METHOD OF MEASURING CARDIAC RELATED PARAMETERS NON-INVASIVELY VIA THE LUNG DURING SPONTANEOUS AND CONTROLLED VENTILATION
An apparatus to measure pulmonary blood flow and cardiac output (Q) comprising: a) a breathing circuit which, at exhalation, keeps exhaled gas separate from inhaled gas and at inhalation, when V E is greater than first gas set (FGS) flow, results in a subject inhaling FGS first and then a second gas set (SGS), for the balance of inhalation; b) a gas sensor for monitoring gas concentrations at the patient-circuit interface; c) a gas flow control means for controlling the rate of FGS flow into the breathing circuit; d) machine intelligence consisting of a computer or logic circuit capable of controlling the gas flow control means which receives the output of the gas sensor means and outputs pulmonary blood flow.
1 - 61 . (canceled)
62 . A method of identifying the alveolar ventilation ({dot over (V)} A ), the method comprising:
(1) using a breathing circuit characterized in that:
i. on exhalation, exhaled gas is kept substantially separate from inhaled gas;
ii. on inhalation, when {dot over (V)} E is less than FGS flow, the subject inhales FGS first and the balance of the minute ventilation is substantially SGS,
and:
(2) setting the FGS flow into the circuit at a rate greater than the subjects minute ventilation ({dot over (V)} E );
(3) measuring the end tidal CO 2 concentration (P ET CO 2 ) in a steady state
(4) progressively lowering the FGS flow into the circuit, either breath by breath or continuously, until after a time equal to the time of recirculation of CO 2 within the patient after a rise in P ET CO 2 above a threshold value is observed;
(5) deriving {dot over (V)} A as the rate of FGS flow at a point of the intersection between two lines comprising:
a. the average P ET CO 2 in steady state; and
b. a line fit to the P ET CO 2 values after the rise begins until the recirculation time.