A system for determining a respiratory effort for a subject, the system comprising an output interface and a user input; the system further comprising a processor configured to: receive a relaxed signal representing a subject breathing in a relaxed manner; receive a forced signal representing the subject breathing in a forced manner, wherein the relaxed signal and the forced signal are EMG signals from the second intercostal space, obtained by at least two EMG electrodes attached to the subject at the second intercostal space; derive a plurality of forced peaks from the forced signal; select candidate peaks from the plurality of forced peaks, wherein a candidate peak is distinguished from a non-candidate peak based on features of the forced peaks; provide the selected candidate peaks on the output interface; obtain a user identified peak through the user input, wherein the user identified peak has been selected by a user from the candidate peaks provided on the output interface; and determine and output a respiratory effort based on the relaxed signal and the user identified peak; and the processor being further configured to provide feedback in real time for each of the forced peaks, wherein the feedback indicates one or more of: whether a forced peak is selected as a candidate peak; the number of candidate peaks currently selected; based on a forced peak not being selected as a candidate peak, why the forced peak was not selected as a candidate peak; the features of one or more of the forced peaks: and feedback on previous forced peaks. the system further comprising a processor configured to: receive a relaxed signal representing a subject breathing in a relaxed manner; receive a forced signal representing the subject breathing in a forced manner, wherein the relaxed signal and the forced signal are EMG signals from the second intercostal space, obtained by at least two EMG receive a relaxed signal representing a subject breathing in a relaxed manner; receive a forced signal representing the subject breathing in a forced manner, wherein the relaxed signal and the forced signal are EMG signals from the second intercostal space, obtained by at least two EMG electrodes attached to the subject at the second intercostal space; derive a plurality of forced peaks from the forced signal; select candidate peaks from the plurality of forced peaks, wherein a candidate peak is distinguished from a non-candidate peak based on features of the forced peaks; derive a plurality of forced peaks from the forced signal; select candidate peaks from the plurality of forced peaks, wherein a candidate peak is distinguished from a non-candidate peak based on features of the forced peaks; provide the selected candidate peaks on the output interface; obtain a user identified peak through the user input, wherein the user identified peak has been selected by a user from the candidate peaks provided on the output interface; and determine and output a respiratory effort based on the relaxed signal and the user identified peak; and the processor being further configured to provide feedback in real time for each of the forced peaks, wherein the feedback indicates one or more of: whether a forced peak is selected as a candidate peak; the number of candidate peaks currently selected; based on a forced peak not being selected as a candidate peak, why the forced peak was not selected as a candidate peak; the features of one or more of the forced peaks: and feedback on previous forced peaks. obtain a user identified peak through the user input, wherein the user identified peak has been selected by a user from the candidate peaks provided on the output interface; and determine and output a respiratory effort based on the relaxed signal and the user identified peak; and the processor being further configured to provide feedback in real time for each of the forced peaks, wherein the feedback indicates one or more of: whether a forced peak is selected as a candidate peak; the number of candidate peaks currently selected; based on a forced peak not being selected as a candidate peak, why the forced peak was not selected as a candidate peak; the features of one or more of the forced peaks: and feedback on previous forced peaks.