Development of an Affordable Spirometry Device for Lung Function Testing at Primary Care Clinics in Ondo State

Spirometry is the diagnostic standard for obstructive and restrictive lung function disorders, but its availability at primary care clinics in Ondo State is limited due to the high cost of imported devices and the need for technical expertise, resulting in under-diagnosis of respiratory disease in the community. This study develops an affordable spirometry device prototype for lung function testing at primary care clinics in Ondo State. The device employs a custom-designed pneumotachometer measuring differential pressure across a fixed resistance screen element using an MPXV7007DP sensor to determine airflow, with volume calculated by digital integration of the flow signal. Signal acquisition and processing are managed by an Arduino Due microcontroller, providing sufficient computational speed for high-resolution flow waveform analysis. Measured parameters include forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1 to FVC ratio, and peak expiratory flow rate. A nine-inch Android tablet serves as the display interface, showing real-time flow-volume and volume-time curves with colour-coded interpretation guidance. Total fabrication cost was estimated at under twenty-five thousand naira. Calibration was performed using a calibrated 3-litre syringe according to ATS/ERS spirometry standards. Validation testing on thirty healthy volunteers comparing prototype output with a reference MIR Spirolab spirometer showed mean FVC difference of 0.08 litres and mean FEV1 difference of 0.06 litres, within the ATS/ERS acceptability threshold of 150 millilitres. The study recommends clinical validation on patients with respiratory disease and assessment of user acceptability by primary care health workers. Keywords: spirometry, lung function testing, pneumotachometer, low-cost device, Ondo State.