Lung volumes and capacities-1.pdf

ppt

1. Lung volumes and capacities
By:
Dr. MawadaAhmed Elnour
Department of physiology
University of Gezira

2. ´Pulmonary ventilation can be studied by recording the volume
movement of air into and out of the lungs (spirometry).
´The air in the lungs is subdivided into volumes and capacities.
´A lung capacity is the sum of two or more lung volumes.

4. Lung volumes
1.Tidal volume: the volume of air inspired or expired with each normal
breath (500 ml in the average adult male).
2.Inspiratory reserve volume :the volume that can be inspired over and
above the tidal volume (3000 ml ).

5. 3.Expiratory reserve volume: is the maximum volume of air that can be
expired by forceful expiration after the end of a normal tidal expiration;
(1100 ml).
4.Residual volume: is the volume of air remaining in the lungs after the
most forceful expiration (1200 ml). Cannot be measured by spirometry.

6. Lung capacities
´They are the summation of two or more lung volumes.
1.Inspiratory capacity: is the sum of tidal volume and IRV.
2.Functional residual capacity (FRC): is the sum of ERV and RV =2300
(is the volume remaining in the lungs after a tidal volume is expired). It
includes the RV, so it cannot be measured by spirometry

7. 3.Vital capacity (VC), or forced vital capacity (FVC): is the volume of air
that can be forcibly expired after a maximal inspiration.is the sum of
tidal volume, IRV, and ERV.
4.Total lung capacity (TLC): Is the sum of all four lung volumes.
includes RV, so it cannot be measured by spirometry.

9. Pulmonary ventilation
´The minute respiratory volume (pulmonary ventilation): the total amount
of new air moved into the respiratory passages each minute.
!"#$%&'%()*∗,,.
500 ml of air moved in and out with each quite breath
500 * 12 = 6000 ml/minute

10. ´Maximal Pulmonary ventilation (MPV):
is the largest volume of gas that can be moved into and out of the lungs in
1min by maximal voluntary effort.
´The normal MPV is 125 to 170 L/min.

11. Distribution of Pulmonary ventilation
there are two main parts of the lung :
´1)dead space: which does not take part in gas exchange ,it subdivided
into
´a)anatomical dead space (airways) conducting zone of the respiratory
system nose, mouth, larynx, trachea, bronchi, and bronchioles (150ml).
´b) physiological dead space = airways + air in alveolar space but does
not exchange
´In healthy human physiological dead space = anatomical dead space.
´2)alveolar space, in which gas exchange takes place.

12. 1)dead space

15. Distribution of Pulmonary ventilation
1)alveolar ventilation:
it represent volume of gas exchanged between atmosphere and alveoli in one
minute.
Alveolar ventilation is less than pulmonary ventilation because not all the
gas moving in and out of the lungs gets down to the site of gas exchange in
the alveoli.
alveolar ventilation =(volume of gas breathed -volume of gas not
exchanged) * RR
= (500-150) 350 * RR= 4000 ml/min

16. Distribution of Pulmonary ventilation
2) dead space ventilation:
represents volume of gas exchanged b/n atmosphere and dead space in one
minute.
= 150* RR =2000 ml/min

17. Restrictive and Obstructive Disorders
obstructive pulmonary disease:
A group of lung diseases characterized by increased airway resistance
resulting from narrowing of the lumen of the (lower) airways.

18. Restrictive pulmonary disease:
inspiration is impaired. decreased lung compliance and increase of elasticity.
The vital capacity is reduced but the rate at which the vital capacity can be
forcibly exhaled is normal.

19. spirometry
Forced expiratory volume (FEV1):
FEV1 is the volume of air that can be expired in the first second of the forced
vital capacity (FVC).
■FEV1 is normally 80% of the forced vital capacity, which is expressed as:
FEV1/ FVC = 0.8.
■In obstructive lung disease, such as asthma, FEV1 is reduced more than
FVC so that FEV1/FVC is decreased.
■In restrictive lung disease, such as fibrosis, both FEV1 and FVC are
reduced and FEV1/FVC is either normal or is increased.

20. Refrences
•Guyton and Hall textbook of medical physiology 13
th
edition.
•Ganong’sReview of Medical Physiology twenty fourth edition.
•Fox Human Physiology 12th edition.