Using with only respiration file and no cardiac file

Dear AFNI experts,

In some of the fMRI runs, the cardiac (pulse) sensor malfunctioned and the cardiac data were either corrupted or flat (the value holds constant over time, which will cause to return [] and crash the program).
Is it possible to use with only the remaining respiration data?

BTW, which one works better, or 3dretroicor?

Thanks a lot!
Best regards,