Compliance of lung

COMPLIANCE OF LUNGS

1. DR NILESH KATE MBBS,MD PROFESSOR DEPT. OF PHYSIOLOGY LUNG ELASTANCE, COMPLIANCE & WORK OF BREATHING.

2. OBJECTIVES. Pulmonary Elastance Elastance of thoracic cage Elastance of Lungs Alveolar surface tension Pulmonary surfactant Pulmonary Compliance Def, NR Measurement Static Vs Specific Work of breathing

3. PULMONARY ELASTANCE Elastance – Def – recoil of Retractive tendency of any structure. Elastance of Thoracic cage Elastance of lungs Friday, May 14, 2021

4. ELASTANCE OF THORACIC CAGE Constant tendency of thoracic cage to expand which is normally kept partially pulled inward. It is because of the elastic nature of ribs, muscles and tendons. Friday, May 14, 2021

5. ELASTANCE OF LUNGS Constant tendency of lungs to collapse Tissue forces Presence of many elastic tissues such as smooth muscle, elastic and collagen in the lung parenchyma Surface forces – alveolar surface tension. Friday, May 14, 2021

6. ALVEOLAR SURFACE TENSION Surface of alveolar membrane lined by liquid Unbalance attraction of liquid molecules at surface creates surface tension -- Vander wall forces. Surface tension increases the tendency of the lungs to deflate/collapse. Friday, May 14, 2021

7. Law of laplace P=2T/r Therefore, small alveoli tend to become still smaller whereas large alveoli tend to become still larger Friday, May 14, 2021

8. PULMONARY SURFACTANT Source – type II alveolar epithelial cells(granular pneumocytes). Composition – DPPC (Dipalmitoyl-phosphatidylcholine) Mechanism of action Hydrophilic portion Hydrophobic portion Friday, May 14, 2021

9. Mechanism of action. Hydrophilic portion Hydrophobic portion This causes spreading of surfactant molecules over the surface of fluid lining the alveoli. Apoproteins and calcium ions are responsible for uniform and quick spreading of surfactant molecules over the surface. Friday, May 14, 2021

10. Functions The tendency of alveoli to collapse Work of breathing Prevents pulmonary oedema Pulls fluid from the capillaries into the interstitial space surrounding the alveoli and into the alveoli leading to pulmonary oedema. Alveolar stabilization. Pulling pressure 18 cm of H 2 O 4 cm of H 2 O Friday, May 14, 2021

11. MECHANISM OF ALVEOLAR STABILIZATION In the presence of surfactant ST = 1/ Surfactant. Other factors Interdependence of alveolar septa Fibrous tissue. Friday, May 14, 2021

12. Factors affecting pulmonary surfactant Friday, May 14, 2021

13. APPLIED ASPECTS. Respiratory distress syndrome of newborn.(Hyaline membrane disease) Adult respiratory distress syndrome Patchy atelectasis. Friday, May 14, 2021

14. PULMONARY COMPLIANCE Definition & Normal value Measurement Procedure Factors affecting compliance Friday, May 14, 2021

15. Definition & Normal value C= δ V/ δ P Transpulmonary pressure = alveolar pressure – pleural pressure. Normal value Both 0.13L/cm of H2O Lung alone 0.22 L/cm of H2O Friday, May 14, 2021

16. Measurement Friday, May 14, 2021

17. PROCEDURE Intra-oesophageal balloon measures intra-pleural pressure. Pt made to inspire 100 ml of air & intrapleural pressure measured. Curved lines due to 2 resistance Viscous resistance Airway resistance. Friday, May 14, 2021

18. FACTORS AFFECTING COMPLIANCE Elastic forces of the lung tissue – mainly due to elastic & collagen fibres (1/3 rd ) Elastic forces caused by surface tension (2/3 rd ) Friday, May 14, 2021

19. Static vs Specific Lung Compliance Static compliance Depend upon size Amount of functional lung tissue. Specific lung compliance Compliance of the lung at relaxation volume i.e. at the end of tidal expiration FRC. Friday, May 14, 2021

20. LUNG COMPLIANCE CHANGES Friday, May 14, 2021

21. Work of breathing Friday, May 14, 2021

22. RESISTANCE TO BREATHING Tissue resistance Airway resistance Friday, May 14, 2021

23. TISSUE RESISTANCE Elastic resistance Thoracic cage Lungs Elastic fibres Surface tension Viscous resistance. Non-elastic tissue. Friday, May 14, 2021

24. AIRWAY RESISTANCE Friction of gas molecules and wall of airways. Factors affecting Rate of gas flow Airway radius. Poiseuille-Hagen formula Resistance α 1/r 4 Length of airway Type of airflow Friday, May 14, 2021

25. CONTROL OF AIRWAY DIAMETER Sympathetic adrenergic – Bronchodilataion Vagus – bronchoconstriction & Mucous formation. Friday, May 14, 2021

26. COMPONENTS OF WORK OF BREATHING Work done to overcome Elastic resistance (65%) Viscous resistance (7%) Airway resistance (28%) Friday, May 14, 2021

27. CALCULATION OF WORK OF BREATHING Work done during inspiration Work done during Expiration Friday, May 14, 2021

28. WORK DONE DURING INSPIRATION Compliance work refers to the work done by respiratory muscles to inflate the lungs against the elastic resistance of chest wall and lungs. It is represented by the triangular area Thus most of the work done (65%) is used to overcome elastic resistance. Friday, May 14, 2021

29. Non-elastic resistance work Work is done to overcome the nonelastic resistance. It includes the work done to overcome: Viscous resistance of lungs (7%) and Airway resistance (28%). Friday, May 14, 2021

30. WORK DONE DURING EXPIRATION Since in quiet breathing, expiration is a passive process so no work is done during expiration. When the lungs are recoiling back some energy is required to overcome non-elastic resistance, i.e. the airway resistance plus viscous tissue resistance. Friday, May 14, 2021

31. WORK OF BREATHING IN RESTRICTIVE LUNG DISEASES Friday, May 14, 2021

32. WORK OF BREATHING IN OBSTRUCTIVE LUNG DISEASES Friday, May 14, 2021

33. APPLIED Work of breathing in Restrictive lung diseases Obstructive lung diseases. Friday, May 14, 2021

34. FACTORS AFFECTING TOTAL WORK OF BREATHING. Total work of breathing in quiet respiration 0.3-0.8 kg mt/min. Increases As resistance increases Muscular exercise. Friday, May 14, 2021

35. Objectives seen…… Pulmonary Elastance Elastance of thoracic cage Elastance of Lungs Alveolar surface tension Pulmonary surfactant Pulmonary Compliance Def, NR Measurement Static Vs Specific Work of breathing Friday, May 14, 2021

36. THANK YOU