Enumerate the causes of respiratory distress in a newborn. How would you differentiate between respiratory distress of respiratory origin and that of cardiac origin ?

Causes of Respiratory Distress in a Newborn

The causes of respiratory distress in a newborn can be broadly categorized into pulmonary, cardiac, and non-pulmonary causes.

1. Pulmonary Causes:

• Hyaline Membrane Disease (HMD): Primarily affects premature infants due to surfactant deficiency.
• Transient Tachypnea of the Newborn (TTN): Delayed clearance of fetal lung fluid, common in cesarean deliveries and infants of diabetic mothers.
• Pneumonia: Infection of the lungs, can be congenital (acquired in utero) or postnatal.
• Meconium Aspiration Syndrome (MAS): Aspiration of meconium-stained amniotic fluid, leading to airway obstruction and inflammation.
• Pneumothorax: Air leakage into the pleural space, causing lung collapse.
• Respiratory Distress Syndrome (RDS) due to other causes: e.g., surfactant protein deficiency.

2. Cardiac Causes:

• Congenital Heart Defects (CHDs): Such as ventricular septal defect (VSD), atrial septal defect (ASD), transposition of the great arteries (TGA), and coarctation of the aorta.
• Persistent Pulmonary Hypertension of the Newborn (PPHN): Failure of normal circulatory transition after birth, leading to right-to-left shunting.
• Myocarditis: Inflammation of the heart muscle.

3. Non-Pulmonary Causes:

• Anemia: Severe anemia can lead to increased cardiac workload and respiratory distress.
• Sepsis: Systemic infection can cause metabolic acidosis and increased respiratory rate.
• Neuromuscular Disorders: Conditions like congenital myasthenia gravis can impair respiratory muscle function.
• Diaphragmatic Hernia: Herniation of abdominal contents into the chest, compressing the lungs.
• Pleural Effusion: Accumulation of fluid in the pleural space.
• Airway Obstruction: Choanal atresia, tracheoesophageal fistula.

Differentiating Respiratory Distress of Respiratory Origin vs. Cardiac Origin

Differentiating between respiratory and cardiac causes of distress is crucial for guiding appropriate management. The following table summarizes key differences:

Feature	Respiratory Origin	Cardiac Origin
Onset	Often immediate or within hours of birth	May be delayed, developing over hours or days
Respiratory Rate	Typically high (>60 breaths/min)	Variable; may be normal or high
Breath Sounds	May be diminished, wheezing, or crackles	Often normal or diminished; may have a gallop rhythm
Heart Sounds	Usually normal	May reveal murmurs, gallops, or irregular rhythms
Oxygen Saturation (Preductal SpO2)	Poor response to supplemental oxygen	May improve initially with oxygen, but often remains low
Peripheral Perfusion	Variable; may be normal or poor	Often poor; cool extremities, weak pulses
Cyanosis	Often present and persistent	May be present, but can be intermittent or positional
Chest X-ray	May show infiltrates, pneumothorax, or lung consolidation	May show cardiomegaly, pulmonary edema, or normal findings
ECG	Usually normal	May show arrhythmias, hypertrophy, or other abnormalities
Response to Treatment	Improves with respiratory support (CPAP, ventilation)	May require prostaglandin E1 (PGE1) to maintain ductal patency or specific cardiac interventions

Important Note: These are general guidelines, and clinical presentation can overlap. Echocardiography is often essential for definitive diagnosis of cardiac causes.