Chapter 12 Pulmonary Structure and Function Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Anatomy of Ventilation • Pulmonary ventilation – Process of air moving in and out of lungs • Anatomy – Trachea – Bronchi – Bronchioles – Alveoli Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition The Lungs • Provide a large surface area (50 − 100 m2) • Highly vascularized to allow for gas exchange Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition The Alveoli • The lungs contain 600 million membranous sacs called alveoli. • Characteristics of alveoli – Elastic – Thin walled • Very small blood–gas barrier Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition The Alveoli • Pores of Kohn allow for even dispersion of surfactant. • Surfactant decreases surface tension. • Pores also allow for gas interchange between alveoli. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Mechanics of Ventilation • Conducting zone (anatomic dead space) – Trachea – Bronchioles • Respiratory zone – Respiratory bronchioles – Alveolar ducts – Alveoli Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Fick’s Law • Explains gas exchange through the alveolar membranes • Gas diffuses through a tissue at a rate proportional to surface area and inversely proportional to its thickness. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Inspiration • During inspiration – Diaphragm contracts and flattens – Chest cavity elongates and enlarges and air expands in lungs – Intrapulmonic pressure decreases – Air is sucked in through nose and mouth Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Expiration • During rest and light exercise, expiration is predominantly passive. – Stretched lung tissue recoils – Inspiratory muscles relax – Air moves to atmosphere • During strenuous exercise – Internal intercostals and abdominal muscles assist Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Surfactant • Resistance to expansion of the lungs increases during inspiration due to surface tension on alveoli. • Surfactant _ a lipoprotein mix of phospholipids, proteins, and Ca2+ produced by alveolar epithelial cells _ mixes with fluid around alveoli. • Surfactant disrupts and lowers surface tension. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Lung Volumes & Capacities • Are measured using a spirometer • Lung volumes vary with – Age – Size (mainly stature) – Gender Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Static Lung Volumes • • • • TV: Tidal volume: 0.4 − 1.0 L air/breath IRV: Inspiratory reserve volume: 2.5 − 3.5 L ERV: Expiratory reserve volume: 1.0 − 1.5 L IRV and ERV decrease during exercise as TV increases • FVC: Forced vital capacity: 3 − 5 L Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Residual Lung Volume • RLV averages 0.8 − 1.4 L • RLV increases with age as lung elasticity decreases. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Total Lung Capacity RLV + FVC = TLC Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Dynamic Lung Volumes • Dynamic ventilation depends upon – Maximal FVC of lungs – Velocity of flow • Velocity of flow is influenced by lung compliance. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition FEV-to-FVC Ratio • FEV1/FVC indicates pulmonary airflow capacity. • Healthy people average ~ 85% of FVC in 1 second. • Obstructive diseases result in significant lower FEV1/FVC. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Maximum Voluntary Ventilation • MVV evaluates ventilatory capacity with rapid and deep breathing for 15 seconds. – MVV = 15 second volume × 4 • MVV in healthy individuals averages 25% > ventilation than occurs during max exercise. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Exercise Implications • Gender Differences in Static and Dynamic Lung Functional Measures – Women have smaller lung function measures than men. – Highly fit women must work harder to maintain adequate alveolar-to-arterial O2 exchange. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Lung Function, Aerobic Fitness, and Exercise Performance • Little relationship exists among diverse lung volumes and capacities and exercise performance. • Maximum exercise is not limited by ventilation. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Pulmonary Ventilation • Volume of air moved into or out of total respiratory tract each minute • Air volume that ventilates only alveolar chambers each minute Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Minute Ventilation • Minute ventilation – Volume of air breathed each minute VE • Minute ventilation increases dramatically during exercise. – Values up to 200 L · min-1 have been reported. – Average person ~ 100 L · min-1 • Despite huge VE, TVs rarely exceed 60% VC. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Alveolar Ventilation • Anatomic dead space – Averages 150 − 200 mL • Only ~ 350 mL of the 500 mL TV enters alveoli. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Dead Space vs. Tidal Volume • Anatomic dead space increases as TV increases. • Despite the increase in dead space, increases in TV result in more effective alveolar ventilation. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Ventilation−Perfusion Ratio • Ratio of alveolar ventilation to pulmonary blood flow • V/Q during light exercise ~ 0.8 • V/Q during strenuous exercise may increase up to 5.0. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Physiologic Dead Space • Occurs when there is either 1. Inadequate ventilation 2. Inadequate blood flow Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Rate vs. Depth • During exercise, both rate and depth of breathing increase. • Initially, larger increases in depth occur. • Followed by increases in rate and depth Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Hyperventilation • An increase in pulmonary ventilation that exceeds O2 needs of metabolism • Hyperventilation decreases PCO2. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Dyspnea • Subjective distress in breathing • During exercise, respiratory muscles may fatigue, resulting in shallow, ineffective breathing and increased dyspnea. Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Valsalva Maneuver • Closing the glottis following a full inspiration while maximally activating the expiratory muscles • Causes increase in intrathoracic pressure • Helps stabilize chest during lifting Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Physiologic Consequences of Valsalva Maneuver • An acute drop in BP may result from a prolonged Valsalva maneuver. – Decreased venous return – Decreased flow to brain • Dizziness or fainting result Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Respiratory Tract During Cold-Weather Exercise • Cold ambient air is warmed as it passes through the conducting zone. • Moisture is lost if the air is cold and dry. • Contributes to – Dehydration – Dry mouth – Irritation of respiratory passages Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition Postexercise Coughing • Related to water loss and the drying of the throat Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
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