Respiratory distress syndrome

Respiratory distress syndrome (RDS) describes any change to frequency and/or quality of breathing pattern in newborns. Breathing rate < 60/minute (can be up to 70/min during the first hours of life and sets to around 40/min) is considered physiologic and newborn should not display any signs of increased work of breathing (dyspnea).

Transition to extra-uterine life is very fast (within seconds to minutes) as a newborn cries, pinks up and then starts to have regular and calm breathing pattern. Successful postnatal adaptation depends mainly on 2 factors:

Spontaneous breathing (water in lungs resorbed into blood/lymphatic vessels = gas exchange = increased pO₂ = pulmonary vasodilation = circulation changes see below)
Circulation transformation (pulmonary blood flow increases as pulmonary hypertension subsides = ductal shunting changes to left-right + increased pO₂ causes ductus arteriosus to close)

Pulmonary causes

hyaline membrane disease (sometimes used interchangeably with RDS, although RDS constitutes multiple origins of breathing problems)
transitory tachypnea
amniotic fluid aspiration
early-onset pneumonia (adnate pneumonia)
air leak syndromes (pulmonary interstitial emphysema, pneumothorax)
bronchopulmonary dysplasia (chronic lung disease)

Extra-Pulmonary causes

infection/sepsis
congenital anomalies (cleft palate, choanal atresia, laryngeal obstruction)
cardiology problems (congenital defects, arrhythmia, cardiomyopathy)
thorax deformities
diaphragm problems (congenital diaphragmatic hernia, diaphragm palsy)
neuromuscular problems (neurological trauma, medication – sedatives, myasthenia, myotonia)
hematological issue (anemia, hypervolemia, hyperviscosity)
metabolic disorders (hypoglycemia, inherited metabolic disorders)
homeostasis problems (hypothermia, hyperthermia, acidosis)

Diagnosis

Clinical Signs

Tachypnea = more than 60 breaths / minute
Dyspnea = worsened breathing (intercostal recessions, nasal flaring)
Apnea = absence of breathing (central x peripheral x mixed)
Grunting = expiration sound phenomenon (breathing against the closed glottis maintains positive pressure in lungs)
Cyanosis = central x peripheral
Tachycardia

Laboratory Findings

Blood gas = hypercapnia + hypoxemia + acidosis (respiratory, mixed)

Imaging

Chest X-ray = depends on the nature of RDS = see individual diagnoses and treatments

Pulmonary causes of Respiratory distress syndrome

Hyaline membrane disease (HMD)

Typical for very low birth weight (VLBW) infants (birth weight < 1500 grams)
Quickly develops during the first hours of life = requires complex treatment (see Therapy)
Uncomplicated HMD lasts usually 3-5 days
a hyaline membrane composed of proteins (intra-alveolar leak) and dead cells inside the alveoli (pathologic histology of lungs of premature newborns)
anatomical and functional prematurity of lungs (i.e. typical for preterm newborns)
→ anatomical = preterm lungs in saccular developmental stage (abundant interstitial tissue and insufficient inner spacing)
→ functional = inability to maintain residual volume due to surfactant deficiency => focal atelectasis surrounded with areas of hyperinflation => reticular granular pattern on chest X-ray (+ intra-alveolar protein leak from plasma to alveoli causing edema and surfactant dysfunction)

Surfactant

surface active agent
prevents alveoli from collapse at the end of expiration
produced and recycled by pneumocytes II during the second half of pregnancy
composed of 90% phospholipids (phosphatidylcholine = lecithin + phosphatidylglycerol) and 10% proteins (SP-A/B/C/D)

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Transitory Tachypnea

“wet lung” syndrome = caused by diminished pulmonary fluid resorption
preterm and term newborns (cesarean delivery, maternal diabetes, perinatal asphyxia)
may require complex therapy, however, usually resolves within 12-24 hours (compared to HMD)

Meconium aspiration syndrome (MAS)

fetal hypoxia = gasping = amniotic fluid aspiration => meconium in the fluid = meconium aspiration syndrome
requires support right after delivery (chest X-ray with focal atelectasis or decreased transparency)
meconium in lungs = inflammation, surfactant dysfunction, PPHN = respiratory failure = mechanical ventilation, surfactant, inhaled nitric oxide

Pneumonia

intrauterine / perinatal aspiration of infectious amniotic fluid (chorioamnionitis)
Streptococcus agalactiae (Group B Streptococcus = GBS), Gram negative bacteria, Ureaplasma spp.
lung inflammation = surfactant dysfunction, PPHN + sepsis (BSI = blood-stream infection) = respiratory-circulatory failure = mechanical ventilation, surfactant, inhaled nitric oxide, antibiotics

Air leak syndromes

air leak to interstitial tissue (PIE = pulmonary interstitial emphysema) or pleural cavity (PNO = pneumothorax)
asymmetrical auscultation + typical chest X-ray findings
Spontaneous = vigorous breathing following amniotic fluid aspiration; can resolve spontaneously
Iatrogenic = artificial ventilation / mechanical ventilation; can cause tension PNO
tension pneumothorax is an emergency presenting with sudden bradycardia and/or desaturations and requires chest drainage (unilateral x bilateral with FR 8/10 tube inserted in the 3rd intercostal space) !

Bronchopulmonary dysplasia

chronic lung disease (CLD/BPD) caused by various factors (infection, degree of prematurity, nutrition, aspiration, oxygen, mechanical ventilation, fetal growth restriction) on immature and developing lung tissue (preterm newborns!) = anatomical and functional changes
alveolar space restriction + interstitial tissue increase + disruption of alveolarization and vascular bed formation
mild BPD = oxygen dependency at day of life (DOL) 28
moderate BPD = oxygen dependency at 36 weeks of gestation (36+0)
severe BPD = mechanical ventilation at 36 weeks of gestation (36+0)
Chest X-ray : lung fibrosis, heterogenous involvement, focal emphysema and atelectasis, diffusely decreased transparency
Treatment (see Therapy)
Eventual resolution – oxygen and functional rejuvenation within 1 year (usually)
Pulmonary hypertension (cor pulmonale) – worse prognosis

Therapy

Antenatal

Transfer in utero (to Perinatal centre)
Corticosteroids

Postnatal

Oxygen (to reduce hypoxic injury, esp. brain; careful with overdosing = hyperoxia = retinal damage); pulse oximetry used to monitor hemoglobin oxygen saturation; oxygen (gas) needs to be warmed and humidified; FiO₂ 0.21 = 21% oxygen concentration = air; FiO₂ 1.0 = 100% oxygen concentration; vital signs monitoring – temperature, blood pressure, saturation, heart rate)
Ventilation support (CPAP = non-invasive; mechanical ventilation = invasive)
Surfactant (causal therapy; animal surfactant from pig lungs; synthetic surfactant; needs to be warmed up before bolus administration; immediate effect = increased lung compliance)
Circulation support (severe RDS, sepsis, PPHN = inhaled nitric oxide)
Parenteral nutrition (energy requirements, antioxidants)
Caffein, Antibiotics, Analgesia/Sedation (during mechanical ventilation = blocks interference)
Surgery if necessary (cleft palate, diaphragmatic hernia, congenital airway malformations, oesophageal atresia, congenital heart defects)
Nursing care (secretions, handling, vitals signs monitoring, comfort and pain scoring, invasive lines check-up – endotracheal tube, cannulas, skin care, enteral feeding, eye care)
Home oxygen therapy (BPD)
Prevention of RSV infection (Synagis = Palivizumab = passive immunisation)

References

① Sweet DG, Carnielli V, Greisen G, et al. European Consensus Guidelines on the Management of Respiratory Distress Syndrome – 2019 Update. Neonatology. 2019;115(4):432-450. doi:10.1159/000499361

② Wang C, Guo L, Chi C, et al. Mechanical ventilation modes for respiratory distress syndrome in infants: a systematic review and network meta-analysis. Crit Care. 2015;19(1):108. Published 2015 Mar 20. doi:10.1186/s13054-015-0843-7

③ Dargaville PA, Gerber A, Johansson S, et al. Incidence and Outcome of CPAP Failure in Preterm Infants. Pediatrics. 2016;138(1):e20153985. doi:10.1542/peds.2015-3985