The Fluidodynamics of Potentially Neoplastic Plumes Produced by Medical Lasers: First Quantitative Non-Tissue-Specific Measurements Using PMMA Samples (Phase I)

Objective: This study has two goals: (1) to identify and discuss key factors that contribute to the spread of potentially dangerous plumes chaotically in the vicinity of patients following surgery with medical lasers and (2) to recommend safety procedures for surgical staff members based on the measurements, analysis of results, and conclusions. Summary Background Data: In the past years, only a few studies have attempted to quantify the risks associated with routine exposure to plumes generated by medical lasers used to treat malignant tissue. The invasive thermodynamic sublimation processes following beam-tissue interaction generate plumes, which also contain particles of tumoral tissue not completely burned by the laser beam itself. These fumes can also be chemical by-products produced by normal tissue combustion. In both cases they retain a certain degree of malignancy (mainly depending on the type of tumor and by-product), which could result in spreading metastasis in the respiratory system of the surgical staff members and of the patient following inhalation. Only a few studies in the literature discuss this phenomenon, but all of them demonstrate clearly that current fume evacuator systems based on fixed air suctioning probes near the tip of the laser's focal head do not guarantee sufficient aspiration of the total dangerous gas volume (mixture of air and fumes) generated during complete surgical intervention. Methods: The author has made several measurements of the size, shape, dimension, and speed of the plumes associated with crater development in polymethylmethacrylate (PMMA) blocks exposed to a pulsed CO₂ laser beam. The laser device has been optimized for visualization via the thermocamera and each smoke burst was measured as follows: 2.5 and 5 inch focal lengths, peak energy of 33 mJ, TEM₀₀ mode, 4 Hz, pulse width t _p = 10 msec, and total exposure time t _e = 10 sec have been used to irradiate 3 × 2 × 3 cm³ PMMA blocks. From a pure thermochemical point of view, PMMA has been used as the gross first approximation medium for a large variety of biological tissues because the aim is to provide a global non-tissue-specific modeling rather than a very detailed investigation of the large variety of possible combinations of tissues exposed to the laser beam. This part of the study is necessary and it will be addressed in Phase II of this project. Results: A quantitative description of the dynamic process present in the production of plumes with PMMA samples has been obtained along with the quantification of seven key parameters, such as ejection velocities and plume size, which accurately describe the process itself. Conclusions: Although this can be only a first approximation study, its results provide a very good idea about the orders of magnitude of the key parameters involved in the processes and dynamics of global plume production. The author suggests how these conclusions can be extrapolated for in vivo applications and can be used as recommendations to design new suctioning devices aimed at increasing safety in the operating room.