Lung volumes & Lung Capacities

1. Lung volumes & Lung Capacities By Dr. Mudassar Ali Roomi (MBBS, M.Phil.) Assist. Prof. Physiology

2. LUNG VOLUMES AND CAPACITIES

3. SPIROMETER

4. 4 Lung Volumes • TV (Tidal Volume) = 500 ml • I.R.V (Inspiratory Reserve Volume) = 3000 ml = 3 L • E.R.V (Expiratory Reserve Volume) = 1100 ml • R.V (Residual Volume) = 1200 ml

5. Tidal Volume (VT) • Volume of air inspired or expired with each normal quiet breath. • Value = 500 ml in adult male.

6. Inspiratory Reserve Volume (IRV) • Extra volume of air that can be inspired over & above normal tidal volume, when person inspires with full force. • Value = 3000 ml.

7. Expiratory Reserve Volume (ERV) • Maximum extra volume of air, that can be expired by forceful expiration after the end of normal tidal expiration. • Value = 1100 ml.

8. Residual Volume (RV) • Volume of air remaining in the lungs after most forceful expiration. • Value = 1200 ml

9. LUNG CAPACITIES(sum of 2 or more lung volumes) • T.V = 500 ml • I.R.V = 3000 ml = 3 L I.C (Inspiratory Capacity) = 3500 ml = 3.5 L T.L.C (Total Lung Capacity) = 5800 ml E.R.V = 1100 ml F.R.C (Functional Residual Capacity) = 2300 ml R.V = 1200 ml V.C (Vital Capacity) = TV + IRV + ERV = 500 + 3000+ 1100 = 4600 ml

10. InspiratoryCapacity (IC) • TV + IRV • Amount of air a person can breathe in beginning at normal expiratory level & distending the lungs to maximum amount. • Value= 3500 ml.

11. Functional residual capacity (FRC) • ERV+ RV • Amount of the air that remains in the lungs at the end of normal expiration. • Value: 2300 ml.

12. Vital capacity (VC) • VC = IRV + TV + ERV • Maximum amount of air a person can expel from the lungs after 1st filling the lungs to their max. extent & then expiring to max. extent. • value= 4600 ml • Calculations based on height • Females:(27.63 - (0.112 x age) x (height in cm) • Males: (21.78 - (0.101 x age) x (height in cm)

13. Total lung capacity (TLC) • Max. volume to which the lungs can be expanded with greatest possible effort. • VC + RV = TLC • Value= 5800 ml

14. FACTORS AFFECTING LUNG VOLUMES & CAPACITIES • Sex: 20 -25 % less in women than in men. • Height & built: Greater in larger people. • Athletes: larger • Small & Asthenic people: Smaller

16. The Forced vital capacity (FVC) of the lung is the volume of air that can be forcibly expelled from the lung from the maximum inspiration to the maximum expiration.

17. Forced expiratory volume in 1 second (FEV1) is the volume of air that can be expelled from maximum inspiration in the first second.

19. Restrictive pattern • Due to conditions in which the lung volume is reduced e.gfibrosingalveolitis, scoliosis. The FEV1 and FVC are reduced proportionately.

20. Obstructive pattern • Due to conditions in which the airways are obstructed e.g. asthma or COPD. The FEV1 and FVC are reduced disproportionately.

22. Grading or Severity of COPD on the basis of FEV1%

23. Forced expiratory ratio (FEV1/FVC ratio) • The FEV1/FVC ratio is the FEV1 expressed as a percentage of the FVC (or VC if that is greater) i.e the proportion of the vital capacity inhaled in the first second. • It distinguishes between restrictive and obstructive lung diseases. • Obstruction is defined as an FEV1/FVC ratio of <70%

26. Restrictive ventilatory pattern FVC reduced <80%FEV1 reducedFEV1/FVC ratio normal Obstructive ventilatory pattern FVC normal or reducedFEV1 reduced <80%FEV1/FVC ratio reduced

27. Flow volume loops • This is the same forced expiration converted electronically to illustrate flow rate as the lung empties. • The x axis represents volume - from full inspiration to full expiration. • The y axis represents the flow rate. • Obstructive disease: ? • Restrictive disease:?