Paediatric Respiratory Reviews 15 (2014) 246–255
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Paediatric Respiratory Reviews
CME article
Chest Wall Abnormalities and their Clinical Significance in Childhood
Anastassios C. Koumbourlis M.D. M.P.H.*
Professor of Pediatrics, George Washington University, Chief, Pulmonary & Sleep Medicine, Children’s National Medical Center
EDUCATIONAL AIMS
1.
2.
3.
4.
The
The
The
The
reader
reader
reader
reader
will
will
will
will
become familiar with the anatomy and physiology of the thorax
learn how the chest wall abnormalities affect the intrathoracic organs
learn the indications for surgical repair of chest wall abnormalities
become familiar with the controversies surrounding the outcomes of the VEPTR technique
A R T I C L E I N F O
S U M M A R Y
Keywords:
Thoracic cage
Scoliosis
Pectus Excavatum
Jeune Syndrome
VEPTR
The thorax consists of the rib cage and the respiratory muscles. It houses and protects the various
intrathoracic organs such as the lungs, heart, vessels, esophagus, nerves etc. It also serves as the so-called
‘‘respiratory pump’’ that generates the movement of air into the lungs while it prevents their total collapse
during exhalation. In order to be performed these functions depend on the structural and functional
integrity of the rib cage and of the respiratory muscles. Any condition (congenital or acquired) that may
affect either one of these components is going to have serious implications on the function of the other.
Furthermore, when these abnormalities occur early in life, they may affect the growth of the lungs
themselves. The following article reviews the physiology of the respiratory pump, provides a comprehensive
list of conditions that affect the thorax and describes their effect(s) on lung growth and function.
ß 2014 Published by Elsevier Ltd.
INTRODUCTION
The thorax comprises the upper body and it consists of multiple
independent bony parts (spinal vertebrae, sternum, ribs) that form
the rib cage, and several muscles that cover it from the outside and
separate it from the abdominal cavity. The rib cage provides the
‘‘scaffolding’’ on which the muscles lay and connect, whereas the
muscles provide stabilization and movement to the rib cage.
Although, it is often viewed as just a ‘‘protective case’’ for the
various intrathoracic organs (lungs, heart, vessels, esophagus,
nerves etc), the thorax is in fact a dynamic apparatus (the so-called
‘‘respiratory pump’’) that performs the actual function of breathing
by, generating the movement of air in and allowing or forcing the
movement of air out of the lungs). Thus, any condition that results
in its malfunction will have significant repercussions on the
function of the respiratory system and frequently on other
intrathoracic organs as well.
* Division of Pulmonary & Sleep Medicine, Children’s National Medical Center,
111 Michigan Ave N.W., Washington DC 20010 Tel.: +001-202-476-3519;
fax: +001-202-476-5864.
E-mail address: [email protected].
1526-0542/$ – see front matter ß 2014 Published by Elsevier Ltd.
http://dx.doi.org/10.1016/j.prrv.2013.12.003
‘‘Chest wall abnormalities’’ refer to any abnormality that affects
the normal structure and/or limit the function of the thorax. Chest
wall abnormalities are often referred to as chest or thoracic
dysplasias or dystrophies. Although there is a certain overlap
between these terms, in this article, dysplasia refers to abnormal
anatomic structures that result from the abnormal growth or
development of cells or tissues, and it is primarily used for bony
abnormalities (e.g. Spondyloepiphyseal dysplasia). The term
dystrophy is conventionally used for muscle abnormalities (e.g.
muscular dystrophy). This article reviews in detail the common
types of chest wall abnormalities and the effects they have on the
respiratory system.
TYPES OF CHEST WALL ABNORMALITIES
Many of the chest wall abnormalities (especially the dysplasias)
are congenital but they can also develop later in life as a result of a
disease (e.g. ankylosing spondylitis) or injury that can be
accidental (e.g. flail chest secondary to trauma), or iatrogenic
(e.g. thoracotomy). Specific genes and modes of inheritance have
been identified for many of the congenital dysplasias, whereas
others are assumed to be caused by accidental exposures. The
chest wall abnormalities are either primary or part of a syndrome
A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255
247
Table 1
Conditions associated with abnormalities of the thorax
CONDITION
Aarskog syndrome
Achondrogenesis
Achondroplasia
Allagile Syndrome (arteriohepatic dysplasia)
Beals syndrome
Camptomelic Dysplasia
Cerebro-Costo-Mandibular syndrome
Chondroectodermal dysplasia
Chondroplasia punctate
CHARGE syndrome
CHILD syndrome
Cleidocranial dysostosis
Coffin-Lowry syndrome
Cohen syndrome
Diastrophic dysplasia
Down syndrome
Dyggve-Melchior-Clausen syndrome
Early Amnion Rupture sequence
Ehlers-Danlos syndrome
Escobar syndrome
Fetal Hydantoin Effects
Fetal Alcohol syndrome
Fetal Aminopterin Effects
Fetal Valproate Effect
Fibrochondrogenesis
Frontometaphyseal dysplasia
Generalized Gangliosidosis syndrome, Type I
Gorlin syndrome
Haldu-Cheney syndrome
Homocystinuria syntrome
Hunter syndrome
Hurler syndrome
Hypophosphatasia
Incontinentia PPigmenti syndrome
Jarcho-Levin syndrome
Jeune syndrome
Klippel-Feil sequence
Kniest Dysplasia
Kozlowski spondyloepiphyseal dysplasia
Langer-Giedion syndrome
Lenz-Majeswski hyperostosis syndrome
Lethal multiple pterygium syndrome
Marfan syndrome
Marinesco-Sjogren syndrome
Maroteaux-mucopolysaccharidosis
Melnick-Needles syndrome
Meningomyelocele
Metaphyseal chondrodysplasias
Metatropic Dysplasia
Morquio syndrome
Mucopolysaccharidosis VII
Multiple synostosis
Multiple Lentigines syndrome
Multiple neuroma syndrome
MURCS association
Neurofibromatosis syndrome
Noonan syndrome
Osteogenesis imperfect
Oto-Palato-Digital syndrome
Pallister Hall syndrome
Partial Trisomy 10q syndrome
Poland anomaly
Progeria syndrome
Proteus syndrome
Pseudoachondroplasia Sponyloepiphyseal dysplasia
Pyle Metaphyseal Dysplasia
Rhizomelic Chondroplasia Punctuta
Robinow syndrome
Rokitansky sequence
Rubenstein-Taybi syndrome
Ruvalcaba syndrome
Sanfilippo syndrome
Seckel syndrome
Short rib syndrome
Shprintzen syndrome
Shwachman syndrome
Sponyloepiphyseal dysplasia congenita
THORACIC SHAPE
STERNUM
RIBS
PE/PC
SPINE
VERTEBRAE
(X)
(X)
X
X
X
X
X
X
Small thoracic cage
Small thoracic cage
X
Small thoracic cage
Small thoracic cage
Small thoracic cage
X
X
X
(X)
X
(X)
X
X
X
X
X
(X)
(X)
(X)
Small thoracic cage
PE/PC
Small thoracic cage
(PE/PC)
PE/PC
(X)
X
X
(X)
(X)
(X)
X
X
(X)
(X)
PE/PC
X
(X)
Small thoracic cage
X
X
(X)
X
(X)
X
(X)
X
X
X
X
X
X
X
(X)
X
X
Small thoracic cage
X
Small thoracic cage
Small thoracic cage
(X)
(X)
X
PE/PC
X
X
(X)
X
X
X
X
X
X
Small thoracic cage
PE/PC
PE/PC
Small thoracic cage
PE/PC
X
X
PE/PC
X
X
Small thoracic cage
Small thoracic cage
PE/PC
PE/PC
Small thoracic cage
(Small thoracic cage)
PE/PC
PE/PC
PE/PC
PE/PC
X
(X)
X
X
X
(X)
X
X
X
X
X
X
(X)
X
(X)
(X)
(X)
(X)
X
(X)
X
X
(X)
(X)
X
(Small thoracic cage)
(X)
Small thoracic cage
X
X
X
(X)
(X)
PE/PC
X
X
X
X
(X)
X
X
X
X
(X)
(X)
X
(X)
X
X
X
X
X
(X)
X
X
(X)
Small thoracic cage
X
(X)
PE/PC
X
A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255
248
Table 1 (Continued)
CONDITION
THORACIC SHAPE
Thanatophoric dysplasia
Trich-Rhino-Pharyngeal syndrome
Trisomy 8, 9, 9p Mosaic syndrome
Trisomy 4p, 13
Trisomy 18, 20
Vater syndrome
Waardenburg syndrome
Williams syndrome
XO, XYY, 18p, XXXXY syndromes
Small thoracic cage
STERNUM
RIBS
SPINE
VERTEBRAE
X
PE/PC
Small thoracic cage
X
(X)
X
(X)
(PE/PC)
PE/PC
(X)
X
X
X
(X)
X
(X)
X
X
(X)
(X)
(X)
Adapted from: Smith’s Recognizable Patterns of Human Malformation / Edition 5., Jones KL Elsevier Saunders, Philadelphia, PA, USA 1988
PE: Pectus Excavatum; PC: Pectus Carinatum; (X): abnormality only occasionally present
Table 2
Chest wall abnormalities on each of the components of the thorax
Abnormalities of the Sternum
Abnormalities of the Ribs
Abnormalities
of the Spine
Abnormalities of the Muscles
Pectus Excavatum
Pectus Carinatum
Fused ribs (e.g. Jarcho-Levin syndrome)
Narrow chest (e.g.Asphyxiating Thoracic
Dystrophy)
Fractured ribs (e.g. Flail chest)
Scoliosis
Kyphosis
Absent muscles (Poland Syndrome)
Muscle weakness (e.g. spinal muscular atrophy)
Lordosis
Absent ribs (e.g. resection of tumors)
Abnormal vertebrae
Defects (e.g. Congenital diaphragmatic hernia);
gastroschisis)
Paralysis (e.g, diaphragmatic paralysis)
Bifid Sternum
(Table 1). Most of the syndromes initially affect a specific
component of the thorax but because of the interrelationship
between the various components eventually the entire thorax may
become deformed. From a clinical standpoint the chest wall
abnormalities can be categorized according to the part of the
thorax that is primarily affected (Table 2) and/or according to the
causes as follows:
Congenital chest wall abnormalities
a) Anomalies of the sternum (e.g. Pectus excavatum, bifid
sternum)
b) Anomalies of the ribs (e.g. Jarcho-Levine Syndrome)
c) Anomalies of the spine (e.g. Scoliosis)
d) Anomalies of the respiratory muscles (e.g. Poland syndrome,
neuromuscular disorders)
spondylitis (that may cause ossification of the ligaments in the
spine and in the rib cage); fibrothorax (that causes fibrosis of the
pleura that in turn limits the expansion of the rib cage), and
scleroderma (that limits the expansion of the rib cage due to the
thickening of the skin that covers the thorax).
Abdominal conditions
Conditions such morbid obesity, accumulation of large amounts
of fluid or air in the peritoneal cavity (e.g. ascites or pneumoperitoneum) or organ enlargement (e.g. significant hepatosplenomegaly) may cause severe limitation in the function of the thorax by
impeding the function of the diaphragm. Defects of the abdominal
wall (e.g. gastroschisis, giant omphalocele) also impede diaphragmatic function, thus limiting the normal expansion of the thorax.
One could also include the normal pregnancy (although it
obviously can ‘‘affect’’ only women of reproductive age) as a
cause of temporary dysfunction of the thorax due to the pressure
that the fetus and the amniotic sac exert on the diaphragm.
Acquired chest wall abnormalities
Trauma
Traumatic injuries to the thorax such as fractures of the ribs, the
sternum or the spine will affect the normal function of the thorax
not only at the time of the injury but potentially in the long-term as
well, due to potentially abnormal healing. Similar short and longterm effects may be produced by accidental trauma to the muscles
(e.g. extensive burns) Or after iatrogenic injuries (e.g. rib and/or
muscle resection due to tumours, sternotomy for cardiac surgery)
Neurologic conditions
Partial or complete paralysis of the respiratory muscles due to
injuries (e.g. spinal cord injury) or diseases (e.g. Guillain-Barre
syndrome), not only prevent the normal breathing but eventually,
can cause significant disfigurement of the thorax because the weak
muscles cannot provide the necessary stability that is required to
maintain its physiologic shape.
Diseases affecting components of the thorax
Various unrelated conditions may affect parts of the thorax
causing significant limitation to its expansion. Typical examples
(although generally rare in children) include ankylosing
Hypoplasia or absence of the lung
Lung agenesis, severe lung hypoplasia (e.g. congenital diaphragmatic hernia), and pneumonectomy can cause significant
disfigurement of the rib cage due to the ‘‘caving’’ of the rib cage on
the affected side as well as due to the hyperinflation of the
contralateral lung that usually herniates to the opposite side thus
rotating the intrathoracic organs and the mediastinum.
Severe upper airway obstruction
Chronic significantly increased work of breathing (e.g. severe
laryngomalacia or subglottic stenosis) may cause irreversible
disfigurement of the chest wall, usually in the form of pectus
excavatum.
ANATOMY & PHYSIOLOGY OF THE THORAX
To understand the effects of the thoracic dystrophies on the
respiratory system, one has to understand the anatomy and
physiology of the normal thorax. The rib cage is formed very early
in fetal life. Primitive elements of the ribs, the clavicles and the
sternum can be detected as early as 6 weeks of gestation
(mesenchymal phase). When fully developed, the thorax resembles
A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255
a truncated cone formed by the sternum anteriorly, by the 12
thoracic vertebrae of the spine posteriorly, and by 12 pairs of ribs
that connect the sternum and the spine in a complex way.
Specifically, all 12 pairs of ribs are connected with the 12 thoracic
vertebrae thus forming the posterior and lateral aspects of the rib
cage. However, only 4 pairs (first, tenth, eleven and twelfth) are
connected with the respective vertebrae, whereas the remaining
pairs (ribs 2-9) are connected with two vertebrae each. The anterior
wall of the thorax is formed by the sternum that is connected only to
the first 7 seven pairs of ribs. Ribs 8-10 are attached only indirectly to
the sternum by being attached to the cartilage of the rib above them,
whereas the eleventh and twelfth ribs are not attached to the
sternum at all. These articulations form a characteristic triangular
opening in the anterior wall. [1]
The ribs are attached to the vertebral bodies as well as to the
sternum with true synovial joints consisting of articular cartilages,
joint capsules and synovial cavities that allow freedom of
movement of the ribs during the respiratory cycle. In neutral
position, the ribs (especially the lower ones) lie in a downward
fashion whereas during inspiration they assume a more horizontal
position thus expanding the rib cage in an upward and outward
fashion. However, not all ribs move the same way. The upper ribs
move in a vertical plane that resembles the movement of an oldfashion pump (pulling the rib cage upwards). The middle ribs move
in a way similar to the handle of a bucket, whereas the lower ribs
move laterally, resembling the movement of a caliper. These
complex movements allow the rib cage to increase significantly its
cross-sectional area thus providing enough space for the lungs to
expand. During infancy the ribs lie normally in an almost
horizontal position, placing the infants at a mechanical disadvantage compared to older children and adults because they cannot
expand their chest outward and so they rely almost exclusively on
diaphragmatic breathing.
The sternum is a few centimeters long at birth but it grows up to
20 cm in adults. It is comprised of three areas (manubrium, body,
and xiphoid). The manubrium is connected via articulation with
the clavicle and the first rib. It is also connected with the body of
the sternum approximately at the level of the junction of the
second rib (angle of Louis). Normally, the bifurcation of the trachea
is located behind the angle of Louis. [1]
The thorax is separated from the abdominal cavity by the
diaphragm. As a result it is subjected directly to the pressures
generated in the abdominal cavity, in part contributed to by the
size of the abdominal organs. The diaphragm consists of two
distinct muscular parts connected by a tendon. The tendon extends
from the xiphoid process of the sternum to the second and third
lumbar vertebral bodies, thereby placing the diaphragm in an
angle in which its anterior portion lies higher than the posterior.
The position of the diaphragm is not fixed and changes during the
respiratory cycle, descending to the bottom of the rib-cage during
inspiration, and ascending to almost half of the rib cage during
maximal expiration.
The thorax is covered by several muscles. The anterior part is
covered by the pectoralis major and minor, the latissimus dorsi, the
serratus anterior, and partially by the cervical muscles (the
sternocleidomastoid and the scalene). The posterior part of the
thorax is covered superficially by the trapezius and latissimus dorsi
muscles whereas the serratus anterior and posterior, levatores and
major and minor rhomboids form a deeper layer. The external
muscles primarily stabilize and protect the thorax and they do not
normally participate in the function of respiration. However, at
times of extreme respiratory distress some of them (the deltoid,
pectoralis, and latissimus dorsi muscles) can indirectly assist the
respiration by ‘‘immobilizing’’ the upper extremities. Muscle injury
or absence (as in the case of the pectoralis major muscle in Poland
syndrome) may affect the physical integrity of the thorax.
249
Underneath the external muscles lay the intercostal muscles
(external, internal, and transverse or innermost).
The intercostal muscles together with the diaphragm comprise
the main muscles of respiration, whereas the sternocleidomastoid
and the scalene muscles, as well as the serratus posterior and the
levatores costarum muscles comprise the secondary muscles of
respiration. The various respiratory muscles perform different
functions. The diaphragm and the external intercostals (and in part
the internal intercostals) are the primary inspiratory muscles
during tidal breathing and during mild/moderate exercise. The
scalene and the sternocleidomastoid muscles are also inspiratory
muscles but they are used primarily at times of maximal exertion
and/or during respiratory distress. The abdominal muscles
enhance the inspiratory function of the diaphragm (especially in
the upright and sitting position) during quiet breathing. When the
diaphragm contracts, it slides downwards over the spine,
effectively ‘‘scooping-out’’ the abdominal contents. The abdominal
muscles create a ‘‘barrier’’ that prevents the outward movement of
the abdominal contents which generates a high intrabdominal
pressure that is transmitted back to the diaphragm causing its
‘‘flattening’’ that in turn causes the outward expansion of the rib
cage. The interaction between the diaphragm and the abdominal
muscles explains the difficulty in breathing or the respiratory
failure that occurs when the abdominal muscles are defective (e.g.
gastroschisis), weak (e.g. in neuromuscular diseases or normally in
the neonatal period), or traumatized (e.g. in abdominal trauma or
after major abdominal surgery). There are no pure expiratory
muscles, because exhalation during tidal breathing is a passive
movement produced by the elastic recoil of the lungs. However,
forced exhalation depends on the internal intercostals and to a
lesser degree on the abdominals. [1]
EFFECTS OF CHEST WALL ABNORMALITIES ON THE
RESPIRATORY SYSTEM
In general, chest wall abnormalities affect the thorax by
impairing or preventing its growth and/or by limiting its movement. In both cases the effects are not limited to the thorax but
they extend to the intrathoracic organs as well.
Effects on the growth of the thorax
Similar to the overall somatic growth, the thorax grows in a
gradual but not completely linear fashion that is characterized by
growth spurts. Under normal circumstances, the thoracic volume
in a newborn infant represents only a small fraction of the thoracic
volume during adulthood. By 5 years of age, the thoracic volume
increases to about 30% of the adult size, and by age 10 it reaches
approximately 50% of its final volume. The remaining 50% develops
during the prepuburtal period and early adolescence. [2] Thus, any
process (congenital or acquired) that limits the growth of the
thorax will have profound long-term effects on the thoracic
volume and on the lungs. What actually limits the growth of the
thorax (and possibly of the lungs) is unclear. In general, the more
severe the abnormality, the more impaired is the thoracic volume
and the lung volume. However, the effects are not linear and they
seem to depend to a large extent on which component of the
thorax (sternum, spine, ribs) is mostly affected. It appears that
abnormalities affecting primarily or exclusively the sternum or the
spine have relatively mild effects on the lung volume. For example
the lung volume in patients with idiopathic pectus excavatum
tends to be within the normal range (although at the lower levels of
normal). [3] Similarly, a large prospective study comparing the
growth of the thoracic volume in children and adolescents (4-16
years of age) with mild/moderate and severe scoliosis revealed that
the thorax grew normally in patients with mild to moderate
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A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255
scoliosis but it was lower in all age groups in patients with severe
scoliosis (although the difference did not seem to be clinically very
important). [4] In contrast, patients with spondyloepiphyseal
dysplasia and fused ribs were found to have very severe restrictive
lung disease with forced vital capacity <30% of the predicted
normal and significant shortening of the posterior length of the
thorax. [5] These findings suggest that in addition to the overall
volume of the thorax what really makes a difference is the degree
to which the affected thorax can expand on inspiration. Although
virtually all chest wall abnormalities limit the thoracic expansion,
the ones associated with rib fusion and/or with severe respiratory
muscle weakness appear to have the worse outcome.
Effects on the Respiratory System Mechanics
The respiratory system compliance (Crs) is the product of the
chest wall compliance (CW) and the lung compliance (CL) and it tends
to be decreased in virtually all the chest wall abnormalities. Because
the latter do not usually affect the lungs directly, the decrease in Crs
is primarily due to the decrease in chest wall compliance. Indeed, as
it can be seen in Fig. 1, using the same inflating pressure in an
anesthetized patient with Jeune syndrome results in a much smaller
lung volume when the chest was closed, compared to the volume
obtained when the thorax was open during a sternotomy and after it
had undergone surgical expansion.
Effects on the Lung Function
The most common effect of chest wall abnormalities on the lung
function is the gradual development of restrictive lung defect that
is characterized by decreased total lung capacity (TLC). In the
majority of the cases, the lung volume tends to be fairly normal at
birth and probably during early infancy, but its growth is gradually
limited by the inability of the thorax to grow resulting into the so-
called ‘‘thoracic insufficiency syndrome’’. [6] In general, the
adverse effects of chest wall abnormalities tend to be more
profound when they are present in the newborn period and early
infancy. Thus, congenital and infantile scoliosis tends to be
associated with significant lung hypoplasia, whereas in idiopathic
adolescent scoliosis of the same degree, the decreased total lung
capacity may be due to lung hypoinflation. The reasons for this
difference are not clear considering that normally about 50% of the
final thoracic volume grows around puberty. A possible explanation is that congenital anomalies may be associated with molecular
abnormalities that may affect the lungs directly. For example, the
various chondrodysplasias are associated with genetic mutations
affecting the transmembrane receptors, and the various spondyloepiphyseal dysplasias are associated with abnormalities involving the proteins involved in the matrix of the cartilage. [7] Even
relatively mild chest wall abnormalities, such as pectus excavatum, seem to have more profound effects when they are associated
with syndromes such as Marfan syndrome. Another possible
explanation is that infancy is the period of rapid lung development
with the appearance of new bronchioles and alveoli and therefore
any process that limits this development will have a much worse
outcome than a process that limits the full inflation of the lung
after all the internal divisions have been completed.
The decreased total lung capacity is often associated with
increased residual volume (RV) resulting into an elevated RV/TLC
ratio suggesting presence of air-trapping despite the absence of
clinical or spirometric evidence of lower airway obstruction. This is a
relatively common finding among patients with pectus excavatum or
scoliosis. [3] It is possible that the increased RV is simply due to the
fact that the chest wall abnormality does not allow the lungs to return
to the normal neutral position and/or that the expiratory muscles are
unable to produce a full exhalation possibly because the expiratory
respiratory muscles are at a mechanical disadvantage. [8,9] The
increase in the residual volume in turn causes a decrease in the vital
capacity. The inspiratory capacity (IC) may or may not be affected
depending on the level of the expiratory reserve volume (ERV).
Effects on the Airway Function
Figure 1. Deflation flow-volume curves (DFVC) obtained intraoperatively in a
patient with Jeune syndrome. Top panel:DFVC were obtained while the chest was
closed. Middle panel: DFVC during median sternotomy. Note the significant
incbrease in the vital capacity (X-axis). Lower panel: DFVC after the sternum was
fixated in a position that allowed an increased lung expansion (Courtesy of Dr.
Etsuro K. Motoyama).
Chest wall abnormalities do not usually affect the airway
function directly. In fact, because of the restrictive lung defect that
tends to be associated with most of them, the expiratory flow-rates
(measured by spirometry and maximal expiratory flow-volume
curves) tend to be very high relative to the lung volume, reflecting
the rapid emptying of the lungs. The flow-volume curves have a
very characteristic tall and narrow appearance (although in milder
cases it may resemble a ‘‘miniature’’ normal curve). Even more
striking are the changes in the inspiratory flow-volume curves that
lose their characteristic ‘‘half-circle’’ shape and instead they
resembles a mirror image of the expiratory flow-volume curve
(Fig. 2). On occasion patients with severe scoliosis may develop a
flattening of the proximal portion of the flow-volume curve that
suggests large/central airway obstruction. Interestingly, this
obstruction can disappear after scoliosis surgery (Fig. 3A & 3B).
A possible explanation is that the obstruction is due to the
asymmetry of the two hemithoraces that leads to the hyperinflation of one lung and hypoinflation of the other. Both conditions
have the potential of ‘‘pulling’’ the main stem bronchi forward or
backward causing some ‘‘kinking’’ that is relieved when the rib
cage becomes more symmetric. [10] Finally, certain patients may
develop evidence of peripheral airway obstruction that is partially
reversible with administration of bronchodilators. This has been
described in a substantial number of patients with pectus
excavatum [3] as well as in patients with neuromuscular disorders
possibly due to development of chronic airway inflammation
secondary to poor airway clearance.
A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255
251
Figure 2. Maximal flow-volume curves in a patient with severe restrictive lung
defetct due to chest wall anormality. Note the characteristic tall and narrow shape of
the flow-volume curve and the ‘‘mirror-image’’ of the inspiratory flow-volume curve.
Effects on the Ventilation and perfusion
Under normal circumstances the right lung of an adult
contributes approximately 55% and the left lung approximately
45% of the overall ventilation and perfusion. This ratio is probably
closer to 50/50 in children. In chest wall abnormalities, because of
the scoliosis that is invariably present, there is asymmetry between
the two hemithoraces and as a result one of the lungs is always
considerably bigger than the other. One would expect that this
asymmetry would alter the normal the normal ratio and that the
bigger lung would contribute the bulk of the ventilation and
perfusion. Using ventilation/perfusion scans it has been found that
the ratio indeed changes and it can increase up to 80% contribution
from one lung. This change can occur in the right or in the left lung. It
is not known whether these changes in the ratio are reversible after
surgical repair. This information could have clinical implications and
specifically it might influence the decision for and/or the extent of
the repair. Interestingly, the lung that contributes most in the
ventilation/perfusion calculation does not seem to correlate directly
with the Cobb angle. Thus, one may have to consider more extensive
evaluation with the use of V/Q scans and then proceed with an
operation that preserves the functioning lung. [11]
Effects on the breathing pattern
In the absence of other underlying disorders, mild to moderate
scoliosis (i.e. angle <70o) actually produces very few symptoms
and signs relating to the respiratory system. Severe scoliosis
(primary or secondary) is associated with significant alterations in
the breathing patterns at rest, on exertion and during sleep. The
respiratory rate tends to be higher than normal whereas the tidal
volume may be normal, higher than normal or lower than normal.
[12,13] However, in all of these cases the tidal volume is actually
increased relative to the vital capacity. This means that the affected
Figure 3. Maximal flow-volume curves in a patient with severe scoliosis. A. The
expiratory flow-volume curve shows extensive ‘‘flattening’’ of its proximal portion
consistent with central airway obstruction. B. Repeat testing after surgical repair of
the scoliosis shows significant resolution of the central airway obstruction.
(Courtesy of Drs. Raul Corrales and Ignacio Dockendorff).
patients need to generate a much higher than normal transdiaphragmatic pressure that requires increased contributions of the rib
cage as well as the abdominal expiratory muscles. These
mechanisms are normally reserved for conditions of increased
metabolic demands such as during exercise. However, when they
are used for regular breathing they increase significantly the risk of
respiratory muscle fatigue and eventual respiratory failure.
Disordered breathing during sleep, consisting of central hypopnoea and/or true apnoea associated with desaturations especially
during REM sleep, has been described and it is possibly quite
common in patients with scoliosis. Although these problems can
be expected to be more common and/or more severe among
patients with severe scoliosis, there is no direct correlation
between them and the degree of scoliosis. In severe cases of
scoliosis (angle >100o), patients are at an increased risk of
developing chronic respiratory failure and pulmonary hypertension (the latter being the product of chronic atelectasis, chronic
hypoxemia and chronic hypercapnia). [12,13]
EFFECS ON THE INTRATHORACIC ORGANS
The thoracic cavity ‘‘houses’’ organs from various systems
including the respiratory (lungs and the intrathoracic trachea),
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A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255
cardiovascular (heart, major arteries and veins), gastrointestinal
(most of the esophagus), lymphatic vessels and various nerves
(including the phrenic and the recurrent laryngeal nerves) that are
‘‘packed’’ tightly together. Thus, when the thoracic cage becomes
distorted, all the intrathoracic organs are displaced in ways that
may directly impede their function. Asymmetry between the two
hemithoraces has significant effects on the lungs causing
hyperinflation on the larger side and hypoinflation (or complete
collapse) on the other. The mediastinum is also shifted together
with the trachea and the major bronchi can become kinked. The
deformation of the thorax limits among other things its anteroposterior diameter thus compressing the heart and preventing it
from increasing its stroke volume. This is believed to be one of the
main mechanisms causing exercise limitation in patients with
significant pectus excavatum. [14,15]
CLINICAL SIGNS & SYMPTOMS
There are several signs and symptoms that are typical among
the various chest wall abnormalities although none of them is
unique and pathognomic. Such signs and symptoms include the
following:
Shortness of breath (SOB) and exercise limitation
Exercise limitation is a typical symptom of chest wall abnormalities but its severity varies widely among patients depending on
the type and severity of the abnormality. In order to meet the
increased metabolic demands that are required during physical
activity, both the lungs and the heart need to increase their output
(i.e. Lungs increase the minute ventilation and the heart increases its
cardiac output). Normally, the increase in the minute ventilation is
achieved by increasing the respiratory rate and especially by
increasing the tidal volume (up to 3-4 times the size of the tidal
volume at rest). Similarly, the heart increases its cardiac output by
increasing the heart rate and its stroke volume (also up to 3-4 times
the size of the stroke volume at rest). Patients with chest wall
abnormalities are unable to mount these physiologic responses due
to a variety of reasons, such as true hypoplasia, fused rib cage,
respiratory muscle weakness and cardiovascular compression. For
patients with significant abnormalities the issue is not exercise but
the ability to meet the demands of daily life and especially whether
they can tolerate the increased work of breathing that is associated
with acute respiratory infections.
SURGICAL REPAIR AND ITS OUTCOMES
Shallow breathing
It is usually seen in moderate to severe chest wall abnormalities
and it is the result of the minimal expansion of the rib cage that
produces a very small tidal volume.
Tachypnoea
It is the compensatory mechanism for the shallow breathing in
order to maintain adequate minute ventilation. Infants (or even
older children) with severe deformities can develop respiratory rates
in excess of 60 (and as high as 100) breaths/minute, thus putting the
patients at a very high risk for muscle fatigue and respiratory failure.
Tachycardia
It is the result of the extra work that patients perform for their
breathing and/or the inability of the heart to increase its stroke
volume.
Failure to thrive
The majority of patients with severe thoracic abnormalities
tend to have a degree of failure to thrive. This is the result of low
caloric intake (e.g. difficulty to eat due to tachypnoea) and high
caloric expenditure necessary to maintain the high respiratory and
heart rates.
Abnormal auscultatory findings
Asymmetrical breath sounds between the two hemithoraces is a
common finding among patients with thoracic abnormalities. In
most of them, the asymmetry is the result of scoliosis that distorts
the shape of the thorax creating a convex (and larger) side and a
concave (and more narrow one). Which side produces the ‘‘better’’
breath sounds is not always clear however. Decrease in the breath
sounds due to limited expansion and underlying atelectasis is
usually evident on the concave side of the chest. However, decreased
breath sounds may also be produced by the massive hyperinflation
of the contralateral lung that does not allow any further expansion.
Finally, in certain dystrophies like the Jeune Syndrome, in which the
thorax is fairly symmetric, the decrease in breath sounds is primarily
due to the limited expansion of the chest.
Many surgical techniques have been developed over the years
for the correction of chest wall abnormalities with variable success.
From a medical standpoint the various interventions can be
summarized as follows:
- Interventions that restore the structural integrity of the thorax to
(near) normal (e.g. repair of idiopathic pectus excavatum in an
otherwise healthy individual) [16]
- Interventions that prevent the deterioration of a chest wall
abnormality (e.g. spinal fusion in order to prevent the worsening
of scoliosis) [12,13]
- Interventions that improve the functionality of the thorax (e.g.
repair of traumatic injury to the chest)
- Interventions that improve the function of the intrathoracic
organs (e.g. the vertical expandable prosthetic titanium rib
(VEPTR) technique for Jeune syndrome) [6]
Whether an intervention could (or should) be made depends on
the careful selection of the objective of the intervention which in
turn will determine whether the outcome was successful or not. The
second area in which the various specialists involved in the care of
complex patients should consider is the careful assessment of
factors other than the chest wall abnormality that may affect both
the feasibility and the success of the outcome. Such factors include:
- The severity of the abnormality (as one might expect the milder
the abnormality, the easier it is to be repaired and vice versa),
- The presence of other abnormalities (e.g. the outcome of
idiopathic scoliosis repair in an otherwise healthy patient is
far more successful compared to that in a patient with a
significant chondrodysplasia),
- The presence of other underlying conditions/syndromes that
may affect the clinical outcome (e.g. attempt to repair the rib cage
of a patient with severe poorly controlled pulmonary hypertension may place the patient at a disproportionately high risk with
very little benefit).
- The timing of the operation (i.e. is there an ‘‘optimal’’ time for the
repair of a chest wall abnormality?).
The timing of the operation (especially of elective ones, such as
repair of pectus excavatum or adolescent idiopathic scoliosis)
A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255
deserves special consideration. For many years it was assumed that
the primary effect of the chest wall deformities was that they
impede the normal growth of the lungs. As a result there had been
attempts to correct chest wall abnormalities early on in life in
order to allow the lungs to grow normally. However, the results
ranged from disappointing (e.g. early attempts to correct the chest
in patients with asphyxiating thoracic dystrophy) [17], to
disastrous (e.g. development of iatrogenic ‘‘asphyxiating thoracic
dystrophy’’ in patients who underwent repair of pectus excavatum
before the 4-5th year of life). [18] In the latter cases it appeared that
the failure was at least in part due to the fact that the rib cage was
not ossified enough to support the repair. In addition, early repair
may impede the changes in the configuration of the thorax that
occur normally especially during the periods of growth spurts.
Thus, the current tendency, if not consensus, is that surgery should
be deferred if possible until the patient is at least 10 years of age or
older. [19] The exception to this is for procedures that allow the
periodic adjustment of the repair (the so called ‘‘growth-friendly’’
procedures) so it can follow the growth of the rest of the body. [2]
The functional outcomes of surgical interventions for chest wall
abnormalities remain rather controversial. [20–29] In general, there
is post-operative improvement in the activity level and exercise
tolerance of patients with pectus excavatum and/or adolescent
idiopathic scoliosis. However, it is not completely clear whether this
is due to improved cardiopulmonary function secondary to
improved thoracic volume or simply because the improved body
image makes the affected patients more likely to exercise. [21]
One aspect of the repair of most abnormalities is that the
enlargement of the thoracic cavity is not accompanied by
improved lung growth. In fact there is evidence that at least in
the short term the repair results into decrease in lung volume. [23–
27] This evidence has been provided by pre- and postoperative
pulmonary function studies in patients with thoracic insufficiency
syndrome who underwent repair with the VEPTR technique. [20]
Although the repair itself seems to have been successful in
enlarging the thoracic cavity and/or improving the scoliosis curve,
the lung volume decreased shortly after the surgery something
that could be attributed to factors such as the operative trauma,
post-operative atelectasis etc. However, long-term follow-up
studies produced results that are at the best contradictory. Thus,
Mayer and Redding reported that the forced vital capacity (FVC)
remained decreased compared to the baseline even at approximately 8 months after the operation. [20]. In contrast, Motoyama
et al. [25] reported that several months after the operation and for
up to almost 3 years the forced vital capacity (FVC) increased at a
rate of 26.8%/year that was similar to that of healthy normal
children. However, the FVC did not show any improvement as
percentage of the predicted normal value. Moreover, in a follow-up
of study of a larger group of patients the same investigators
reported that the FVC increased by only 11.1%/year. [26] Even more
disappointing were the results from a study of lung function
performed approximately 10 years after the surgery in which the
average FVC of the patient population was <60% of that of agematched controls. [22] Interestingly, both studies provided
evidence that the effects of the surgery on the lung volume and
function depend on multiple factors. For example, Motoyama et al.
[26] found that the rate of growth was much better among children
operated before 6 years of age compared with the adolescent
patients (14.5% vs. 6.5%) although the respiratory system
compliance actually decreased overtime in all age groups, a
finding that the authors attributed to increasing stiffness of the
thorax with growth. In contrast, Karol et al. [22] reported that the
outcomes varied depending on whether the surgery involved
primarily the proximal or the caudal spine (the proximal having
worse outcome). A possible explanation for the post-operative
decrease (or at least not improvement) in lung volume may be that
253
all the currently available surgical techniques are focused on the
stabilization/reconstruction of the bony parts of the thorax (spine,
ribs, sternum). There is however, no information on how the
changes in the configuration of the thorax affects the respiratory
muscles. It is conceivable that changes in the rib cage may actually
place the respiratory muscles at a mechanical disadvantage
compared to their pre-operative position. It is also possible that
some of the chest wall abnormalities may be associated with
impaired lung parenchyma that precludes its normal growth
regardless of the thoracic volume. It should be noted that it is not
possible to make direct comparisons between these studies
because they included very heterogeneous populations in terms
of their underlying diseases and abnormalities, operated at
different ages and with a variety of procedures. Moreover, the
lung function was evaluated with different techniques that may
affect the outcomes. For example, in the measurements made with
the deflation flow-volume curve technique used in the studies by
Motoyama et al. [25,26], the measurements are usually made after
the patient had received sigh breaths that help recruit atelectatic
lung. In contrast, the raised volume technique used by Mayer and
Redding [29], the lung is inflated by the ‘‘stacking’’ multiple
breaths that may not be able to recruit as much of the atelectatic
lung and thus it will produce much lower values.
In summary, chest wall abnormalities are diverse conditions
associated with high morbidity and occasionally mortality. Chest
wall abnormalities are generally associated with decreased lung
volume. This decrease can be the result of associated primary lung
hypoplasia, of inability to grow due to a restrictive rib cage or due
to chronic hypoinflation is not clear and it is likely to be due to a
combination of some or all of the aforementioned factors.
Currently available surgical techniques may delay or may prevent
the worsening of the abnormality and in certain conditions such as
idiopathic pectus excavatum and idiopathic adolescent scoliosis
the surgical repair may reconstruct them to a satisfactory often
near normal level. However, the effect of the surgical repair on the
lung growth and function remains rather controversial.
PRACTICE POINTS
1. Chest wall abnormalities are mostly congenital and often
part of a syndrome
2. Idiopathic chest wall abnormalities tend to have less
severe course and better outcomes after surgical repair
3. Development of restrictive lung defects are characteristic
of most chest wall abnormalities and they are caused
primarily by the chronic hypoinflation secondary to the
inability of the rib cage to fully expand.
4. Surgical repair of chest wall abnormalities rarely results in
significant improvement of the lung growth and function
but it may be necessary to prevent its deterioration.
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CME SECTION
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European Board for Accreditation in Pneumology (EBAP). You
can receive 1 CME credit by successfully answering these
questions online.
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Drongowski RA, Farley FA. Vertical expandable prosthetic titanium rib device
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MS. Effects on lung function of multiple expansion thoracoplasty in children
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4. The ribs are attached to the spine and the sternum with true
synovial joints
5. The anterior portion of the diaphragm is lower than its
posterior portion
Effects of Chest Wall Abnormalities on the Respiratory System
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upon completion of the test.
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administrative charge).
CME QUESTIONS
Types of Chest Wall Abnormalities
1. Chest wall abnormalities refer to congenital anomalies of the
thorax. They can also be acquired
2. Chest wall abnormalities refer to abnormalities of the rib.
They can also be due to abnormalities of the sternum, the
spine and/or of the respiratory muscles
3. Burns can cause chest wall abnormalities
4. Subglottic stenosis can lead t o the development of barrel
chest, upper airway obstruction tends to be associated with
the development of pectus excavatum
5. Spinal muscular atrophy leads to the development of chest
wall abnormalities.
1. The thoracic volume increases most rapidly during infancy,
by 5 years of age the thoracic volume increases to only 30% of
its final size)
2. The lung growth depends primarily on the ability of the
chest to expand and not on the overall size of the thoracic
volume
3. The lung compliance is severely decreased in patients with
chest wall abnormalities, chest wall abnormalities decrease
primarily the chest wall compliance not the lung compliance.
The latter may decrease as a result of the atelectasis that
often develops).
4. Chest wall abnormalities are associated with air-trapping,
although chest wall abnormalities usually cause a restrictive lung defect, they are often associated with airtrapping as well due to the inability of the thorax to
return to neutral position during exhalation and allow the
lung to empty)
5. Idiopathic pectus excavatum is always associated with
severe restrictive lung defect, the majority of patients with
idiopathic pectus excavatum tend to have lung volumes that
are at the lower levels of normal)
Anatomy & Physiology of the Thorax
Effecs on the Intrathoracic Organs & Signs & Symptoms
1. The rib cage is formed in the second trimester of pregnancy
2. Each pair of ribs is connected with an individual vertebral body
3. Only some of the ribs are connected directly to the sternum,
only the first 7 pairs are connected directly to the stenum
1. Scoliosis causes atelectasis on both lungs. Scoliosis is
characterized by asymmetry between the two hemithoraces
that causes hyperinflation on the larger side and hypoinflation or complete collapse on the other).
A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255
2. Exercise intolerance in pectus excavatum is due to the small
lung volume. The displacement of the sternum decreases the
anterioposterior diameter of the thorax and prevents the
heart from increasing its stroke volume, thus leading to
exercise intolerance).
3. Chest wall abnormalities can cause airway abnormalities.
The displacement of the mediastinum can lead into ‘‘kinking’’
of the main stem bronchii and and development of large
airway obstruction).
4. Decreased breath sounds in a patient with severe scoliosis
can be heard both in the convex and the concave
hemithorax. Although breath sounds are usually decreased
in the concave hemithorax due to atelectasis, massive
hyperinflation on the convex side may have the same
effect).
5. Failure to thrive is common in patients with chest wall
abnormalities due to associated gastrointestinal abnormalities. Although patients with chest wall abnormalities
may have associated abnormalities from other organ
systems, the failure to thrive is usually the result of low
caloric intake (secondary to difficulty to eat/drink due to
tachypnea, muscle weakness etc), and the high caloric
expenditure for their breathing)
Surgical Repair and its Outcomes
1. Repair of pectus excavatum is indicated in early age in order
to allow normal lung growth. Repair of pecrus excavatum in
infancy has the potential of causing iatrogenic asphyxiating
thoracic dystrophy).
2. Repair of severe scoliosis is not followed by increases in lung
volume. Scoliosis repair very rarely result in improvement in
lung volume. In fact the lung volume actually decreases
immediately post-operatively and it slowly recovers within
1-2 years)
3. Improved exercise tolerance after repair of chest wall abnormalities is due to increased lung volume. The improvement is
more likely to be due to improved cardiovascular function)
4. The VEPTR technique in infants with chest wall abnormalities
is not followed by significant lung growth. The results of
pulmonary function testing in infants who underwent repair
of chest wall deformities with the VEPTR technique have been
controversial. After an initial decrease, there appears to be
increase in lung growth but not at the levels of a normal child)
5. The outcome of scoliosis surgery depends on which part of the
spine is affected. Surgery in the proximal spine tend to be associated with worse outcomes than surgery in the caudal spine.
255