Dynamic cooling of human skin using a nontoxic cryogen with no ozone depletion and minimal global warming potential

Abstract

A method and apparatus for performing a laser treatment of a patient includes applying a positive pressure impulse on a predetermined target site on the patient with sufficient positive pressure arising from the momentum flux of sprayed material incident on the target site to momentarily lessen pain sensation during irradiation during or proximate in time to irradiation of the target site. The predetermined target site is cooled by applying a predetermined amount of coolant or cryogen onto the target site. The target site is radiated with energy to produce heat in tissue at the target site while leaving a superficial part of the target site substantially undamaged due to dynamic cooling of the superficial part of the target site by the coolant. Mediation of the pain sensation arising from the radiation is at least partially masked or lessened by the positive pressure impulse and/or by the temperature of the coolant.

1 . A method for performing an energy beam treatment of a patient comprising:
 applying a positive pressure impulse on a predetermined target site on the patient with sufficient positive pressure arising from the momentum flux of sprayed material incident on the target site to momentarily lessen pain sensation during irradiation of the target site during or proximate in time to irradiation of the target site;   cooling the predetermined target site by applying a predetermined amount of coolant onto the target site; and   radiating the target site with energy to produce heat in tissue at the target site while leaving a superficial part of the target site substantially undamaged due to dynamic cooling of the superficial part of the target site by the coolant,   so that mediation of pain sensation arising from the radiation is at least partially masked or lessened by the positive pressure impulse and/or by the temperature of the coolant.   
     
     
         2 . The method of  claim 1  where applying the positive pressure impulse on the predetermined target site on the patient comprises applying a momentum flux of sprayed liquid carbon dioxide expanded through at least one nozzle applicator to form carbon dioxide snow impinging on the target site. 
     
     
         3 . The method of  claim 2  where applying a momentum flux of sprayed liquid carbon dioxide comprises applying a momentum flux of a slurry of carbon dioxide snow and liquid carbon dioxide. 
     
     
         4 . The method of  claim 2  where applying a momentum flux of sprayed liquid carbon dioxide comprises applying a momentum flux of substantially all carbon dioxide snow in a solid state. 
     
     
         5 . The method of  claim 1  where cooling the predetermined target site by applying the predetermined amount of coolant onto the target site comprises cooling the predetermined target site with the same material used to apply the positive pressure impulse to the target site. 
     
     
         6 . The method of  claim 1  where cooling the predetermined target site by applying the predetermined amount of coolant onto the target site comprises cooling the predetermined target site at least in part with a different material than that used to apply the positive pressure impulse to the target site. 
     
     
         7 . The method of  claim 1  where applying a positive pressure impulse on a predetermined target site to momentarily lessen pain sensation during irradiation of the target site during or proximate in time to irradiation of the target site further comprises applying a cooling temperature impulse to the predetermined target site during irradiation of the target site during or proximate in time to irradiation of the target site. 
     
     
         8 . The method of  claim 7  where applying a cooling temperature impulse to the predetermined target site during irradiation of the target site during or proximate in time to irradiation of the target site comprises applying a temperature impulse by means of a spurt of cryogen snow. 
     
     
         9 . The method of  claim 8  where applying a temperature impulse by means of a spurt of cryogen snow comprises applying a spray of frozen liquid carbon dioxide expressed through at least one nozzle. 
     
     
         10 . The method of  claim 1  where applying the positive pressure impulse on a predetermined target site comprises applying 0.005 to 0.15 MPa of positive pressure at the target site. 
     
     
         11 . The method of  claim 1  where cooling the predetermined target site by applying the predetermined amount of coolant onto the target site comprises disposing the coolant on the target site in a solid state so that pooling of any substantial amount of coolant and consequent uneven cooling is substantially avoided. 
     
     
         12 . The method of  claim 11  where disposing the coolant on the target site in a solid state so that pooling of any substantial amount of coolant and consequent uneven cooling is substantially avoided comprises disposing carbon dioxide snow on the target site. 
     
     
         13 . The method of  claim 12  where disposing carbon dioxide snow on the target site comprises disposing a slurry of carbon dioxide snow and liquid carbon dioxide on the target site. 
     
     
         14 . The method of  claim 12  where disposing carbon dioxide snow on the target site comprises disposing substantially only carbon dioxide snow on the target site. 
     
     
         15 . The method of  claim 1  further comprising accurately controlling the time duration of the application of the positive pressure impulse to the target site by operating a high pressure valve at or above 5 MPa. 
     
     
         16 . The method of  claim 15  where operating the high pressure valve comprises operating the valve at liquid carbon dioxide storage pressures at room or an elevated temperature with openings controlled to an accuracy within 0.1 to 25 msec of a predetermined time duration. 
     
     
         17 . An apparatus for thermally mediating a biological tissue comprising:
 an energy source directed to deliver radiation to a selected location of the biological tissue;   a source of liquid carbon dioxide;   a controller coupled to the source of liquid carbon dioxide; and   a spray applicator having at least one nozzle communicated with the source of liquid carbon dioxide, coupled to and controlled by the controller to spray a predetermined amount of liquid carbon dioxide through at least one nozzle in coordination with radiation of the target site by the energy source in order to apply a positive pressure impulse on a predetermined target site on the biological tissue arising from the momentum flux of sprayed carbon dioxide incident on the biological tissue sufficient to at least partially mediate pain sensation arising from the radiation by the positive pressure impulse, a sound impulse, and/or by the temperature of the carbon dioxide.   
     
     
         18 . The apparatus of  claim 17  where the spray applicator applies a positive pressure impulse of up to 0.15 MPa on a predetermined target site on the biological tissue. 
     
     
         19 . The apparatus of  claim 17  where the spray applicator applies a positive pressure impulse in the range of 40 kPa (300 mm Hg) to 67 kPa (500 mmHg) on the predetermined target site in the biological tissue. 
     
     
         20 . The apparatus of  claim 17  where the spray applicator having at least one nozzle sprays the predetermined amount of liquid carbon dioxide through the at least one nozzle to create carbon dioxide snow to apply a positive pressure impulse on a predetermined target site on the biological tissue arising from the momentum flux of sprayed carbon dioxide snow incident on the biological tissue. 
     
     
         21 . An apparatus for performing laser treatment of a biological tissue comprising:
 a laser directed to deliver energy to a selected location of the biological tissue;   a source of liquid carbon dioxide;   a controller; and   a spray applicator having at least one nozzle communicated with the source of liquid carbon dioxide, coupled to and controlled by the controller to spray a predetermined amount of liquid carbon dioxide through at least one nozzle to expand the liquid carbon dioxide to create a controlled amount of carbon dioxide snow which impinges onto the selected location of the biological tissue and wherein the carbon dioxide snow is substantially all deposited on the biological tissue in a solid state,   so that deposition of the carbon dioxide snow on the biological tissue substantially all in the solid state avoids pooling of any substantial amount of liquid state carbon dioxide and consequent uneven cooling of the biological tissue.   
     
     
         22 . An apparatus for performing laser treatment of a biological tissue comprising:
 a laser directed to deliver energy to a selected location of the biological tissue;   a source of liquid carbon dioxide under high pressure at room or elevated temperature;   a controller to accurately control a predetermined time period of liquid carbon dioxide release from the source; and   a spray applicator having a high pressure valve and at least one nozzle communicated with the source of liquid carbon dioxide, coupled to and controlled by the controller to spray a predetermined amount of liquid carbon dioxide through the at least one nozzle to expand the liquid carbon dioxide to create an accurately controlled amount of carbon dioxide snow which impinges onto the selected location of the biological tissue,   so that precise control of the duration of the time-controlled pulses of carbon dioxide are achieved by use of the high pressure valve.   
     
     
         23 . An apparatus for thermally mediating a biological tissue comprising:
 an energy source directed to deliver radiation to a selected location of the biological tissue;   a source of liquid cryogen;   a controller coupled to the source of liquid cryogen; and   a spray applicator having at least one nozzle communicated with the source of liquid cryogen, coupled to and controlled by the controller to spray a predetermined amount of liquid cryogen through the at least one nozzle to cool the liquid cryogen to form cryogenic snow which applies a positive pressure impulse on a predetermined target site on the biological tissue arising from the momentum flux and temperature of the sprayed cryogenic snow incident on the biological tissue sufficient to mediate pain arising from the radiation.