Provided according to embodiments of the invention are methods of improving the effectiveness of chest compressions as part of cardiopulmonary resuscitation (CPR). Such methods include monitoring PPG signals from a PPG sensor secured to a nose during at least one chest compression and increasing, decreasing or maintaining a at least one of the depth, duration and frequency of at least one subsequent chest compression based on a waveform parameter of the PPG signals. Related devices and systems are also provided.
