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Pulmonary & Critical Care Bulletin
Vol. VII, No. 3, July 15, 2001
In this issue :

From Editor's Desk

AEROSOL THERAPY
(Dr. Uma Maheswari,)

ONCE - DAILY ASTHMA PREVENTION THERAPY
(R. S. Bedi & U.S. Bedi)

16th Annual Meeting on Pulmonary and Critical Care Medicine
(Dr. S. K. Jindal)



Publihed under the auspices of:
Pulmonary C. M. E. Programme



Editorial Board :


Department of Pulmonary Medecine
Post Graduate Institute of Medical Education & Research (PGIMER) Chandigarh. INDIA-160012


Subscription :


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.

Pathology

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.

Clinical Features

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.

Pathophysiology

Atelectasis due to absence of surfactant results in intrapulmonary shunting and hypoxemia. As the disease progresses respiratory and metabolic acidosis may occur.

Etiology

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.

Treatment

Therapy is directed at correcting respiratory failure through administration of oxygen, assisted ventilation, correction of acid-base imbalance, temperature and metabolic homeostasis.

Prognosis

The mortality rate is approximately 20%, however, the gestational age greatly influences survival rates. The outlook for survivors is excellent.

Other Disorders

Several other respiratory disorders occur in the newborn infant:

1. Apnea of the premature
2. Aspiration of meconium stained amniotic fluid
3. Spontaneous pneumothoroax
4. Transient tachypnea of the newborn
5. Pneumonia (group B- hemolytic streptococcus)
6. Bronchopulmonary dysplasia
7. Congenital malformations

A number of congenital malformations present with respiratory distress in the newborn, most of which are life threatening. Fortunately these are rare.

Congenital Malformations :
A.
-
Upper airway obstruction :
Bilateral choanal atresia
- Laryngeal web, stenosis
- Pierre-Robin syndrome
B. Lower airway obstruction:
Tracheo-esophageal fistula
Tracheomalacia
Vascular ring
Bronchial stenosis
C. Lung Malformation :
Agenesis
Hypoplasia (Potter's Syndrome)
Congenital lobar emphysema
Bronchogenic cyst
Cystadenomatoid malformation
Congenital lymphangiectasis
AV fistula - sequestration
D. Extrapumonary :
Teratoma
Diaphragmatic Hernia
Chylothorax

Lung Disease in Infancy (Less than 2 years of age)

Bronchiolitis

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.

Pathology

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.

Pathophysiology

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.

Treatment

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.

Course

- progresses rapidly (a few hours) recovery in 24-48 hours
- mortality rate below 1% (5-6% In infants under 6 months)
- adenovirus may produce permanent epithelial damage and interference with mucociliary clearance leading to recurrent or chronic lower respiratory tract infection.

Croup. (Acute laryngotracheobronchitis, spasmodic laryngitis, epiglottitis)

- Inspiratory stridor, brassy cough, hoarseness due to varying degrees of laryngeal obstruction
- Common - viral - usually occurs in children 1-4 years of age - often recurs in the same child
- may be associated with acute URI
- Abrupt onset (nocturnal) or laryngeal obstruction
- Edema and inflammation and spasm of vocal cords and subglottic area
- Usually subsides in a few hours and often recurs the next night or two
- Marked apprehension of child and parents

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
- slightly older age range than viral croup
- due to Hemophilus influenza type B
- cherry-red epiglottis with edema
- may cause complete airway obstruction
- abrupt onset, fever, cough, inspiratory stridor, pain, toxic appearance, neck tenderness, drooling and voice change
- cautious examination with minimal stimulation, since spasm and complete obstruction may result

Treatment: Humidity (mist), oxygen, reassurance, antibiotics (ampicillicin)
- no proven beneficial effect of steroids
- tracheotomy or nasotracheal intubation may be necessary

2. Bronchopneumonia

- a majority are viral - preceding URI, bronchitis or bronchiolitis
- bacterial pneumonia in infants under two years may be due to pneumococcus, staphylococcus, streptococcus, rarely H influenza

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
- usually lobar bronchus but occasionally the main stem is obstructed
- ball-valve obstruction - hyperinflation of one lung diagnosed by inspiratory and expiratory chest radiograph
- may result in wheezing
- one of the few indications for bronchoscopy in children.

4. Asthma

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

Pneumonia

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.

Treatment:

- facilitate removal of secretions (hydration, mist, chest clapping, postural drainage),
- antibiotics
- nutrition (pancreatic insufficiency - malabsorption) replace salt losses
- psychosocial (patient, parents, family).

Dr. S.K. Jindal
Professor & Head (Pulmonary Medicine)
P.G.I.M.E.R. Chandigarh

Dr. S.K. Jindal



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