The present invention relates to novel lip/cheek probes for detection of pulse-based differences in light absorbence across the vascularized tissue of a lip or cheek of a patient. These probes are fabricated to provide signals to estimate arterial oxygen saturation, and/or to obtain other photoplethysmographic data. The present invention also relates to a combined probe/cannula. The present invention also relates to other devices that combine a pulse oximeter probe with a device supplying oxygen or other oxygen-containing gas to a person in need thereof, and to sampling means for exhaled carbon dioxide in combination with the novel lip/cheek probes. In certain embodiments, an additional limitation of a control means to adjust the flow rate of such gas is provided, where such control is directed by the blood oxygen saturation data obtained from the pulse oximeter probe.