CO2 and Nd:YAG laser-induced pulmonary parenchymal lung injury in a rabbit model.

Abstract

Laser exposure of the pulmonary parenchyma during treatment of emphysema and other clinical indications causes acute lung injury. Animal investigations are needed to understand and control laser-induced lung injury. We hypothesized that lung injury is deeper from Nd:YAG laser exposures than CO2 exposures because of deeper penetration of Nd:YAG wavelength light. We compared the temporal evolution of histologic injury in rabbits resulting from continuous mode shallow CO2 and Nd:YAG laser pulmonary parenchymal exposures applied in rabbits. Forty-six New Zealand white (NZW) rabbits underwent treatment with CO2 laser (n=18), Nd:YAG laser (n=18), or sham thoracotomy control (n=10) to the visceral pleural surface using 1 min of exposure (5 watts, defocused to 70 W/cm2 power density for both lasers). Animals were killed at 0, 4, 7, 21, and 49 d after exposure. Lung injury, similar to that seen clinically in humans, developed in all laser-treated animals. Injury progressed from ischemia and vascular congestion, to edema and necrosis, followed by pleural and parenchymal fibrosis. The acute injury was qualitatively distinct and slightly deeper in CO2 than Nd:YAG-treated animals (p<0.02) despite the shallower depth of penetration of the CO2 laser. These findings may imply that higher absorption coefficient for CO2 laser energy results in greater focal temperatures and injury in the areas of direct exposure, and suggest that Nd:YAG laser exposure at these settings may cause shallower injury than CO2 lasers in humans undergoing clinical treatment.

Effects of Nd:YAG laser irradiation on morphometry and lung function in elastase-induced emphysema in rats

“…What we observed on the peripheral portion was similar to the process of healing. In the past, there have been some reports about the pathological examination of lung parenchyma after laser irradiation [17][18][19]. Although both Cole and Brenner viewed peripheral changes as a side effect of lung injury after irradiation, we hypothesized that dense ne- crotic peripheral alveoli was not merely a side effect, but one of the most conspicuous effects that could bring on normalization of lung compliance.…”

Thermal effect of endoscopic thermal vapour ablation on the lung surface in human ex vivo tissue

“…For some investigations of the effect of thermal ablation in the lung, ex vivo tissue is not a suitable model because the differences are too large [15]. However, because the primary aim of this study was to examine the potential for injury at the lung surface due to vapour, human ex vivo tissue represents a suitable ‘worst case’ model as compared to in vivo for four reasons.…”

“…For these parameters only one and two of the 71 treatments respectively created a thermal effect larger than the 0.53 injury threshold. Considering the rapid development in thermal ablation of lung tissue technology from laser [15] to lung perfusion [23] to radio frequency [17, 24, 25] to vapour, a characterisation of the frequency factor and activation energy for thermal injury of pulmonary tissue is needed. Characterisation of thermal injury parameters for pulmonary tissue would allow for more precise analysis.…”