Bio102

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• Bio102
• Laboratory 9
• Respiratory PhysiologyVital CapacityEffect of
  CO2 on Breathing

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Objectives for todays lab

• Define respiratory volumes and capacities
• 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 (in
  medullary rhythmicity center)
• The respiratory membrane
• Simple squamous epithelium of the alveoli and
  capillaries
• Basement membrane between them
• Terms used to describe breathing

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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/Drive
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, AP Applications
Manual, Benjamin Cummings, 2006
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Respiratory Rates and Volumes

• Respiratory rate
• Number of breaths per minute or resp/min (RPM)
• 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 37.2, page 556, in Mariebs 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 Mariebs 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 37.2, page 556, in Mariebs Laboratory
Manual for a similar figure
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Another Way of Looking at Things
Figure from http//commons.wikimedia.org/wiki/Fil
eLungVolume.jpg
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Tabular Method of Calculating Volumes/Capacities
Approximate Standard Lung Volumes and Capacities

TLC 6.0 L IC 3.0 L IRV 2.5 L VC 4.5 L
TLC 6.0 L IC 3.0 L TV 0.5 L VC 4.5 L
TLC 6.0 L FRC 3.0 L ERV 1.5L VC 4.5 L
TLC 6.0 L 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
TLC 6.2L IC ? IRV ? VC 5.1L
TLC 6.2L IC ? TV ? VC 5.1L
TLC 6.2L FRC ? ERV 1.7L VC 5.1L
TLC 6.2L 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 IC TV
IRV 6.0L 0.5L ? 1.0L ?
0.5L ?
Solution VC TV IRV ERV
IRV VC TV ERV .06L 0.5L ?
1.0L ? 6.0L 0.5L 1.0L
IC TV IRV? 0.5L 4.5L
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)?

TLC ? IC ? IRV ? VC 6.0L
TLC ? IC ? TV 0.5L VC 6.0L
TLC ? FRC ? ERV 1.0L VC 6.0L
TLC ? 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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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 TODAY for Lab 9
• Laboratory Reports for Part A (Spirometry)
• Part B (Factors Influencing Rate/Depth of
  Breathing)
• For Lab 10 (next lab)
• Complete the Respiratory Practice Questions
  handed out today and bring with you. We will
  review these and do some more practice questions.

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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