a method for determining the maximum and minimum lung pressure during the breathing cycle of a patient undergoing positive pressure breathing therapy by utilizing a respiration system which includes a console with a gas supply and control unit located at a substantial distance from the patient , and a transfer unit in proximity to the patient . the delivery hose from the transfer unit to the patient is very short and of relatively small volume , so that a pressure sensor located in the transfer unit can monitor the system pressure at a point which has a relatively low volume spacial separation from the patient &# 39 ; s lungs . in accordance with the method , a pressure versus time characteristic is generated from the sensed pressure , and the maximum and minimum lung pressures during each breathing cycle are determined from the characteristic by the pressure ordinates of readily identifiable discontinuities in the slope of the characteristic , the discontinuities being reliably indicative of the maximum and minimum lung pressures .