Insufflation device with intelligent control of smoke evacuation

[0001] This application is a National Stage entry of PCT/DE2019/000176, filed Jul. 5, 2019, which claims the benefit of German application No. 10 2018 005 314.9, filed Jul. 5, 2018, the contents of which are incorporated herein by reference.

[0002] The present invention relates to an insufflator with integrated smoke evacuation. A novel control method of the smoke evacuation enables to maintain the pressure in the patient even when leakages occur, and to limit the evacuation volumetric flow rate in case of high leakages.

[0003] Insufflators offering the possibility of a simultaneous smoke evacuation are known from prior art (see, e.g., WO 2015/043570 A1). This insufflator comprises a hose, through which a medical gas is fed into a body cavity (e.g., an abdomen). The gas generates a positive pressure, which expands the body cavity, in order that there is sufficient space for visual inspections or therapeutic interventions. Through a second hose, the gas is evacuated again from the abdomen. In the case of therapeutic interventions by means of electrical surgery or laser, obnoxious smoke gases may be formed that are discharged and filtered by the insufflator via this second hose. The surgeon selects a desired target evacuation volumetric flow rate. The evacuation pump is regulated to the desired target evacuation volumetric flow rate. It is a problem when a larger leakage volumetric flow occurs or the resistance to flow of the insufflation line increases. In either case, the insufflator is not capable of insufflating the additionally necessary amount of CO₂. The consequence is that the cavity partially or completely collapses. In order to reduce this effect, according to the state of the art, the evacuation volumetric flow rate is limited or reduced in such situations. One possibility of implementation is to detect whether the measured pressure in the cavity differs from the desired target value, and then to reduce the maximum evacuation volumetric flow rate.

[0004] Most insufflators available on the market operate with a pulse-like method, in order to regulate the volumetric flow rate to be insufflated. Herein, insufflation phases alternate with so-called “measurement pauses”. In the measurement pauses, the volumetric flow is turned off for a few hundred milliseconds, so that the pressure in the hose and the pressure in the cavity are balanced. Thereby, the insufflator can measure, by a pressure sensor in the insufflation line, for a short time the pressure in the cavity. Through the length of the insufflation phases, then the mean insufflation volumetric flow rate is controlled. When high volumetric flow rates are required, long insufflation phases are performed. In such a pulsed insufflation method, another possibility of regulating the evacuation flow is to use the length of an insufflation phase as a criterion for a decrease or an increase of the evacuation volumetric flow rate. When, for instance, the necessary length of the insufflation phase exceeds a predefined value, the smoke evacuation is reduced.

[0005] In the practice, it has been found that these two methods for limiting the evacuation volumetric flow rate have drawbacks. The most important drawback is that the pressure in the cavity must already have been reduced, in order that the evacuation volumetric flow rate is adjusted. This means that, when opening leakages, undesired pressure drops will occur, which can lead to delays in the surgery. An example is a larger leakage that occurs during the surgery.

[0006] Advanced insufflators are capable of generating insufflation volumetric flow rates of higher than 30 lpm. Thereby, even high leakages can be balanced, and simultaneously, a sufficient reserve for evacuation can be provided. This has, however, the following drawback: Even with high leakages, wherein, for surgeons, in fact, no evacuation would be required, the evacuation is not reduced. The evacuation continues with full evacuation power and stresses the patient by an additional cooling and drying process of the tissue. In order to reduce this drawback, in U.S. Pat. No. 5,199,944, a method is proposed, which only starts the smoke evacuation when smoke gases are generated. Further state of the art follows from the document US 2018/0133416 A1. In the present patent document, an alternative method is described.

[0008] The present invention relates to an insufflator for minimally invasive surgery, including a) a pressure and flow rate-regulating unit equipped with a proportional valve, a pressure sensor and a flow rate measurement device, b) a supply line with an optional filter and connection to a first trocar, c) a second trocar with an evacuation hose and an optional filter, connected to an evacuation device with controllable evacuation power, d) an optional flow rate measurement device in the evacuation line, e) an electronic or mechanical regulating unit, and f) a novel method for adjustment of the evacuation volumetric flow rate.

[0009] With small leakages, the insufflator is operated, as is described in the state of the art (WO 2015/043570 A1). The gas connection (1) leads via a line (2) to the pressure and flow rate-regulating unit (3) of the supply line (4). In the pressure and flow rate unit (3) is provided a pressure sensor, in order to monitor the pressure in the line. Furthermore, a flow rate-measurement device (5) is mounted for volumetric flow rate measurement behind the pressure and flow rate unit (3). Further, a filter for protection of the patient is provided (6). The supply line (7) terminates in a first trocar (8) that can fill the body cavity with gas. The insufflator further includes a second hose (10) serving as an evacuation hose. A second trocar (9) introduced into the body cavity (9) is connected by means of this evacuation hose (10) to the insufflator. The evacuation hose, too, comprises an optional filter (11) and leads via a line (13) to an evacuation pump (14). The evacuation power of the evacuation pump is controllable. Via a line (15), the smoke is discharged from the insufflator (16). The evacuation volumetric flow rate can be measured either through the optional flow rate sensor (12) or can be determined by the power of the evacuation pump (14). Different from insufflators of prior art, the insufflator according to the invention comprises a novel intelligent control method of the evacuation volumetric flow rate.

[0010] A controller is operatively connected to the pressure and flow rate regulating unit and the evacuation device. The controller controls the evacuation device so as to adjust the evacuation volumetric flow rate based at least in part on a defined maximum volumetric flow rate and a determined leakage volumetric flow rate.

[0011] The novel method for adjustment of the evacuation volumetric flow rate comprises the following steps:

• • [0012] (a) Determination of the current maximum insufflation power: The maximum insufflation volumetric flow rate is mainly dependent on the resistance to flow of the used trocar-instrument combination and the maximum pressure. This pressure is typically set to a value, which leads to a still acceptable risk for the patient and must not further be increased. In order to determine the maximum possible insufflation volumetric flow rate, different methods can be used. For instance, an algorithm can be used, which determines the characteristic of the trocar instrument. Alternatively, mathematical models, such as the Kalman filter or Luenberger observer, can be used to determine the maximum insufflation power.
  • [0013] (b) Determination of the current leakage volumetric flow rate q_Leakage: The leakage, too, can be estimated by a mathematical model. Alternatively, the mean leakage can also approximately be calculated by a subtraction of the mean evacuation volumetric flow rate from the mean insufflation volumetric flow rate.
  • [0014] (c) Calculation of the maximum possible evacuation volumetric flow rate q_{Evacuation,max}: By subtraction of the determined leakage from the maximum insufflation flow rate and subsequent multiplication with a safety factor between 0 and 1, which defines, with which load the insufflator ideally is stressed. The value is typically between 0.6 and 0.9.
  • [0015] (d) Verification whether a maximum exchange flow is exceeded:

[0016] In order to prevent that a high evacuation volumetric flow rate remains adjusted, even when in this situation leakages cause already a high gas exchange, the evacuation volumetric flow rate is additionally limited. For this purpose, a maximum exchange volumetric flow rate q_Exchange,max is defined. Typical values for q_Exchange,max are between 10 and 20 lpm. The value either can be adjusted via a graphical interface or is fixedly configured in the insufflator or adjusted by the software. The maximum evacuation volumetric flow rate q_Exchange,max is then limited such that the equation q_{Evacuation,max}+q_Leakage≤q_Exchange,max is satisfied. In other words: The sum of the maximum evacuation volumetric flow rate and the estimated leakage must not be larger than a defined value for q_Exchange,max.

• • [0017] (d) If the evacuation volumetric flow rate adjusted by the surgeon is larger than the calculated maximum evacuation volumetric flow rate q_Exchange,max, the target evacuation volumetric flow rate is limited to the maximum allowed evacuation volumetric flow rate q_{Evacuation,max}.
  • [0018] (e) The calculation is cyclically repeated (for instance every second), in order that the maximum allowed evacuation volumetric flow rate can continuously be adapted to changes in leakage or changes in the trocar-instrument combination.

[0019] A calculation example for illustration:

• • [0020] (a) The characteristic of the trocar-instrument combination is determined as q_Instrument=0.2 lpm/mmHg×p_Hose with the volumetric flow rate q_Instrument and the pressure in the hose p_Hose. The pressure for acceptable safety may be 100 mmHg. Then follows a maximum volumetric flow rate of q_max=0.2 lpm/mmHg×100 mmHg=20 lpm.
  • [0021] (b) The leakage is estimated by an observer or another method to be 10 lpm.
  • [0022] (c) The safety factor is selected as 0.8. Then follows a maximum evacuation flow q_{Evacuation,max}=20 lpm×0.8-10 lpm=6 lpm.
  • [0023] (d) When the surgeon has selected an evacuation volumetric flow rate of for instance 8 lpm, this is reduced to the maximum evacuation volumetric flow rate q_{Evacuation,max}=6 lpm, in order to prevent that the pressure is reduced too much by the selected evacuation.
  • [0024] (e) When the maximum exchange volumetric flow rate q_Exchange,max was configured to be 18 lpm, the condition q_{Evacuation,max}+q_Leakage≤q_Exchange,max is satisfied. Thus, there is no further reduction of the evacuation volumetric flow rate by the maximum exchange volumetric flow rate. When the maximum exchange volumetric flow rate q_Exchange,max would have been configured to be 12 lpm, the evacuation volumetric flow rate would be reduced to 2 lpm.
  • [0025] (f) The calculation is cyclically repeated, and when for instance the maximum insufflation power q_max is reduced, q_{Evacuation,max} is also adjusted.