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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. The reader will become familiar with the and physiology of the

2. The reader will learn how the chest wall abnormalities affect the intrathoracic organs

3. The reader will learn the indications for surgical repair of chest wall abnormalities

4. The reader will 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:

The thorax consists of the cage and the respiratory muscles. It houses and protects the various

Thoracic cage

intrathoracic organs such as the , , vessels, , etc. It also serves as the so-called

Scoliosis

‘‘respiratory pump’’ that generates the movement of air into the lungs while it prevents their total collapse

Pectus Excavatum

during . In order to be performed these functions depend on the structural and functional

Jeune Syndrome

VEPTR integrity of the 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 followingarticlereviewsthe physiology of the respiratory pump, providesa comprehensive

list of conditions that affect the thorax and describes their effect(s) on growth and function.

ß 2014 Published by Elsevier Ltd.

INTRODUCTION ‘‘Chest wall abnormalities’’ refer to any abnormality that affects

the normal structure and/or limit the function of the thorax. Chest

The thorax comprises the upper body and it consists of multiple wall abnormalities are often referred to as chest or thoracic

independent bony parts (spinal vertebrae, , ) that form dysplasias or dystrophies. Although there is a certain overlap

the rib cage, and several muscles that cover it from the outside and between these terms, in this article, dysplasia refers to abnormal

separate it from the . The rib cage provides the anatomic structures that result from the abnormal growth or

‘‘scaffolding’’ on which the muscles lay and connect, whereas the development of cells or tissues, and it is primarily used for bony

muscles provide stabilization and movement to the rib cage. abnormalities (e.g. Spondyloepiphyseal dysplasia). The term

Although, it is often viewed as just a ‘‘protective case’’ for the dystrophy is conventionally used for muscle abnormalities (e.g.

various intrathoracic organs (lungs, heart, vessels, esophagus, muscular dystrophy). This article reviews in detail the common

nerves etc), the thorax is in fact a dynamic apparatus (the so-called types of chest wall abnormalities and the effects they have on the

‘‘respiratory pump’’) that performs the actual function of .

by, generating the movement of air in and allowing or forcing the

movement of air out of the lungs). Thus, any condition that results TYPES OF CHEST WALL ABNORMALITIES

in its malfunction will have significant repercussions on the

function of the respiratory system and frequently on other Many of the chest wall abnormalities (especially the dysplasias)

intrathoracic organs as well. are congenital but they can also develop later in life as a result of a

(e.g. ankylosing spondylitis) or that can be

accidental (e.g. flail chest secondary to trauma), or iatrogenic

(e.g. ). Specific genes and modes of inheritance have

* Division of Pulmonary & Sleep Medicine, Children’s National Medical Center,

been identified for many of the congenital dysplasias, whereas

111 Michigan Ave N.W., Washington DC 20010 Tel.: +001-202-476-3519;

fax: +001-202-476-5864. others are assumed to be caused by accidental exposures. The

E-mail address: [email protected]. chest wall abnormalities are either primary or part of a syndrome

1526-0542/$ – see front matter ß 2014 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.prrv.2013.12.003

A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255 247

Table 1

Conditions associated with abnormalities of the thorax

CONDITION THORACIC SHAPE STERNUM RIBS SPINE VERTEBRAE

Aarskog syndrome PE/PC (X) (X)

Achondrogenesis Small thoracic cage X

Achondroplasia Small thoracic cage X

Allagile Syndrome (arteriohepatic dysplasia) X X

Beals syndrome X X

Camptomelic Dysplasia Small thoracic cage X (X) X

Cerebro-Costo-Mandibular syndrome Small thoracic cage X X

Chondroectodermal dysplasia Small thoracic cage

Chondroplasia punctate X (X)

CHARGE syndrome (X)

CHILD syndrome (X)

Cleidocranial Small thoracic cage (X)

Coffin-Lowry syndrome PE/PC X X

Cohen syndrome X X

Diastrophic dysplasia Small thoracic cage X

Down syndrome (PE/PC) (X) (X)

Dyggve-Melchior-Clausen syndrome PE/PC X X

Early Amnion Rupture sequence X

Ehlers-Danlos syndrome (X)

Escobar syndrome X (X) X

Fetal Hydantoin Effects X

Fetal Alcohol syndrome (X) (X)

Fetal Aminopterin Effects (X)

Fetal Valproate Effect (X) X

Fibrochondrogenesis Small thoracic cage X

Frontometaphyseal dysplasia X

Generalized Gangliosidosis syndrome, Type I X (X) X

Gorlin syndrome X X (X)

Haldu-Cheney syndrome (X) X

Homocystinuria syntrome PE/PC X

Hunter syndrome X

Hurler syndrome X X

Hypophosphatasia Small thoracic cage

Incontinentia PPigmenti syndrome X (X)

Jarcho-Levin syndrome Small thoracic cage X

Jeune syndrome Small thoracic cage X

Klippel-Feil sequence (X) (X) X

Kniest Dysplasia X X

Kozlowski spondyloepiphyseal dysplasia PE/PC X

Langer-Giedion syndrome X X

Lenz-Majeswski hyperostosis syndrome X

Lethal multiple pterygium syndrome Small thoracic cage

Marfan syndrome PE/PC X (X)

Marinesco-Sjogren syndrome PE/PC (X)

Maroteaux- X X X

Melnick-Needles syndrome Small thoracic cage PE/PC X X

Meningomyelocele X

Metaphyseal chondrodysplasias Small thoracic cage X

Metatropic Dysplasia Small thoracic cage X X

Morquio syndrome X X X

Mucopolysaccharidosis VII PE/PC X (X)

Multiple X

Multiple Lentigines syndrome PE/PC

Multiple neuroma syndrome PE/PC (X)

MURCS association (X) X

Neurofibromatosis syndrome (X) (X) (X)

Noonan syndrome PE/PC (X) (X) X

Osteogenesis imperfect Small thoracic cage PE/PC X

Oto-Palato-Digital syndrome (Small thoracic cage) PE/PC X X

Pallister Hall syndrome (X) X

Partial Trisomy 10q syndrome PE/PC X X (X)

Poland anomaly X (X)

Progeria syndrome (Small thoracic cage) X

Proteus syndrome (X) X (X)

Pseudoachondroplasia Sponyloepiphyseal dysplasia Small thoracic cage X X

Pyle Metaphyseal Dysplasia X (X) X

Rhizomelic Chondroplasia Punctuta X

Robinow syndrome (X) X

Rokitansky sequence X

Rubenstein-Taybi syndrome (X)

Ruvalcaba syndrome PE/PC X X

Sanfilippo syndrome X X

Seckel syndrome X (X)

Short rib syndrome Small thoracic cage X

Shprintzen syndrome (X)

Shwachman syndrome

Sponyloepiphyseal dysplasia congenita PE/PC X

248 A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255

Table 1 (Continued)

CONDITION THORACIC SHAPE STERNUM RIBS SPINE VERTEBRAE

Thanatophoric dysplasia Small thoracic cage X

Trich-Rhino-Pharyngeal syndrome PE/PC

Trisomy 8, 9, 9p Mosaic syndrome Small thoracic cage X X

Trisomy 4p, 13 X X (X)

Trisomy 18, 20 (X) X X

Vater syndrome X X

Waardenburg syndrome (X) (X) (X)

Williams syndrome (PE/PC)

XO, XYY, 18p, XXXXY syndromes PE/PC (X) (X) (X)

Adapted from: Smith’s Recognizable Patterns of Malformation / Edition 5., Jones KL Elsevier Saunders, Philadelphia, PA, USA 1988

PE: ; PC: ; (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 Abnormalities of the Muscles

of the Spine

Pectus Excavatum Fused ribs (e.g. Jarcho-Levin syndrome) Absent muscles ()

Pectus Carinatum Narrow chest (e.g.Asphyxiating Thoracic Muscle weakness (e.g. )

Dystrophy)

Bifid Sternum Fractured ribs (e.g. ) Defects (e.g. Congenital diaphragmatic );

gastroschisis)

Absent ribs (e.g. resection of tumors) Abnormal vertebrae Paralysis (e.g, diaphragmatic paralysis)

(Table 1). Most of the syndromes initially affect a specific spondylitis (that may cause ossification of the in the

component of the thorax but because of the interrelationship spine and in the rib cage); fibrothorax (that causes fibrosis of the

between the various components eventually the entire thorax may pleura that in turn limits the expansion of the rib cage), and

become deformed. From a clinical standpoint the chest wall scleroderma (that limits the expansion of the rib cage due to the

abnormalities can be categorized according to the part of the thickening of the that covers the thorax).

thorax that is primarily affected (Table 2) and/or according to the

causes as follows: Abdominal conditions

Conditions such morbid obesity, accumulation of large amounts

Congenital chest wall abnormalities of fluid or air in the peritoneal cavity (e.g. ascites or pneumoper-

itoneum) or enlargement (e.g. significant hepatosplenome-

a) Anomalies of the sternum (e.g. Pectus excavatum, bifid galy) may cause severe limitation in the function of the thorax by

sternum) impeding the function of the diaphragm. Defects of the abdominal

b) Anomalies of the ribs (e.g. Jarcho-Levine Syndrome) wall (e.g. gastroschisis, giant omphalocele) also impede diaphrag-

c) Anomalies of the spine (e.g. Scoliosis) matic function, thus limiting the normal expansion of the thorax.

d) Anomalies of the respiratory muscles (e.g. Poland syndrome, One could also include the normal pregnancy (although it

neuromuscular disorders) obviously can ‘‘affect’’ only women of reproductive age) as a

cause of temporary dysfunction of the thorax due to the pressure

that the and the amniotic sac exert on the diaphragm.

Acquired chest wall abnormalities

Hypoplasia or absence of the lung

Trauma Lung agenesis, severe lung hypoplasia (e.g. congenital dia-

Traumatic to the thorax such as fractures of the ribs, the phragmatic hernia), and can cause significant

sternum or the spine will affect the normal function of the thorax disfigurement of the rib cage due to the ‘‘caving’’ of the rib cage on

not only at the time of the injury but potentially in the long-term as the affected side as well as due to the hyperinflation of the

well, due to potentially abnormal healing. Similar short and long- contralateral lung that usually herniates to the opposite side thus

term effects may be produced by accidental trauma to the muscles rotating the intrathoracic organs and the .

(e.g. extensive burns) Or after iatrogenic injuries (e.g. rib and/or

muscle resection due to tumours, sternotomy for cardiac ) Severe upper

Chronic significantly increased work of breathing (e.g. severe

Neurologic conditions or ) may cause irreversible

Partial or complete paralysis of the respiratory muscles due to disfigurement of the chest wall, usually in the form of pectus

injuries (e.g. injury) or (e.g. Guillain-Barre excavatum.

syndrome), not only prevent the normal breathing but eventually,

can cause significant disfigurement of the thorax because the weak ANATOMY & PHYSIOLOGY OF THE THORAX

muscles cannot provide the necessary stability that is required to

maintain its physiologic shape. To understand the effects of the thoracic dystrophies on the

respiratory system, one has to understand the anatomy and

Diseases affecting components of the thorax physiology of the normal thorax. The rib cage is formed very early

Various unrelated conditions may affect parts of the thorax in fetal life. Primitive elements of the ribs, the and the

causing significant limitation to its expansion. Typical examples sternum can be detected as early as 6 weeks of gestation

(although generally rare in children) include ankylosing (mesenchymal phase). When fully developed, the thorax resembles

A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255 249

a truncated cone formed by the sternum anteriorly, by the 12 Underneath the external muscles lay the

of the spine posteriorly, and by 12 pairs of ribs (external, internal, and transverse or innermost).

that connect the sternum and the spine in a complex way. The intercostal muscles together with the diaphragm comprise

Specifically, all 12 pairs of ribs are connected with the 12 thoracic the main , whereas the sternocleidomastoid

vertebrae thus forming the posterior and lateral aspects of the rib and the , as well as the serratus posterior and the

cage. However, only 4 pairs (first, tenth, eleven and twelfth) are levatores costarum muscles comprise the secondary muscles of

connected with the respective vertebrae, whereas the remaining respiration. The various respiratory muscles perform different

pairs (ribs 2-9) are connected with two vertebrae each. The anterior functions. The diaphragm and the external intercostals (and in part

wall of the thorax is formed by the sternum that is connected only to the internal intercostals) are the primary inspiratory muscles

the first 7 seven pairs of ribs. Ribs 8-10 are attached only indirectly to during tidal breathing and during mild/moderate . The

the sternum by being attached to the of the rib above them, scalene and the sternocleidomastoid muscles are also inspiratory

whereas the eleventh and twelfth ribs are not attached to the muscles but they are used primarily at times of maximal exertion

sternum at all. These articulations form a characteristic triangular and/or during respiratory distress. The abdominal muscles

opening in the anterior wall. [1] enhance the inspiratory function of the diaphragm (especially in

The ribs are attached to the vertebral bodies as well as to the the upright and sitting position) during quiet breathing. When the

sternum with true synovial consisting of articular , diaphragm contracts, it slides downwards over the spine,

capsules and synovial cavities that allow freedom of effectively ‘‘scooping-out’’ the abdominal contents. The abdominal

movement of the ribs during the respiratory cycle. In neutral muscles create a ‘‘barrier’’ that prevents the outward movement of

position, the ribs (especially the lower ones) lie in a downward the abdominal contents which generates a high intrabdominal

fashion whereas during inspiration they assume a more horizontal pressure that is transmitted to the diaphragm causing its

position thus expanding the rib cage in an upward and outward ‘‘flattening’’ that in turn causes the outward expansion of the rib

fashion. However, not all ribs move the same way. The upper ribs cage. The interaction between the diaphragm and the abdominal

move in a vertical plane that resembles the movement of an old- muscles explains the difficulty in breathing or the respiratory

fashion pump (pulling the rib cage upwards). The middle ribs move failure that occurs when the abdominal muscles are defective (e.g.

in a way similar to the handle of a bucket, whereas the lower ribs gastroschisis), weak (e.g. in neuromuscular diseases or normally in

move laterally, resembling the movement of a caliper. These the neonatal period), or traumatized (e.g. in or

complex movements allow the rib cage to increase significantly its after major abdominal surgery). There are no pure expiratory

cross-sectional area thus providing enough space for the lungs to muscles, because exhalation during tidal breathing is a passive

expand. During infancy the ribs lie normally in an almost movement produced by the elastic recoil of the lungs. However,

horizontal position, placing the infants at a mechanical disadvan- forced exhalation depends on the internal intercostals and to a

tage compared to older children and adults because they cannot lesser degree on the abdominals. [1]

expand their chest outward and so they rely almost exclusively on

diaphragmatic breathing. EFFECTS OF CHEST WALL ABNORMALITIES ON THE

The sternum is a few centimeters long at birth but it grows up to RESPIRATORY SYSTEM

20 cm in adults. It is comprised of three areas (manubrium, body,

and xiphoid). The manubrium is connected via articulation with In general, chest wall abnormalities affect the thorax by

the and the first rib. It is also connected with the body of impairing or preventing its growth and/or by limiting its move-

the sternum approximately at the level of the junction of the ment. In both cases the effects are not limited to the thorax but

second rib (angle of Louis). Normally, the bifurcation of the they extend to the intrathoracic organs as well.

is located behind the angle of Louis. [1]

The thorax is separated from the abdominal cavity by the Effects on the growth of the thorax

diaphragm. As a result it is subjected directly to the pressures

generated in the abdominal cavity, in part contributed to by the Similar to the overall somatic growth, the thorax grows in a

size of the abdominal organs. The diaphragm consists of two gradual but not completely linear fashion that is characterized by

distinct muscular parts connected by a . The tendon extends growth spurts. Under normal circumstances, the thoracic volume

from the xiphoid of the sternum to the second and third in a newborn infant represents only a small fraction of the thoracic

lumbar vertebral bodies, thereby placing the diaphragm in an volume during adulthood. By 5 years of age, the thoracic volume

angle in which its anterior portion lies higher than the posterior. increases to about 30% of the adult size, and by age 10 it reaches

The position of the diaphragm is not fixed and changes during the approximately 50% of its final volume. The remaining 50% develops

respiratory cycle, descending to the bottom of the rib-cage during during the prepuburtal period and early . [2] Thus, any

inspiration, and ascending to almost half of the rib cage during process (congenital or acquired) that limits the growth of the

maximal expiration. thorax will have profound long-term effects on the thoracic

The thorax is covered by several muscles. The anterior part is volume and on the lungs. What actually limits the growth of the

covered by the and minor, the latissimus dorsi, the thorax (and possibly of the lungs) is unclear. In general, the more

serratus anterior, and partially by the cervical muscles (the severe the abnormality, the more impaired is the thoracic volume

sternocleidomastoid and the scalene). The posterior part of the and the lung volume. However, the effects are not linear and they

thorax is covered superficially by the and latissimus dorsi seem to depend to a large extent on which component of the

muscles whereas the serratus anterior and posterior, levatores and thorax (sternum, spine, ribs) is mostly affected. It appears that

major and minor rhomboids form a deeper layer. The external abnormalities affecting primarily or exclusively the sternum or the

muscles primarily stabilize and protect the thorax and they do not spine have relatively mild effects on the lung volume. For example

normally participate in the function of respiration. However, at the lung volume in patients with idiopathic pectus excavatum

times of extreme respiratory distress some of them (the deltoid, tends to be within the normal range (although at the lower levels of

pectoralis, and latissimus dorsi muscles) can indirectly assist the normal). [3] Similarly, a large prospective study comparing the

respiration by ‘‘immobilizing’’ the upper extremities. Muscle injury growth of the thoracic volume in children and adolescents (4-16

or absence (as in the case of the pectoralis major muscle in Poland years of age) with mild/moderate and severe scoliosis revealed that

syndrome) may affect the physical integrity of the thorax. the thorax grew normally in patients with mild to moderate

250 A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255

scoliosis but it was lower in all age groups in patients with severe called ‘‘thoracic insufficiency syndrome’’. [6] In general, the

scoliosis (although the difference did not seem to be clinically very adverse effects of chest wall abnormalities tend to be more

important). [4] In contrast, patients with spondyloepiphyseal profound when they are present in the newborn period and early

dysplasia and fused ribs were found to have very severe restrictive infancy. Thus, congenital and infantile scoliosis tends to be

lung disease with forced vital capacity <30% of the predicted associated with significant lung hypoplasia, whereas in idiopathic

normal and significant shortening of the posterior length of the adolescent scoliosis of the same degree, the decreased total lung

thorax. [5] These findings suggest that in addition to the overall capacity may be due to lung hypoinflation. The reasons for this

volume of the thorax what really makes a difference is the degree difference are not clear considering that normally about 50% of the

to which the affected thorax can expand on inspiration. Although final thoracic volume grows around puberty. A possible explana-

virtually all chest wall abnormalities limit the thoracic expansion, tion is that congenital anomalies may be associated with molecular

the ones associated with rib fusion and/or with severe respiratory abnormalities that may affect the lungs directly. For example, the

muscle weakness appear to have the worse outcome. various chondrodysplasias are associated with genetic mutations

affecting the transmembrane receptors, and the various spondy-

Effects on the Respiratory System Mechanics loepiphyseal dysplasias are associated with abnormalities invol-

ving the proteins involved in the matrix of the cartilage. [7] Even

The respiratory system compliance (Crs) is the product of the relatively mild chest wall abnormalities, such as pectus excava-

chest wall compliance (CW) and the lung compliance (CL) and it tends tum, seem to have more profound effects when they are associated

to be decreased in virtually all the chest wall abnormalities. Because with syndromes such as . Another possible

the latter do not usually affect the lungs directly, the decrease in Crs explanation is that infancy is the period of rapid lung development

is primarily due to the decrease in chest wall compliance. Indeed, as with the appearance of new bronchioles and alveoli and therefore

it can be seen in Fig. 1, using the same inflating pressure in an any process that limits this development will have a much worse

anesthetized patient with Jeune syndrome results in a much smaller outcome than a process that limits the full inflation of the lung

lung volume when the chest was closed, compared to the volume after all the internal divisions have been completed.

obtained when the thorax was open during a sternotomy and after it The decreased total lung capacity is often associated with

had undergone surgical expansion. increased residual volume (RV) resulting into an elevated RV/TLC

ratio suggesting presence of air-trapping despite the absence of

Effects on the Lung Function clinical or spirometric evidence of lower airway obstruction. This is a

relatively common finding among patients withpectus excavatum or

The most common effect of chest wall abnormalities on the lung scoliosis. [3] It is possible that the increased RV is simply due to the

function is the gradual development of restrictive lung defect that fact that the chestwallabnormalitydoesnot allowthe lungs toreturn

is characterized by decreased total lung capacity (TLC). In the to the normal neutral position and/or that the expiratory muscles are

majority of the cases, the lung volume tends to be fairly normal at unable to produce a full exhalation possibly because the expiratory

birth and probably during early infancy, but its growth is gradually respiratory muscles are at a mechanical disadvantage. [8,9] The

limited by the inability of the thorax to grow resulting into the so- 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

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 hyperinfla-

tion 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

Figure 1. Deflation flow-volume curves (DFVC) obtained intraoperatively in a

reversible with administration of bronchodilators. This has been

patient with Jeune syndrome. Top panel:DFVC were obtained while the chest was

described in a substantial number of patients with pectus

closed. Middle panel: DFVC during median sternotomy. Note the significant

excavatum [3] as well as in patients with neuromuscular disorders

incbrease in the vital capacity (X-). Lower panel: DFVC after the sternum was

fixated in a position that allowed an increased lung expansion (Courtesy of Dr. possibly due to development of chronic airway inflammation

Etsuro K. Motoyama). 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

Figure 3. Maximal flow-volume curves in a patient with severe scoliosis. A. The

the scoliosis that is invariably present, there is asymmetry between expiratory flow-volume curve shows extensive ‘‘flattening’’ of its proximal portion

the two hemithoraces and as a result one of the lungs is always consistent with central airway obstruction. B. Repeat testing after surgical repair of

the scoliosis shows significant resolution of the central airway obstruction.

considerably bigger than the other. One would expect that this

(Courtesy of Drs. Raul Corrales and Ignacio Dockendorff).

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 patients need to generate a much higher than normal transdiaph-

the ratio indeed changes and it can increase up to 80% contribution ragmatic pressure that requires increased contributions of the rib

from one lung. This change can occur in the right or in the left lung. It cage as well as the abdominal expiratory muscles. These

is not known whether these changes in the ratio are reversible after mechanisms are normally reserved for conditions of increased

surgical repair. This information could have clinical implications and metabolic demands such as during exercise. However, when they

specifically it might influence the decision for and/or the extent of are used for regular breathing they increase significantly the risk of

the repair. Interestingly, the lung that contributes most in the respiratory muscle fatigue and eventual .

ventilation/perfusion calculation does not seem to correlate directly Disordered breathing during sleep, consisting of central hypop-

with the Cobb angle. Thus, one may have to consider more extensive noea and/or true apnoea associated with desaturations especially

evaluation with the use of V/Q scans and then proceed with an during REM sleep, has been described and it is possibly quite

operation that preserves the functioning lung. [11] common in patients with scoliosis. Although these problems can

be expected to be more common and/or more severe among

Effects on the breathing pattern patients with severe scoliosis, there is no direct correlation

between them and the degree of scoliosis. In severe cases of

o

In the absence of other underlying disorders, mild to moderate scoliosis (angle >100 ), patients are at an increased risk of

o

scoliosis (i.e. angle <70 ) actually produces very few symptoms developing chronic respiratory failure and pulmonary hyperten-

and signs relating to the respiratory system. Severe scoliosis sion (the latter being the product of chronic , chronic

(primary or secondary) is associated with significant alterations in hypoxemia and chronic hypercapnia). [12,13]

the breathing patterns at rest, on exertion and during sleep. The

respiratory rate tends to be higher than normal whereas the tidal EFFECS ON THE INTRATHORACIC ORGANS

volume may be normal, higher than normal or lower than normal.

[12,13] However, in all of these cases the tidal volume is actually The ‘‘houses’’ organs from various systems

increased relative to the vital capacity. This means that the affected including the respiratory (lungs and the intrathoracic trachea),

252 A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255

cardiovascular (heart, major and ), gastrointestinal Shortness of breath (SOB) and exercise limitation

(most of the esophagus), lymphatic vessels and various nerves

(including the phrenic and the recurrent laryngeal nerves) that are Exercise limitation is a typical symptom of chest wall abnorm-

‘‘packed’’ tightly together. Thus, when the thoracic cage becomes alities but its severity varies widely among patients depending on

distorted, all the intrathoracic organs are displaced in ways that the type and severity of the abnormality. In order to meet the

may directly impede their function. Asymmetry between the two increased metabolic demands that are required during physical

hemithoraces has significant effects on the lungs causing activity, both the lungs and the heart need to increase their output

hyperinflation on the larger side and hypoinflation (or complete (i.e. Lungs increase the minute ventilation and the heart increases its

collapse) on the other. The mediastinum is also shifted together cardiac output). Normally, the increase in the minute ventilation is

with the trachea and the major bronchi can become kinked. The achieved by increasing the respiratory rate and especially by

deformation of the thorax limits among other things its antero- increasing the tidal volume (up to 3-4 times the size of the tidal

posterior diameter thus compressing the heart and preventing it volume at rest). Similarly, the heart increases its cardiac output by

from increasing its stroke volume. This is believed to be one of the increasing the heart rate and its stroke volume (also up to 3-4 times

main mechanisms causing exercise limitation in patients with the size of the stroke volume at rest). Patients with chest wall

significant pectus excavatum. [14,15] abnormalities are unable to these physiologic responses due

to a variety of reasons, such as true hypoplasia, fused rib cage,

CLINICAL SIGNS & SYMPTOMS respiratory muscle weakness and cardiovascular compression. For

patients with significant abnormalities the issue is not exercise but

There are several that are typical among the ability to meet the demands of daily life and especially whether

the various chest wall abnormalities although none of them is they can tolerate the increased work of breathing that is associated

unique and pathognomic. Such signs and symptoms include the with acute respiratory .

following:

SURGICAL REPAIR AND ITS OUTCOMES

Shallow breathing

Many surgical techniques have been developed over the years

It is usually seen in moderate to severe chest wall abnormalities for the correction of chest wall abnormalities with variable success.

and it is the result of the minimal expansion of the rib cage that From a medical standpoint the various interventions can be

produces a very small tidal volume. summarized as follows:

Tachypnoea - Interventions that restore the structural integrity of the thorax to

(near) normal (e.g. repair of idiopathic pectus excavatum in an

It is the compensatory mechanism for the shallow breathing in otherwise healthy individual) [16]

order to maintain adequate minute ventilation. Infants (or even - Interventions that prevent the deterioration of a chest wall

older children) with severe deformities can developrespiratory rates abnormality (e.g. spinal fusion in order to prevent the worsening

in excess of 60 (and as high as 100) breaths/minute, thus putting the of scoliosis) [12,13]

patients at a very high risk for muscle fatigue and respiratory failure. - Interventions that improve the functionality of the thorax (e.g.

repair of traumatic injury to the chest)

Tachycardia - Interventions that improve the function of the intrathoracic

organs (e.g. the vertical expandable prosthetic titanium rib

It is the result of the extra work that patients perform for their (VEPTR) technique for Jeune syndrome) [6]

breathing and/or the inability of the heart to increase its stroke

volume.

Whether an intervention could (or should) be made depends on

the careful selection of the objective of the intervention which in

Failure to thrive

turn will determine whether the outcome was successful or not. The

second area in which the various specialists involved in the care of

The majority of patients with severe thoracic abnormalities

complex patients should consider is the careful assessment of

tend to have a degree of failure to thrive. This is the result of low

factors other than the chest wall abnormality that may affect both

caloric intake (e.g. difficulty to eat due to tachypnoea) and high

the feasibility and the success of the outcome. Such factors include:

caloric expenditure necessary to maintain the high respiratory and

heart rates.

- The severity of the abnormality (as one might expect the milder

the abnormality, the easier it is to be repaired and vice versa),

Abnormal auscultatory findings

- The presence of other abnormalities (e.g. the outcome of

idiopathic scoliosis repair in an otherwise healthy patient is

Asymmetrical breath sounds between the two hemithoraces is a

far more successful compared to that in a patient with a

common finding among patients with thoracic abnormalities. In

significant chondrodysplasia),

most of them, the asymmetry is the result of scoliosis that distorts

- The presence of other underlying conditions/syndromes that

the shape of the thorax creating a convex (and larger) side and a

may affect the clinical outcome (e.g. attempt to repair the rib cage

concave (and more narrow one). Which side produces the ‘‘better’’

of a patient with severe poorly controlled pulmonary hyperten-

breath sounds is not always clear however. Decrease in the breath

sion may place the patient at a disproportionately high risk with

sounds due to limited expansion and underlying atelectasis is

very little benefit).

usually evident on the concave side of the chest. However, decreased

- The timing of the operation (i.e. is there an ‘‘optimal’’ time for the

breath sounds may also be produced by the massive hyperinflation

repair of a chest wall abnormality?).

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 The timing of the operation (especially of elective ones, such as

due to the limited expansion of the chest. repair of pectus excavatum or adolescent idiopathic scoliosis)

A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255 253

deserves special consideration. For many years it was assumed that all the currently available surgical techniques are focused on the

the primary effect of the chest wall deformities was that they stabilization/reconstruction of the bony parts of the thorax (spine,

impede the normal growth of the lungs. As a result there had been ribs, sternum). There is however, no information on how the

attempts to correct chest wall abnormalities early on in life in changes in the configuration of the thorax affects the respiratory

order to allow the lungs to grow normally. However, the results muscles. It is conceivable that changes in the rib cage may actually

ranged from disappointing (e.g. early attempts to correct the chest place the respiratory muscles at a mechanical disadvantage

in patients with asphyxiating thoracic dystrophy) [17], to compared to their pre-operative position. It is also possible that

disastrous (e.g. development of iatrogenic ‘‘asphyxiating thoracic some of the chest wall abnormalities may be associated with

dystrophy’’ in patients who underwent repair of pectus excavatum impaired lung parenchyma that precludes its normal growth

th

before the 4-5 year of life). [18] In the latter cases it appeared that regardless of the thoracic volume. It should be noted that it is not

the failure was at least in part due to the fact that the rib cage was possible to make direct comparisons between these studies

not ossified enough to support the repair. In addition, early repair because they included very heterogeneous populations in terms

may impede the changes in the configuration of the thorax that of their underlying diseases and abnormalities, operated at

occur normally especially during the periods of growth spurts. different ages and with a variety of procedures. Moreover, the

Thus, the current tendency, if not consensus, is that surgery should lung function was evaluated with different techniques that may

be deferred if possible until the patient is at least 10 years of age or affect the outcomes. For example, in the measurements made with

older. [19] The exception to this is for procedures that allow the the deflation flow-volume curve technique used in the studies by

periodic adjustment of the repair (the so called ‘‘growth-friendly’’ Motoyama et al. [25,26], the measurements are usually made after

procedures) so it can follow the growth of the rest of the body. [2] the patient had received sigh breaths that help recruit atelectatic

The functional outcomes of surgical interventions for chest wall lung. In contrast, the raised volume technique used by Mayer and

abnormalities remain rather controversial. [20–29] In general, there Redding [29], the lung is inflated by the ‘‘stacking’’ multiple

is post-operative improvement in the activity level and exercise breaths that may not be able to recruit as much of the atelectatic

tolerance of patients with pectus excavatum and/or adolescent lung and thus it will produce much lower values.

idiopathic scoliosis. However, it is not completely clear whether this In summary, chest wall abnormalities are diverse conditions

is due to improved cardiopulmonary function secondary to associated with high morbidity and occasionally mortality. Chest

improved thoracic volume or simply because the improved body wall abnormalities are generally associated with decreased lung

image makes the affected patients more likely to exercise. [21] volume. This decrease can be the result of associated primary lung

One aspect of the repair of most abnormalities is that the hypoplasia, of inability to grow due to a restrictive rib cage or due

enlargement of the thoracic cavity is not accompanied by to chronic hypoinflation is not clear and it is likely to be due to a

improved lung growth. In fact there is evidence that at least in combination of some or all of the aforementioned factors.

the short term the repair results into decrease in lung volume. [23– Currently available surgical techniques may delay or may prevent

27] This evidence has been provided by pre- and postoperative the worsening of the abnormality and in certain conditions such as

pulmonary function studies in patients with thoracic insufficiency idiopathic pectus excavatum and idiopathic adolescent scoliosis

syndrome who underwent repair with the VEPTR technique. [20] the surgical repair may reconstruct them to a satisfactory often

Although the repair itself seems to have been successful in near normal level. However, the effect of the surgical repair on the

enlarging the thoracic cavity and/or improving the scoliosis curve, lung growth and function remains rather controversial.

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

PRACTICE POINTS

studies produced results that are at the best contradictory. Thus,

Mayer and Redding reported that the forced vital capacity (FVC)

1. Chest wall abnormalities are mostly congenital and often

remained decreased compared to the baseline even at approxi-

part of a syndrome

mately 8 months after the operation. [20]. In contrast, Motoyama

2. Idiopathic chest wall abnormalities tend to have less

et al. [25] reported that several months after the operation and for

severe course and better outcomes after surgical repair

up to almost 3 years the forced vital capacity (FVC) increased at a

3. Development of restrictive lung defects are characteristic

rate of 26.8%/year that was similar to that of healthy normal

of most chest wall abnormalities and they are caused

children. However, the FVC did not show any improvement as

primarily by the chronic hypoinflation secondary to the

percentage of the predicted normal value. Moreover, in a follow-up

inability of the rib cage to fully expand.

of study of a larger group of patients the same investigators

4. Surgical repair of chest wall abnormalities rarely results in

reported that the FVC increased by only 11.1%/year. [26] Even more

significant improvement of the lung growth and function

disappointing were the results from a study of lung function

but it may be necessary to prevent its deterioration.

performed approximately 10 years after the surgery in which the

average FVC of the patient population was <60% of that of age-

matched controls. [22] Interestingly, both studies provided

evidence that the effects of the surgery on the lung volume and

References

function depend on multiple factors. For example, Motoyama et al.

[26] found that the rate of growth was much better among children

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4. The ribs are attached to the spine and the sternum with true

CME SECTION

synovial joints

This article has been accredited for CME learning by the

5. The anterior portion of the diaphragm is lower than its

European Board for Accreditation in Pneumology (EBAP). You

posterior portion

can receive 1 CME credit by successfully answering these

questions online.

Effects of Chest Wall Abnormalities on the Respiratory System

(A) Visit the journal CME site at http://www.prrjournal.com/

(B) Complete the answers online, and receive your final score 1. The thoracic volume increases most rapidly during infancy,

upon completion of the test. by 5 years of age the thoracic volume increases to only 30% of

(C) Should you successfully complete the test, you may its final size)

download your accreditation certificate (subject to an 2. The lung growth depends primarily on the ability of the

administrative charge). chest to expand and not on the overall size of the thoracic

volume

3. The lung compliance is severely decreased in patients with

CME QUESTIONS

chest wall abnormalities, chest wall abnormalities decrease

primarily the chest wall compliance not the lung compliance.

Types of Chest Wall Abnormalities

The latter may decrease as a result of the atelectasis that

often develops).

1. Chest wall abnormalities refer to congenital anomalies of the

4. Chest wall abnormalities are associated with air-trapping,

thorax. They can also be acquired

although chest wall abnormalities usually cause a restric-

2. Chest wall abnormalities refer to abnormalities of the rib.

tive lung defect, they are often associated with air-

They can also be due to abnormalities of the sternum, the

trapping as well due to the inability of the thorax to

spine and/or of the respiratory muscles

return to neutral position during exhalation and allow the

3. Burns can cause chest wall abnormalities

lung to empty)

4. Subglottic stenosis can lead t o the development of barrel

5. Idiopathic pectus excavatum is always associated with

chest, upper airway obstruction tends to be associated with

severe restrictive lung defect, the majority of patients with

the development of pectus excavatum

idiopathic pectus excavatum tend to have lung volumes that

5. Spinal muscular atrophy leads to the development of chest

are at the lower levels of normal)

wall abnormalities.

Anatomy & Physiology of the Thorax Effecs on the Intrathoracic Organs & Signs & Symptoms

1. The rib cage is formed in the second trimester of pregnancy 1. Scoliosis causes atelectasis on both lungs. Scoliosis is

2. Each pair of ribs is connected with an individual vertebral body characterized by asymmetry between the two hemithoraces

3. Only some of the ribs are connected directly to the sternum, that causes hyperinflation on the larger side and hypoinfla-

only the first 7 pairs are connected directly to the stenum tion or complete collapse on the other).

A.C. Koumbourlis / Paediatric Respiratory Reviews 15 (2014) 246–255 255

2. Exercise intolerance in pectus excavatum is due to the small

Surgical Repair and its Outcomes

lung volume. The displacement of the sternum decreases the

anterioposterior diameter of the thorax and prevents the

1. Repair of pectus excavatum is indicated in early age in order

heart from increasing its stroke volume, thus leading to

to allow normal lung growth. Repair of pecrus excavatum in

exercise intolerance).

infancy has the potential of causing iatrogenic asphyxiating

3. Chest wall abnormalities can cause airway abnormalities.

thoracic dystrophy).

The displacement of the mediastinum can lead into ‘‘kinking’’

2. Repair of severe scoliosis is not followed by increases in lung

of the main stem bronchii and and development of large

volume. Scoliosis repair very rarely result in improvement in

airway obstruction).

lung volume. In fact the lung volume actually decreases

4. Decreased breath sounds in a patient with severe scoliosis

immediately post-operatively and it slowly recovers within

can be heard both in the convex and the concave

1-2 years)

hemithorax. Although breath sounds are usually decreased

3. Improved exercise tolerance after repair of chest wall abnorm-

in the concave hemithorax due to atelectasis, massive

alities is due to increased lung volume. The improvement is

hyperinflation on the convex side may have the same

more likely to be due to improved cardiovascular function)

effect).

4. The VEPTR technique in infants with chest wall abnormalities

5. Failure to thrive is common in patients with chest wall

is not followed by significant lung growth. The results of

abnormalities due to associated gastrointestinal abnorm-

pulmonary function testing in infants who underwent repair

alities. Although patients with chest wall abnormalities

of chest wall deformities with the VEPTR technique have been

may have associated abnormalities from other organ

controversial. After an initial decrease, there appears to be

systems, the failure to thrive is usually the result of low

increase in lung growth but not at the levels of a normal child)

caloric intake (secondary to difficulty to eat/drink due to

5. The outcome of scoliosis surgery depends on which part of the

tachypnea, muscle weakness etc), and the high caloric

spine is affected. Surgery in the proximal spine tend to be as-

expenditure for their breathing)

sociated with worse outcomes than surgery in the caudal spine.