Photo and description are kindly provided by Dr. David Chinn, for an upcoming ARTP article.

“McDermott, dry bellows, digital spirometer with calibrating weight and orifice, 1980 Garw Electronic Instruments, Glamorgan, South Wales

This 6V, battery operated, low resistance dry bellows spirometer was used extensively in epidemiological field studies from the 1970s to the 1990s. The example shown is a rigid frame model but another model with collapsible legs was available to increase its portability. The initial models of the spirometer displayed the FEV₁ (or FEV_0.75) and FVC. A later, digital version was developed that recorded volume expired in 10ms increments and displayed additionally the PEF, MEF₅₀ and MEF₇₅. The data could be processed to replay the flow-volume curve at a reduced speed on any cheap, slow responding XY printer. In addition, the increments could be stored digitally on a magnetic cassette tape for later processing in the laboratory. The spirometer was excellent for recording Helium-Oxygen flow volume curves and for generating off-line moments analysis applied to the spirogram (Mean Transit Time, Moments Ratio etc).”