echo - endoscopes are much stiffer and thicker than regular endoscopes . during the procedure of endoscopic ultrasound ( eus ) procedure ,
water irrigation is a very useful for imaging but very dangerous if the patient receive the procedure under anesthesia without intubation . in this study
, we evaluated the safety and effectiveness of nitrous oxide ( n2o ) ( 70% ) for eus .
among 4230 patients who underwent eus from december 2012 to december 2013 , 347 out patients who need irrigation during the procedure were enrolled and divided into group a. group a ( n2o sedation group , n = 162 ) and group b ( no sedative group , n = 185 ) . for group
the mixture rate of n2o and o2 was 45 - 65% and controlled by nurses according to individual effect .
the cardiorespiratory functions , procedure duration , complications , and visual analog scale ( vas ) of the patient and examiner satisfaction were compared .
  both group had comparable diagnostic accuracy , but vas of the patients who received n2o sedation was higher than that in group b ( 7.5 vs. 4.5 , p < 0.05 ) and the examiner procedural satisfaction ratings of group a was also better than that of group b ( 8.1 vs. 5.1 , p < 0.05 ) ; most patients in group a reported willingness to reconsider n2o for a future eus .
n2o for eus is comfortable , safe and feasible , especially for the procedures that need irrigation .
 objective : echo - endoscopes are much stiffer and thicker than regular endoscopes . during the procedure of endoscopic ultrasound ( eus ) procedure , 
 water irrigation is a very useful for imaging but very dangerous if the patient receive the procedure under anesthesia without intubation . in this study 
 , we evaluated the safety and effectiveness of nitrous oxide ( n2o ) ( 70% ) for eus.methods:among 4230 patients who underwent eus from december 2012 to december 2013 , 347 out patients who need irrigation during the procedure were enrolled and divided into group a. group a ( n2o sedation group , n = 162 ) and group b ( no sedative group , n = 185 ) . for group a , patients received n2o by inhalation during the procedure . 
 the mixture rate of n2o and o2 was 45 - 65% and controlled by nurses according to individual effect . 
 the cardiorespiratory functions , procedure duration , complications , and visual analog scale ( vas ) of the patient and examiner satisfaction were compared.results : both group had comparable diagnostic accuracy , but vas of the patients who received n2o sedation was higher than that in group b ( 7.5 vs. 4.5 , p < 0.05 ) and the examiner procedural satisfaction ratings of group a was also better than that of group b ( 8.1 vs. 5.1 , p < 0.05 ) ; most patients in group a reported willingness to reconsider n2o for a future eus . 
 no pulmonary aspiration occurred in this study.conclusions:n2o for eus is comfortable , safe and feasible , especially for the procedures that need irrigation . 
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