Yes, the MAXREFDES101 can be used to extract respiratory rate. MAXREFDES101 has both ECG and PPG sensing capabilities built into it and both signals can be used to measure the respiration rate.
Hence to measure respiration from PPG signal you may use Empirical Mode Decomposition technique which is particularly suitable for wearables.
If you prefer to extract the respiration rate from ECG data you may use Discreet Wavelet Transform.
You may find the following links to be quite helpful: