Patent ID: 8479731

Claim:
A method for determining the presence or absence of a pulmonary embolism in a patient, said method comprising the steps of: (a) measuring the amount of CO 2 expired by the patient during the expiration of breathing gases by the patient using a breathing gas CO 2 concentration sensor; (b) measuring the volume (V) of breathing gases expired during the expiration of breathing gases by the patient using a flow sensor; (c) determining a slope in a measurement apparatus, the slope defined by a change in the amount of expired CO 2 divided by a change in breathing gas volume in an alveolar expiration phase of patient expiration; (d) measuring an amount of CO 2 in the lungs of the patient at the end of expiration using the breathing gas CO 2 concentration sensor; (e) measuring the amount of CO 2 in the blood of the patient; (f) determining the difference in the measurement apparatus between the amount of CO 2 in the blood and the amount of CO 2 in the lungs of the patient at the end of expiration; (g) establishing a relationship in the measurement apparatus between the determination of step (f) and the determination of step (c) to produce a quantity for use in determining the presence or absence of a pulmonary embolism in the patient, and (h) defining the alveolar expiration phase of patient expiration as that in which the quantity produced in step (c) is reduced to a given percentage of a corresponding quantity produced for a previous phase of expiration.