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January / June 2017

Group project with William Pepera, Carla Urbano and Jiachen Yu
Winner of the Design Engineering Selected Innovation Reward (DESIRE)

What is a Spirometer?

A spirometer is a medical device to measure lung volume in order to provide diagnosis of various lung conditions.

What is Spiro?

Spiro is a low cost spirometer designed for use in less economically developed countries (LEDCs) to collect data.

My Contribution

In this group project, I lead the team by organising meetings and delegating tasks. I was personally responsible for the design of the turbine blades, all CAD models and had joint responsibility for manufacturing the look - a - like model.

Reusable mouthpeices


Solar panel for recharging


Nitrogen sensor


Durable carry case


Works like prototype

Measuring inspired and expired air volume

A turbine mounted within a mouthpiece rotates as air passes through it. Each turbine blade has a magnet attached to it. The frequency at which these blades rotate is found using a hall-effect sensor which can detect changes in magnetic field. This frequency can then be converted into an expired volume of air.

An Arduino was used to collect the data, this worked in conjunction with a processing script to output the data to an excel file.

By using both Solidworks flow simulation and rapid prototyping methods, the most suitable set of blades were chosen.

The full assembly allowed for interchangeable blades as we prototyped and held the hall-effect sensor in position.

Residual Lung Volume

The volume of air that is not expired from the lungs when a person exhales as hard as possible.

FRC = 



Cexhaled, N2

Calveolar, N2

Where FRC = Functional Residual Capacity, V = Volume and C = Concentration. The alveolar concentration of nitrogen is the concentration of nitrogen in the lungs before the test begins, this is equal to the concentration of nitrogen in the air.

Although the technology used to measure residual lung volume was not modelled, it would have been the nitrogen washout technique.

The patient inhales 100 % oxygen meaning that over time the amount of nitrogen in their expired breath decreases, measured by the nitrogen sensor attachment.

Looks like model

Solidworks surfaces were used to model Spiro, including design for injection moulding.

A look-a-like model was manufactured to demonstrate the ergonomics and visual aesthetics of the design. 

The handle body was made by CNC milling chemiwood and then spray painting it to give a glossy finish.

The main handle containing the turbines that the patient will hold.

The nitrogen washout attachment that allows the residual volume to be measured. This was made from pine wood and again, spray painted.

The handle fully assembled with the nitrogen washout attachment and mouthpiece/filter. The mouthpieces were 3D printed in ABS.

A solar panel positioned within the lid can be left outside to charge up one of the batteries. This was modelled using laser cut acrylic. Cushioning foam cut to size allows each part to snugly fit within the case, preventing damage during transportation.

When the solar panel is taken out, it reveals storage of essential components including mouthpieces, filters, noseclips, tubing and wires

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