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Pulmonary Function During Exercise

Chapter 10. Pulmonary Function During Exercise. The Respiratory System. Provides gas exchange between the environment and the body Regulates of acid-base balance during exercise. Ventilation. Moving Air. Conducting zone Conducts air to respiratory zone Humidifies, warms, and filters air

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Pulmonary Function During Exercise

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  1. Chapter 10 Pulmonary Function During Exercise

  2. The Respiratory System • Provides gas exchange between the environment and the body • Regulates of acid-base balance during exercise

  3. Ventilation • Moving Air

  4. Conducting zone Conducts air to respiratory zone Humidifies, warms, and filters air Components: Trachea Bronchial tree Bronchioles Respiratory zone Exchange of gases between air and blood Components: Respiratory bronchioles Alveolar sacs Conducting and Respiratory Zones

  5. Pathway of Air to Alveoli

  6. Mechanics of Breathing • Ventilation • Movement of air into and out of the lungs via bulk flow • Inspiration • Diaphragm pushes downward, lowering intrapulmonary pressure • Expiration • Diaphragm relaxes, raising intrapulmonary pressure • Resistance to airflow • Largely determined by airway diameter

  7. The Mechanics of Inspiration and Expiration

  8. Pulmonary Volumes and Capacities • Measured by spirometry • Vital capacity (VC) • Maximum amount of air that can be expired following a maximum inspiration • Residual volume (RV) • Air remaining in the lungs after a maximum expiration • Total lung capacity (TLC) • Sum of VC and RV

  9. Pulmonary Volumes and Capacities • Inspiratory Reserve volume (IRV) • Maximum amount of air that can be inspired following a normal inspiration • Expiratory reserve volume (ERV) • Air remaining in the lungs after a normal expiration

  10. A Spirogram Showing Pulmonary Volumes and Capacities

  11. Check measurements to find: • Norms for body sizes • Indications of healthy lung function • Indications of diseases/conditions that affect ventilation • Asthma • Emphysema

  12. . Pulmonary Ventilation (VE) • The amount of air moved in or out of the lungs per minute • Product of tidal volume (VT) and breathing frequency (FB) • (looks similar to Q = SV x HR? ) . VE = VTx FB .

  13. Respiration • Movement of gasses

  14. Diffusion of Gases • Gases diffuse from high  low partial pressure • From lungs to blood and back to lungs • From blood to tissue and back to blood

  15. PO2 = 0.2093 x 760 = 159 mmHg Partial Pressure of Gases • Each gas in a mixture exerts a portion of the total pressure of the gas • The partial pressure of oxygen (PO2) • Air is 20.93% oxygen • Expressed as a fraction: 0.2093 • If total pressure of air = 760 mmHg, then

  16. Partial Pressure and Gas Exchange

  17. O2 Transport in the Blood • O2 is bound to hemoglobin (Hb) for transport in the blood • Oxyhemoglobin: O2 bound to Hb • Carrying capacity • 201 ml O2•L-1 blood in males • 150 g Hb•L blood-1 x 1.34 mlO2•g Hb-1 • 174 ml O2•L-1 blood in females • 130 g Hb•L blood-1 x 1.34 mlO2•g Hb-1

  18. Oxyhemoglobin Dissociation Curve

  19. O2-Hb Dissociation Curve: Effect of pH • Blood pH declines during heavy exercise • Results in a “rightward” shift of the curve • Bohr effect • Favors “offloading” of O2 to the tissues

  20. O2-Hb Dissociation Curve: Effect of pH Amount of O2 unloaded 20 18 16 14 12 10 Oxygen Content (ml O2 / 100 ml blood) 8 6 4 2

  21. O2-Hb Dissociation Curve: Effect of Temperature • Increased blood temperature results in a weaker Hb-O2 bond • Rightward shift of curve • Easier “offloading” of O2 at tissues

  22. O2-Hb Dissociation Curve: Effect of Temperature Amount offloaded Oxygen Content (ml O2 / 100 ml blood)

  23. O2 Transport in Muscle • Myoglobin (Mb) shuttles O2 from the cell membrane to the mitochondria • Higher affinity for O2 than hemoglobin • Even at low PO2 • Allows Mb to store O2

  24. Dissociation Curves for Myoglobin and Hemoglobin

  25. Carbon Dioxide Transport • Not identical to oxygen transport

  26. CO2 Transport in Blood • Dissolved in plasma (10%) • Bound to Hb (20%) • Bicarbonate (70%) CO2 + H2O  H2CO3  H+ + HCO3- binds to Hb Carbonic Acid Muscle Normal Metabolism Bicarbonate

  27. CO2 Transport in Blood • Dissolved in plasma (10%) • Bound to Hb (20%) • Bicarbonate (70%) CO2 + H2O  H2CO3  H+ + HCO3- Ventilation Lung O2 replaces on Hb

  28. CO2 Transport in Blood • Dissolved in plasma (10%) • Bound to Hb (20%) • Bicarbonate (70%) CO2 + H2O  H2CO3  H+ + HCO3- • Also important for buffering H+ Ventilation Lung Muscle Intense Exercise

  29. Release of CO2 From Blood

  30. Effect of Respiratory Gases on Ventilation • How do these gasses affect breathing?

  31. Control of Ventilation • Respiratory control center in the brainstem • Regulates respiratory rate • Receives neural and humoral input • Feedback from muscles • PO2, PCO2, H+, and K+ in blood • PCO2 and H+ concentration in cerebrospinal fluid

  32. Effect of Arterial PO2 on Ventilation

  33. Effect of Arterial PCO2 on Ventilation

  34. Ventilation and Acid-Base Balance • Blood pH is regulated in part by ventilation • An increase in ventilation causes exhalation of additional CO2 • Reduces blood PCO2 • Lowers H+ concentration H+ + HCO3-  H2CO3  H2O + CO2 Exhalation

  35. Ventilatory Control During Submaximal Exercise

  36. Incremental Exercise • Linear increase in ventilation • Up to ~50-75% VO2max • Exponential increase beyond this point • Ventilatory threshold (Tvent) • Inflection point where VE increases exponentially . .

  37. Ventilatory Response to Exercise:Tvent

  38. Is This Trainable? • Does an endurance trained person breathe less? • Does an endurance trained person need less oxygen?

  39. Effect of Training on Ventilation • Ventilation is lower at same work rate following training • May be due to lower blood lactic acid levels • Results in less feedback to stimulate breathing • Well trained produce less CO2 – stim. for breathing

  40. Effects of Endurance Training on Ventilation During Exercise

  41. Ventilatory Response to Exercise:Trained vs. Untrained • In the trained runner • Decrease in arterial PO2 near exhaustion • more oxygen extracted • pH maintained at a higher work rate • less lactic acid produced – “aerobic metab.” • Tvent occurs at a higher work rate • lower relative intensity

  42. Ventilatory Response to Exercise:Trained vs. Untrained

  43. Do the Lungs Limit Exercise Performance? • Sub maximal exercise • Pulmonary system not seen as a limitation • Maximal exercise • Not thought to be a limitation in healthy individuals at sea level • May be limiting in elite endurance athletes

  44. Questions?

  45. End

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