Lab 9: Spirometry
Technique used to assess pulmonary function, specifically measuring lung volumes

Lab 9 – Spirogram
Figure 13.18
A tracing or graph of respiratory movement (or ventilation) made by a spirometer
1 3
2
4
1 Tidal volume (TV) Amount of air inhaled or exhaled in one breath
Inspiratory reserve volume (IRV) Amount of air in excess of tidal inspiration that can be inhaled with maximum effort
Expiratory reserve volume (ERV) Amount of air in excess of tidal expiration that can be exhaled with maximum effort
Residual volume (RV) Amount of air remaining in the lungs after maximum expiration; keeps alveoli inflated between breaths
and mixes with fresh air on next inspiration
8
5
7
6
Vital capacity (VC) Amount of air that can be exhaled with maximum effort after maximum inspiration (ERV + TV + IRV); used
to assess strength of thoracic muscles as well as pulmonary function
Inspiratory capacity (IC) Maximum amount of air that can be inhaled after a normal tidal expiration (TV + IRV)
Total lung capacity (TLC) Maximum amount of air the lungs can contain (RV + VC)
Amount of air remaining in the lungs after a normal tidal expiration (RV + ERV)
Functional residual capacity (FRC)
= summation of
2 or more lung
volumes

Lab 9 – Pulmonary Function Tests
Group of noninvasive tests how well your lungs work
Common measurements:
• Vital Capacity (VC): Amount of air that can be exhaled with maximum effort after
maximum inspiration
• (FEV1): Volume of air that is forcefully exhaled within
1 second after a maximum inspiration.
• (FEV1/VC): proportion of VC that can be forcefully
exhaled in 1 second; in a healthy individual, it is > .80
These measurements, particularly FEV1/VC, indirectly assess [force expiratory]

Lab 9 – Underlying Mechanism of Ventilation- Lung
Mechanics and Properties
3. Compliance:
How easily the lungs
stretches
2. Airway resistance :
Resistance to airflow
η = fluid viscosity
L = length of the tube
8/π = a mathematical constant
r = inside radius of the tube
R =
8 L η
π r4
F = Airflow (L/min)
R = Resistance to airflow
Palv = Alveolar pressure
1. Pressure gradients:
Pressure difference
between points
Patm = Atmospheric pressure

Lab 9 – Underlying Mechanism of Ventilation –Lung
Mechanics
Figure 13.14
Inspiration
(a) (b)
Expiration
(c) (d)
4. Elasticity (Elastic recoil):
Tendency for lungs and chest wall
to oppose stretching or distortion;
If structure is stretch, it will tend
to recoil back to it’s original shape
5. Skeletal muscle contraction
and relaxation

Lab 9 – Pulmonary Diseases: Obstructive vs
Restrictive
Obstructive Lung Disease
Airways are obstructed which makes
airflow difficult 
Examples:
• Asthma: Chronic inflammation of airways 
causes the smooth muscle to contract 
decrease radius
• Emphysema: Atrophy and collapse of lower
airways  decrease radius
Restrictive Lung Disease
Impaired respiratory movements
because of abnormalities in the
lung tissue, the pleura, the chest
wall, or the neuromuscular
machinery, but airflow is not
affected 
Example:
Pulmonary Fibrosis: Lung tissue is
damaged and scarred  tissue is thicken
and stiffen
From drugs.com
From pennmedicine. org
Chest x-ray of healthy lung
From mayoclinic.org
Chest x-ray of pulmonary fibrosis lung
From wikipedia.org

• Identify lung measurements on a spirogram and explain the underlying
physiological mechanisms of each measurement.
• Recall typical average values of the following lung volumes:
 Residual volume (RV): female = 1100mL, male = 1200mL
• Recall and calculate lung capacities, FEV1/VC ratio, and percentage change from
control to disease state.
• Compare and contrast lung measurements between the three pulmonary
conditions (normal, obstructive, and restrictive).
• Diagnose the pulmonary pathology based on the spirogram/lung
measurements and predict how the symptoms would affect the lung
measurements.
Lab 9 – Goals (aka Learning Outcomes)

Lab 9 – Experimental setup in BioPac
Animal model: Human!
Experimental Setup:
This technique is very sensitive to baseline offset, so recording procedure must be followed
exactly and subject must use maximal effort to obtain accurate results.
Equipment for each lab group
Device which measures air flow and then
convert to volumes
Breath into the “Inlet” Port
Rubber stopper
Yellow belt and green ratchet
Pulse oximeter

Lab 9 – Experimental setup in BioPac
Control Baseline:
Obstructive lung disease model:
Restrictive lung disease model:

Lab 9 – Data Display in BioPac
Channel Setup Measurement Setup Measurement Value
Channel 1 (CH1) and the blue plot represents airflow through the spirometer (L/second)
Channel 2 (CH2) and the red plot represents the spirogram (L).

Lab 9 – BioPac Navigating the graphs
Spirometry measurements
• Delta T: The difference in time between the end and beginning of the selected area.
• Delta: The difference in amplitude between the end and beginning of the selected area.
• P-P (Peak-to-Peak): The difference between the maximum and minimum amplitude
values in the selected area.