PPT for Difference

1. Respiratory System:
Anatomical and Physiological differences
between adults and children
Robyn Smith
Department of Physiotherapy
UFS
2012

2. Learning outcomes
• At the end of this module the learner should:
Be able to identify both key anatomical and
physiological differences between the respiratory
systems of child and a adult
Understand and explain the impact of these
differences on the clinical findings, observations
and respiration of a child
Describe the impact of preferential nasal breathing
on respiration in babies

3. The main reason for
hospital admissions
in children under
the age of 4 years
worldwide is
respiratory illness

4. Important to understand
children are not simply
mini adults

5. Background
• The respiratory system of children differs both
anatomically and physiologically from that of
adults
• These differences have important
consequences for the physiotherapy care of
children in terms of assessment, treatment
and choice of techniques

6. Background
• The principles of adult chest physiotherapy
cannot be directly transposed to a child.
• Chest physiotherapy as provided to children has
become a specialised area on its own for this
reason

7. Chest wall anatomy

8. Muscles of the chest wall

9. Mechanics of respiration
• Air moves in and out of the lungs due to
changes in pressure gradients created by
movement of the chest wall and muscular
action
• Inspiration active process
– Diaphragm
– Intercostals
– Accessory muscles
• Expiration is passive
• Forced expiration involves abdominal muscles e.g.
cough

10. Components of respiratory system
• Most of the components of the respiratory
system are present at birth but
– are underdeveloped,
– and immature
• This poses certain challenges to the child
regarding breathing

11. Development of the respiratory
system

12. ANATOMICAL DIFFERENCES

13. Anatomical differences include:
• The chest or thorax
– Shape
– Ribcage
– Mechanism of breathing
• Breathing pattern
• Diaphragm
• Internal organs
• Airway diameter
• Bronchial walls
• Surfactant
• Alveoli
• Collateral ventilation
• Exposure to toxins and
allergens

14. Thorax: Chest shape
• Cross sectional area of the thorax is
cylindrical and not elliptical as in adults

15. Infant chest shape
• Anterior view • Lateral view

16. Thorax: Ribcage
• The ribcage of the newborn and infant is
relatively soft and cartilaginous
compared to the rigid chest wall of older
children and adults
• Ribs run horizontally to the vertebrae
and sternum compared to the more
oblique angle of older children and
adults.

17. Thorax: Ribcage
• The bucket handle movement of ribcage
as seen in older children and adults is
therefore not possible.
• This mechanism is used to increase lung
volumes during
inspiration.

18. Thorax: Ribcage
• Infant can therefore only increase the anterior-posterior
or transverse diameter of their chest
• The intercostal muscles are inactive and poorly
developed in infancy.
• The abdominal muscles are not yet stabilising the
ribcage (only from about 3-4 months)
• The interaction of gravity and the musculoskeletal
system play an important role in the development of the
thorax.

19. Thorax.... clinical implications
• With the limited chest expansion the child can only
increase their lung volumes by increasing their
respiration rate, this explains why small children have
a higher RR than adults
• NB!!!! No head down position for postural drainage
premature infants or neonates (1month).
Even older infants need to monitored on how they
copes when put in a head down position.
• Infants are diaphragmatic breathers, therefore they
are positioned in a head up position to ease the work
of breathing

20. Thorax.... clinical implications
• Premature infants & children with hypotonic need to be
positioned correctly to avoid chest deformities e.g.
scoliosis or kyphosis
• Rib flaring and a high riding ribcages are common in
children with weak abdominal muscles and children with
cerebral palsy as it does not anchor and pull down the
ribcage
• Infants with chronic cardio-respiratory conditions
associated with prematurity or CHD paradoxal breathing
may occur over a long period of time resulting in chest
deformities forming over time e.g. pectus excavatum or
carniatum because the chest wall is still so pliable.

21. Abnormal chest forms
• Flaring ribs • Barrel chest

22. Abnormal chest forms
• Pectus carniatum • Pectus excavatum

23. Postural deformities
• Scoliosis • Kyphosis

24. Preferential nasal breathing
• Shape and orientation of the head and neck in
babies means that the airway prone to
obstruction
• NB!!! Infants up to about 6 months are
preferential nose breathers

25. Preferential nasal breathing
...clinical implications
• Children with upper respiratory tract infections and
nasal secretions may have compromised respiration if
the nose is blocked
• Constant oxygen therapy dries out the mucociliary
escalator.
• As physiotherapists we need to ensure adequate
humidification e.g. saline inhalations or saline nose
drops and
• Keep the nose clear by suctioning or aspiration

26. Preferential nose breathing

27. Diaphragm
• Angle of insertion of the diaphragm in infants is
more horizontal
• Diaphragm works at a mechanical disadvantage
• Diaphragm in infants has a lower-content of
high-endurance muscle fibres and also more
susceptible to fatigue

28. Diaphragm
• The diaphragm is the most important inspiratory
muscle in children due to the immaturity and
inactivity of the intercostal muscles
• Weak accessory muscles and the abdominals as
well in small babies

29. Diaphragm...clinical implications
Ventilation is compromised in
infants where the function of
the diaphragm is impaired:
Examples of such cases
include:
– abdominal distension
– Phrenic nerve paralysis
– When placed in the head down
position
– Congenital diaphragmatic hernia

30. Internal organs
• Heart and other organs are relatively large
in relation to the infants size

31. Internal organs... clinical
implications
This leaves less place for chest expansion

32. Airway diameter
• Trachea is short and narrow about a 1/3 of
diameter adult in neonate.
• Generally all airways are narrower.
• This makes respiratory resistance higher and the
work of breathing greater.
• Narrowest part of the airway is
the cricoid ring
• Right bronchus less angled
• During the first few years of life
there is significant growth in the
diameter of the airways

33. Airway diameter...clinical
implications
• Tracheal swelling as a result of intubation can
heighten the resistance
• Inflexible cricoid ring leaves child more vulnerable
to post extubation mucosal oedema and stridor
• Children are often intubated into
the right bronchus resulting in
collapse of left lung
• Children more likely to have
tracheal injury after intubation
(stenosis/ulceration)

34. Bronchial walls
• Bronchial walls are supported by cartilaginous
rings. However the support provided in children
is far less than in adults making airways more
prone to collapse
• The bronchial wall has proportionally more
cartilage, connective tissue and goblet cells
than in adults and less muscle tissue is present
• Beta adrenergic receptors are immature

35. Bronchial walls...clinical
implications
• Airways are more prone to collapse
• Lung tissue less complaint
• Less smooth muscles makes them less
responsive to bronchodilator therapy until the
age of 12 years (but especially in the first 1-2
years of life)

36. Cilia
• At birth cilia are poorly developed

37. Cilia
Clinical implication...
• Ineffective mucociliary
escalator
• Risk of secretion retention
and airway obstruction is
greater in premature
infants and neonates

38. Primary Ciliary Dyskinesia
• Rare genetic disorder
• Also known as Kartagener’s
Syndrome
• Cilial motility is severely
reduced
• Due to structural defect in
the cilia
• Results in recurrent sinusitis
or bronchiectasis due to the
impaired sputum clearance

39. Surfactant
• Surfactant is a phospholipid produced by the
type II pneumocytes in the lungs
• Function is to reduce the surface tension at the
air liquid interface in the alveoli making it easier
to expand the alveoli
• Secreted from 23 weeks gestation, with a surge
in production at 30-34 weeks as the lungs
become fully mature

40. Surfactant.... clinical implications
• Premature infants have insufficient
surfactant resulting in:
– ↑ surface tension with alveoli that are difficult
to expand
– ↑ Work of breathing
– more easily develop respiratory distress and-
failure than adults
– More easily develop atelectasis/lung collapse

41. Alveoli
• Very few, small alveoli are present at birth
• Alveoli develop after birth in terms of
increasing numbers and in size.
• The majority of the development occurs
within the first 2 years.
• Alveoli are important for gaseous
exchange

42. Alveoli structures critical to
gaseous exchange

43. Alveoli....clinical implications
• Smaller alveoli in infants make them more
susceptible to collapse and atelectasis
• Smaller alveoli also provides a smaller area for
gaseous exchange

44. Collateral ventilation
• Ensures that distal lung units are ventilated
despite the obstruction of a main airway
• The collateral ventilatory channels are poorly
developed in children under 2-3 years

45. Collateral ventilation.... clinical
implications...
• Makes the child more susceptible to
alveolar collapse

46. Height and exposure to pollution
• Children have a higher
RR, spend more time
outdoors exposing them to
allergens and pollutants
• Their height also exposes
the child to other
pollutants e.g. exhaust
fumes
• Passive smoking

47. PHYSIOLOGICAL
DIFFERENCES

48. Physiological differences include:
• Lung compliance
• V/Q matching
• Closing volume
• Oxygen consumption
• Muscle endurance
• Breathing pattern

49. Lung compliance
• Measure of the pressure required to increase
the volume air in the lungs
• Combination of lung- and chest wall
compliance
• Lung compliance in a child is comparable to
an adult and is directly proportional to the
child’s size
• Compliance in a child is reduced by the high
proportion of cartilage in the airways
• Premature infants with insufficient surfactant
show reduced compliance

50. Chest wall compliance
• The chest wall of the infant is cartilaginous and
very soft and compliant.
• In the case of respiratory distress the chest is
drawn inwards. Substernal, subcostal and
intercostal recession is common in such
cases.
• This is the reason for paradoxal breathing, if
this persists over long period of time it can
result in chest deformities

51. Closing volume
• Lung volume at which the small airways close
• In infants the closing volume is greater than the FRC,
airway closure may thus occur before the end of
expiration, a consideration when using manual
techniques e.g. Vibrations. One may further reduce the
lung volumes resulting in widespread atelectasis
• In respiratory distress children grunt (adducting the
vocal cords) in an attempt to reduce the expired volume
of air in order to minimise alveolar collapse
• It is harder to re-inflate collapsed alveoli in children

52. Ventilation & perfusion
• Ventilation and perfusion in both adults and children
are preferentially distributed to the dependant lung.
• The best ventilation/perfusion and gaseous exchange
will occur in the dependent lung areas.
• In child the ventilation is best in the uppermost lung
whilst perfusion remains best in the dependent area,
resulting in a natural V/Q mismatch
• Clinically significant in unilateral lung disease where
the affected lung is placed uppermost for postural
drainage but impairs ventilation perfusion matching.

53. Ventilation & perfusion
• Children have a natural ventilation perfusion
mismatch.
• The difference in ventilation distribution in infants is
due to compliance of the ribcage, compressing the
dependent areas of the lung.
• In adults the abdominal content provides a
preferential load on the dependant diaphragm,
improving its contractility.This does not happen in
the infant die to the smaller and narrower abdomen.

54. Oxygen consumption
• Infants have a higher resting metabolic rate than an adult
• Higher oxygen consumption rate, therefore they develop
hypoxia more quickly
• Infants respond to hypoxia with
bradycardia and pulmonary
vasoconstriction whilst adults
become tachycardic and systemic
vasoconstriction

55. Muscle fatigue
• Respiratory muscles of infants tire
more easily than that of an adult
due to the smaller proportion of
fatigue resistant type I muscle
fibres (30%) in their diaphragms
than in adults (55%).
• This proportion is brought inline
with that of an adult by the age of 1
year.
• Excessive muscle fatigue in infants
results in respiratory distress and
apnoea.

56. Breathing pattern
• Irregular breathing and episodes of apnoea are
more common in neonates and premature
infants and is related to immature
cardiorespiratory control centre of the brain

57. References
• Smith, M. & Ball, V. 1998. Paediatric Management in
Cardiovascular/Respiratory Physiotherapy. Mosby,
London pp 254-256
• Ammani Prasad, S & Main, E. 2009. Paediatrics in
Physiotherapy for respiratory and cardiac problems.
Adults and children. Pryor, J.A. & Ammani Prasad, S
(eds.) 4th ed. Churchill Livingstone elsevierEdinburgh pp
330-335

58. References
• van der Walt, R. 2009. Development of the chest wall
presented at the Baby NDT course 2010, Bloemfontein
(unpublished)
• Images courtesy of GOOGLE images