Presentation of Muni lakshmi elasticity of lungs.pptx

Elasticity of lungs

1. ELASTICITY OF LUNGS BY Dr. T. MUNI LAKSHMI 1 st YEAR POST GRADUATE MODERATOR-DR SURYANARAYANA,ASST PROFESSOR DEPARTMENT OF ANAESTHESIA NRIIMS

2. CONTENTS : Introduction Components Compliance Types of compliance Pressure – Volume Curve Elastance Factors affecting Pathophysiology

3. Introduction : Respiratory system Conducting zone Transition Zone Respiratory zone

4. Two Components: Compliance & Elastance Compliance : The Measure of ability of the lungs to expand. It is the volume change in lungs per unit pressure. C = ∆ Volume ∆ Pressure Transpulmonary pressure = Transalveolar pressure - Intrapleural pressure Normally , compliance of both the lungs is 200ml / cm of H2O

5. Tennis Ball vs. Balloon

6. Types of compliances Static Compliance Dynamic Compliance

7. Static Compliance: Pulmonary compliance at a given fixed volume when there is no airflow . Therapeutically it serves to select the ideal levels of PEEP which is calculated based on formula. Cstat = V / ( Pplat – PEEP) where Pplat = Plateau pressure.

8. Dynamic Compliance : It is a continuous measure of pulmonary compliance during movement of gas in and out of the airway . Monitors both the elastic and airway resistance. Due to this variables Specific compliance = Compliance / FRC

9. Pressure – Volume Curve (Hysteresis Curve)

10. The pressure along the X axis is often plotted as transpulmonary pressure (Alveolar pressure – Intrapleural pressure) The relationship is curvilinear (Typical of an elastic structure) Initially, as can be seen from the above curve at lower lung volumes, the compliance of lung is poor and later greater pressure change is required to cause a change in volume

11. At FRC compliance is optimal since the elastic recoil of lung towards collapse balanced by tendency of chest wall to spring outwards. At higher lung volumes the compliance of lung again becomes less as the lung becomes stiffer.

12. Expiration is passive process due to elastic recoil of lung. Due to this, inspiratory curve is not identical to expiratory curve. This is known as hysteresis.

13. Factors affecting: Elastic property of lung tissue: Due to collagen fibres & elastic fibres meshed inside the Lung parenchyma. Hook’s law: The elastin fibres of pulmonary tissue resist stretching & exhibit property of returning to original length.

14. The pleural pressure is lower in the upper regions. So, in the upright subject the transpulmonary pressure is higher in apical than in basal regions. Thus lower lung regions expand more for a given increase in transpulmonary pressure than upper units.

15. Elastance : Also known as elastic resistance is reciprocal of compliance i.e., pressure change required to eliciit unit volume change E =Pressure change / volume change Total elastance of lung n chestwall = 10cm of H2O It is the measure of work that has to be done by muscles of inspiration to expand lung.

16. In smaller alveoli High concentrate Decrease in ST Prevent collapse In larger alveoli Less concentrate Increase in ST Prevent overdistension of alveoli

17. Compliance of chest wall Compliance of chest wall = ∆ in chest volume ∆ in transthoracic pressure * Transthoracic pressure = Atmospheric pressure – I ntrapleural pressure Normal value 0.2 L / cm H2O

18. Physiological conditions affecting compliance of lung: In Obesity - Lung compliance decreases Ageing - Decrease In muscle strength Decreases chestwall compliance - L oss of elasticity Increase lung compliance

19. Pathology affecting lung compliance : Decreased in Fibrotic lung disease Idiopathic fibrosis Sarcoidosis

20. Increased in Emphysema COPD Asthma Chestwall compliance : decreased in scoliosis

21. Pressure-volume curves of the lung in healthy and lung-disease

22. In fibrosis, The slope of the curve is flatter, reflecting considerable increases in pressure variation and in respiratory work . In asthma or bronchitis, There is a parallel  (upward)  shift of the pressure-volume curve, indicating an increase in lung volume but no change in compliance .

23. In emphysema, The slope of the curve is steeper, reflecting tissue loss and possible increased compliance. However, in emphysema, asthma, or bronchitis, the airway resistance is increased; This increases work of breathing and overrides any benefit from increased compliance.

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