Lung volumes Lung Capacities By Dr Mudassar Ali
Lung volumes & Lung Capacities By Dr. Mudassar Ali Roomi (MBBS, M. Phil. ) Assist. Prof. Physiology
LUNG VOLUMES AND CAPACITIES
SPIROMETER
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
Tidal Volume (VT) • Volume of air inspired or expired with each normal quiet breath. • Value = 500 ml in adult male.
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.
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.
Residual Volume (RV) • Volume of air remaining in the lungs after most forceful expiration. • Value = 1200 ml
• T. V = 500 ml • I. R. V = 3000 ml = 3 L E. R. V = 1100 ml R. V = 1200 ml V. C (Vital Capacity) = TV + IRV + ERV = 500 + 3000+ 1100 = 4600 ml I. C (Inspiratory Capacity) = 3500 ml = 3. 5 L F. R. C (Functional Residual Capacity) = 2300 ml T. L. C (Total Lung Capacity) = 5800 ml LUNG CAPACITIES (sum of 2 or more lung volumes)
Inspiratory Capacity (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.
Functional residual capacity (FRC) • ERV+ RV • Amount of the air that remains in the lungs at the end of normal expiration. • Value: 2300 ml.
Vital capacity (VC) • VC = IRV + TV + ERV • Maximum amount of air a person can expel from the lungs after 1 st 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)
Total lung capacity (TLC) • Max. volume to which the lungs can be expanded with greatest possible effort. • VC + RV = TLC • Value= 5800 ml
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
• 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.
• Forced expiratory volume in 1 second (FEV 1) is the volume of air that can be expelled from maximum inspiration in the first second.
• Restrictive pattern • Due to conditions in which the lung volume is reduced e. g fibrosing alveolitis, scoliosis. The FEV 1 and FVC are reduced proportionately.
• Obstructive pattern • Due to conditions in which the airways are obstructed e. g. asthma or COPD. The FEV 1 and FVC are reduced disproportionately.
• Grading or Severity of COPD on the basis of FEV 1% <80% = mild <60% = moderate <40% = severe
Forced expiratory ratio (FEV 1/FVC ratio) • The FEV 1/FVC ratio is the FEV 1 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 FEV 1/FVC ratio of <70%
• Restrictive ventilatory pattern • Obstructive ventilatory pattern • FVC reduced <80% FEV 1 reduced FEV 1/FVC ratio normal • FVC normal or reduced FEV 1 reduced <80% FEV 1/FVC ratio reduced
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: ?
- Slides: 27