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Pulmonary & Critical Care Bulletin
Vol. VII, No. 3, July 15, 2001
In this issue :
From Editor's Desk
Basics of Pediatric Pulmonology for Physicians (Part-II)
Many neonatal pulmonary problems present with similar clinical signs including tachypnea, subcostal and intercostal retractions, expiratory grunting and flaring of the alae nasae. Abnormal events of pregnancy, labour and delivery may provide important clues in making the diagnosis, e.g., prematurity, fetal bradycardia, low Apgar score. The chest radiograph is exceedingly helpful in the diagnosis of neonatal pulmonary disorders.
Hyaline Membrane Disease (HMD) (Idiopathic Respiratory Distress syndrome)
Hyaline membrane disease is the commonest pulmonary disorder of the newborn infant. The incidence increases with decreasing gestational age.
There are focal areas of atelectasis throughout the lungs with dilated terminal bronchioles and alveolar ducts. The so-called "hyaline membranes" are derived from fibrin and other plasma proteins and line the dilated air spaces. They are not necessarily present in infants dying in the first few hours of life and are assumed to be secondary to capillary leakage. Analysis of lung extracts reveals deficient surface active material.
The infant is usually in marked respiratory distress with tachypnea (0-110/min.), chest wall retractions, grunting and see-saw respiration, nasal flaring, and cyanosis. The course usually worsens for 48 to 72 hours with gradual improvement over 2 to 7 days. Severe cases are associated with lung injury and may take several weeks to recover.
X-ray Reticulogranular appearance of parenchyma with air bronchograms.
Atelectasis due to absence of surfactant results in intrapulmonary shunting and hypoxemia. As the disease progresses respiratory and metabolic acidosis may occur.
Not entirely known. The relationship to prematurity and the deficiency of surfactant suggests biochemical (phospholipid) and histological (Type II alveolar cells) immaturity. Fetal hypoxia may play a role.
Therapy is directed at correcting respiratory failure through administration of oxygen, assisted ventilation, correction of acid-base imbalance, temperature and metabolic homeostasis.
The mortality rate is approximately 20%, however, the gestational age greatly influences survival rates. The outlook for survivors is excellent.
Several other respiratory disorders occur in the newborn infant:
1. Apnea of the premature
A number of congenital malformations present with respiratory distress in the newborn, most of which are life threatening. Fortunately these are rare.
Congenital Malformations :
Lung Disease in Infancy (Less than 2 years of age)
Definition : inflammation of the bronchioles - a term generally applied to a clinical syndrome characterized by rapid respiration, chest retraction and wheezing.
Bronchiolitis is the commonest respiratory tract infection requiring hospitalization in infants under one year of age. It occurs frequently after 2 years of age. The infant usually develops mild rhinorrhea and cough and often a low grade fever followed in 1-2 days by rapid respirations, use of accessory muscles, increased A-P diameter, chest retractions and wheezing (high pitched rhonchi). The radiographic appearance is one of diffuse hyperinflation of both lungs with flattening of the diaphragms and usually patchy peribronchial infiltrates.
The etiology is almost always viral; most commonly respiratory syncytial (RS) with other viruses such as adenovirus, parainfuluenza virus types I and III, enterovirus and influenza.
There is inflammation of the bronchiolar respiratory epithelium, damage and destruction of mucosal cells, edema, congestion, exudation, mononuclear cell infiltration, occasionally proliferation of cells, obstruction of lumen with mucus and cellular debris, severe sloughing of epithelium and interference with ciliary activity.
Usually a "ball-valve" type of bronchiolar obstruction resulting in trapped air and hyperinflation and a marked increase in airway resistance (inspiratory and expiratory), increased work of breathing abnormal VA/Q (hypoventilation of some area, hyperventilation of others) - Pa CO 2 remains normal or decreases due to an increase in VE. Tidal volume and frequency are increased. Pa O2 decreases as airway obstruction increases. VE may drop, and then Pa CO2 rises.
O2 for hypoxemia and adequate hydration. Antibiotics are used only if evidence of secondary infection exists. Bronchodilators are usually ineffective. Rarely, endotracheal intubation and ventilatory assistance are required.
- progresses rapidly (a few hours) recovery in 24-48 hours
Croup. (Acute laryngotracheobronchitis, spasmodic laryngitis, epiglottitis)
- Inspiratory stridor, brassy cough, hoarseness due to varying degrees of laryngeal obstruction
Treatment: high humidity or mist, reassurance
Lung Disease in Older Infants and Children
The incidence of acute pulmonary infection decreases while the incidence of chronic respiratory disease increases with age. It has been estimated that chronic pulmonary disease (asthma, cystic fibrosis, bronchitis, bronchiectasis, recurrent lower respiratory tract infection) afflicts approximately 10-15% of the pediatric population and accounts for more than 50% of all chronic diseases of children.
1. Acute epiglottitis
- a severe rapidly progressive infection
Treatment: Humidity (mist), oxygen, reassurance, antibiotics (ampicillicin)
- a majority are viral - preceding URI, bronchitis or bronchiolitis
Pathology : same as in older children and adults - rarely limited to one lobe - exudation - consolidation
Clinical : fever, toxic appearance, cough (productive), tachypnea, grunting respirations, retractions, rhonchi, rales
Differential diagnosis: depends on chest radiograph (perihilar densities, patchy infiltrates and consolidation).
3. Foreign Body Aspiration
- may be lethal - peanuts prime offender - vegetable oils inflammatory reaction of repspiratory mucosa
Asthma is the commonest pulmonary problem of older children. The consequences and seriousness of childhood asthma are not generally appreciated.
The pathophysiology of asthma in children is similar to that in adults. The various approaches to comprehensive treatment and management are too numerous and complex to include in this section
Most childhood pneumonitis is viral or due to mycoplasma. Many children with bronchiolitis, tracheobronchitis croup and sometimes with upper respiratory infection, will also have infection of the terminal airways and alveoli (pneumonia).
The greatest challenge to the clinician is differentiation between bacterial and viral pneumonia. Epidemiologic, and some characteristic clinical patterns assist in this differentiation. There are few laboratory determinants that help.
RS virus is the commonest virus association with pneumonia in infancy and early childhood, followed by parainfluenza 3. Other common causes are parainfluenza 1 and 2, adenoviruses and influenza virus A and B.
Bacterial pneumonias present in a variety of patterns with many features similar to the adult and include many gram negative and gram positive organisms. Group B hemolytic streptococcus is a common cause of pneumonia in the newborn and infants up to 6 weeks of age.
Other etiologic agents include Pneumocystis carinii (almost always in an immunologically compromised host) and chlamydia.
There is a propensity for pneumonia in children less than 4 years to be followed by atelectasis (segmental or lobar) perhaps due to less well developed channels of collateral ventilation following complete obstruction of segmental bronchi.
6. Cystic Fibrosis (fibrocystic disease of the pancreas)
A chronic debilitating pulmonary disease, associated with pancreatic deficiency, high sweat chloride and occasionally cirrhosis. It is an autosomal recessive disease occurring with a frequency of 1:2,000 in Whites. It is the most frequent lethal genetic disease among children.
Exocrine glands are affected, however, no morphologic or histochemical changes are seen except as the disease progresses. Pancreatic pathology includes dilatation of ducts and flattening of epithelium which enlarge to form cysts - diffuse fibrosis. Salivary glands may also be affected.
Pulmonary pathophysiology: Thick, viscid pulmonary secretions - bronchiolar obstruction initially - later mucopurulent secretions block main bronchi leading to chronic lung disease (pneumonia, atelectasis, bronchiectasis).
Increased airway resistance, leads to an increase in the FRC, VA/Q inequality (decreased Pa O2), alveolar hypoventilation (increased Pa CO2) and cor pulmonale.
- facilitate removal of secretions (hydration, mist, chest clapping, postural drainage),
Dr. S.K. Jindal
Dr. S.K. Jindal
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