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Understanding Respiratory Physiology: Ventilation and Capacities

Discover the intricate mechanisms of respiration, including inspiratory and expiratory processes, respiratory muscle actions, lung volumes, and pulmonary disorders. Explore how the respiratory system plays a vital role in maintaining blood acid-base balance.

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Understanding Respiratory Physiology: Ventilation and Capacities

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  1. Chapter 39 Respiratory Physiology

  2. Mechanisms of respiration • Pulmonary ventilation • Inspiration • Expiration • Respiratory muscles • Diaphragm • External intercostal • Others

  3. Mechanisms of respiration • Steps of ventilation • Contraction of diaphragm and external intercostal muscles • Increase of thoracic volume • Expansion of the pleural cavities and lungs • Decrease of lung pressure below atmospheric pressure

  4. Mechanisms of respiration • Inspiration • Lung pressure becomes equal to atmospheric pressure • Air stops to flow inside • Relaxation of respiratory muscles • Recoiling of the lung tissue

  5. Mechanisms of respiration • Decrease of intrathoracic and intrapulmonary volumes • Increase of pulmonary pressure • Expiration

  6. Mechanisms of respiration • Pneumothorax it is the entry of air into the pleural cavity • It breaks the fluid bond between the visceral and parietal pleura • It will cause the lung to collapse – atelectasis

  7. Respiratory volumes and capacities • Spirometry • Tidal volume (TV) • It is the amount of air inspired or expired with each breath under resting conditions • 500 ml

  8. Respiratory volumes and capacities • Inspiratory reserve volume (IRV) • It is the amount of air that can be forcefully inspired after a normal tidal inspiration • 3100 ml

  9. Respiratory volumes and capacities • Expiratory reserve volume (ERV) • It is the amount of air that can be forcefully expired after a normal tidal expiration • 1200 ml • It is reduced in conditions in which the elasticity of the lungs is decreased

  10. Respiratory volumes and capacities • Vital capacity (VC) • It id the maximum amount of air that can be expired after a maximal inspiration • 4800 ml • VC = TV + IRV + ERV

  11. Respiratory volumes and capacities • Residual volume (RV) • It is the amount of air that remains in the lung after a ERV • 1200 ml

  12. Respiratory volumes and capacities • Functional residual capacity (FRC) • It is the amount of air that remains in the lung after a quiet respiratory cycle • 2400 ml • FRC = ERV+RV

  13. Respiratory volumes and capacities • Total lung capacity (TLC) • It is the total volume of the lungs • 6000 ml • TLC = VC+RV

  14. Respiratory volumes and capacities

  15. Respiratory volumes and capacities • Nonrecording spirometer • Handheld dry spirometer • Measures only expired air • Wet spirometer • Measures only expired air • Recording spirometer • Measures inspired and expired air

  16. Pulmonary disorders • Obstructive • Bronchitis • Asthma • Restrictive • Tuberculosis • Poliomyelitis

  17. Respiratory volumes and capacities • Forced vital capacity (FVC) • It is the amount of air expired after a deep inspiration and a forced and quick expiration • Reduced in restrictive pulmonary diseases

  18. Respiratory volumes and capacities • Forced expiratory volume measurement (FEV1%) • It is the percentage of vital capacity that is exhaled during specific intervals of time • It is reduced in obstructive diseases

  19. Respiratory rate and depth • Respiratory centers • Medulla oblongata • Pons • Keep the RR at 12-18 respirations/minute • Respiratory receptors • Stretch receptors in the lung • Change RR

  20. Respiratory rate and depth • Nerve vagus • Factors that changes the RR • Exercise • Coughing • Waking • Talking • Laughing, etc

  21. Respiratory rate and depth • O2 concentration in the blood • monitored by chemoreceptors in the aortic and carotid bodies • CO2 concentration in the blood • Directly stimulates the respiratory centers • Blood pH • Monitored by chemoreceptors in the aortic and carotid bodies

  22. Respiratory sounds • Bronchial sounds • Heard below the larynx • Vesicular sounds • Air filling the alveolar sacs • Heard over the chest • Crepitation (crackles) • Wheezing – a whistling sound

  23. Role of respiratory system in acid-base balance of blood • Blood pH • 7.35-7.45 • Carbonic acid-bicarbonate buffer • The main body buffer

  24. Acid-base imbalance • Alkalosis • Blood pH above 7.45 • Respiratory or metabolic • Acidosis • Blood pH bellow 7.35 • Respiratory or metabolic

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