Respiration During Exercise PDF

Respiration during exercise Fundamentals of Sport and Exercise Science PSA762 Dr Laura A. Barrett Objectives 1. Explain the principle physiological function of the pulmonary system. 2. Outline the major anatomical components of the respiratory system. 3. List major muscles invol...

Respiration during exercise Fundamentals of Sport and Exercise Science PSA762 Dr Laura A. Barrett Objectives 1. Explain the principle physiological function of the pulmonary system. 2. Outline the major anatomical components of the respiratory system. 3. List major muscles involved in inspiration and expiration at rest and during exercise. 4. Discuss the importance of matching blood flow to alveolar ventilation in the lung. 5. Explain how gases are transported across the blood-gas interface in the lung. Objectives 6. Discuss the major transportation modes of O2 and CO2 in the blood. 7. Discuss the effects of increasing temperature, decreasing pH, and increasing levels of 2–3 DPG on the oxygen-hemoglobin dissociation curve. 8. Describe the ventilatory response to constant- load, steady-state exercise.  Function of the Lung Function of the Lung Means of gas exchange between the external environment and the body – Replacing O2 – Removing CO2 – Regulation of acid-base balance Ventilation – Mechanical process of moving air into and out of lungs Diffusion – Random movement of molecules from an area of high concentration to an area of lower concentration  Structure of the Respiratory System Major Organs of the Respiratory System Figure 10.1  Structure of the Respiratory System Position of the Lungs, Diaphragm, and Pleura Figure 10.2  Structure of the Respiratory System Conducting and Respiratory Zones Figure 10.4  Mechanics of Breathing Mechanics of Breathing Movement of air occurs via bulk flow – Movement of molecules due to pressure difference Inspiration – Diaphragm pushes downward, ribs lift outward – Volume of lungs increases – Intrapulmonary pressure lowered Expiration – Diaphragm relaxes, ribs pulled downward – Volume of lungs decreases – Intrapulmonary pressure raised  Mechanics of Breathing The Muscles of Respiration Figure 10.7  Pulmonary Volumes and Capacities Lung Volumes and Capacities Figure 10.9  Mechanics of Breathing Airway Resistance Airflow depends on: – Pressure difference between two ends of airway – Resistance of airways P1 – P 2 Airflow = Resistance Airway resistance depends on diameter – Chronic obstructive lung disease – Asthma and exercise-induced asthma  Diffusion of Gases Partial Pressure of Gases Dalton’s law – The total pressure of a gas mixture is equal to the sum of the pressure that each gas would exert independently Pair = PO2 + PCO2 + PN2 Calculation of partial pressure Gas % in air Fraction Barometric P Partial P O2 20.93 0.2093 x 760 mmHg = 159 mmHg CO2 0.03 0.0003 x 760 mmHg = 0.3 mmHg N2 79.04 0.7904 x 760 mmHg = 600.7 mmHg Total 100 760 mmHg  Diffusion of Gases Diffusion of Gases Fick’s law of diffusion – The rate of gas transfer (V gas) is proportional to the tissue area, the diffusion coefficient of the gas, and the difference in the partial pressure of the gas on the two sides of the tissue, and inversely proportional to the thickness. A V gas = x D x (P1 – P2) T V gas = rate of diffusion A = tissue area T = tissue thickness D = diffusion coefficient of gas P1 – P2 = difference in partial pressure  Diffusion of Gases Partial Pressures of O2 and CO2 and Gas Exchange  Blood Flow to the Lung The Pulmonary and Systemic Circulation Figure 10.12  Ventilation-Perfusion Relationships Ventilation-Perfusion Relationships  Efficient gas exchange between the blood and the lung requires proper matching of blood flow to ventilation (called ventilation-perfusion relationships).  The ideal ratio of ventilation to perfusion is 1.0 or slightly greater, since this ratio implies a perfect matching on blood flow to ventilation.  O2 and CO2 Transport in Blood O2 Transport in the Blood 99% of O2 is transported bound to hemoglobin (Hb) – Oxyhemoglobin: Hb bound to O2 – Deoxyhemoglobin: Hb not bound to O2 Amount of O2 that can be transported per unit volume of blood is dependent on the Hb concentration  O2 and CO2 Transport in Blood Oxyhemoglobin Dissociation Curve Deoxyhemoglobin + O2  Oxyhemoglobin Direction of reaction depends on: – PO2 of the blood – Affinity between Hb and O2 At the lung – High PO2 = formation of oxyhemoglobin At the tissues – Low PO2 = release of O2 to tissues  O2 and CO2 Transport in Blood Oxygen-Hemoglobin Dissociation Curve Figure 10.15  O2 and CO2 Transport in Blood Effect of pH, Temperature, and 2–3 DPG on the O2-Hb Dissociation Curve pH – Decreased pH lowers Hb-O2 affinity – Results in a “rightward” shift of the curve  Favors “offloading” of O2 to the tissues Temperature – Increased blood temperature lowers Hb-O2 affinity – Results in a “rightward” shift of the curve 2–3 DPG – Byproduct of RBC glycolysis – May result in a “rightward” shift of the curve  During altitude exposure  Not a major cause of rightward shift during exercise  O2 and CO2 Transport in Blood O2 Transport in Muscle Myoglobin (Mb) – Shuttles O2 from the cell membrane to the mitochondria Mb has a higher affinity for O2 than hemoglobin – Even at low PO2 – Allows Mb to store O2  O2 reserve for muscle  O2 and CO2 Transport in Blood CO2 Transport in Blood Dissolved in plasma (10%) Bound to Hb (20%) Bicarbonate (70%) CO2 + H2O Carbonic anhydrase H2CO3 H+ + HCO3– – At the tissue:  H+ binds to Hb  HCO3– diffuses out of RBC into plasma  Cl– diffuses into RBC (chloride shift) – At the lung:  O2 binds to Hb (drives off H+)  Reaction reverses to release CO2  Ventilation and Acid-Base Balance Ventilation and Acid-Base Balance Pulmonary ventilation removes H+ from blood by the HCO3– reaction Lung CO2 + H2O Carbonic anhydrase H2CO3 H+ + HCO3– Muscle – Increased ventilation results in CO2 exhalation  Reduces PCO2 and H+ concentration (pH increase) – Decreased ventilation results in buildup of CO2  Increases PCO2 and H+ concentration (pH decrease)  Ventilatory and Blood-Gas Responses to Exercise The Transition From Rest to Exercise Figure 10.21 Ventilatory Response to Incremental Exercise  Do the Lungs Adapt to Exercise Training? Effect of Training on Ventilation No effect on lung structure and function at rest Normal lung exceeds demand for gas exchange – Adaptation is not required for the lung to maintain blood-gas homeostasis One exception: Elite endurance athletes – Failure of lung to adapt to training results in hypoxemia  Does the Pulmonary System Limit Maximal Exercise Performance? Does the Pulmonary System Limit Exercise Performance? Low-to-moderate intensity exercise – Pulmonary system not seen as a limitation Maximal exercise – Historically not thought to be a limitation in healthy individuals at sea level  New evidence that respiratory muscle fatigue does occur during high intensity exercise (>90% VO2 max) – May be limiting in elite endurance athletes  40–50% experience hypoxemia Example Exam Questions 1. What is the primary function of the pulmonary system? What secondary function does it serve? 2. List and discuss the major anatomical components of the respiratory system. 3. What muscle groups are involved in ventilation during rest? During exercise? 4. What is the functional significance of the ventilation- perfusion ratio? How would a high V/Q ratio affect gas exchange in the lung? 5. Discuss the factors that influence the rate of diffusion across the blood-gas interface in the lung. Example Exam Questions 6. Graph the relationship between hemoglobin-O2 saturation and the partial pressure of O2 in the blood. What is the functional significance of the shape of the O2-hemoglobin dissociation curve? What factors affect the shape of the curve? 7. Discuss the modes of transportation for CO2 in the blood. 8. Graph the ventilatory response in the transition from rest to constant-load submaximal exercise. What happens to ventilation if the exercise is prolonged and performed in a hot/humid environment? Why? Reading  Powers, S.K. and Howley, E.T. (2015) Exercise physiology: theory and application to fitness and performance. McGraw Hill International Edition. Chapter 10 (read sections as indicated by the power point slide headings).  And look-up respiratory during exercise in any other recommended exercise physiology textbook for a second view and opinion.