This document describes a digital spirometer that measures lung function. Spirometry measures how fast and how much air the lungs can inhale and exhale. The digital spirometer uses a turbine flow sensor and proximity sensor to detect air flow pulses and send the data to a PIC microcontroller for display. The microcontroller counts the pulses to calculate air volume and displays the output on an LCD screen. An alarm can also be triggered if measurements fall outside normal ranges.

1. Digital Pulmonary Function Test – Spirometry
ABSTRACT:-
Pulmonary function test is helpful in diagnosis lung diseases. It
helps the doctor to detect the range of respiratory diseases. This test can be
helpful to cure respiratory diseases if detected early. The simplest test is
spirometry, which measures how fast the lungs can breath in and out, and
also the volume of air lung can exhaled in the first and second of test. A
peak flow meter can determine how much a patient’s airways have
narrowed.
Our aim is to make a microcontroller based spirometer which displays
the output in form of signals.
Spirometry (meaning the measuring of breath) is the most common of the
Pulmonary Function Tests (PFTs), measuring lung function, specifically the
measurement of the amount (volume) and/or speed (flow) of air that can be
inhaled and exhaled. Spirometry is an important tool used for generating
pneumotachograph to assessing conditions such as asthma, pulmonary
fibrosis, and COPD.
The basic FVC test varies slightly depending on the equipment used.
Generally, the patient is asked to take the deepest breath they can, and then
exhale into the sensor as hard as possible, for as long as possible. It is
sometimes directly followed by a rapid inhalation (inspiration), in particular

2. when assessing possible upper airway obstruction. Sometimes, the test will
be preceded by a period of quiet breathing in and out from the sensor (tidal
volume), or the rapid breath in (forced inspiratory part) will come before the
forced exhalation.
During the test, soft nose clips may be used to prevent air escaping through
the nose. Filter mouthpieces may be used to prevent the spread of
microorganisms, particularly for inspiratory maneuvers.
SENSOR:
We have used a Turbine Flow sensor to measure the Tidal Volume. If
air is blown into the sensor, the fan inside the sensor rotates and a
proximity sensor kept nearby will generate an series of pulse signals,
which is then amplified and given as a pulse input to the PIC
Microcontroller for Display.
For Eg: if the 7ml of gas goes to the rotor and rotor will give 1 pulse.so
we have taken 1pulse=7ml.and as per the count we make program for
microcontroller to count pulses.

3. Block Diagram:
Alarm
Alarm
Driver
Power
PIC 16F877 Supply
Microcontroller
LCD Display
Voltage
Comparator
Divider
Proximity
Sensor
Sensor
Air in 
FAN Air Out 

4. Block Diagram:
Alarm
Alarm
Driver
Power
PIC 16F877 Supply
Microcontroller
LCD Display
Voltage
Comparator
Divider
Proximity
Sensor
Sensor
Air in 
FAN Air Out 

5. Block Diagram:
Alarm
Alarm
Driver
Power
PIC 16F877 Supply
Microcontroller
LCD Display
Voltage
Comparator
Divider
Proximity
Sensor
Sensor
Air in 
FAN Air Out 

6. Block Diagram:
Alarm
Alarm
Driver
Power
PIC 16F877 Supply
Microcontroller
LCD Display
Voltage
Comparator
Divider
Proximity
Sensor
Sensor
Air in 
FAN Air Out 