Size Selective Characterization and Particle Emission Rates during a Simulated Medical Laser Procedure

A laboratory-based simulated surgical procedure was designed to characterize the medical laser-generated air contaminant (LGAC) particles generated during surgical procedures and to estimate exposures in theoretical rooms. Laser operational parameter settings were varied between levels to investigate the influence of parameter settings on LGAC generation.;Two medical lasers, the carbon dioxide at a wavelength of 10,600 nanometers (CO2, lambda =10,600 nm) and the holmium yttrium aluminum garnet (Ho:YAG) laser at the wavelength of 2100 nanometers (Ho:YAG, lambda =2100 nm) were used, varying three operational parameters (beam diameter, pulse-repetition frequency [PRF], and power) between two levels and the resultant plume was collected using two real-time size selective particle counters in a laboratory emission chamber. Analysis of variance (ANOVA) was used to determine the influence of operational parameter settings on size-specific particle emission rate. Particles from a limited number of experiments were also collected on polycarbonate filters and imaged using a scanning electron microscope (SEM) in backscatter mode to study the particle characteristics and if mechanism of formation could be determined. Particles on each filter were counted and a determination on shape (irregular versus homogenous) and diameter was made. Size-specific particle emission rates were then used to demonstrate potential concentration range using a two-zone exposure model.;Results indicate power and beam diameter were statistically significant influential parameters for both lasers and for all particle size ranges, but pulse repetition frequency was only a statistically significant influential parameter for the smallest particles generated. An increase in power and decrease in beam diameter led to an increase in particle emission for the Ho:YAG laser. For the CO2 laser, higher power led to a decrease in emission rates of small particles and an increase for large particles while a smaller beam diameter led to an increase of particle emissions for most size ranges (<10microm). Beam diameter was the most influential variable in the generation of laser-generated particles at all sizes, and the three operational parameters we tested had the most influence on the generation of the smallest particle size ranges. Particle size varied, with the Ho:YAG laser producing particles in the 1--10 microm range and the CO2 laser producing particles between 1 and 50 microm in diameter. Particle shape was variable, with fibers, foam, and conglomerate particles present in our samples. Modeled concentrations for the near-field ranged between 0.03 and 0.5 mg/m3 and between 0.01 and 0.4 mg/m3 in the far-field. Results indicate concentrations in the simulated scenarios were similar to those obtained from previously reported field assessments conducted in hospital operating rooms (ORs).;The methods used in this study provide a foundation for future investigations to better estimate particle-size dependent emission rates for additional laser operational parameters in order to inform occupational exposure control strategies.