Lung volumes and capacities refer to the amount of air in the lungs during respiration. Lung volumes are directly measured using spirometry, while lung capacities are inferred from volumes. There are four main lung volumes: tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume. Various lung capacities are combinations of these volumes and measure the maximum amounts of air that can be inhaled or exhaled. Common lung capacities include inspiratory capacity, expiratory capacity, functional residual capacity, vital capacity, and total lung capacity. Spirometry is used to measure volumes and capacities to assess respiratory muscle strength and diagnose pulmonary diseases.

2. ⦿Lungvolumes and lung capacities refer
to the volume of air associated with
different phases of the respiratory cycle.
⦿ Lung volumes are directly measured;
Lung capacities are inferred from lung
volumes
⦿Instrument isspirometry

3. ⦿Four types
1. Tidal volume
2. Inspiratory reserve volume
3. Expiratory persevere volume
4. Residual volume

4. ⦿Normal volume of air inspired or expired
during quiet breathing
⦿TV =500 ml

6. ⦿Extra volume of air inhaled after tidal
volume by max inspiratory effort
⦿3000ml in adult male
(or)
⦿3300 / 1900 =M/F

7. ⦿Extra volume of air that can be exhaled
after tidal volume by max expiratory
efforts
⦿1100 in a normal adult male
(or)
⦿1200/700 =M/F

8. ⦿Volume of the air left out in lungsafter
forceful expiration or complete
expiration
⦿1200/1100 =M/F

10. ⦿These are combinations of two or more
lung volumes
1
. I
nspiratory capacity
2. Expiratory capacity
3. Functional residual capacity
4. Vital capacity
5
. T
otal lung capacity

11. ⦿Max volume of air that can be inspired
after normal tidal expiration
⦿IC =TV+IRV
= 500 +3000
=3500 ml

12. ⦿Max volume of air that can be expired
after normal tidal inspiration
⦿EC=TV+ERV (500+1100=1600ml)

13. ⦿Volume of air remaining in lungsafter
normal tidal expiration
⦿FRC= ERV +RV ( 1100 +1200 =2300ml)

14. ⦿Significance ?
› Continues exchange of gases
› So that conc of O2 and CO2 ismaintained
› Breath holding ismade possible
› Dilution of toxic inhaled gases
› Prevents colapse of lungs
› reduces workload of respiratory muscles
and rt ventrcle

15. ⦿ Old age
⦿Obstructive and restrictive lung diseases

16. ⦿Max Amount of air expelled after
deepest possible inspiration
⦿VC =TV+IRV+ERV
⦿500+3000+1100=4600ml

17. ⦿ To asses strength of respiratory muscles
⦿Factors affecting VC
› Age
› Sex
› Strength of respiratory muscles
› Gravity
› Pregnancy
› Ascites
› Pulmonary diseases

18. ⦿Volume of air present in lung after max
inspiration
⦿TLC =VC +RV ( 4600+1200 =5800ml )

21. ⦿Timed vital capacity or FVC
⦿FVC isvolume of the air that can be
expired rapidly with max force following
a max inspiration , and itstimed by a
spirograph

22. ⦿FEV1 –volume of air expired in the first
second of FVC
⦿Fev1 isflow rate
⦿Fev1 isexpressed in percentage
⦿Fev1 =80%
⦿Fev2 =90 %
⦿Fev3 =98-100 %
⦿

23. 0 3
5000
4000
3000
2000
1000
0
1 2
Time (sec)
Volume
(ml)
FEV1 = (5000 ml -1000 ml) / 5000ml
= 4000 ml / 5000 ml
= 80%

24. ⦿Low in obstructive lung diseases
⦿ Normal or high in restrictive lung diseases

25. ⦿It’s the mean expiratory flow rate during
the middle 50%of FVC
⦿Normal is300L/min in 0.5 sec

27. ⦿Aka pulmonary ventilation
⦿Volume of air inspired or expired per
minute
⦿RMV =TV *RR ( 500*12 =6000 ml)
⦿6 –7.5 L/min

28. ⦿ Aka MVV
⦿ Max volume of air that can be ventilated
voluntarily for given interval of time
⦿ Subject asked to breath rapidly and deeply
, for 15 seconds
⦿ Recorded by a spirometer or Douglas bag
⦿ Normal is80- 170 L/min
⦿ Reduced in pt with emphysema and
respiratory muscle weakness

29. ⦿Maximum amount of air above the PV
that can be inspired or expired in one
min
⦿PR =MVV –PV
⦿Pulmonary reserve is expressed as %
of
MVV and isknown as dyspnoeic index

30. ⦿ Normal DI is60 –90%
⦿Average of 75%
⦿Importance is dyspnoeia results when DI
becomes lessthan 60%