Spirometer suitable for measuring residual lung capacity - has mouthpiece connected by valves to inhalation and exhalation tubes fitted with pressure differential transducers

摘要

A mouthpiece (1) is connected to an inhalation tube (3) by a non return valve (5) and to an exhalation tube (4) by a second non return valve (6). The exhalation tube (4) vents to atmosphere and the inhalation tube is connected to an air and helium mixture (8). The flow of air and helium mixture is kept constant by a reservoir (11) during residual lung capacity measurements and a valve (12) allows pure air to be used for simple flow measurement. The inhalation and exhalation tubes (3,4) are fitted with pressure differential transducers for flow measurement. ADVANTAGE - The spirometer is accurate, economical and remains cleaner for longer.