Lung capacity testing prototype for covid-19 and other chronic resiratory diseases severity assessment

Abstract

To estimate the severity of different Covid-19 infections, the current lung capabilities of patients are one of the most important inspects. This paper explores practical redesigns of a spirometer, in this way, when patients exhale, the volume and time can be recorded, using comparatively inexpensive load cells as a substitute for commercial spirometers. When exhaling into the one end of a tube, the plate at the other end will be deflected. With this plate connected to a beam and load cell, the force of a patient’s respiration can be recorded over time. This data can be applied to calculate the required metrics at a small cost. Before actual prototyping the device, sample data of normal breathes will determines the geometry of the beam, primarily the length. Reasonable length is estimated which would create deflection given a range of expected forces. In order to apply the load cell in an effective way, Wheatstone bridge circuit is necessary. To make sure the output voltage reflects the force input correctly, the bridge needs to be balanced. The signal is amplified using an IC-741 op amp. The need for gain is calculated in accordance with a range of flow rates; a healthy person ought to create an output of 0-2 volts with a breath, so that it allows for high resolution output from the DAQ. Another amplifier is utilized to eliminate aliasing. To ensure accurate datum, the load cell is tuned with known weight output on the end of the beam. This configuration gauged the force and volume output from a bicycle pump.)