# Resting Lung Volumes

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```					Resting Lung Volumes

An Introduction to Spirometry
Spirometer Tracing
Measurement
• Static lung volumes can be measured
using a spirometer creating a paper trace
• Residual lung volume measurement is
difficult because the volume can not be
exhaled
We will use a method known as nitrogen
dilution
Residual Lung Volume
• The volume of air left in the lungs after a
maximal expiration
• Small passageways close before all of the
air from the alveoli is expelled
• If the alveoli were to be completely
emptied, they would stick together and be
very difficult to reopen
Why measure RV?
• Basic scientific interest
• Get an accurate density from hydrostatic
weighing
• Determine whether or not it aids
performance in sports (especially of
interest are water sports)
• Determine whether it is anatomical or can
change based on training
Basic Procedure
• Subject maximally expires to residual
volume
• Subject breathes in and out 100% oxygen
from a spirometer (of a known volume)
• After an equilibrium has been reached the
Nitrogen level in the spirometer is
measured
Nitrogen Dilution Technique
• Nitrogen is metabolically inert (it is neither
produced nor consumed by the body)
• Nitrogen dilution is merely balancing an
equation

Initial Amount of N2 = Final Amount N2
Components of Initial Amount of N2
• Nitrogen in the Spirometer
FN2ispirometer x Vispirometer
*Spirometer Volumes include the bell
• Nitrogen in the Lungs
FN2iLung x RV
– FN2iLung is the fraction of Nitrogen inspired
(79%)
– RV is the Residual Volume
Components of Final Amount of N2
• Nitrogen in the connected system of the
spirometer and lungs measured during
equilibrium
FN2f x Vf
– FN2f
• The fraction of nitrogen in the lungs and spirometer
at equilibrium
• A measured variable
– Vf
• The sum of the volume of the spirometer (including
both the dead space and the bell) and the Residual
Volume
Distribution of Nitrogen in the
System
Calculating RV
• Using the information on the last three
slides RV can be calculated from the three
measured variables (initial fraction N2, final
fraction N2, and initial spirometer volume)
• The BTPS correction factor must be used
to determine the actual volume of gas in
the conditions inside the lungs
Dynamic Lung Volumes
• Forced Expiratory Volume in 1.0 seconds
(FEV 1.0)
• Forced Expiratory Volume in 3.0 seconds
(FEV 3.0)
• Maximum Voluntary Ventilation (MVV)
Forced Expiratory Volumes
• The percent of vital capacity expelled in a
set time period
• Give indications of health problems not of
fitness or training
• FEV 1.0 normal value ~80% of FVC
• FEV 3.0 normal value ~98% of FVC
FEV Spirometer Examples
Maximum Voluntary Ventilation
• Maximum amount that can be exhaled per
unit time
• Usually measured over 12 seconds
• Units are in L/min
• Debatable application to fitness, training
status, or athletic performance
Factors Influencing Lung
Volumes
•   Height
•   Gender
•   Age
•   Ethnic Background
•   Disease
•   These factors are used in determining
prediction equations for lung volumes
Standardizing Gas Volumes
• Gas volumes change as temperature and
pressure change
• These relationships are determined by
Charles’ Law and Boyle’s Law
Water Vapor Pressure
• The amount of water vapor that can be
held in the air increases as temperature
increases
• This increases the pressure measured
• Therefore when gas volumes are
measured the water vapor pressure must
be taken into account as part of the
pressure change
Correction Factors
• The difference in conditions between the
lab (where the volume is measured) and
inside the body (the volume we are hoping
to determine) must be corrected for
BTPS/STPD Correction
• The conditions in the lab are called ATPS or
ambient temperature pressure and saturation
• In order for comparison of volumes in different
circumstances STPD or the standard
temperature and pressure dry is used
• In order to determine the actual volume of air
that the lungs contain, BTPS or body
temperature pressure and saturation conditions
are used

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 views: 68 posted: 8/10/2011 language: English pages: 20