Download - Lung volumes & Lung Capacities
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
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
E.R.V = 1100 mlR.V = 1200 ml
F.R.C (Functional Residual Capacity) = 2300 ml
V.C (Vital Capacity)= TV + IRV + ERV= 500 + 3000+ 1100= 4600 ml
T.L.
C (T
otal
Lun
g Ca
paci
ty) =
580
0 m
l
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 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)
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 (FEV1) 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 FEV1 and FVC are reduced proportionately.
• Obstructive pattern• Due to conditions in which the airways are
obstructed e.g. asthma or COPD. The FEV1 and FVC are reduced disproportionately.
• Grading or Severity of COPD on the basis of FEV1%
FEV1%
<80% = mild <60% = moderate <40% = severe
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%
• Restrictive ventilatory pattern
• FVC reduced <80%FEV1 reducedFEV1/FVC ratio normal
• Obstructive ventilatory pattern
• FVC normal or reducedFEV1 reduced <80%FEV1/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:?