On-airway pulmonary function tester
View Patent ↗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.
1. For use in a mainstream respiratory gas analyzer, the combination comprising:
a. tubular pneumotachometer having a mouthpieces at a first end and respiratory gas outlet at a second end;
b. an arcuate light guide formed in an interior wall of a toroid, the light guide having a C—shaped cross-section with an interior surface having a light reflective coating thereon;
c. a light source disposed at a first end of the arcuate light guide and at least one light detector at a second end thereof; and
d. a respiratory gas impact plate positioned concentrically in said toroid in spaced-apart relation relative to the arcuate light guide member and the respiratory gas outlet of the pneumotachometer to divert a total flow of inspiratory and expiratory gases onto the light reflective surface of the arcuate light guide member;
e. a valve positioned to selectively block and unblock the respiratory gas outlet of the pneumotachometer, wherein the valve comprises an inflatable elastomeric bladder adhered to a surface of the impact plate.
2. The combination as in claim 1 and further including:
a. means for optionally delivering ambient air or a test gas through said mouthpiece.
3. The combination of claim 2 and further including means for preventing mixing of inspired ambient air or test gas with expired respiratory7 gas in the light guide member.