Transcript Lecture 1 - gserianne.com

Bio102
Laboratory 9
Respiratory Physiology:
Vital Capacity
Effect of CO2 on Breathing
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Objectives for today’s lab
• Define respiratory volumes and capacities and
solve for an unknown volume or capacity
• Perform simple spirometry measurements and
record/calculate your own respiratory
parameters
• Describe how CO2 levels influence breathing
rate and depth
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CO2 and HCO3• Carbon dioxide can travel in several ways
– Dissolved in plasma (7%)
– As carbaminohemoglobin (15-25%)
– As HCO3- ion (70%)
• Carbonic anhydrase in RBCs accelerates
interconversion between CO2 and HCO3• H+ combines with or dissociates from Hb
• HCO3- diffuses into plasma or into RBCs
• Cl- diffuses into RBC (chloride shift) as HCO3- exits
• Diffusion of CO2 is related to PCO2 in alveoli
and tissues
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Control of Breathing
• Rate of breathing is affected by several control
centers
–
–
–
–
–
Central chemoreceptors in the medulla
Peripheral chemoreceptors in aortic and carotid bodies
Largely dependent upon [H+]
The most powerful respiratory stimulant is CO2
Normal, rhythmic breathing – DRG/VRG
• The respiratory membrane
– Simple squamous epithelium of the alveoli and
capillaries
– Basement membrane between them
• Terms used to describe breathing (know these)
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Hypoxia and Hyperventilation
• Hypoxia is a low level of oxygen in the tissues
– Hypoxic hypoxia (e.g., high altitude)
– Histotoxic hypoxia (e.g., alcohol, CN-)
– Stagnant (ischemic) hypoxia (e.g., cardiovascular
problems)
– Hypemic hypoxia (e.g., CO poisoning)
• Hyperventilation is a rapid breathing that
causes loss of excessive amounts of CO2 to be
blown off (we will do this today…)
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CO2 and Respiratory Demand
Note that with normal
respiration, CO2 levels
will stimulate breathing
well before decreasing
levels of O2 result in
hypoxic effects
Compare this with
stimulation of
breathing after
hyperventilation
(after holding breath)
Figure from: Martini & Welch, “A&P Applications Manual”, Benjamin Cummings, 2006
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Respiratory Rates and Volumes
• Respiratory rate
– Number of breaths per minute
– Resting adult: 12-18 bpm
– Resting child: 18-20 bpm
• Respiratory cycle = 1 inspiration followed by 1
expiration (part of ventilation)
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Respiratory Volumes
Volumes of air moved in and out of the lungs. These are
measured by spirometry using a spirometer.
• tidal volume – volume moved in or out during a normal
(eupneic) breath ( 500 ml)
• inspiratory reserve volume – additional volume that can be
inhaled following a normal inhalation ( 3.0 L/1.9L)
• expiratory reserve volume – additional volume that can be
exhaled following a normal exhalation ( 1.1 L/0.7 L)
• residual volume – volume that remains in lungs at all times
( 1.2 L) ** Cannot be removed during life
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Respiratory Volumes and Capacities
Figure from: Martini,
Anatomy & Physiology,
Prentice Hall, 2001
See Figure 37.7, page 561, in Marieb’s Laboratory Manual for a similar figure
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Respiratory Capacities
Note that capacities are derived (calculated) from
volumes (which can be measured by spirometry)
• inspiratory capacity = TV + IRV
• functional residual capacity = ERV + RV
• vital capacity = TV + IRV + ERV
• total lung capacity = VC + RV
How would you express these capacities in words?
(See Marieb’s Lab Manual page 552 for some help…)
Know how these are expressed in words for the lab exam
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Respiratory Volumes and Capacities
• IC = TV + IRV
• FRC = ERV + RV
• VC = TV + IRV + ERV
• TLC = VC + RV
Figure from:
Martini, Anatomy &
Physiology, Prentice
Hall, 2001
See Figure 37.7, page 561, in Marieb’s Laboratory Manual for a similar figure
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Another Way of Looking at Things…
Figure from: http://commons.wikimedia.org/wiki/File:LungVolume.jpg
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Tabular Method of Calculating Volumes/Capacities
Approximate Standard Lung Volumes and Capacities
(See your Laboratory Guide, “Alveolar Ventilation” from Levitzky)
IRV = 2.5 L
IC = 3.0 L
TV = 0.5 L
VC = 4.5 L
TLC = 6.0 L
ERV = 1.5L
FRC = 3.0 L
RV = 1.5 L
IC = TV + IRV
FRC = ERV + RV
VC = TV + IRV + ERV
TLC = VC + RV
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Tabular Method of Calculating Volumes/Capacities
Example of how to use the Standard Lung Volume and Capacity Table
to Solve for unknown lung volumes/capacities
Problem: Given the values in the table below, solve for the RV
IRV = ?
IC = ?
TV = ?
VC = 5.1L
TLC = 6.2L
ERV = 1.7L
FRC = ?
(Solve for this)
RV = ?
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Sample problem using equations…
• The vital capacity = 6000 ml, tidal volume =
500 ml, and expiratory reserve volume = 1000
ml. What is the inspiratory capacity (IC)?
Equations…
VC = TV + IRV + ERV
6.0L 0.5L
?
1.0L
IC = TV + IRV
?
0.5L
?
Solution…
VC = TV + IRV + ERV
.06L = 0.5L + ? + 1.0L
IC = TV + IRV
? = 0.5L + 4.5L
IRV = VC – TV – ERV
?
6.0L – 0.5L – 1.0L
IC = 5.0L
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SAME Sample Problem Using Tabular Method
• The vital capacity = 6000 ml, tidal volume = 500 ml,
and expiratory reserve volume = 1000 ml. What is the
inspiratory capacity (IC)?
IRV = ?
IC = ?
TV = 0.5L
VC = 6.0L
TLC = ?
ERV = 1.0L
FRC = ?
RV = ?
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Minute and Alveolar Ventilation
minute ventilation (volume)
• tidal volume (TV)
multiplied by breathing
rate
•amount of air that is
moved into/out of the
respiratory passageways
each minute
• typically about 6 L/min
alveolar ventilation
• major factor affecting
concentrations of oxygen
and carbon dioxide in the
alveoli
• volume of air that
reaches alveoli – always
less than minute
ventilation
• tidal volume minus
anatomic dead space
then multiplied by
breathing rate
• about 4.2 L/min
Alveolar ventilation = breaths/min x (TV – Dead space)
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Review
• A respiratory cycle consists of 1 inspiration
and 1 expiration
• Spirometry is used to measure the different
volumes of air in the lungs
–
–
–
–
Tidal Volume
Inspiratory Reserve Volume
Expiratory Reserve Volume
Residual Volume
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Review
• Capacities are quantities derived from volumes
– Vital capacity (what does this actually mean in
words?)
– Inspiratory capacity
– Functional residual Capacity
– Total lung capacity
• Ventilation (quantity of air moved per minute)
– Minute ventilation
– Alveolar ventilation
• Always less than minute ventilation
• Takes anatomical dead space into account
– Specific terms dealing with rates of breathing
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What to do for lab today
• Record and analyze respiratory parameters using the
dry, portable spirometer
• Use the instructions distributed today as a guide
• Hand in Laboratory Reports for Part A (Spirometry)
and Part B (Factors Influencing Rate/Depth of
Breathing)
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