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:

• Respiratory Distress Syndrome (RDS): Primarily due to surfactant deficiency, common in premature infants.
• Transient Tachypnea of the Newborn (TTN): Delayed clearance of fetal lung fluid, often seen in term infants delivered by Cesarean section.
• 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.
• Pulmonary Hypoplasia: Underdevelopment of the lungs, often associated with congenital diaphragmatic hernia.

2. Cardiac Causes:

• Congenital Heart Defects (CHDs): Such as Ventricular Septal Defect (VSD), Atrial Septal Defect (ASD), Tetralogy of Fallot, Transposition of the Great Arteries. These defects can lead to increased pulmonary blood flow or decreased systemic blood flow, causing respiratory distress.
• Heart Failure: Inability of the heart to pump sufficient blood to meet the body's needs.

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 affecting the muscles of respiration, such as congenital myasthenia gravis.
• Diaphragmatic Hernia: Protrusion of abdominal contents into the chest cavity, compressing the lungs.
• Pleural Effusion: Accumulation of fluid in the pleural space.
• Airway Obstruction: Choanal atresia (blockage of nasal passages) or tracheoesophageal fistula.

Differentiating Respiratory Distress of Respiratory Origin vs. Cardiac Origin

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

Feature	Respiratory Origin	Cardiac Origin
Onset	Often rapid, may be present at birth or develop within hours	May be delayed, can worsen over days or weeks
Respiratory Rate	Typically high (>60 breaths/min)	Variable, may be normal or elevated
Work of Breathing	Nasal flaring, grunting, retractions (intercostal, subcostal, suprasternal) prominent	May have mild retractions, but often less pronounced than in respiratory distress
Heart Sounds	Normal or may have adventitious sounds (wheezes, crackles)	May have a heart murmur, gallop rhythm, or irregular heart rate
Oxygen Saturation (SpO2)	Often low, may not improve significantly with supplemental oxygen	May be normal initially, but can decrease with worsening heart failure
Peripheral Perfusion	Variable, may be normal or decreased	Often poor, cool extremities, delayed capillary refill
Chest X-ray	May show infiltrates, pneumothorax, or lung hypoplasia	May show cardiomegaly, pulmonary edema, or normal findings
Response to Oxygen	Limited improvement with supplemental oxygen alone	May show transient improvement with oxygen, but underlying problem persists
Response to Diuretics	No response	May show improvement in pulmonary edema

Further investigations like echocardiography are essential to confirm cardiac diagnoses. Arterial blood gas analysis helps assess the degree of hypoxemia and acid-base balance. Pulse oximetry is a continuous monitoring tool, but can be misleading in certain cardiac defects.