Jacobs Journal of Surgery

Reducing the Risk of Mutagenicity Following Plumes Inhalation During Treatment of Malignant Tumors by Using Pulsed CO2 Medical Lasers in Operating Room: A Quantitative Study

*Franco Canestri
Department Of General Surgery, University Of Tel Aviv;, Israel

*Corresponding Author:
Franco Canestri
Department Of General Surgery, University Of Tel Aviv;, Israel
Email:franco.canestri@orginform.com

Published on: 2017-07-24

Abstract

Keywords

Plume Evacuator; Patient Vicinity; OR; Surgical Devices; Medical Lasers; Tissue Sublimation; PMMA; Biological Tissue; Automated Controls

Copyright: © 2017 Franco

Introduction: Danger of Surgical Smoke Inhalation and Current Removal Methods

During the past few years, only a few studies [1-10] have examined with greater details the potential adverse effects to patients, physicians and other health-care workers exposed to smoke generated by the combustive and ablative processes taking place during laser-beam and biological tissue interaction. This can happen in both research laboratories and much more frequently during surgery. Klesly [1] has recently identified several chemicals present in the smoke plume which could induce the generation of neoplastic tissue following inhalation. The most common ones are : alkyl benzenes, benzene, carbon monoxide, hydrogen cyanide, propane, toluene and xylene. Hystological changes have been identifying in rat lungs exposed to laser plumes, suggesting that these compounds represent strong risks of mutagenicity.

The hazards of surgical smoke are depending on 3 main areas of concerns :

-     Odor

-     Size and viability of the particulates present in the mix air-plumes or aerosol 

_    Endoscopic plumes not removed outside from the patient’s body during the surgical procedures. 

The size of the particulate [6] range from 1 to 5 microns in size, while there are some 600 compounds that have not yet properly identified, such as polycyclic aromatic hydrocarbons, benzene, toluene, formaldehyde and other ones already well identified as carcinogens.

The size and the viability of these particulate cause a serious danger during repeated exposure and following penetration in the alveoli of lungs, no matter if they are present in form of wet aerosol of a dry mix of multiple gasses. They can cause several pathological conditions ranging from pulmonary or bronchial congestions to cancer, also because viable bacteria can survive with intact viral DNA in surgical plume [16-18] and consequently grow.

During endoscopic treatments, if the surgical plume is not efficiently evacuated, there could be formations of methaemoglobin and carboxyhaemoglobin into the blood circulation which can cause severe damages to the oxygenation system of the whole patient’s body. Additionally, the presence of surgical smoke (for instance) in the abdomen not only obscures visibility but can cause unwanted biochemical reactions leading to malignancies [13].

Research Groups, but also Agencies and Medical Institutions around the world, are now changing their mentality about the way of treating surgical smoke : from a typical ‘advisory’ approach, in which only selected particulate and gases ‘should’ be removed, to a more ‘mandatory’ legislation in which all carcinogens and not-carcinogens surgical smoke types ‘must / shall’ be removed [9].

The main current procedures are three : in-line filters (1/4” wall suction line between the wall connection and the fluids suction canister), individual portable smoke evacuators using charcoal filters or ULPA / HEPA filters (Ultra Low Penetration Air / High Efficiency Particulate Air) and hospital centralized smoke evacuation systems. All these methods are associated to the additional regular optimization of surgical masks, gloves and eye glasses during laser surgery.

This Paper proposes a universal design of smoke evacuator that can be used directly next to the laser’s tip, both in endoscopic and non-endoscopic configurations, allowing the plume to be removed directly at the tissue impact location through strong suctioning, thus promoting greater plume capturing.

However, in order to achieve the best removal performance, the speed of the ejected plume bursts along with their size, width and height away from the impact spot must be carefully quantitatively measured. For instance, the pulsed beam allows to obtain geometrically well defined, separated and well visible smoke bursts, while the CW during both crater and cut creation generates a single, irregular and bigger cloud which is much more difficult to measure from a quantitative point of view.

Materials and Methods

The Author made several experiments to measure sizes, ejection velocities and dimensions of smoke bursts in presence of pulsed beam delivery, which allows the best visual observation of geometrically well-defined and easy-tolocate quantities of smoke volumes in air. The Author has used a ‘Synrad’ CO2 (Gaussian “Transverse Electromagnetic Mode” - TEM00) medical laser installed at the Sackler Faculty of Medicine and Exact Science of the Tel Aviv University, Tel Aviv, Israel.

In Fig. 1 the Experimental set-up is shown : several blocks of polymethylmethacrylate (PMMA) measuring 3 cm x 2 cm x 3 cm have been irradiated by the focal spot of the laser configured for two different sets of experiments. The first one was : 2.5 “ focal length, peak energy of 33 mJoules, TEM00 mode, 4 Hz, pulse width of 10 msec, total exposure time ttot = 10 s. The second set of experiments has been performed with the laser configured in the same way except for the focal length, which was changed to 5”. Each block has been horizontally irradiated over one surface and a high precision thermo-camera has been positioned in such a way that both ejection direction and shape of each smoke burst per pulse was recorded and measured via thermal contrast against a calibrated ruler located immediately under the exposed area. The horizontal irradiation mode has been intentionally decided in order to create more difficult plumes removal conditions compared to those ones created during vertical irradiation.

Measurement Results

The selection of the total irradiation time, the peak energy and emission frequency has been carefully calibrated in order to :

1) achieve the best visual observation while measuring each distinct and separate burst of smoke as unequivocal effect of each single ablative pulse ;

2) allow enough time to each burst of smoke to either reach a steady position or start to become non-visible along a measurable distance from the surface ;

3) allow enough total exposure time to produce measurable and realistic bursts, meaning that the total ablative capacity of the laser has decreased to zero at the end of the total exposure time. This is also equivalent to reaching the ablation threshold in Joules / cm2 along the crater for each single particular laser set-up. This means that this methodology can also be used to find the thermo- ablative threshold conditions of any given media treated by pre-defined invasive pulsed laser-beam [12-15].

Due to the small quantities of smoke next to the ablation threshold to be measured, an on-line gas-chromatographic method is recommended, mainly to precisely measure the ‘total smoke emission time’, which is the total time needed to reach the point of absence of smoke (Fig.1).

The final geometrical dimensions of the crater are depending on the latent heath of ablation of the irreversibly damaged crater’s walls. This continues to melt the media with micro emissions of plume which can be measured with gas-chromatographic methods only. For the purpose of this Study, the associated micro movements can be ignored because clinically not relevant. On the contrary, the volume of irreversibly damaged tissue can still considerably grow across the media even if the crater development has stopped : the growth depends on the media’s thermal conductivity and on the difference between the temperature of the crater walls (at the point of total absence of measurable smoke quantities) and the thermal damage threshold temperature of the media itself [13-22].

The following Table 1 summarizes the most important results obtained with the two proposed experimental set-ups for Gaussian laser profiles (see also Fig. 2) :

These results correlate with the ones already reported in Literature [12] about the velocities of ejected parts of treated tissue and brings additional knowledge about the relationship between the focal-related setup parameters of the laser and the overall final behavior of the plume bursts. The velocities and the distances reached by these are also separately reported and compared, showing totally different situations for the same energy used to treat the tissue by changing the focal and the measuring time.

In case of CW delivery, both X and Y parameters cannot be clearly and uniquely measured with enough reproducibility: this means that the removal efficiency of known quantities of dangerous plumes is worse than the one obtained with PW delivery regardless the removal method in use.

From a more mathematical point of view, the correct formula for the parameter Z (crater depth and smoke ejection, Table 1, Fig. 3) has the form of :

where the dimensions of k are :

The interpolation curves in cm. amongst the experimental data of the crater depths Zb (Table 1, Fig 1 and 3) as function of the focal lengths and exposure time are:

whereas regarding the lengths (also in cm.) of the bursts Za away from the sample’s surface, and therefore invading the patient vicinity towards the surgeon, we have (Fig. 3) :

For pulses below tc = 0.25 s. the generated bursts are shorter than the one generated at 0.25 s. itself (due to lower power density on spot) and therefore have the same effect as the ones obtained with longer exposure times. It is important to notice here that the deeper the crater develops, the shorter the bursts are ejected away from the surface : therefore, the equations above can help in predicting and monitoring themutual development of the crater shape in one direction whit the generated plume burst growing in the opposite direction for the same time interval (Fig. 3).

The two curves in Fig. 3 clearly divide the quadrant in 4 parts : χ marks the area with the highest danger for the surgeon, δ is the one with low risk but also with the lowest cutting performance of the laser, β is the one with the lowest risk but the end of the sublimation process while α represents the target area to work into, offering optimal operating and lowest risk conditions. Different procedures can be adopted to allow safe operating conditions present in the area α: the intersection point Φ must be moved and kept as much as possible on the left of the graphic for all treated tissues.

Ultimately, the power density on spot and the TEM (Transversal Electromagnetic Mode) of the beam profile also play a key role for the development of the depth of crater and associated quantity of the produced plume : future Studies will be specifically dedicated to clinically address all these very important topics.

Discussion

The Author proposes a new concept of ‘SRS’ (Smoke Removal System) which provides new advanced computer-driven hardware solutions specifically developed to optimize the removal of enough, if not all, dangerous plumes (Fig. 2). The biggest innovation which this solution presents is the dynamic self-positioning in real-time mode of the ‘SRS’ tip relative to a set of coordinates X and Z over the operative field.

The description of these two Approaches are :

1) access to a mathematical model based on all the key tissue and laser set-up variables and manufacturer’s specifications able to predict the position of at least 95% of the smoke quantity to be removed. This complex theoretical task is corroborated by a pre-defined data base where several experimental data (collected with different laser set-ups, tissue types and operative conditions) are used as feedback loop to validate the calculated X(t) and Z(t) to be then effectively deployed pulse-by-pulse. In this example (frequency and output energy as described), the ‘srs spoon’ has to calculate and reach the correct position [X, Z] within a time window of ?t =240 msec.

This window decreases with increasing frequency and/or output power. The viceversa is also true : it increases with decreasing frequency and/or output power.

2) the same calculation of X and Z can be carried out via a precision gas-chromatograph device which scans at the media’s absorption wavelengths the volume around each plume burst. After having located the correct burst’s volume, it interpolates X(t) and Z(t) and directs the SRS’ tip to the correct location for plume removal, aiming to target the 95% along Z or more, as already suggested.

Depending on the technology available, the precision gaschromatographic or a thermo-camera can be mounted either on a conveniently location not directly near the patient’s operating field or directly mounted and integrated on the SRS itself. Both Approaches are not equally efficient if the laser-beam is delivered in CW. In this case, a traditional continuous suctioning air flow device can be implemented, but the accuracy and the overall effectiveness of this solution is very questionable, as mentioned. Also, the beam’s TEM00 mode produces the highest burst ejection speeds.These coordinates are calculated by a computerized solution in order to dynamically reach the plumes with great accuracy to remove them. The tip has the shape of a spoon which contains a motion sensor device connected to a main processor unit which calculates the values of X and Z in two possible ways, the first being more cost-effective but maybe less accurate, the second one being more expensive, however it provides higher geometric accuracy.

Conclusions

Five important aspects have been reported :

1) The very high ejection velocities measured (Tab. 1) suggest and confirm the results reported in both [3] and [12] with an accent on focal and pulse lengths. The extrapolation and interpolation equations are presented in order to calculate and forecast both the dimensions and speeds of the ejected bursts also across different pulse widths and laser set-ups (Fig. 3).

2) The standard focal lengths, exposure times, pulse lengths and irradiation energy used in this Study allow a fast extrapolation to other set-ups in OR.

3) Due to the progression of the crater into the tissue after each pulse, only the first pulse (which generates the highest plume distance from the surface and the highest ejection velocity) is the most critical one to handle by the SRS. All the others are regressive and therefore easier to control (Fig. 2).

4) The rotating tip of the SRS can be positioned sufficiently away from the focal spot area, therefore the risks of interferences with the laser beam is minimal.

5) The SRS design concept is easy to install in the ORIT System and use.

This Proposal is the first attempt published on Literature to address the problem of plumes removal in OR in a more scientific and structured way. The Author believes to propose an interesting new technique in OR which addresses both the safety issues and the data collection about the chemical types and the thermo-mechanical dynamics of the plumes produced by medical lasers.

This will help to better understand the thermo-chemical processes taking place during the laser-beam interaction with biological tissue and investigate new mathematical models to propose as interpretative tools.

Also, after having created this knowledge data-base, the next step will consist in developing new surgical tools and techniques which aim to eliminate a specific targeted type of plume or a wider selection of them, still maintaining all the benefits of the laser-beam deployment in Surgery.

Acknowledgement

The Author wishes to thank Prof. A. Katzir of the Sackler School of Medicine and Exact Science of the Tel Aviv University, Tel Aviv, Israel for making the medical laser available to conduct the experiments needed to write this Paper.

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