Thermal damage produced by high‐lrradiance continuous wave CO₂ laser cutting of tissue

Thermal damage produced by continuous wave (cw) CO₂ laser ablation of tissue in vitro was measured for irradiances ranging from 360 W/cm² to 740 kW/cm² in order to investigate the extent to which ablative cooling can limit tissue damage. Damage zones thinner than 100 μm were readily produced using single pulses to cut guinea pig skin as well as bovine cornea, aorta, and myocardium. Multiple pulses can lead to increased damage. However, a systematic decrease in damage with irradiance, predicted theoretically by an evaporation model of ablation, was not observed. The damage‐zone thickness was approximately constant around the periphery of the cut, consistent with the existence of a liquid layer which stores heat and leads to tissue damage, and with a model of damage and ablation recently proposed by Zweig et al.