Bio102 Laboratory 9 Respiratory Physiology: Vital Capacity Effect of CO 2 on Breathing

1. Bio102 Laboratory 9 Respiratory Physiology:Vital CapacityEffect of CO2 on Breathing

2. Objectives for today’s 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

3. 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

4. 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

5. 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…)

6. 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, “A&P Applications Manual”, Benjamin Cummings, 2006

7. 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)

8. 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

9. Respiratory Volumes and Capacities Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 See Figure 37.2, page 556, in Marieb’s Laboratory Manual for a similar figure

10. 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

11. 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 Marieb’s Laboratory Manual for a similar figure

12. Another Way of Looking at Things… Figure from: http://commons.wikimedia.org/wiki/File:LungVolume.jpg

13. Tabular Method of Calculating Volumes/Capacities Approximate Standard Lung Volumes and Capacities IC = TV + IRV FRC = ERV + RV VC = TV + IRV + ERV TLC = VC + RV

14. 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

15. 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

16. 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)?

17. 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)

18. 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.

19. 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

20. 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