The mean depth of CC ( 57.0 [ 56.0-59 .0 ] vs 55.0 [ 49.5-57 .5 ] , P < .001 ) was significantly deeper , and the compression force ( 33.8 [ 29.3-36 .4 ] vs 23.3 [ 20.4-25 .3 ] , P < .001 ) was stronger in the assistant-push group .