Abstract: A compact, on-airway, respiratory gas analyzer for performing pulmonary function tests incorporates an IR spectroscopy light guide having a curved, rather than linear, sample chamber that lies transverse to a direction of respiratory gas flow. Cooperating with the sample chamber is an impact plate that functions to steer respiratory and test gases impinging on the impact plate into the curved sample chamber. A source of IR energy is at one end of the sample chamber and an electro-optical sensor responsive to IR energy is disposed at an opposite end of the chamber. The respiratory gas analyzer also includes gas flow paths and valving for carrying out lung capacity and lung diffusion tests.

Abstract: The present invention describes an apparatus and method for determining the energy expenditure of a subject by indirect calorimetry where respiratory gases O2 and CO2 are captured in a tent mask coupled through a pneumotach flow meter to a vacuum inlet of a blower fan whose speed is controlled by a computer running a program that ensures that the bias flow being drawn through the mask always exceeds the subject's peak expiratory flow. VO2 and VCO2 and flow values are measured on a breath-by-breath basis and used in arriving at a bias flow adjustment voltage to be applied to the blower fan for adjusting its speed.