Prospective Comparison Between the AirSeal ® System Valve-Less Trocar and a Standard Versaport ™ Plus V2 Trocar in Robotic-Assisted Radical Prostatectomy

Introduction

R adical prostatectomy is currently the most frequently performed robot-assisted surgical intervention in urology and has in many regions superseded open radical prostatectomy. ¹ Robotic-assisted radical prostatectomy (RARP) can be either performed by a transperitoneal or an extraperitoneal approach. ² At present, most surgical teams prefer a transperitoneal approach due to its easier access and its wider surgical space. The extraperitoneal approach is in contrast considered more difficult and less frequently performed although it offers some distinct advantages by avoiding the abdominal cavity. Regardless of the surgical approach, a stable pneumoperitoneum or pneumoextraperitoneum is equally important for both techniques.

Abdominal pneumocavities are routinely generated by conventional, standard laparoscopic CO₂ insufflation systems, and standard laparoscopic trocars with either silicone or door trap valves that maintain intra-abdominal gas pressure. Recently, a new generation of valve-less and barrier-free surgical trocars has been developed and has become commercially available under the name: AirSeal^® System (SurgiQuest, Inc., Milford, CT). ^3,4

The AirSeal System is comprised of the intelligent flow system (IFS) AirSeal control, the AirSeal valve-less Trocar, and the AirSeal Mode Evacuation (ASM-Evac) Tri-lumen Filter Tube Set. The AirSeal Trocar helps maintain intra-abdominal pressure by the integrated tiny circumferential CO₂ nozzles within the proximal trocar housing that act as an invisible gas curtain or AirSeal barrier, which is greater in strength than the intra-abdominal pressure. This invisible barrier replaces mechanical valves associated with all other conventional trocars. CO₂ circulation is facilitated by the IFS AirSeal control unit, which connects to the trocar via the ASM-Evac tri-lumen Filter Tube Set. Within this tri-lumen tube, one lumen is responsible for the CO₂ abdominal inflow (max. 40 L/minutes), a second lumen is used for CO₂ abdominal outflow back to the IFS control unit, and the third lumen is dedicated for real-time and constant pressure sensing. The tri-lumen tube is contiguous with a filter that fits into the IFS unit and serves to remove pathogens from smoke as it is circulated from the patient's abdomen. Once initial insufflation reaches set pressure the AirSeal System L/min flow is automatically reduced to 3 L/m, while maintaining the set pressure. The AirSeal Trocar easily connects to the tri-lumen tube integrated with the AirSeal System control unit and allows rapid inflow to maintain stable intra-abdominal pressure even during constant aspiration or sudden gas loss.

In a first published clinical evaluation, Herati et al reported in 25 patients with laparoscopic renal surgery, their clinical impression of a decreased camera smudging, a better vision due to constant smoke evacuation, a more stable pneumoperitoneum, and an easier specimen and needle retrieval when using the valve-less trocar system. ⁴ This report, however, did not include a reference group.

In a more recent article, the same group performed a prospective comparison in 51 patients who also underwent laparoscopic renal surgery with either an AirSeal (n=26) or a standard trocar (n=25). In this study, a significant shorter surgical time, a lower CO₂ consumption, and most importantly, a reduced patient systemic CO₂ absorption were described in the AirSeal group. ⁵

Additionally, in a recently published theoretical article, Nepple et al proved in a bench top model with a rigid box system that the valve-less trocar system better maintains pressure than conventional, standard trocars in case of sudden or continuous gas loss. ⁶ Altogether these limited, but trustworthy data motivated us to further evaluate the potential benefit of the AirSeal System Trocar in robotic radical prostatectomy.

Patients and Methods

Two cohorts of consecutive patients were prospectively compared. In the first, the AirSeal Trocar and in the second, a 12 mm Versaport™ Plus V2 Trocar were used as assistant insufflating trocars. The AirSeal group comprised 19 and the Versaport group 17 patients. Age, body mass index, tumor characteristics, and preoperative prostate-specific antigen (PSA) of the patients were similar in both groups without significant differences (Table 1). According to our surgical and clinical approach, both groups contained patients with either an extra- or transperitoneal approach. Patients with high and intermediate prostate cancer received an extended lymph node dissection with a transperitoneal approach and those with low-risk prostate cancer, a limited lymph node dissection with an extraperitoneal approach. Following this, 14 patients of the AirSeal and 11 of the Versaport group had a transperitoneal approach and 5 and 6 an extraperitoneal approach, respectively. In both groups, the trans- and extraperitoneal approach were performed equally. The technique has been previously described ^{7 –9} and was in brief as follows: All RARPs were performed with a three arm standard da Vinci^® surgical system. In the transperitoneal approach, a Hasson minilaparotomy above the umbilicus was chosen to insert the camera trocar. ¹⁰ Both 8 mm robotic trocars were placed with a distance of 8–10 cm laterally to the camera port just below the umbilicus. Additionally, two assistant ports were placed: one 5 mm port between the camera and the right robotic port and one 12 mm port (AirSeal or Versaport Plus V2) 6–8 cm laterocaudally to the right robotic port. In the extraperitoneal approach, the extraperitoneal space was created by a dilating balloon and blunt finger dissection. The number and the pattern of the ports were equal to the transperitoneal approach with all trocars placed 2–3 cm more caudally.

For all patients, the following data were prospectively monitored and recorded during each surgical intervention on case report forms: All episodes of pressure loss below 8 mm/Hg with a standard pressure setting at 12 mm Hg measured by the insufflation systems were counted and recorded by one observing robotic specialist (H.K.). The same was done with trocar manipulations at the insufflating assistant port. This was especially important during lymph node dissection, since the lymph node tissue was extracted during dissection in separate portions depending on the location of their retrieval. Thereby, it was frequently necessary in the Versaport group to screw off the head of the trocar with the valve to safely and entirely remove the tissue with an assistant clamp through the trocar. Besides that, all other manipulations like, for example, for needle retrieval were also included into this category. Next, all episodes of camera cleaning were recorded during the interventions. Thereby, it was differentiated between internal cleaning with the water jet of the suction device directed on to the camera and external cleaning of the camera, which necessitated each time extraction of the camera out of the abdominal cavity. Finally, total CO₂ consumption and other clinical data like surgical time, blood loss, and the occurrence of emphysemas were recorded.

The Student's t test was applied if the normal distribution was observed and the Wilcoxon test if not. The chi-squared test was used for categorical values. A p-value of <0.05 was considered to show a significant difference (JMP version 10.0; SAS, Cary, NC).

Results

As a general impression, the insertion of both the AirSeal and the Versaport V2 Plus Trocar were equally safe and feasible in both the extra- and transperitoneal approach. In comparison, the AirSeal Trocar was a little bit more difficult to enter the abdominal wall, because it is not furnished with a cutting blade like the Versaport V2 Plus. Therefore, to increase abdominal resistance, the flow rate of the initial standard insufflation was increased to 40 mL/min before its insertion.

With regard to the study parameters, significantly less episodes of pressure loss below 8 mm Hg (at a setting of 12 mm Hg) occurred when using the AirSeal System in comparison to the Versaport and conventional, standard insufflator. Whereas in the Versaport group, in mean 38 episodes of pressure loss, episodes below 8 mm Hg were recorded; only one episode was noted in the AirSeal group (Table 2). Also, the number of performed trocar manipulations was significantly lower in the AirSeal than in the Versaport group. Whereas in mean 15 trocar manipulations were performed in the Versaport group, no trocar manipulation was recorded when using the AirSeal system.

In contrast to these clear differences, camera cleaning did not differ significantly between both groups. Whereas internal camera cleaning was performed more often in the Versaport group, external camera cleaning was more frequent in the AirSeal group. In mean per intervention internal camera cleaning was performed 2.6 times in the Versaport and 1.8 in the AirSeal group, and external camera cleaning 2.5 times versus 3.2 times, respectively. Also, regarding CO₂ consumption no significant differences were found between both study groups. In average, 1044 (range 245–1674) CO₂ were consumed in the Versaport group and 1205 (range 400–2758) CO₂ in the AirSeal group.

Other relevant clinical surgical data like blood loss and overall surgical time did not differ significantly. Patient CO₂ absorption was not evaluated. A higher incidence of subcutaneous emphysemas regardless of the approach was observed in the AirSeal group in comparison to the Versaport group (AirSeal n=5 vs. Versaport n=1, p<0.05).

Further subgroup analysis of all mentioned study parameters of patients either operated by an extra- or transperitoneal approach did not reveal any other significant differences between both trocar groups and their approaches.

Discussion

Similar to results in the literature also in this study, the AirSeal trocar proved to offer a significantly more stable pneumoperitoneum and pneumoextraperitoneum than the standard port system. ^{4 –6} This was impressively shown by the less frequent loss of pressure episodes in the AirSeal group than in the Versaport group. In the Versaport group, a sudden pressure loss below 8 mm Hg occurred most often when the cap of the trocar was taken off and the mechanical valves that otherwise retained CO₂ were removed. In contrast to that, these situations were completely avoided by the AirSeal trocar since due to its open and barrier-free access channel, no further trocar manipulations were required and the AirSeal gas barrier was easily passed by specimen and needles. These specimens were also more likely to be intact.

In the Versaport group, episodes of pressure loss below 8 mm Hg additionally occurred during continuous suction even in the absence of other air leaks. This furthermore demonstrated the limited capability of the Versaport, together with its standard insufflation system to maintain intra-abdominal pressure under these conditions. This observation was in contrast to the AirSeal System, in which even continuous suction did not result in pressure loss episodes, impressively demonstrating stable pneumoperitoneum with real-time adaptation to dynamic changes of intra-abdominal pressures.

Next to suction and trocar manipulations, air leaks especially around the camera trocar were commonly observed as potential sources of gas loss in patients of both study groups. According to our opinion, this was mainly attributed to the Hasson technique, ^4,5 which was used to insert the camera trocar. In this technique, the camera trocar is brought into the abdominal cavity under vision through a minilaparotomy. This, however, happens at the expense that the fascia often does not encircle the trocar as tightly as if it was punctured directly through the fascia. Even though the skin was carefully closed around the camera trocar by a running suture to reduce CO₂ leaks, they were commonly observed in both trocar groups. Whereas in the Versaport group, these leaks often caused additional episodes of pressure loss; this never occurred in the AirSeal group. This again proved the much better capacity of the AirSeal System trocar over the Versaport trocar used in conjunction with a standard insufflator system to maintain intra-abdominal pressure even in case of bigger gas leaks.

Whereas one recent study by Herati et al in standard renal laparoscopy described a decreased CO₂ consumption when using the AirSeal trocar, ^4,5 this was not the case in our evaluation. In the present evaluation, a slightly higher overall CO₂ consumption was observed in the AirSeal group than in the Versaport group. The most probable explanation was according to our opinion the aforementioned gas loss, which was successfully compensated in the AirSeal group, but additionally caused a higher gas consumption.

The second most important advantage of the AirSeal trocar experienced in the present study was the significant reduction of necessary trocar manipulations down to zero in comparison to the standard Versaport. This was most apparent during lymph node dissection in which specimen retrieval was performed in separated anatomical portions through the port system by a Johann forceps. Whereas in the Versaport group a 2-handed disconnection of the trocar head was necessary each time to avoid tissue damage by the trocar valves; this was not the case due to its barrier-free entrance with the AirSeal trocar. Also, needle insertion and extraction was much easier and not associated with pressure loss as mentioned before. As a major advantage, this easier trocar handling enabled the table-side surgeon to make single-handed insertions and extractions leaving his other hand free to maintain traction or suction or perform other tasks.

Besides these two advantages of the AirSeal System, other parameters analyzed in the present study revealed no differences. Even though intra-abdominal CO₂ pressure was significantly more stable in the AirSeal group, the number of counted internal and external camera cleaning episodes was not lower in the AirSeal group. This was in contrast to other studies in standard laparoscopy in which the use of an AirSeal trocar was associated with less camera smudging and a better visibility. ^4,5 However, there the camera was directly inserted through the AirSeal port and not like in the present study through a classical camera port with valves.

Besides camera cleaning, also surgical time and blood loss were similar and did not differ between both groups. This was partially in contrast to the study by Herati et al who observed a significant time reduction in laparoscopic renal surgery with the AirSeal trocar. ⁵ In the present study, even though the AirSeal trocar offered some clear advantages in terms of a more stable pneumoperitoneum and a less trocar manipulation, in our experience, these advantages did not translate into other measured surgical advantages like a reduced surgical time or less blood loss.

A minor disadvantage of the AirSeal trocar system seems to be at first an increased noise level due to intracannula flow intensity. In the robotic setting, this was initially disturbing since the communication between the console surgeon and the surgical crew is transmitted by loudspeakers that in consequence had to be turned up. However, after a short period of adaptation, this was no more considered a burden by the surgical teams.

Second, like in other studies, subcutaneous emphysemas—even though clinically not relevant—occurred in this study. In the present study, five AirSeal and one patient of the Versaport group had subcutaneous emphysemas. Also, Herati et al reported in their initial series of 25 patients subcutaneous emphysemas in two patients. ⁵ The most probable explanation for these emphysemas was for them as well as for us a possible intermittent dislocation of the distal end of the AirSeal trocar system into the subcutaneous tissue, which then caused subcutaneous emphysemas by the gas flow directed into the subcutaneous tissue layers. To further avoid these emphysemas, we consider similar to Herati et al, a deep enough penetration and a trocar fixation with appropriate intra-abdominal maintenance of the black line situated at the AirSeal distal cannula tip, which was not consequently done in our study, a possible solution.

One limitation of the present study is the heterogenous groups that comprised both patients with an extraperitoneal and a transperitoneal approach. To furthermore evaluate these differences, we performed a subgroup analysis looking at possible differences of study parameters between both approaches and the different trocar systems. However, no additional significant or differences in tendency were found in these analyses that would have shown the AirSeal or the Versaport more favorable for the trans- or extraperitoneal approach. Nevertheless, from the authors' point of view, the AirSeal trocar was especially appreciated in the extraperitoneal approach since its advantage of a more stable pneumocavity impressively became of value in the smaller cavity where gas loss has a much higher consequence.

As a conclusion, this study proved a better pressure control and an easier trocar handling in robotic-assisted radical prostatectomy when the AirSeal System was used. However, this did not result in further surgical advantages for the patients like shorter surgical time or less blood loss in the present study.