Patent ID: 8613707

Claim:
A method for monitoring cardiac output (pulmonary blood flow) of a subject, the method including: (i) making a first measurement of a gas species breathed by said subject at a first time to determine a first measurement value; (ii) determining a first pulmonary blood flow of said subject at said first time; (iii) making a second measurement of said gas species breathed by said subject at a second time later than said first time to determine a second measurement value; and (iv) determining a pulmonary blood flow of said subject at said second time on the basis of a product of said first pulmonary blood flow and a square of a ratio of the first measurement value and the second measurement value; wherein: (a) said first measurement value represents a net rate of pulmonary uptake or elimination of said gas species by said subject at said first time, and said second measurement value represents a net rate of pulmonary uptake or elimination of said gas species by said subject at said second time; or (b) said first measurement value represents a difference in partial pressures of said gas species between inspired and end-tidal gas at said first time, and said second measurement value represents a difference in partial pressures of said gas species between inspired and end-tidal gas at said second time; or (c) said first measurement value represents a partial pressure in end-tidal gas of said gas species at said first time, and said second measurement value represents a partial pressure in end-tidal gas of said gas species at said second time.