver metastases, ultrasound measurement, ventilation strategies, Oslo University Hospital