PULMONARY: CONTROL OF VENTILATION Dr. Dalay Olson Email: [email protected] Office: 3-120 Jackson Hall OUTLINE ✓ Control of ventilation ✓ Applications for the pulmonary system ✓ Review of difficult topics in pulmonary physiology (if we have time) LEARNING OBJECTIVES • Explain the role of the brainstem in determining the basic pattern of respiration • Describe the location and function of the central and peripheral chemoreceptors + • Discuss the mechanisms of plasma levels of CO2 and O2 and H in the control of ventilation + • Identify plasma CSF levels of O2, CO2 and H that would increase or decrease ventilation through central, peripheral or both sets of receptor. • Physiological applications for what we have learned • Breathing at altitude • Blood doping • Carbon monoxide poisoning BIG PICTURE: RCC=Respiratory RESPIRATORY CONTROL SYSTEM control center PaO2 or PaCO2 Decreased PaO2 Chemoreceptors Afferent RCC Increase PaO2 back to normal levels Somatic motor nerves Intercostal and diaphragm Increased contraction Central Chemorecpetors (responsible for detecting changes in PaCO2) How do central chemorecpetors sense CO2? Peripheral Chemorecpetors (responsible for detecting changes in PaO2 & PaCO2) Where are the peripheral chemoreceptors located? 1. Aortic Arch 2. Carotid Body What do they sense? Changes in arterial PaO2, PaCO2 and pH Vander Fig 13-33 How do peripheral chemorecpetors sense changes in arterial gases? Peripheral chemoreceptors sense changes in PaO2, PaCO2 and pH. Central chemoreceptors only sense PaCO2 levels. Control of Breathing Oxygen Carbon Dioxide 30 30 20 20 10 10 Minute Ventilation (L/min) Ventilation Minute Minute Ventilation (L/min) Ventilation Minute 20 40 60 80 100 40 44 48 Arterial PO (mmHg) 2 Arterial PCO2 (mmHg) Your body cares a lot about CO2 levels because it cares about maintaining the pH! Concept map– be able to follow each of these pathways for the exam Changing our oxygen carrying capacity What happens when you… What happens when you magically appear on the top of Everest? You have magically just appeared at the peak of Mount Everest, the highest point in the world! After taking in the view for a few minutes, you begin to feel uncomfortable. Physiologically, your alveolar PO2 has fallen from 100mmHg (in Minneapolis) to only 28mmHg!!! What is your hemoglobin percent saturation at this new PalvO2? How will your respiratory system respond to this situation? What else could you do to restore your PalvO2 and PaO2? What causes altitude sickness? Respiratory alkalosis at altitude WHAT HAPPENS WHEN YOU BLOOD DOPE? • Injections of EPO • Erythropoietin is a hormone produced by the kidneys that regulates the production of blood cells • Are there natural ways to enhance EPO production? • Injections of synthetic oxygen carriers • Perfluorocarbons (PFC’s) • Transfusion with whole blood (autotransfusion) BLOOD DOPING: AUTO-TRANSFUSION WHAT HAPPENS WHEN YOU BREATH CARBON MONOXIDE? “THE QUIET KILLER” Properties 1. Colorless, tasteless and odorless 2. Binds over 200x more than O2 to hemoglobin 3. Binding of CO blocks oxygen binding Critical thinking… Do you think PaO2 will change dramatically in the plasma? How about oxy-hemoglobin percent saturation? Total oxygen content? Would ventilation change as a result of exposure to CO? Why or why not? What do the chemoreceptors (central and peripheral) sense? Are these parameters changing? REVIEW OF DIFFICULT TOPICS IN PULMONARY PHYSIOLOGY (IF WE HAVE TIME) O2 AND CO2 LEVELS IN THE BODY Lung: [O2] [CO2] Both oxygen and CO2 will move from regions of high concentration to low Blood: concentration [O ] [CO ] throughout the body 2 2 Tissue: [O2] [CO2] Pearson Education 2013 Air movement in the lung 2 Alveoli 1 At rest 0 -1 intrapleural -3 -4 Exhalation Inhalation -5 Various pressures during breathing (mmHg) breathing during pressures Various -6 -7 Lung volume 500 250 Tidal Volume (mL) Volume Tidal 0 Changes in pressure are all compared to atmospheric which is usually set to 0 Surface Tension and The Law of LaPlace Pressure inside of a bubble formed by a fluid film is the function of two factors: 1. Surface tension 2. The Radius Law of LaPlace More surfactant decreases surface tension. Larger bubble Smaller bubble P = pressure r = 2 r = 1 T = surface tension r = 2 r = 1 T = 3 T = 3 r = radius T = 2 T = 1 P = (2 3)/2 P = (2 3)/1 According to the law of LaPlace, P = (2 2)/2 P = (2 1)/1 P = 3 P = 6 if two bubbles have the same P = 2 P = 2 surface tension, the smaller bubble will have higher pressure. Surfactant ( ) DISSOLVED VS. BOUND Dissolved and bound to Dissolved hemoglobin DISSOLVED CONTENT Dissolved Dissolved Content TOTAL CONTENT AND PERCENT SATURATION Dissolved and bound to Bound Content hemoglobin Total Oxygen Content (total amt O2 in the blood.) = Bound Content + Dissolved Content Percent Saturation– percent of available hemoglobin sites bound to O2.