Low-Pressure AirSeal Versus Conventional Insufflation in Major Minimally Invasive Hepatopancreatobiliary Surgery

Minimally invasive (MIS) Hepato-Pancreato-Biliary (HPB) surgery depends fundamentally on the ability to maintain a stable pneumoperitoneum and consistently clear visualization. Unlike other minimally invasive domains, HPB procedures uniquely combine prolonged operative duration, heavy energy-device smoke, frequent suctioning, and exposure of large vascular structures. In this environment, even transient loss of pressure or visualization is not trivial-it disrupts operative flow and may translate into bleeding, technical difficulty, or conversion to open surgery. Conventional insufflation systems have been shown to generate pressure instability under leak conditions such as suctioning and instrument exchanges, which are particularly relevant in complex procedures.

Current practice in MIS HPB surgery reflects a compromise between exposure and physiology. Pneumoperitoneum is typically maintained at 10-14/15 mmHg, often combined with low central venous pressure (CVP) strategies to limit back-bleeding during liver parenchymal transection. While effective for hemostasis, this approach introduces a physiologic trade-off: higher intra-abdominal pressure improves exposure and reduces bleeding but increases the pressure gradient favoring gas entry into exposed hepatic veins, thereby increasing the risk of gas embolism; conversely, lower pressure may mitigate this risk and improve respiratory physiology, but often at the expense of exposure unless pneumoperitoneum is exceptionally stable.

Conventional insufflation systems are not designed for the demands of complex MIS HPB surgery. Their intermittent pressure regulation is inherently reactive, leading to pressure fluctuations during suctioning, smoke evacuation, and instrument exchanges. These limitations are magnified in long, technically demanding operations and may compromise both workflow and safety. Continuous pressure insufflation systems such as AirSeal® (CONMED) were developed to address these challenges. Through a valveless design with real-time flow regulation, AirSeal maintains pneumoperitoneum despite leaks, enables simultaneous suction and smoke evacuation, and minimizes pressure variability. Experimental and clinical data confirm superior pressure stability under leak conditions compared with conventional systems.

The most consistent advantage observed with valveless insufflation systems is improved visualization and operative stability. Randomized data demonstrate higher surgeon-rated visualization despite similar CO₂ absorption, end-tidal CO₂ (EtCO₂), and postoperative pain outcomes. However, these benefits are predominantly qualitative and are not well captured by traditional endpoints such as operative time or blood loss. This limitation is particularly relevant in HPB, where subtle differences in exposure, stability, and operative flow may have disproportionate clinical consequences.

From a physiologic perspective, the potential value of AirSeal lies in enabling lower-pressure pneumoperitoneum without compromising exposure. Lower intra-abdominal pressure has been associated with improved respiratory mechanics and reduced postoperative pain in several studies, although results are inconsistent when pressure is held constant across groups. This suggests that the benefit is not intrinsic to the device itself, but rather to the strategy it may enable: maintaining adequate exposure at lower pressures.

Despite this compelling rationale, HPB-specific evidence remains limited and unbalanced. In pancreatic surgery, AirSeal is widely adopted in robotic workflows but supported primarily by technical and implementation reports without comparative outcome data. In liver surgery, the available literature is more robust but largely focused on safety-particularly venous gas embolism (VGE).

Venous gas embolism is a recognized risk during laparoscopic liver resection due to exposure of hepatic veins under pneumoperitoneum. A multicenter study reported a 5% incidence of symptomatic VGE and identified AirSeal use at 12 mmHg as a potential risk factor, although without associated mortality. At the same time, studies using physiologic surrogate definitions of embolism-based on changes in EtCO₂, oxygen saturation, and blood pressure-may overestimate true embolic events, particularly during liver transection where such fluctuations are common. The consistent association of these events with venous exposure suggests that embolic risk is driven primarily by surgical context rather than the insufflation system alone.

A distinct and potentially underrecognized mechanism relates to the valveless design itself. During high-flow suction, AirSeal systems may entrain ambient air to maintain pneumoperitoneum, introducing poorly soluble gases into the operative field. Experimental data suggest that this could increase the clinical impact of embolic events when they occur, particularly during hepatic venous exposure. While the clinical significance of this phenomenon remains uncertain, it reinforces the need for careful, procedure-specific evaluation.

Taken together, the available evidence supports a clear but untested hypothesis: AirSeal may act as an enabler of a low-pressure operative strategy in complex HPB surgery, allowing surgeons to maintain adequate exposure while potentially improving physiologic parameters and early recovery. However, this strategy must be evaluated alongside its feasibility in real-world complex cases and its safety profile, particularly with respect to potential embolic events, where no robust data exist.

Accordingly, the investigators designed the CALM-HPB trial (Controlled AirSeal at Low mmHg) as a prospective randomized feasibility study to test this hypothesis in major MIS HPB surgery. The primary objective is to determine whether a low-pressure AirSeal strategy (target 8 mmHg, 6-10 mmHg) can be maintained for the majority of operative time without the need for sustained rescue pressures, thereby establishing proof of concept that low-pressure pneumoperitoneum is achievable in complex HPB procedures. A co-primary objective is to evaluate the safety of this strategy using standardized perioperative endpoints.

Secondary objectives are designed to capture the downstream clinical implications of this approach, including effects on respiratory physiology (EtCO₂, peak inspiratory pressure), postoperative pain and opioid consumption, pulmonary complications, and operative workflow metrics such as visualization, stability, and need for rescue interventions. This study aims to test whether stable low-pressure pneumoperitoneum can be safely achieved in complex HPB surgery, and whether doing so translates into measurable perioperative benefit.