LUNG DEVELOPMENT (1).Pre-natal lung development :- The lung bud arises as a pouch from the primitive foregut at 22-26 days gestation. The bronchial tree develops between 5 and 16 wks gestation by continuous budding and branching of the airways . airways branching ends at 16 wks . further growth occurs by an increase in diameter and length but not by increase in air ways number . Insults to lung before 16 wks gestation decrease both air ways number and subsequent alveolar growth and number and the insult after 16 wks affect only alveolar number and growth. (2).post-natal lung development :--- Approximately 60 million primitive alveoli exist at birth ,the lung grows most rapidly in alveolar number during the 1st 2 years . the growth rates decrease thereafter ,until the adult number of approximately 375 million alveoli is reached at age 8-12 yrs .
Common pathologic features of pulmonary :-1-underlying pathologic process : Most lung diseases in children are classified as
A-.Obstruction (airway narrowing ) may be caused by intraluminal secretion , edema or inflammation , hyper trophy or contraction of the bronchial smooth muscles or extrinsic compression
B-Restriction (impaired lung expansion) may be caused by decrease lung compliance ., atelactasis or pneumothorax causing lung collapse ,neuromuscular diseases and disorder of chest wall .
• (2). Pathophysiology :• (a) .hypoxemia (deficient oxygenation of blood ) most commonly caused by ventilation – perfusion abnormalities but may be the result of intra cardiac or intra pulmonary shunt or hypoventilation .
• (b) .hyper capnia (excess carbon dioxide in the blood ) caused commonly by hypoventilation due to upper air way obstruction , neuromuscular weakness or CNS depression
(3). Pathogenic factors :(a) The small airway of the child result in high airway resistance and put the child at great risk for develop of obstructive lung diseases. boys are affected more than and more severely than girls in part because the peripheral airway in boys younger than 5 yrs are smaller than those in girls.
(b) the young child lack specific immunity
( c) in children most pulmonary diseases has a single cause, whereas in adult ,pulmonary diseases is apt to be multifactorial in etiology .
CONGENITAL MALFORMATIONLARYNGOMALACIA AND TRACHEOMALACIA (congenital strider )
Strider persisting or appearing after the first few days of life usually result from disturbance to the larynx .
The most common of these are laryngomalacia and tracheomalacia due to flabbinees of the epiglottis and subglottic and weakness of the airway walls leading to collapse and sometime air way obstruction with inspiration .
Clinical features :Noisy respiration sound usually associated with inspiration are relatively common during the neonatal period and the first years of life ,strider may present at birth or may appear at two months ,male affected more than female ,symptom can be intermittent and are worse when affected infant lie on the back .
Some infant develop dyspnea and inspiratory retraction in the supraclavicular ,intercostals and subcostal spaces .
The strider typically is loudest when the child is feeding or quietly relaxing or in neck flexion position ,and the strider diminished during sleeping or when the child is crying
The strider usually resolves by the age 2 months but may recur with respiratory infection until about three years of age .
Diagnosis :-Is diagnosed by fibroptic bronchoscopy or direct laryngoscopy .
Is usually not needed ,parent should be reassured and provide slow careful feeding ,sometime need small nipple .
Rarely tracheostomy is required when the strider occur in failure to thrive or with life threatening apnea or obstruction .
SUBGOTTIC STENOSISIs a common problem that may be congenital or iatrogenic due to aggressive management of premature infant with intubation and mechanical ventilation may produce residual damage to the larynx .
Infant with down syndrome appear to have a small larynx and more susceptible or sub glottic stenosis .
Subglottic stenosis will produce strider and evidence of obstruction will be present on expiration and inspiration with increasing degrees of respiratory effort ,the strider will worsen with viral infection .
Definitive diagnoses requires endoscopic evaluation .
Treatment may necessitate tracheostomy ,however milder congenital cases improve with age as the larynx grows .
VASCULAR RINGCongenital anomalies of the aortic arch or its branches can create a ring around the airway that compromises respiration .
Clinical features :
If the vascular ring produce compression of trachea and esophagus symptoms are frequently present at infancy , chronic strider and wheezing is exacerbated by crying , feeding and flexion of the neck .
Extension of the neck tends to relieves the noisy respiration .
Vomiting is frequent
X-ray examination of the barium filled esophagus , arteriography , two
dimensional ECHO , MRI ,CT or angiography .
Bronchoscopy may be used to assess air way narrowing .
The condition not improve with age.
Treatment with surgical correction of the defect .HEMANGIOMA
A number of mass lesion affect the larynx ,but the most common is hemangioma ,that usually found in the subglottic space .
Infant with strider should be examined head to toe for coetaneous hemangioma because The presence of such lesion greatly increase the likelihood that the strider due to subglottic hemangioma .
The airway obstruction usually worsen with cry and may produce pulmonary hypertension .
The diagnosis depend on endoscopy and may be by AP x-ray of the larynx .
Treatments are controversial ,may need trachiostomy , others laser therapy or steroid.
As with cutaneous hemangioma ,spontaneous regression is the rule ,but may need years .
PULMONARY SEQUESRATIONA cyst like mass of non-functioning lung tissue which lack normal communications with tracheo –bronchial tree .sometime develops at the embryo .
Most often within the lower lobe , the non functioning part is nourished by systemic arteries . Clinical features :
Infection can result if a fistula develop between the sequestration .
Children usually present with history of recurrent persistent progressive pulmonary sepsis or lung abscess .
Diagnosis of lung sequestration :
1. x-ray usually shows the sequestration as area of density with displacement of the bronchovascular marking .
2-Contrast bronchography shows sequestration as area fail to fill with contras .
3-Arteriography will delineate the anomalous artery supply from the aorta .
The treatmet is surgical removal of the sequestration
FOREIGN BODY ASPIRATIONThe majority of patient are less than 4 yrs and most of death also occur in this age . Younger children most commonly aspirate foods ,toys .
Clinical features :
A high number of children who aspirate foreign bodies will present with either a clear –cut history of choking or physical or x-ray evidence of foreign body ,however a small percentage of patients with foreign body aspirate will have negative history because un observed or unrecognized events .
Physical finding consistent with acute foreign body aspirate include unilateral absence of breath sound ,localized wheeze ,strider or bloody sputum .
X-ray may reveal the presence of radiopaque , when aspiration suspected ,expiratory films should be requested .
Because the right main bronchus is a more direct continuation of the trachea than the left main bronchus ,foreign bodies tend to enter the right lung more .
Some foreign bodies especially nuts or seeds may migrate from place to place in the air way and even lodge in the larynx on coughing totally occluding the air way .
Foreign bodies also may lodge in the esophagus and compress the trachea producing respiratory symptoms .
Diagnosis :-The majority of foreign bodies are small and quickly coughed out ,but many may remain in the lung for long period before diagnosis and may come to medical attention because of symptoms of fever ,cough sputum production or chest pain .
Patient with persistent wheeze unresponsive to bronchodilators therapy, persistent atelactasis ,recurrent or persistent pneumonia or persistent cough without other explanation should be suspected foreign body aspiration .
If there is good evidence in history ,physical examination or by film for bronchial foreign body ,the patient should undergo rigid bronchoscopy .
Flexible bronchoscopy may be very useful diagnosis when presentation is not straight forward .
The best approach to foreign body aspirate is to educate parents .
Infant should not have food that must be easily broken into small pieces .
Toys should be free of small parts that may be aspirate .