Lung Functions
Lab 3.3.2
Spirometry
• Spirometry is a common office test used to
diagnose asthma, chronic obstructive
pulmonary disease (COPD) and certain other
conditions that affect breathing.
• Spirometry may also be used periodically to
check how well your lungs are working once
you're being treated for a chronic lung
condition.
• Spirometry measures airflow.
– By measuring how much air you exhale, and how
quickly, spirometry can evaluate a broad range of
lung diseases.
– Accomplished by a spirometer
Tidal Volume
• lung volume representing the normal volume
of air displaced between normal inspiration
and expiration - no extra effort is given
• Normal value = 0.4 – 0.5 L
Inspiratory Reserve
• The amount of air that can be inhaled by
forcible inspiration.
• Normal value = 2.5 -3.5 L
Expiratory Reserve
• when you breathe out as much as you can, the
extra volume of air breathed out (expiration)
is called the expiratory reserve volume.
• Normal = 1.0 – 2.0
Vital Capacity
• the maximum amount of air a person can
expel from the lungs after a maximum
inspiration
• VC = TV + IRV + ERV
• Normal value = 4.5 – 6.0
• Value is really important to looking at how
well the lungs are functioning
Residual Volume
• the amount of air that is left in the lung even
after we try our best to get everything out
• Residual volume is important to respiratory
function because it provides a supply of
oxygen between breaths
Total Lung Capacity
• the maximum volume to which the lungs can
be expanded with the greatest possible
inspiratory effort
• = Vital Capacity + Residual Volume
• Very important to analyzing lung function
Minute Volume
• Volume of air breathed in one minute without
conscious effort
• A person requires a minimum of 6 to 8 litres of
minute volume for the proper oxygenation of the
tissues and the removal of carbon dioxide from
the lungs.
• The minute volume increases at times of stress
and exercise.
• During light activities minute volume may be
around 12 litres per minute.
• = TV X (breaths/minute)
Lung Disorders
• Performing spirometry can help diagnose any
lung disorders that one may have.
• Values are different due to body size and
physical activity
– Singers
– Runners
Why Do We Need Oxygen?
• Oxygen is need in the cells to make ATP
• Glucose + Oxygen
H2O + CO2 + ATP
See Handout for Practice Problem