Analysis and design of a low cost peak flow meter for asthma patients

Abstract

Asthma cannot be completely cured and only the control can be achieved by proper medication. Peak Flow Meter (PFM) is an essential device which is used for initial diagnose and continuous monitoring of asthma. Affordable price is the main objective of the project therefore mechanical type methods were concerned. Based on that two conceptual designers ( Counter gravity & torsion spring) were proposed and variable orifice torsion spring design was selected as user friendliest design. Torsion spring design was modeled using SOLIDWORKERS and analyzed using ANSYS FLUENT. Analyzing past literature of several existing designs, geometry of the mouthpiece and diameter of the main flow path were selected same as the values of well known WRIGHT PFM as initial fixed parameters. Angular displacement of the baffle varied for range of 60l/min-800l/min peak expiratory floe rates to calculate torque acting on the baffle. Analysis results showed that the best angular displacement as 0-60 degrees and spring constant as 0.16Nm/rad. Calibration was carried out an a rapid prototype model by means of compressed air as the air supply source orifice place as the measuring technique.