Transient Tachypnea of the Newborn (TTN)
Definition and Pathophysiology
TTN is a self-limiting respiratory disorder caused by delayed clearance of fetal lung fluid at birth, typically resolving within 3-4 days without significant long-term complications 1, 2. The condition results from inadequate resorption of alveolar fluid during the transition from intrauterine to extrauterine life 3.
Clinical Presentation
TTN presents within the first 2 hours of life with the following features 1, 2:
- Tachypnea (respiratory rate >60 breaths/minute) 3
- Signs of respiratory distress including grunting, nasal flaring, and intercostal retractions 4
- Mild to moderate hypoxemia requiring oxygen supplementation in most cases 4
- Symptoms typically mild enough that invasive ventilation is rarely needed 4
Risk Factors
The highest risk populations include 4:
- Male infants (63.5% of cases) 4
- Cesarean section delivery, particularly elective LSCS without labor (70.3% of cases) 4
- Late preterm infants (34-36 weeks gestation) 2, 4
- Term infants delivered before 39 weeks 3
Diagnosis
Lung ultrasound is the preferred first-line imaging modality, as it is as accurate as chest X-ray but provides more specific diagnostic findings 1.
Characteristic Ultrasound Findings 1:
- Bilateral confluent B-lines in dependent lung areas
- Normal or near-normal lung appearance in superior fields (this distinguishes TTN from RDS)
- Pleural line thickening
- Alternating pattern of interstitial syndrome with areas of normal lung
Differential Diagnosis
TTN must be distinguished from 1:
- Respiratory Distress Syndrome (RDS): Shows diffuse bilateral confluent B-lines throughout ALL lung fields without any spared areas 1
- Pneumonia: Shows consolidations with dynamic air bronchograms and pleural effusion 1
- Meconium Aspiration Syndrome: Different clinical history and imaging pattern 1
Treatment
Respiratory Support
Oxygen supplementation is the mainstay of therapy, with most infants requiring only supplemental oxygen without mechanical ventilation 4. The approach should be 5:
- CPAP for spontaneously breathing infants with respiratory distress rather than immediate intubation 5
- PEEP (positive end-expiratory pressure) to assist in establishing functional residual capacity 5
- Pulse oximetry to guide oxygen therapy 6
Fluid Management
The evidence for fluid restriction is very uncertain 2, 3. One trial showed reduced hospital stay with fluid restriction (15-20 mL/kg/d less than standard), but the certainty of evidence is very low 2. Given the lack of clear benefit and potential for electrolyte disturbances, standard fluid administration is reasonable 2.
Pharmacologic Interventions
Salbutamol may reduce the duration of tachypnea slightly (mean reduction of 16.83 hours), but evidence is of low certainty 3. The evidence is very uncertain for epinephrine, corticosteroids, and diuretics 3.
Antibiotic Use
Newborns diagnosed with TTN without prenatal risk factors and a negative C-reactive protein test do not need antibiotics 7. Antibiotics should be reserved for cases where infection cannot be excluded based on clinical presentation and laboratory findings 7.
Predictors of Prolonged Course
Factors associated with longer duration of distress and NICU stay include 4:
- Higher Downes' score at presentation
- Low birth weight
- Preterm delivery
- Cesarean section delivery
Prognosis
TTN is a benign, self-limiting condition with excellent prognosis 4. The typical course includes 2, 4:
- Resolution within 3-4 days in most cases 4
- Mean hospital stay of 5-7 days 7
- Severe complications are rare 4
- No long-term respiratory sequelae expected 3
Meconium Aspiration Syndrome (MAS)
Definition and Pathophysiology
MAS is respiratory distress in a neonate born through meconium-stained amniotic fluid (MSAF) with symptoms that cannot otherwise be explained 8. Aspiration can occur before delivery, during birth, or during resuscitation, leading to airway obstruction, chemical pneumonitis, and surfactant dysfunction 5, 8.
Clinical Presentation
MAS presents with early onset respiratory symptoms in term and near-term infants 8:
- Respiratory distress (tachypnea, grunting, retractions) 8
- Poor lung compliance 8
- Hypoxemia often requiring significant oxygen support 8
- Radiographic findings: Hyperinflation and patchy opacifications on chest X-ray 8
- May progress to persistent pulmonary hypertension in severe cases 5
Risk Factors
- Post-term pregnancy (>42 weeks) 8
- Fetal distress during labor 8
- Intrauterine hypoxia or acidosis 8
- Maternal conditions causing placental insufficiency 8
Diagnosis
Diagnosis is clinical, based on 8:
- History of delivery through MSAF
- Respiratory distress that cannot be explained by other causes
- Characteristic chest X-ray findings (hyperinflation, patchy infiltrates) 8
Initial Management at Delivery
Routine tracheal intubation and suctioning is no longer recommended for nonvigorous infants born through MSAF, as it likely delays ventilation without improving outcomes 5, 6. This represents a major shift from historical practice.
Current Approach 6:
For vigorous infants:
- Allow infant to remain with mother and receive routine newborn care 6
- Gentle clearing of meconium from mouth and nose with bulb syringe if necessary 6
For nonvigorous infants:
- Proceed immediately with appropriate resuscitation measures without routine direct laryngoscopy and tracheal suctioning 6
- A team skilled in tracheal intubation should be present at delivery due to increased risk of requiring resuscitation 6
- Intubation and suctioning should be considered only if there is evidence of airway obstruction 6
Respiratory Support
Oxygen Therapy 6:
- Initiate resuscitation with room air for term infants 6
- Use pulse oximetry to guide oxygen therapy 6
- Titrate oxygen to maintain appropriate saturations 6
Ventilatory Support 6:
- Consider PEEP to assist in establishing functional residual capacity 6
- Avoid high peak pressures during mechanical ventilation as these can worsen lung injury 9
- May require mechanical ventilation for severe cases with respiratory failure 5
Supportive Care
Maintain normothermia, as hypothermia increases mortality risk 6. Additional supportive measures include 5:
- Continuous monitoring of heart rate, oxygen saturation, blood pressure, and temperature 9
- Treatment of persistent pulmonary hypertension if present 5
- Antibiotics if infection cannot be excluded 8
Complications
- Persistent pulmonary hypertension of the newborn
- Pneumothorax or pneumomediastinum
- Chronic lung disease requiring prolonged oxygen support 5
- Neurologic injury from severe hypoxemia 5
Prognosis
Prognosis depends on severity of aspiration and presence of complications 8. Most infants with mild to moderate MAS recover fully, but severe cases with persistent pulmonary hypertension carry significant morbidity and mortality risk 5, 8. Long-term respiratory sequelae including reactive airway disease may occur in survivors of severe MAS 5.