Patent ID: 8469027

Claim:
A method for determining the extent to which a change in the functional residual capacity of a patient, occurring responsive to an alteration in a PEEP applied to the patient, results from recruitment/de-recruitment of lung volume, said method comprising the steps of: (a) providing breathing gases to the patient from a source of breathing gases during inspiration and allowing the removal of breathing gases from the patient during expiration; (b) applying a PEEP to the lungs of the patient at the end of expiration; (c) establishing an initial level of PEEP for the patient; (d) determining the functional residual capacity of the patient at the initial PEEP level; (e) altering the PEEP from the initial level to a higher or lower level; (f) determining the functional residual capacity of the patient at the altered PEEP level; (g) obtaining the relationship between lung gas pressures and breathing gas volumes during inspiration and expiration by the patient with the lower of the initial or altered PEEP levels applied to the patient; and (h) determining the difference in lung volume between the functional residual capacity for the higher of the initial or altered PEEP levels and the lung volume indicated by the lower PEEP level, pressure-volume relationship at a pressure corresponding to the higher PEEP level, the difference in lung volume comprising the lung volume recruited/de-recruited as a result of the alteration of the PEEP.