Assessment of a respiratory condition of a subject, by acquiring a temporally varying hemodynamic waveform signal related to blood flow in a tissue； deriving from the hemodynamic waveform signal an evaluation of blood CO2； acquiring at least one more signal； and determining the medical condition based on the blood CO2 and the at least one more signal. A device for performing the assessment may include an implement disposable on the subject's skin and structured to acquire a temporally varying hemodynamic waveform signal and derive from the signal a blood CO2 value or a close approximation thereof； an oximeter disposable on the subject's skin and structured to provide an oxygen saturation value of the blood of the subject or a close approximation thereof； and an apparatus structured to evaluate the medical condition of the subject based on the blood CO2 and oxygen saturation or close approximations thereof.
