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Breathing and Exercise

Breathing and Exercise. Respiration Requires the Interaction of Physiological Systems. Ventilation (1). Gas Exchange (2). Gas Transport (3). Gas Exchange (4). Cell Respiration (5). Conducting Zone: Structure-Function. Nasal Cavity is rich in blood supply which warms inspired air.

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Breathing and Exercise

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  1. Breathing and Exercise

  2. Respiration Requires the Interaction of Physiological Systems Ventilation (1) Gas Exchange (2) Gas Transport (3) Gas Exchange (4) Cell Respiration (5)

  3. Conducting Zone: Structure-Function • Nasal Cavity is rich in blood supply which warms inspired air. • Moist lining humidifies. • Upper airways are mainly cartilaginous plates that are ‘stiff’ and conduct air efficiently. • Lower airways contain more smooth muscle which can regulate airflow by relaxing and expanding. • Mucociliary ‘elevator’ filters.

  4. Respiratory Zone - Structure-Function • Type 1 epithelial cells are thin (0.1 to 0.5 µm) making gas exchange with blood efficient. • Type 2 epithelial cells make surfactant which keep alveoli ‘open’. • Alveolar macrophages remove bacteria and other contaminants. • Highly branched allows for great surface area for gas exchange.

  5. (Patm - Palv) Flow = Airway Resistance End-Expiration

  6. Inspiration (Patm - Palv) Flow = Airway Resistance

  7. (Patm - Palv) Flow = Airway Resistance Expiration

  8. Inspiration

  9. Inspiratory Muscle Action

  10. Expiration

  11. Expiration

  12. 6 4 Volume (liters) 2 0 Time

  13. Lung Volumes and Capacities in Healthy Subjects Males Females Measures (20-30 yrs) (20-30 yrs) VC 4800 3200 RV 1200 1000 FRC 2400 1800 TLC 6000 4200 RV/TLC x 100 20% 24% Measurements are in ml except where indicated.

  14. Lung Volumes and Capacities in Healthy Subjects Males Females Males Measures (20-30 yrs) (20-30 yrs) (50 to 60 yrs) VC 4800 3200 3600 RV 1200 1000 2400 FRC 2400 1800 3400 TLC 6000 4200 6000 RV/TLC x 100 20% 24% 40% Measurements are in ml except where indicated.

  15. Dead Space • Anatomical Dead Space (ADS) is the volume of air needed to fill the conducting zone. • Physiological Dead Space (PDS) is ADS + nonfunctional alveoli. • Healthy people: ADS = PDS • Some pulmonary diseases: ADS < PDS

  16. Ventilation of Dead Space and Alveoli VT is volume required to fill dead space (VD) + alveoli (VA). In healthy subjects: VT = ~500 ml VD = ~150 ml VA = ~350 ml

  17. Ventilatory Adjustments and Respiratory Efficiency • Increase tidal volume • alveolar ventilation increases • dead space ventilation is unchanged • Increase respiratory frequency • alveolar ventilation increases • dead space ventilation increases • Increasing tidal volume more efficient!!!

  18. Lung and Chest Wall Compliance Tissue and Airway Resistance What Determines the Work of Breathing?

  19. Elastic Properties of the Lung are a Determinant of Compliance Lung Volume Compliance = y/x Transpulmonary Pressure

  20. Lung Volume is a Determinant of Compliance Total Lung Capacity (elastic elements are stretched) Lung Volume (% Total Lung Capacity) Functional Residual Capacity Residual Volume (airways are compressed) Transpulmonary Pressure (cm H2O)

  21. Resistance • Tissue resistance (~20% of total resistance) • Airway resistance (~80% of total resistance) • Airway dimensions • Smooth muscle contraction • Intrapleural pressure

  22. Airways constricted by: Parasympathetic stimulation Acetylcholine Histamine Leukotrienes Thromboxane A2 Serotonin -adrenergic agonists Decreased PCO2 Airways dilated by: Sympathetic stimulation (2 receptors) Circulating 2 agonists Nitric oxide Increased PCO2 in small airways Decreased PO2 in small airways Regulation of Airway Smooth Muscle

  23. Lung Volume is Invesrsely related to Airway Resistance High Intrapleural Pressures Compress Airways Airway Resistance Low Intrapleural Pressures Distend Airways Lung Volume

  24. Airway Compression and Intrapleural Pressure

  25. Respiration Requires the Interaction of Physiological Systems Ventilation (1) Gas Exchange (2) Gas Transport (3) Gas Exchange (4) Cell Respiration (5)

  26. Regulation of Pulmonary Vascular Blood Flow • Pulmonary artery pressure • Extravascular events • Chemical regulation of pulmonary vascular smooth muscle • Gravity

  27. Increased Pressure decreases Vascular Resistance in the Pulmonary Circulation Pulmonary Vascular Resistance Mean Pulmonary Artery Pressure (mmHg)

  28. Recruitment Distension

  29. Regional Ventilation Increased by high CO2 Regional Circulation Decreased by low O2 Ventilation-Perfusion Matching Ensures regions of the lung that are well ventilated are also well perfused

  30. Respiration Requires the Interaction of Physiological Systems Ventilation (1) Gas Exchange (2) Gas Transport (3) Gas Exchange (4) Cell Respiration (5)

  31. O2 P2 CO2 A P1 A D  V ( P P ) T = - T gas 1 2 Diffusion of Gases

  32. Surface Area for Pulmonary Gas Exchange is Influenced by: • Body position • Body size • Exercise • Some pulmonary diseases

  33. Partial Pressures of Respiratory Gases as they Enter and Leave the Lungs at Sea Level

  34. O2 159 0.03 CO2 40 104 45 40 Gas Pressure Gradients in the Lung Pulmonary Capillary Environment Alveoli 104 Artery 40 Tissue Metabolism Vein Air-Blood Barrier Values are PO2 and PCO2 in mmHg

  35. O2 159 0.03 CO2 104 104 25 40 40 60 Gas Pressure Gradients in the Lung: Light to Moderate Exercise Pulmonary Capillary Environment Alveoli Artery Tissue Metabolism Vein Air-Blood Barrier Values are PO2 and PCO2 in mmHg

  36. Dissolved O2 = 5 Dissolved O2 = 5 • 5 O2 molecules are dissolved in solution on both sides of the semi-permeable membrane (no net movement). Hemoglobin as an O2 Carrier

  37. Dissolved O2 = 5 Dissolved O2 = 1 • Hemoglobin now binds 4 O2 molecules, leaving only one in solution. There is now a 5:1 dissolved O2 ratio (O2 now moves from left to right). Hb Hemoglobin as an O2 Carrier

  38. Dissolved O2 = 5 Dissolved O2 = 5 • 5 O2 molecules are dissolved in solution on both sides of the semi-permeable membrane (no net movement). Hemoglobin as an O2 Carrier

  39. RBC transit in pulmonary capillary at rest is 1.0 sec RBC transit in pulmonary capillary during exercise is as little as 0.5 sec

  40. RBC transit in pulmonary capillary at rest is 1.0 sec RBC transit in pulmonary capillary during exercise is as little as 0.5 sec

  41. Diffusion - Limited Transfer in the Lung Presence of an end capillary to alveolus partial pressure difference

  42. Perfusion-Limited Transfer in the Lung • Absence of an end capillary partial pressure difference • An increase in blood flow increases gas exchange with air by sending more blood through pulmonary capillaries.

  43. Diffusion of O2 to Tissues Diffusion-Limited

  44. Diffusion of CO2 from Tissues Perfusion-Limited

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