Abstract: A pneumotachograph having an improved air flow to pressure differential transducer is disclosed for producing a pressure differential during inspiration and expiration of respirative air to and from a hospital patient. Typically, the air flow to pressure differential transducer is attached to endotracheal tubing between the patient's trachea and the respirator valve. Specifically, the transducer provides the endotracheal tube with an enlarged and typically cylindrical volume having offset air passages communicating to the endotracheal tube. The unit area of the measuring chamber is greater than the unit area of the communicated endotracheal tubing and is typically cylindrical with respect to such tubing. Likewise, the area of the communicated endotracheal tube is preferably less than one quarter the cross-sectional area of the chamber.