Characterisation of trocar associated gas leaks during laparoscopic surgery

Abstract

Background: During laparoscopy, the abdominal cavity is insufflated with carbon dioxide (CO₂) that could become contaminated with viruses and surgical smoke. Medical staff is potentially exposed when this gas leaks into the operating room through the instruments and past trocar valves. No detailed studies currently exist that have quantified these leakage pathways. Therefore, the goal of this study was to quantify the gas leakages through trocars and instruments, during minimally invasive procedures.

Methods: A model of the surgical environment was created, consisting of a rigid container with an interface for airtight clamping of laparoscopic equipment such as trocars and surgical instruments. The model was insufflated to 15 mm Hg using a pressure generator and a pneumotachograph measured the equipment gas leak. A protocol of several use cases was designed to simulate the motions and forces the surgeon exerts on the trocar during surgery.

Results: Twenty-three individual trocars and twenty-six laparoscopic instruments were measured for leakage under the different conditions of the protocol. Trocar leakages varied between 0 L/min and more than 30 L/min, the instruments revealed a range of leakages between 0 L/min and 5.5 L/min. The results showed that leakage performance varied widely between trocars and instruments and that the performance and location of the valves influenced trocar leakage.

Conclusions: We propose trocar redesigns to overcome specific causes of gas leaks. Moreover, an international testing standard for CO₂ leakage for all new trocars and instruments is needed so surgical teams can avoid this potential health hazard when selecting new equipment.

Keywords: Carbon dioxide; Gas leak; Laparoscopic equipment; Surgical safety; Surgical smoke.

Fig. 1

a Trocar dimensions and valve types, d_nom was used for categorization. The distances between the valves and the lumen diameters were measured. Six different types of valves could be distinguished: diaphragm, segmented diaphragm, flap, barrel, bicuspid and quadcuspid valve. b The leak measurement setup and leak pathways: A rigid container that was pressurized using an external pressure source. The flow needed to keep the rigid container pressurized was measured at the inlet, the inlet flow equalling the leak through the trocar and/or instrument. In an OR setting, CO₂ can leak through three pathways: through the instrument, through the trocar and between the trocar and tissue. In this setup a silicone membrane was used to prevent leak through the tissue pathway

Fig. 2

a Manipulations of the rod within the trocar, in axial (2), pivotal (3) and radial (4) directions. Axial manipulation oscillation are performed with a 5 cm amplitude. During the pivotal and radial manipulation the rod is maximally displaced. b During the instrument insertion test, a grasper with a fenestrated structure was inserted into the trocar and kept in contact with both valves to allow for an open passage of gas

Fig. 3

a Baseline flow measurements in trocars at 15 mm Hg. Along the x-axis the trocar names are noted, the colours correspond to the trocar type. The type of valve 2 is denoted by a symbol under the result of each trocar and is detailed in Table 1. As trocar k had only one valve, it does not have a symbol. b Flow through measured instruments. The bar height indicates the median leak for each group, the crosses shows the inter-quartile range and the dots represent the result of each individual instrument

Fig. 4

Leak through trocar caused by different manipulations with a solid shaft. The symbols below the bars indicate the type of valve 1 that was used on each trocar. The shaft size, number of valves and adapter valve are indicated below the graph. Trocar I was equipped with a third valve. *Single valve. ⁺Removable diaphragm 5 mm adapter valve

Fig. 5

a Leak during instrument insertion trocars grouped per trocar size and used instrument size, median and inter-quartile range per group. b The effect of valve distance compared to the tool tip length of the surgical instrument, in this case longer or shorter than 28 mm. The height of the boxes is the median value, the whiskers represent the inter-quartile range and the crosses are each individual trocar