RESPIRATORY CONDITIONS
Transient Tachypnoea of the Newborn
A practical guide for paediatric registrars · Retained fetal lung fluid ("wet lung") in the newborn infant
BUT A DIAGNOSIS
OF EXCLUSION
Delayed lung fluid clearance
At birth, ENaC sodium channels (driven by labour, catecholamines and cortisol) switch the lung from secretion to absorption. Delay leaves fluid behind - the core mechanism.
Pulmonary oedema
Retained interstitial and alveolar fluid reduces lung compliance.
Air trapping
Fluid in the airways causes partial obstruction and hyperinflation (flat diaphragms).
Mild V/Q mismatch
A widened diffusion distance gives mild hypoxaemia; the baby compensates with tachypnoea, and CO₂ stays normal or low.
Self-resolving
As clearance catches up over hours to days, the fluid reabsorbs and the distress settles.
🩺CLINICAL FINDINGS
- Onset within the first 1-2 hours of life
- Tachypnoea is the dominant sign (often 60-120 breaths/min)
- Mild distress only: grunting, flaring, mild recession; cyanosis mild or absent
- Low or no oxygen requirement (often FiO₂ <40%)
- Barrel-shaped, hyperinflated chest with good air entry
- Otherwise well; distress plateaus and improves rather than progressively worsening
🔬INVESTIGATIONS
- CXR ("wet lung"): hyperinflation, prominent perihilar streaking, fluid in the horizontal fissure, small effusions; clears within 24-48h
- Pre/post-ductal SpO₂ (usually normal)
- ABG if more distressed: mild hypoxaemia with normal or low CO₂ (acidosis points elsewhere)
- Blood glucose
- Sepsis screen (FBC, CRP, culture) - early pneumonia/sepsis is indistinguishable
- A diagnosis of exclusion - if it doesn't fit, look again
🚩COMPLICATIONS & RED FLAGS
- Usually none - benign and self-limiting
- Reconsider if distress worsens or persists, FiO₂ climbs above ~40%, or there is significant hypoxaemia
- Hypercapnia or acidosis is not TTN - think RDS, pneumonia/sepsis, pneumothorax, PPHN or cardiac
- Aspiration risk if fed while very tachypnoeic
- A prolonged course (>72h) warrants re-evaluation
Add a de-identified CXR here
Classic appearances: hyperinflation, prominent perihilar streaking, fluid in the minor (horizontal) fissure, small laminar pleural effusions and indistinct "fuzzy" vessels. Heart size is normal, and the changes usually clear within 24-48h.
MANAGEMENT
Supportive and watchful - most babies need little beyond observation, oxygen and feeding caution while it settles.
Supportive Care
- Admit for observation; minimal handling and thermoregulation
- Oxygen to maintain SpO₂ - most babies need little or none
- CPAP if increased work of breathing or higher oxygen needs - helps clear fluid and hold FRC
- Monitor respiratory rate, work of breathing and saturations
Feeding & Fluids
- If RR remains persistently elevated (>80), consider whether to withhold oral feeds and use IV fluids instead
- Enteral feeds once RR settles and the infant is stable
- Oral feeds / breastfeeding as tachypnoea resolves (no oral feeds while on CPAP)
Sepsis & Reassessment
- TTN mimics early sepsis/pneumonia - take a sepsis screen
- Consider empiric antibiotics if risk factors, unwell or atypical; stop at 36-48h if cultures are negative and improving
- Expect improvement within 24-72h; if not, reconsider the diagnosis and call NETS
- Not needed: surfactant, diuretics or routine salbutamol
How do you tell TTN, RDS and early-onset pneumonia apart at the cot side in the first hours?
At what respiratory rate do you withhold feeds, and when do you resume?
Why is TTN a "diagnosis of exclusion," and what would make you abandon it?
What does the evidence actually say about diuretics and salbutamol in TTN?
Take-home message: TTN is the commonest cause of newborn respiratory distress - delayed clearance of fetal lung fluid causing tachypnoea that settles within 24-72h. Care is supportive: oxygen, sometimes CPAP, and feeding caution while tachypnoeic. Because it mimics RDS and early sepsis and is a diagnosis of exclusion, cover for infection when in doubt and think again if the baby is not improving.
For educational purposes only. Always align management to current ANZCOR/NRP guidelines and your local SCN/NICU or NETS protocols.