A computer controlled ventilation system was employed to maintain a constant end-expired CO2percentage (FECO2) during a series of studies on young dogs aimed at measuring brain temperature differences during surface cooling hypothermia. The conclusion is that an FECO2of six per cent or more is desirable if brain temperature differences are to be minimized. Additional experiments showed that ethyl alcohol and sodium nitroprusside infusions during cooling did not decrease brain temperature differences.
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