LIU Chuan Yong 刘传勇 Department of Physiology Medical School of SDU Tel 88381175 (lab)

1. LIU Chuan Yong 刘传勇 Department of Physiology Medical School of SDU Tel 88381175 (lab) 88382098 (office) Email: liucy@sdu.edu.cn Website: www.physiology.sdu.edu.cn

2. Chapter 3 Elastic Properties of the Respiratory System

3. Reference - Textbook P 29 – 40 P 210 - 218 P 471 – 475

4. Reference – Course Website

5. An Overview of Key Steps in Respiration

6. Key Steps in Respiration • Ventilation: Movement of air into and out of lungs • Gas exchange between air in lungs and blood • Transport of oxygen and carbon dioxide in the blood • Internal respiration: Gas exchange between the blood and tissues

7. Newborn RDS : Signs and Syndrome • Baby Aldridge • Premature infant (28 weeks gestation) • Breathing very fast • Dyspnea • Chest was indrawing with each breath • Making a grunting sound • Question • The mechanism? • Treatment and prevention

8. Outline • Part I Intrapleural Pressure and Mechanism of the Ventilation • Part IILung Compliance • Part III The Effect of Disease

9. Part I Intrapleural Pressure and Mechanism of the Ventilation

10. Ventilation • Occurs because the thoracic cavity changes volume • Insipiration uses external intercostals and diaphragm • Expiration • passive at rest • uses internal intercostals and abdominals during severe respiratory load • Breathing rate is 10-20 breaths / minute at rest, 40 - 45 at maximum exercise in adults

11. Rib Cage Contract IntercostalsContractto Lift Spine Rib Diaphragm Volume Volume Ribs Mechanisms of Breathing: How do we change the volume of the rib cage ? • To Inhale is an ACTIVE process • Diaphragm • External Intercostal Muscles Both actions occur simultaneously – otherwise not effective

12. Flail Chest （连枷胸）

13. Pleura

14. Pleural fluid produced by pleural membranes • Acts as lubricant • Helps hold parietal and visceral pleural membranes together

15. Intrapleural Pressure

16. Penumothorax

17. Penumothorax

18. 胸腔闭式引流术

20. Alveolar Pressure Changes During Respiration

21. Conducting Airways Lungs Gas Exchange Pleural Cavity Very small space Maintained at negative pressure Transmits pressure changes Allows lung and ribs to slide Chest Wall (muscle, ribs) Diaphragm (muscle) Pleural CavityImaginary Space between Lungs and chest wall Principles of Breathing Functional Unit: Chest Wall and Lung Follows Boyle’s Law:Pressure (P) x Volume (V) = Constant

22. CW Principle of Breathing Follows Boyle’s Law: PV= C At Rest with mouth open Pb = Pi = 0 Pb Airway Open A Pi PS D 1

23. Principle of Breathing Follows Boyle’s Law: PV= C • At Rest with mouth open Pb = Pi = 0 • Inhalation: • Increase Volume of Rib cage • Decrease the pleural cavity pressure- Decrease in Pressure inside (Pi) lungs Pb Airway Open A Pi PS CW D 2

24. Principle of Breathing Follows Boyle’s Law: PV= C • At Rest with mouth open Pb = Pi = 0 • Inhalation: • Pb outside is now greater than Pi- Air flows down pressure gradient • Until Pi = Pb Pb Airway Open A Pi CW PS D 3

25. Principle of Breathing Follows Boyle’s Law: PV= C Pb • At Rest with mouth open Pb = Pi = 0 • Exhalation: Opposite Process • Decrease Rib Cage Volume Airway Open A Pi CW PS D 4

26. Principle of Breathing Follows Boyle’s Law: PV= C • At Rest with mouth open Pb = Pi = 0 • Exhalation: Opposite Process • Decrease Rib Cage Volume • Increase in pleural cavity pressure - Increase Pi Pb Airway Open A Pi CW PS D 5

27. Principle of Breathing Follows Boyle’s Law: PV= C • At Rest with mouth open Pb = Pi = 0 • Exhalation: Opposite Process • Decrease Rib Cage Volume • Increase Pi • Pi is greater than Pb • Air flows down pressure gradient • Until Pi = Pb again Pb Airway Open A Pi CW PS D 6

29. Resistance of the Ventilation • Elastic Resistance • Determined by the Compliance • Lung and Thoracic Cage Compliance • Inelastic Resistance • Airway Resistance

30. Part II Lung Compliance

31. What is lung compliance? • Change in lung volume for each unit change in transpulmonary pressure = stretchiness of lungs • DV/DP • Transpulmonary pressure is the difference in pressure between alveolar pressure and pleural pressure.

32. Compliance diagram of lungs • There are 2 different curves according to different phases of respiration. • The curves are called : • Inspiratory compliance curve • Expiratory compliance curve • Shows the capacity of lungs to “adapt” to small changes of transpulmonary pressure. • Hysteresis （滞后现象）

33. How do lungs adapt and why? • Compliance of lungs occurs due to elastic forces. • Elastic forces of the lung tissue itself • Elastic forces of the fluid that lines the inside walls of alveoli and other lung air passages B A Elastin + Collagen fibres • Surface Tension

34. Why is B the most important mechanism? Conclusion of this experiment: Tissue elastic forces (A) = represent 1/3 of total lung elasticity Fluid air surface tension (B) = 2/3 of total lung elasticity. Experiment: • By adding saline solution there is no interface between air and alveolar fluid. (B forces were removed) • surface tension is not present, only elastic forces of tissue (A) • Transpleural pressures required to expand normal lung = 3x pressure to expand saline filled lung.

35. Surface tension • water molecules are attracted to one another. • The force of surface tension acts in the plane of the air-liquid boundary to shrink or minimize the liquid-air interface • In lungs = water tends to attract forcing air out of alveoli to bronchi = alveoli tend to collapse (!!!) surface tension elastic force Elastic contractile force of the entire lungs (forces B)

36. Why are we talking about surfactant? • Surface active agent in water = reduces surface tension of water on the alveolar walls

37. Pulmonary surfactant • Phospholipid produced by alveolar type II cells. • Develop at 24 weeks’ gestation • Produces surfactant at 34 weeks • Lowers surface tension. • Reduces attractive forces of hydrogen bonding • by becoming interspersed between H20 molecules.

38. Laplaces law • “The pressure inside a balloon is calculated by twice the surface tension, divided by the radius.” • Pressure to collapse generated by alveoli is inversely affected by radius of alveoli • the smaller a bubble, the higher the pressure acting on the bubble • Smaller alveoli have greater tendency to collapse

39. AirFlow Expand Collapse Effect of Surface Tension on Alveoli size

40. Surfactant prevents alveolar collapse

41. Physiology Importance of Surfactant • Reduces surface tension and elastic recoil, • making breathing easier • Reduces the tendency to pulmonary edema • Equalize pressure in large and small alveoli • Produces hysteresis, which “props” alveoli open

42. Compliance of thorax and lung together • The compliance of lungs + thorax = 1/2 of lungs alone.

43. Part III The Effect of Disease • Lung fibrosis （肺纤维化） • Emphysema (肺气肿） • Respiratory Distress Syndrome (RDS) of the Newborn （新生儿呼吸窘迫综合症）

44. Lung fibrosis • The lungs are stiffened • By the laying down of collagen and fibrin bundles • Compliance is reduced

45. Emphysema • Destroy of the parenchyma • Less elastic recoil • Compliance increase

46. Newborn RDS : Signs and Syndrome • Baby Aldridge • Premature infant (28 weeks gestation) • Breathing very fast • Dyspnea • Chest was indrawing with each breath • Making a grunting sound • Question • The mechanism? • Treatment and prevention

47. Newborn RDS • Most common respiratory illness in NICU • Occur in premature neonate • Surfactant deficiency • Risk factors • Asphyxia （窒息） • Male • Acidosis • DM mother

48. Relationship between Gestational Age and RDS Morbidity

49. 早产 窒息 低体温 剖宫产 糖尿病母亲婴儿（IDM） 肺泡 PS 肺泡不张 V/Q  PaO2  PaCO2  通气  呼吸性酸中毒 代谢性酸中毒 严重酸中毒 肺毛细血管通透性 透明膜形成 气体弥散障碍

50. collapsed alveoli filled with hyaline membranes