Page 481 - Textbook of Pathology, 6th Edition

1. Death. The mortality rate in neonatal ARDS is high (20 to squames and meconium. Scattered aerated areas of the 465
30%) and is still higher in babies under 1 kg of body weight. lung are hyperinflated causing interstitial emphysema and
The stiff lung in adult ARDS fails to respond to oxygen pneumothorax.
therapy and is acutely serious and severe respiratory problem
which may be fatal. COLLAPSE. Pulmonary collapse or secondary atelectasis in
2. Resolution. Milder cases of neonatal ARDS recover with children and adults may occur from various causes such as
adequate oxygen therapy by ventilator-assist methods in a compression, obstruction, contraction and lack of pulmonary
few days, while in adult ARDS control of the trigger which surfactant. Accordingly, collapse may be of the following
initiated it may result in resolution. The hyaline membrane types:
is liquefied by the neutrophils and macrophages and thus 1. Compressive collapse. Pressure from outside causes
absorbed. The cell debris in alveolar lumina are cleared by compressive collapse e.g. by massive pleural effusion,
the macrophages and restore the normal aeration of the haemothorax, pneumothorax, intrathoracic tumour, high
alveoli. diaphragm and spinal deformities. Compressive collapse
3. Other sequelae. Besides the two extremes—death and involves subpleural regions and affects lower lobes more than
recovery, other long-term sequelae of ARDS are as under: the central areas.
i) Some cases of neonatal ARDS who recover may develop 2. Obstructive/absorptive collapse. Obstruction of a
bronchopulmonary dysplasia later on. bronchus or many bronchioles causes absorption of oxygen
ii) In both neonatal and adult ARDS, there may be develop- in the affected alveoli followed by collapse e.g. by viscid
ment of desquamative interstitial pneumonia (DIP) due to mucus secretions in bronchial asthma, chronic bronchitis,
pneumocytes proliferation supervened with inflammation. bronchiectasis, bronchial tumours and aspiration of foreign
iii) Patients of adult ARDS who survive acute episodes may bodies. Obstructive collapse is generally less severe than the
develop widespread interstitial fibrosis later and progress compressive collapse and is patchy.
to diffuse fibrosing alveolitis (Hamman Rich syndrome). 3. Contraction collapse. This type occurs due to localised
fibrosis in lung causing contraction followed by collapse.
BRONCHOPULMONARY DYSPLASIA CHAPTER 17
Bronchopulmonary dysplasia occurs as a complication in BRONCHIOLITIS AND BRONCHIOLITIS OBLITERANS
infants treated for neonatal ARDS with oxygen and assisted Bronchiolitis and bronchiolitis obliterans are the inflam-
ventilation. The toxicity of oxygen and barotrauma from high matory conditions affecting the small airways occurring
pressure of oxygen give rise to subacute or chronic fibrosing predominantly in older paediatric age group and in quite
condition of the lungs termed bronchopulmonary dysplasia. elderly persons. A number of etiologic factors have been
The condition is clinically characterised by persistence of stated to cause this condition. These include viral infection
respiratory distress for upto 3 to 6 months. (frequently adenovirus and respiratory syncytial virus),
bacterial infection, fungal infection, inhalation of toxic gases
Microscopically, there is organisation of hyaline memb- (e.g. in silo-fillers’ disease) and aspiration of gastric contents.
ranes resulting in fibrous thickening of the alveolar walls,
bronchiolitis, peribronchial fibrosis, and development of Microscopically, the lumina of affected bronchioles are The Respiratory System
emphysema due to alveolar dilatation. Many bronchioles narrow and occluded by fibrous plugs. The bronchiolar
show squamous metaplasia.
walls are inflamed and are infiltrated by lymphocytes and
plasma cells. There are changes of interstitial pneumonitis
ATELECTASIS AND COLLAPSE
and fibrosis in the alveoli around the affected bronchioles.
Atelectasis in the newborn or primary atelectasis is defined as
incomplete expansion of a lung or part of a lung, while SUDDEN INFANT DEATH SYNDROME
pulmonary collapse or secondary atelectasis is the term used Sudden infant death syndrome (SIDS) or crib death is an
for reduction in lung size of a previously expanded and well- uncommon condition seen mainly in the western countries.
aerated lung. Obviously, the former occurs in newborn It affects infants in the age group of 2 to 6 months. The
whereas the latter may occur at any age.
condition is seen in premature babies born to mothers who
ATELECTASIS. Stillborn infants have total atelectasis, while have been smokers and indulged in drug abuse.
the newborn infants with weak respiratory action develop Microscopically, at autopsy the upper respiratory airways
incomplete expansion of the lungs and clinical atelectasis. and lungs invariably show petechial haemorrhages.
The common causes are prematurity, cerebral birth injury,
CNS malformations and intrauterine hypoxia.
PULMONARY VASCULAR DISEASE
Grossly, the lungs are small, dark blue, fleshy and non- As stated before, diseases of the heart affect the lungs and
crepitant diseases of the lungs affect the heart. This is because of the
Microscopically, the alveolar spaces in the affected area peculiar characteristics of pulmonary vasculature. The
are small with thick interalveolar septa. The alveolar pressure in the pulmonary arteries is much lower than in
spaces contain proteinaceous fluid with a few epithelial
the systemic arteries. The pulmonary arterial system is