1. Static lung volumes include tidal volume, inspiratory reserve volume, expiratory reserve volume, residual volume, vital capacity, inspiratory capacity, functional residual capacity, and total lung capacity. 2. Dynamic lung volumes include maximum voluntary ventilation and forced expiratory volume, which measure the maximum volume of air that can be moved in and out of the lungs over time. 3. Pulmonary ventilation is the amount of air inhaled or exhaled during normal breathing per minute, while alveolar ventilation is the volume of fresh air entering the respiratory zone and participating in gas exchange.

1. Pressure Changes
during ventilation, Lung
volumes and capacities
Dr. Sai Sailesh Kumar G
Assistant Professor
Department of Physiology
RDGMC

2. Ondine’s Curse
An infant named Yatharth is under treatment at
Delhi’s Sir Ganga Ram Hospital is suffering from a
rare disease, called Congenital Central
Hypoventilation Syndrome (CCHS).

3. Ondine’s Curse
1. Congenital central hypoventilation syndrome
2. Very rare disease (1000 cases through out world
approx.)
3. Breathing may be normal when awake
4. Automatic control over breathing is lost.
5. If fall asleep stops breathing and lose life
6. Mutation in the gene PHOX2B responsible for
development of nerve cells that control breathing.

4. Pressure changes
1. Atmospheric pressure / Barometric pressure –
760 mmHg
2. Intra pulmonary / Intra alveolar pressure – 760
mmHg (can be positive or negative)
3. Intra pleural pressure – 756 mmHg (always
negative)

5. Pressure changes
1. Atmospheric pressure / Barometric pressure is 0
mmHg
2. Intra pulmonary / Intra alveolar pressure is 0
mmHg
3. Intra pleural pressure is -4 mmHg (always
negative)

6. Intra pulmonary pressure
The pressure developed inside the alveoli is
called intra pulmonary pressure
As alveoli are in connection with the
atmosphere, at the end of normal expiration,
intra pulmonary pressure is equal to
atmospheric pressure.
Atmospheric pressure, which is equal to 760
mmHg, is taken as zero atmospheres.

7. During different phases of respiration

8. Intra pulmonary pressure
 At the beginning of inspiration, the intra pulmonary
pressure is equal to atmospheric pressure. (0 mmHg)
 During inspiration lungs will expand
 Increase in the lung volume
 Decrease in the intra pulmonary pressure ( Boyle’s law)
 Intra pulmonary pressure decreases and becomes -1 at
mid inspiration (less than atmospheric pressure)

9. Intra pulmonary pressure
 At the middle of inspiration, as the intra pulmonary
pressure is sub-atmospheric, air enters the lungs
 Down the pressure gradient
 Till the pressure on both sides becomes equal
 By end of inspiration, intra pulmonary pressure and
atmospheric pressure becomes equal (0 mmHg)

10. During different phases of respiration

11. Intra pulmonary pressure
 At the beginning of expiration, the intra pulmonary
pressure is equal to atmospheric pressure. (0 mmHg)
 During expiration lungs will recoil
 Decrease in the lung volume
 Increase in the intra pulmonary pressure ( Boyle’s law)
 Intra pulmonary pressure decreases and becomes +1
at mid inspiration (more than atmospheric pressure)

12. Intra pulmonary pressure
 At the middle of expiration, as the intra pulmonary
pressure is more than atmospheric pressure, air moves
out the lungs.
 Down the pressure gradient
 Till the pressure on both sides becomes equal
 By end of expiration, intra pulmonary pressure and
atmospheric pressure becomes equal (0 mmHg)

13. Intra pleural pressure
It is the pressure developed in between the two
layers of pleura.
This pressure is always sub-atmospheric i.e., it
is always negative.
Atmospheric pressure, which is equal to 760
mmHg, is taken as zero atmospheres.
Normal intra pleural pressure is -4 to -7 mm Hg

14. Negative intra pleural Pressure
 Three reasons
1. Elasticity of the lungs – Offer resistance to
stretch. It always tries to recoil the lungs (deflate).
It pulls visceral pleura away from parietal pleura.
2. Surface tension – Develops due to air water
interface. Always tries to collapse the lungs. Pulls
visceral pleura away from the parietal pleura.

15. Negative intra pleural Pressure
 Three reasons
1. Elasticity of the chest wall – Push the chest wall.
Tries to expand the chest wall. Pulls parietal pleura
away from visceral pleura.
 Because of the dynamic interplay between these
forces (harmonious antagonism), the volume of the
pleural cavity increases. As per Boyle’s law, the
pressure in the pleural cavity decreases and
becomes negative.

16. Negative intra pleural Pressure
1. Bring two glass slides
2. Put a drop of water between them
3. Try to pull them apart
4. You cant.. Why?
5. When you pull away, negative pressure is
created between them which prevents you from
pulling them apart.

17. During different phases of respiration

18. Variations in Intra pleural
pressure
 When two surfaces comes close to each other,
they create positive pressure
 When two surfaces moves away from each
other, they create negative pressure

19. Variations in Intra pleural
pressure
 During inspiration, chest wall expands and moves away
from the lungs – intra pleural pressure becomes more
negative.
 This negative pressure helps for entry of air into the
lungs
 During expiration, chest wall recoils and moves closer to the
lungs – intra pleural pressure becomes less negative.

20. Will intra pleural pressure
becomes positive
 Yes
 Stab wound to the chest. Pressure in the pleura
becomes equal with atmospheric pressure
 Valsalva Maneuver – Forced expiration against
clossed glottis. Eg: Micturition, defecation,
child birth etc.

21. Intra pleural pressure and
esophageal pressure
 Esophageal pressure must be equal to intra pleural
pressure
 If the esophageal pressure is more than intra
pleural pressure, the esophagus expands
 If the esophageal pressure is less than intra pleural
pressure, the esophagus collapse

22. Measurement
Pleural pressure is measured as esophageal
pressure (PES) through dedicated catheters
provided with esophageal balloons.
It requires placing a nasogastric balloon-
tipped catheter into the distal esophagus,
which registers pleural pressure changes.

23. Importance of negative
Intra pleural pressure
It increases venous return. During inspiration,
the increased negative pressure in the
mediastinum helps to suck the blood from
periphery towards great veins and to the heart.
Maintains alveolar stability
Keeps the airways open
Prevents collapse of lungs

24. Trans pulmonary pressure
 Intra pulmonary pressure – Intra pleural
pressure.
 Trans pulmonary pressure = 0 mm H g- (-4 mmHg)
 +4 mmHg
 This is positive pressure which helps the lungs to
inflate.

25. Trans respiratory pressure
 Intra pulmonary pressure – Atmospheric
pressure.
 Trans respiratory pressure = 0 mm Hg- (0mmHg)
 0 mmHg

26. Trans thoracic pressure
 Intra pleural pressure – Atmospheric pressure.
 Trans thoracic pressure = (-4 mmHg) – 0 mmHg
 -4 mmHg
 This is negative pressure which helps the lungs to
deflate.

27. Lung volumes and capacities
Spirometry - technique
Spirometer - device
Spirogram - record.
Hutchinson devised spirometer in 1846

28. Spirometer

29. Procedure
 The subject is asked to breath normally through a mouth
piece connected to the spirometer and the volume of the
air that is taken in or given out with each normal breath is
recorded.
 The subject is asked to inhale maximally and then to
exhale rapidly and completely into the mouth piece.
 It should be taken care that the subject nose is clipped
properly so that he breath only through the nose piece.
 Time on x axis and volume in mL in the y axis.

30. Lung volumes and capacities
Lung volumes and capacities are divided into
1. Static lung volumes and capacities
2. Dynamic lung volumes and capacities

31. Spirogram

32. Static Lung volumes
1. Static lung volumes are lung volumes
whose values do not change with time

33. Static lung volumes and
capacities
Lung volumes
 Tidal volume (TV)
 Inspiratory reserve
volume (IRV)
 Expiratory reserve
volume (ERV).
 Residual volume (RV)
Lung capacities
 Vital capacity (VC)
 Inspiratory capacity (IC)
 Functional residual
capacity (FRC)
 Total lung capacity
(TLC)

34. Tidal volume
1. Volume of air inspired or expired during normal
breath
Normal values
 Newborn – 15-20 mL
 Males – 600 mL
 Females – 450 mL

35. Inspiratory reserve volume
1. Extra volume of air that can be inspired over
and above the normal tidal volume
Normal values
3-3.2 mL

36. Expiratory reserve volume
1. Extra volume of air that can be expired by
forceful expiration at the end of normal
expiration
Normal values
1.1 mL

37. Residual volume
1. Volume of air remaining in the lungs even after the
most forceful expiration.
2. This volume can not be measured by spirometry
Normal values
 1.2 mL

38. Functions of Residual volume
1. It acts as a buffer in between the breaths to
accelerate the pulmonary capillary blood
2. Medico legal importance- To detect the
baby was still born (born dead) or born
alive.

39. Lung capacities
1. Lung capacities are combination of specific
lung volumes

40. Inspiratory capacity
1. The volume of air that can be inspired by a
forceful effort after a normal expiration
2. IC = TV + IRV
Normal values
3500 mL

41. Functional residual capacity
1. Volume of air remaining in the lungs after a
normal expiration
2. FRC = ERV + RV
Normal values
2300 mL

42. Importance of FRC
1. It helps in the continuous exchange of gases
between lungs and blood in between two
breaths
2. It prevents marked raise or fall in the
concentration of blood gases in between the
breaths

43. Total lung capacity
1. The volume of air in the lungs after maximum
inspiration
2. TLC = TV + IRV+ERV+RV
Normal values
 6000 mL
 TLC decreases in pulmonary edema and
pneumothorax

44. Vital capacity
1. Volume of the air that can be expired rapidly
and forcefully after maximum inspiration
2. VC = IRV + TV + ERV
Normal values
4600 mL

45. Factors affecting vital capacity
1. Age- VC is maximum in young adults
2. Sex- VC is more in males
3. Height – VC varies with height
In males – Height in cm x 25 mL
In females – Height in cm x 20 mL

46. Factors affecting vital capacity
4. Posture- VC is maximum when the person
is seated in a slightly reclined posture. VC is
decreased in lying down and standing posture

47. Variations in vital capacity
1. Physiological decrease - In pregnancy, due
to inability of diaphragm to move down
satisfactorily, there will be decrease in VC.
2. Pathological decrease –
 Neurological diseases affecting muscles of respiration
like poliomyelitis
 Diseases of muscles like myasthenia Gravis
 Diseases of lung and pleura

48. Importance of vital capacity
1. VC has prognostic value during treatment of
respiratory problem. If the vital capacity increases
with the treatment it means that the patient is
responding to the treatment.
2. We can assess the progress of chronic diseases like
emphysema. If there is a rapid reduction in the vital
capacity, it means the disease is rapidly progressing
and mortality is higher.

49. NOTE
TLC, FRC and RV cannot be measured using
an ordinary spirometer since RV cannot be
expelled out.

50. Dynamic lung volumes and
capacities
1. Maximum voluntary ventilation (MVV)
2. Forced expiratory volume or Timed vital
capacity (FEV or TVC)

51. Maximum voluntary ventilation or
Maximum ventilator volume or
Maximum breathing capacity
1. Maximum volume of air that can be moved
in and out of the lungs in one minute by
maximum voluntary effort
Normal values
125- 170 L/ min

52. Timed vital capacity
1. It is the fraction of vital capacity that is expired
during the first sec (FEV1), during second sec
(FEV2) and during third sec (FEV3) of forced
expiration
Normal values
FEV1= 83%, FEV2= 93%, FEV3=97%

53. Importance of Timed vital
capacity
1. In the early stages of many chronic diseases
like emphysema, VC may remain with in
normal limits but TVC shows abnormality. So it
helps in the early detection of diseases like
emphysema.
2. TVC is a very important index to differentiate
between obstructive and restrictive diseases.

54. Importance of Timed vital
capacity
Restrictive diseases are those which restricts
the movement of thoracic cage or lungs like
kyphosis.
Obstructive lung disease eg: bronchial
asthma, COPD ( problem in the bronchi,
bronchioles)

55. Importance of Timed vital
capacity
Type of lung
disease
Vital
Capacity
Timed Vital
Capacity
Obstructive Normal Decrease
Restrictive Decrease Normal

56. Ventilation
1. Ventilation is a cyclic process by which there is
mass movement of air in and out of the lungs.
Ventilation is divided into two.
Pulmonary ventilation / Respiratory minute
volume / Minute ventilation
Alveolar ventilation

57. Pulmonary Ventilation
1. Amount of air that is taken in or given out
during quiet normal respiration for 1 min.
Pulmonary ventilation = TV x RR
RR= Respiratory rate
500 x 12 = 6000 mL/min

58. Alveolar Ventilation
1. Volume of the fresh air entering the
respiratory zone in one minute.
Alveolar ventilation = (TV – RDS) X RR
RR= Respiratory rate
(500 – 150 mL) x12 = 4.2 L/min

59. Respiratory dead space
1. Portion of tidal volume that do not take part
in gas exchange is respiratory dead space.
It is divided into
Anatomical dead space
Physiological dead space

60. Respiratory dead space
1. In normal subjects
Anatomical dead space = Physiological dead
space.
2. In patients with lung disease the
physiological dead space will be larger due to
inequity of blood flow and ventilation in lungs.

61. Anatomical dead space
Volume of air in the respiratory passages
from nose to terminal bronchiole which do
not take part in gas exchange. (conducting
zone)
Normal volume 150 ml in a person weighing
150 pounds

62. Alveolar dead space
It is the air in the non-functional alveoli
Non functional- under perfused or non-
perfused alveoli ( pulmonary embolism)
Normally alveolar dead space is 0 mL
There should not be any alveolar dead space

63. Physiological dead space
 Volume of air in the respiratory system that is not
equilibrating with blood.
 Physiological dead space= Anatomical dead space +
Alveolar dead space
 Normally Physiological dead space = Anatomical dead
space
 If Physiological dead space > Anatomical dead space it
indicates alveoli are ventilated but not perfused properly

64. Variations in dead space
Age – As age advances, there is increase in the
anatomical dead space due to loss of elasticity
of respiratory system
Sex – In females anatomical dead space is less
than males due to decrease body size.
Posture - anatomical dead space is decreased
in lying down posture.

65. THANK YOU