an endotracheal tube or tracheostomy tube in place a turbine blower 14 operated by a mechanically coupled electrical motor 16 receives air or breathable gas at an inlet 18 thereof and supplies the breathable gas at a delivery pressure to a delivery tube hose 20 having connection at the other end thereof with the nose mask 12 breathable gas thus is provided to the subject 39 s airway for the purpose of providing assisted respiration with the subject 39 s expired breath passing to atmosphere by an exhaust 22 in the delivery tube 20 typically located proximate to the mask 12 a pneumotachograph 24 is placed in the deliver tube 20 between the mask 12 and the exhaust 22 to provide two pressure signals p 2 and p 1 across the pneumotachograph each passed by hoses 28 30 to a differential pressure sensor 32 a determination of the flow of gas in the mask 12 is made the differential pressure p 2 p 1 resulting in a flow signal f d the mask pressure p 2 also is passed to a pressure sensor 34 by a tapped line 36 taken from the respective hose 28 to generate a delivery pressure signal p m output from the pressure sensor 34 both the flow signal f d and the pressure signal p m are passed.