Development of lungs & pulmonary function test - simplified

1. Dr Chethan Channegowda
03-01-2018

2. ▪Primary goal : Large gas exchange area
Thin air - blood barrier
STAGES
1. Embryonic (3 -7 weeks)
2. Pseudoglandular( 5–17 weeks)
3. Canalicular (16–26 weeks)
4. Saccular ( 24–38 weeks)
5. Alveolar ( 36 weeks to 18 months postnatal )

3. FORMATION OF THE LUNG BUDS
▪Starts when Embryo is 4 weeks old .
▪Respiratory diverticulum (lung bud) appears as an
outgrowth from the ventral wall of the foregut .

4. TRIGGERS : Fibroblast growth factors (FGFs),
Retinoic acid from adjacent mesoderm
-Instructs endoderm to form respiratory diverticulum
- So all lining Epithelium are endodermal
- All connecting tisuue [muscle,cartilage ]are
mesodermal

5. In open connection with
foregut
expands caudally
Formation of
tracheoesophageal
ridge/groove
Dorsal esophagus ,
Ventral Trachea

6. ▪Abnormal partition of the esophagus and trachea by the
tracheoesaphageal septum result in esophageal atresia /
tracheoesaphageal fistulas (TEFs).
▪1/3000 births
▪Could be a component of VACTERL
▪Early signs
- Polyhydramnios
- Pneumonitis
- Pneumonia

8. ▪At 5th week – lung bud forms Trachea
Bronchial buds (2)

9. 5WEEKS
6WEEKS
8WEEKS

10. BRANCHING

11. ▪Concurrent DE-NOVO vasculogenesis by organisation of
vascular precursors
▪By the end of the embryonic stage, pulmonary arteries and
veins connect this plexus to the atria .
▪the pulmonary arteries and veins grow into the lung by
angiogenesis, with new branches arising from pre-existing
vessels.

12. •At this stage developing lung is having
characteristics of tubulo-acinus gland.
▪No respiratory bronchiole or alveoli
▪It is The stage of conductive airway formation.
▪ The entire air-conducting bronchial tree up to
the terminal bronchioli are set down in this phase

13. ▪This primordial airways are lined by CUBOIDAL cells
future ciliated epithelium and secretory cells
▪Type 2 Pneumocytes are first to appear !
▪Secretion of amniotic fluid begins in this phase.

14. ▪ Canaliculi form out of the terminal bronchiole
▪The canaliculi compose the proper respiratory part of
the lungs, the pulmonary parenchyma
▪ACINI is formed in this phase
- respiratory bronchiole
- alveolar ducts
- alveolar sacculi

15. Characteristic feature :
• alteration of the epithelium and the surrounding
mesenchyma.
• invasion of capillaries into the mesenchyma
• forms the foundation for the later exchange of gases
• The lumen of the tubules becomes wider and a part of
the epithelial cells gets flatter
• From the cubic type II pneumocytes develop
the flattened type I pneumocytes.
• Maximum amniotic fluid secretion
• Surfactant production starts

17. ▪Surface active agent – begins @ 24weeks
▪Type 2 pneumocytes (2%)
▪Lamellar bodies → storage granules
▪Composition
- PHOSPHOLIPIDS → PHOSPHOTIDYLCHOLINE
PHOSPHOTIDYLGLYCEROL
- NEUTRAL LIPIDS
- PROTEINS → SPA , SPB , SPC , SPD (help in spreading ,
reuptake )

19. ▪Last phases of air sacs , smooth walled coated with type 1 ,
type 2 cells
The capillaries multiply
around the acini.
Form a common basal
membrane with that of the
epithelium.

20. The blood-air barrier in the
lungs is reduced to 3 thin
layers :
• Type I pneumocyte
• Fusioned basal membrane
• Endothelium of the
capillary.

21. ▪ BIRTH – marks the end of saccular stage
▪ All generations of the conducting and respiratory
branches have been generated.
▪Alveolar type I cells continue to differentiate and
constitute an increased proportion of the distal lung
surface, thereby increasing the effective area for gas
exchange.

22. ▪True alveoli are generated from terminal saccules
▪Reduction in primary septae
▪Thinning and elongation of secondary septae
▪Alveolarisation continues till 18 months
▪Septation leads to inc from 30million to 300 million !

26. ▪ Langman’s Medical Embryology

27. ▪ Battery of tests carried out using standardized equipments to measure lung
function.
▪ Diagnose
▪ Nature
▪ Progression/severity
▪ Effectiveness of Rx

28. ▪ BED SIDE PULMONARY FUNCTION TESTS
▪ STATIC LUNG VOLUMES & CAPACITIES – VC, IC, IRV, ERV, RV, FRC.
▪ DYNAMIC LUNG VOLUMES
▪ GAS‐ EXCHANGE TESTS

29. SABRASEZ BREATH HOLDING TEST
▪ Ask the patient to take a full breath & hold it as long as possible.
• >25 SEC.‐NORMAL Cardiopulmonary Reserve (CPR)
• 15‐25 SEC‐ LIMITED CPR
• <15 SEC‐ VERY POOR CPR

30. ▪ SCHNEIDER’S MATCH BLOWING TEST:
▪ To assess Maximum Breathing Capacity
▪ To blow a match stick @ 15 cms
▪ Mouth wide open
▪ No purse lipping
▪ No head movement
▪ Mouth and match at the same level

31. ▪WRIGHT PEAK FLOW METER: Measures PEFR (Peak Expiratory Flow Rate)

32. ▪ Portable
▪ Monitoring changes in airflow limitation in asthma
▪ Response to treatment
▪ Disadvantage
• Effort dependent
• Underestimates the severity in acute asthma.

33. As subject blows → whistle blows, leak
hole is gradually increased till the
intensity of whistle disappears.
At the last position at which the whistle
can be blown , the PEFR can be read
off the scale.

34. ▪ SPIROMETRY : CORNERSTONE
OF ALL PFTs.
▪ John Hutchinson
▪ Measures the volume of air an
individual inhales or exhales
as a function of time.”

35. ▪GOLD std Asthma (diagnose/ monitor)
▪Children with chronic cough, persistent wheezing .
▪Obstructive vs Restrictive
▪Monitor thalessemics , SCA , CTDs
▪Kids with chest deformity
▪preoperative lung function
▪To screen school children

36. CONTRAINDICATIONS
▪ Respiratory tract infection
▪ Pneumothorax
▪ Hemoptysis
▪ Recent thoracic , eye , abd sx

37. - Name , ID,weight , height , sex to be entered
in software
- Atleast 3 tests of good effort – reproducible
- Lack of artefact – cough , leak , glottic closure
- Good start (no cough / hesitation)
- Satisfactory exhalation : min 6 sec ,
continuous , plateau
- Loose clothing
- Light meal
- No bronchodilator / exercise

38. ▪ Sitting/Standing
▪ Nose clip
▪ Disposable mouthpiece
inhale deep → blow as fast as possible → continue to blow → till no air is left
No pause / cough
Fast and forcefull
# In preschool children (2–6 years of age), nearly 82.6% (214/259) of
children aged 3–6 years

39. ▪ MODFICATION IN PRESCHOOL CHILDREN (2-6Y) BY ATS/ERS
▪ Small initial volume is sufficient
▪ No need of plateau
▪ Smooth decending curve is sufficient
▪ 2 spirograms is enough (FVC diff of <100ml)

40. (1) Acceptability and repeatability
(2) identifying the spirometry pattern (normal, obstructive, restrictive,
or mixed)
(3) grading the severity of the pattern identified
(4) diagnosing and treating the condition or investigating further.

44. Four Lung volumes
Tidal volume
Inspiratory Reserve Volume
Expiratory Reserve Volume
Residual Volume
Five capacities
Inspiratory Capacity
Expiratory Capacity
Vital Capacity
Functional Residual Capacity
Total Lung Capacity

45. ▪ Tidal Volume (TV): volume of air inhaled or exhaled with each breath during quiet
breathing (6‐7 ml/kg)
▪ Inspiratory Reserve Volume (IRV): maximum volume of air inhaled from the end
inspiratory tidal position .
▪ Expiratory Reserve Volume (ERV): maximum volume of air that can be exhaled
from resting end‐expiratory tidal Position.
▪ Residual Volume (RV):Volume of air remaining in lungs after maximium exhalation
(20‐25 ml/kg)

46. ▪ Total Lung Capacity (TLC): Sum of all volume compartments or volume of air in
lungs after maximum inspiration
▪ Vital capacity (VC): the greatest volume of air that can be expelled from the lungs
after taking the deepest possible breath. (60‐70 ml/kg)
▪ Inspiratory capacity : IRV + TV
▪ Expiratory capacity : ERV + TV
▪ Functional Residual Capacity (FRC):is the volume of air present in the lungs at the
end of passive expiration.

47. FUNCTIONAL RESIDUAL CAPACITY (FRC)
Outward recoil of CHEST WALL = inward recoil of LUNG
No exertion by the diaphragm or other respiratory muscles.
FRC = ERV + RV
It cannot be estimated through spirometry
Measured by nitrogen washout, helium dilution or body plethysmography.

51. POOR EFFORT COUGH Premature finish
+
Restart

55. 55
▪ Obstructive
▪ Restrictive
▪ Mixed

56. 56
▪ Interpretation of % predicted:
▪ 80 % Normal
▪ 70-79% Mild reduction
▪ 50%-69% Moderate reduction
▪ <50% Severe reduction

57. 57
▪ Interpretation of % predicted:
▪ >80% Normal
▪ 65-79% Mild obstruction
▪ 50-64% Moderate obstruction
▪ <49% Severe obstruction

58. 58
% predicted
FVC > 80%
FEV1 > 80%
FEF25-75% > 70%
PEFR > 80%
FEV1/FVC > 80% absolute value

61. ▪ Characterized by a
limitation of expiratory
airflow
➢Asthma
➢Emphysema
➢Cystic Fibrosis
➢Mucus secretions
➢Bronchospasm

62. ▪ Characterized by
diminished lung volume
▪ Reduced compliance
▪ Decreased TLC, FVC
▪ Normal or increased:
FEV1/FVC ratio
▪ Interstilial lung disease
▪ Scoliosis
▪ Neuromuscular ds

63. ▪Obstructive Disorders
▪FVC N or ↓
▪FEV1 ↓
▪FEF 25-75% ↓
▪FEV1/FVC ↓
▪TLC nl or ↑
▪Restrictive Disorders
▪FVC ↓
▪FEV1 ↓
▪FEF 25-75% nl to ↓
▪ FEV1/FVC nl to ↑
▪ TLC ↓

66. ▪ Diffusion capacity of lung for CO
▪ CO – has high affinity to Hb ,Tracer gas
▪ Diffusion α capillary flow , Hb conc , membrane thickness
▪ DLCO = CO Uptake in ml/min
Alveolar pressure of CO

67. ▪Fowler method
▪Breathes 100% oxygen, and all nitrogen in the lungs
is washed out.
▪The exhaled volume and concentration of N2 is
measured.
▪ To measure FRC , Closing volume .

68. - Patient breathes into pneumo-tachometer
▪ Based on BOYLE’s LAW : V α 1/ P
@ constant temp
▪ Airway Resistance
▪ Airway conductance

69. ▪ Almost independent of patient cooperation
▪ Valid for all ages from 4 years and older children, adult
▪ Quite breathing i.e Tidal volume breathing for 30 seconds
▪ Measures impedance at different frequencies indicative of central and peripheral
airway resistance