3.1.1e Spirometry & Lung Function Flashcards
What factors cause the amount of gas exchange needed in your lungs to vary
Vary depending on your size and level of activity.
The gaseous exchange system must be able to respond to the differing demands of your body
3 different ways to measure the volume of air drawn in & out of the lungs
- A peak flow meter
- Vitalographs
- Spirometer
How can a peak flow meter be used to measure the volume of air drawn in & out of the lungs
A simple device that measures the rate at which air can be expelled from the lungs. Ppl who have asthma often use these to monitor how well their lungs are working
How can Vitalographs be used to measure the volume of air drawn in & out of the lungs
More sophisticated versions of the peak flow meter. The patient being tested breathes out as quickly as they can through a mouthpiece, and the instrument produces a graph of the amount of air they breath out & how quickly it is breathed out - This volume of air is called the forced expiratory volume in 1 second
How can a spirometer be used to measure the volume of air drawn in & out of the lungs
Commonly used to measure different aspects of the lung volume, or to investigate breathing patterns. Can be used to measure the volume of gas breathed in & out under diff conditions. There are many different forms of the spirometer but they all use the basic principles (shown in dia in ss)
see diagram of a spirometer in images
Different aspects of the lung volume that can be measured
- Tidal volume
- Vital capacity
- Inspiratory reserve volume
- Expiratory reserve volume
- Residual volume
- Total lung capacity
Components of lung volume: Tidal volume
Volume of air that moves into & out of the lungs during a normal breath
(Usually about 0.4dm^3)
Components of lung volume: Vital capacity
The maximum volume of air that can be breathed during a forced breath in & then out
Components of lung volume: Inspiratory reserve volume
The maximum volume of air (in excess of the tidal volume) we can breathe IN during one forced breath
Components for lung volume: Expiratory reserve volume
The maximum volume (in excess of the tidal volume) we can breathe OUT in one forced breath
Components of lung volume: Residual volume
The amount of air left in the lungs after a forced breath out. You cannot measure this using a spirometer
Components of lung volume: Total lung capacity
The sum of the Vital capacity and the Residual volume
see diagram of recordings from spirometer on Goodnotes
Only need to know vital capacity, tidal volume, breathing rate & oxygen uptake
How does the pattern & volume of breathing change
As the demands of the body changes
What is breathing rate
The number of breaths taken per minute
What is ventilation rate
The total volume of air inhaled in one minute
Equation for calculating ventilation rate
Ventilation rate = Tidal volume x Breathing rate (per min)
dm^3 –> cm^3
x1000
What is ventilation rate measured in
dm^3
What is Tidal volume measured in
dm^3
What is breathing rate measured in
Breaths per minutes
What happens to the tidal volume when oxygen demands of the body increases (eg during exercise)
The tidal volume of air moved in & out of the lungs with each breath can increase from 15% to as much as 50% of the vital capacity
What happens to the breathing rate when oxygen demands of the body increase (eg during exercise)
The breathing rate increases
WHY does the tidal volume and breathing rate increase when oxygen demands of the body increase (eg during exercise)
This way, the ventilation of the lungs and therefore the oxygen uptake during gaseous exchange can be increased to meet the demands of the tissues
What is spirometry
Spirometry is a pulmonary function (PFT). It is used to measure 2 things relating to inhalation & exhalation of air:
- volume (how much air a person can hold in their lungs)
- speed (flow rate at which ppl can do this)
Why are spirometers used
For assessing conditions such as asthma, pulmonary fibrosis, chronic pulmonary obstructive disorders (CPOD)
Also used in sport science testing as an indicator of lung function
What can a spirometer give readings of
- Tidal volume
- Vital capacity
- Breathing rate
- Oxygen uptake
How do spirometers work
- A spirometer has an oxygen-filled chamber w a moveable lid
- The person breathes through a tube connected to the oxygen chamber
- As the person breathes in & out, the lid of the chamber moves up & down
- These movements can be recorded by a pen attached to the lid of the chamber - this writes on a rotating drum, creating a spirometer trace.
OR the spirometer can be hooked up to a motion sensor - this will use the movements to produce electronic signals, which are picked up by a data logger - The soda lime in the tube the subject breathes into absorbs CO2
What is Oxygen consumption OR Oxygen uptake
The rate at which an organism uses up oxygen
SEE PG75 FOR DIA OF SPIROMETER
Why does the total volume of gas in the chamber decrease overtime in spirometer
- The air that’s breathed out is a mixture of oxygen & CO2.
- The CO2 is absorbed by the soda lime - so there only oxygen in the chamber which the subject inhales from.
- As this oxygen gets used up by respiration, the total volume decreases
MUST SEE PG75 ANALYSING GRAPH TO WORK OUT BREATHING RATE, TIDAL VOL, VITAL CAPACITY, OXYGEN CONSUMPTION
How to calculate breathing rate from a graph
Count how many ‘peaks’ there are within 1 minute
(_ breaths per minute)
How to calculate tidal volume from a graph
Find distance between peak & bottom of the trace
(_dm^3)
How to calculate vital capacity from a graph
Find distance between the maximum (biggest) peak & the lowest point in the trace
How to calculate oxygen consumption from a graph
This is the decrease in the volume of gas in the spirometer chamber
Take the average slope of the trace
(_dm^3/min)
