A gas concentration monitoring system (100, 600) may include a processor (110, 610) configured to detect a concentration of a selected gas in a sample gas flow obtained from a physical interface (107) to a patient (101)； form a dataset including a plurality of data points, each data point corresponding to the detected concentration of the selected gas within the sample gas flow during a sampling time； group the data points according to a frequency of occurrence of the data points within the sampling time； and/or determine at least one of a signal confidence and signal quality based on relative characteristics between the groups of data points.
