Neonatal & Pediatric Disease Processes

Objectives — Identify the major neonatal and pediatric disease processes: their pathophysiology, clinical manifestations, and treatment.

---

RDS (Hyaline Membrane Disease)

Respiratory distress syndrome affects 60,000–70,000 infants every year and is also known as hyaline membrane disease, a lung disease of prematurity. Its incidence increases as gestational age decreases (an inverse relationship).

• Cause: surfactant deficiency (below 34 weeks), decreased alveolar surface area, increased small-airway compliance, and presence of the ductus arteriosus.
• Low oxygenation/ventilation → increased PVR → right-to-left shunting (worsens with hypoxemia); acidosis further reduces surfactant.
• Signs: tachypnea, retractions, paradoxical breathing, audible grunting, nasal flaring; decreased breath sounds or fine crackles; CXR shows reticulogranular densities, air bronchograms, low lung volumes.
• Treatment: CPAP and PEEP; HFV for rapid deterioration; optimize PEEP/CPAP to improve oxygenation, FRC, and ventilation.

---

TTN — Transient Tachypnea of the Newborn

Also known as Type II RDS, TTN is the most common respiratory disorder of newborn patients.

• Pathophysiology: slow clearance of lung fluid post-delivery. During most births, two-thirds of this fluid is expelled by the squeeze of the birth canal; this is impaired during cesarean section. Retained fluid → decreased compliance and increased airway resistance.
• Clinical: tachypnea; CXR shows diffuse haziness and perihilar streaking.
• Treatment: increased FiO₂ via oxyhood or nasal cannula; CPAP or HFNC is very beneficial (increased intrapulmonary pressure displaces fluid into the lymphatics/capillaries). TTN resolves within 24–48 hours.

---

Apnea of Prematurity (AOP)

A common, controllable disorder among premature infants.

• Infants can have apnea of 5–10 seconds followed by rapid respirations to compensate.
• Complications occur if apnea lasts beyond 15 seconds, or with cyanosis, hypotonia, pallor, or bradycardia.
• Pathophysiology: immature control of ventilation (CNS and peripheral chemoreceptors). Instead of increasing both Vt and RR to compensate for rising CO₂, only Vt increases, with a small CO₂ rise — repeated episodes cause acidosis.
• Treatment: theophylline, caffeine, CPAP, and stimulation in less severe cases. Generally self-limiting, ending at 37–44 weeks.

---

PPHN — Persistent Pulmonary Hypertension of the Newborn

Also known as persistent fetal circulation.

• Pathophysiology: hypoxemia, metabolic and respiratory acidosis, and overdeveloped pulmonary vasculature constrict pulmonary blood flow. As pulmonary capillaries constrict, PVR rises above SVR, so blood continues to shunt through the foramen ovale and ductus arteriosus even after birth.
• Clinical: SAT or PaO₂ change rapidly regardless of incremental FiO₂ changes. A ≥ 5% pre/post-ductal saturation difference (right arm vs. left leg) indicates a patent ductus arteriosus and suggests PPHN.
• Treatment: remove the underlying cause (correct acidosis, FiO₂, surfactant). If no improvement, intubation and mechanical ventilation/HFV.

---

BPD — Bronchopulmonary Dysplasia

A progressive disease and a combination of factors that destroy and dysfunction the lungs: immaturity, genetics, malnutrition, O₂ toxicity, and mechanical ventilation.

• RT-relevant factors: atelectrauma (lung collapse) and volutrauma (large tidal volumes).
• Hyperoxia produces super-oxidants that destroy tissue; preterm infants lack the immune development to defend against them, leading to inflammation and injury of the alveolar-capillary membrane and bronchial tree.
• The longer the patient is ventilated — and the higher the Vt and FiO₂ needed — the more progressive pulmonary damage develops.
• Clinical: similar to adult COPD with increased atelectasis and emphysema; fibrosis from hyaline membrane buildup increases airway resistance.
• Treatment: prevention is primary — appropriate Vt and FiO₂ (like preventing adult ARDS), optimal PEEP/FRC with lung-protective tidal volumes, surfactant delivery, and proper FiO₂ to reach the desired PaO₂.

---

MAS — Meconium Aspiration Syndrome

A disease of term and near-term infants involving inhalation of fetal bowel movements (bile, cholesterol, and GI contents).

• Normally meconium is not passed until after delivery, but a distressed fetus may pass it early — and aspiration can occur in utero.
• Clinical: meconium streaking, fetal tachycardia before birth, gasping retractions after delivery, an APGAR of 5 or less, and low umbilical pH.
• MAS causes severe air trapping and airway obstruction due to its viscous nature; large quantities cause PPHN, hypoxemia with acidosis, and airway collapse.
• Treatment: in severely depressed infants with meconium streaking, intubate and apply direct suction of the ETT immediately — until no meconium is noted or after 2–4 aspirations. Suction is regulated between −70 and −100 mmHg. Leave a clean ETT in place and initiate mechanical ventilation or HFV.

---

CDH — Congenital Diaphragmatic Hernia

A rare defect where the contents of the abdominal cavity make their way into the thoracic cavity.

• Clinical: there are lesser and more severe versions. A chest x-ray reveals the intestines, stomach, and maybe liver in the thoracic cavity. This increases pulmonary resistance, severely damages the one lung the infant is subsisting on, and may impact the heart and reduce blood pressure.
• Treatment: remove the patient's bowel gas, slowly suction the abdominal contents back to their normal positions, and close the breach.

---

ROP — Retinopathy of Prematurity

• Retinal capillaries begin branching at 16 weeks, growing from the optic nerve toward the ora serrata (the retina's anterior end).
• In the presence of high FiO₂ (high PaO₂), capillaries constrict, necrose, and die. Surviving capillaries proliferate into the eye, eventually necrose and bleed, causing large hematomas, vision obstruction, and possible retinal detachment.
• Prevention/treatment: maintain PaO₂ < 80 mmHg in premature infants. Limiting high oxygen plus laser eye surgery reduces incidence (ROP develops in 25–35% of premature infants). Maintain oxygenation between > 88% and < 94%.

---

PIE — Pulmonary Interstitial Emphysema

• Pathophysiology: occurs due to mechanical ventilation — chronic high PEEP, high PIP, and prolonged I-times. Air dissects and collects in the interstitial space, compressing small airways and capillaries → V/Q mismatch and deteriorating ABGs.
• The instinct to increase ventilator pressures and PEEP in response actually worsens PIE and perpetuates gas collection.
• Treatment: lower airway pressures while maintaining oxygenation and ventilation. High-frequency jet ventilation (HFJV) is ideal — it prevents air leaks while ventilating. Discontinue conventional ventilation (CMV) and place the patient on HFJV.

PIE increases the likelihood of developing BPD.

---

Abdominal Wall & GI Disorders

Gastroschisis

A congenital birth defect of the abdominal wall. The intestines are found outside the body, exiting through a hole beside the belly button (umbilicus). It causes multiple complications for respiratory therapists.

NEC — Necrotizing Enterocolitis

A common infection of the intestine in neonates. Premature infants (born before 38 weeks) have low blood flow to the intestines and underdeveloped intestinal tracts. This combination, plus early introduction of gut bacteria, can infect the intestinal wall, killing the wall tissue, causing sepsis and possible death.

---

Common Infant & Pediatric Diseases

SIDS — Sudden Infant Death Syndrome

• The leading cause of death for infants under age 1, within the first 1–4 months of life. About 7,000 infants die of SIDS each year in the U.S.
• A previously healthy infant dies unexpectedly, most often during sleep. Autopsies show evidence of repeated episodes of hypoxemia or ischemia; otherwise the cause is unknown.
• Risk factors: winter, a prior apparent life-threatening event (cyanotic, apneic, limp), and the prone sleeping position.
• Prevention is key: keep the child supine or side-lying and remove excess blankets and toys to reduce accidental suffocation. (Intentional suffocation and SIDS are very difficult to distinguish.)

GERD — Gastroesophageal Reflux Disease

Regurgitation of stomach contents. GERD can cause reactive airway diseases, pneumonia, and other upper-airway issues.

Bronchiolitis

An acute infection of the lower respiratory tract, usually caused by respiratory syncytial virus (RSV).

• Nearly 1 in 10 infants younger than 2 acquire it; less than 1% of those hospitalized die of respiratory failure.
• The primary at-risk groups are infants with BPD or who are immunologically suppressed — very similar to NICU patients.
• Clinical: inflammation and obstruction of the small bronchi and bronchioles, commonly soon after a viral upper respiratory infection. A small cough progresses to dyspnea and tachypnea; progressive inflammation causes expiratory wheezes and increased airway resistance. CXR shows hyperinflation with areas of consolidation.
• Treatment: often prophylaxis — infants/children with congenital disorders, BPD, or respiratory issues can be passively immunized against RSV.

---

Upper Airway Obstructions

Croup (Laryngotracheobronchitis)

• Subglottic swelling and obstruction (steeple sign / "picket fence") seen on an A-P neck x-ray — a narrowing of the trachea at the level of the cricoid cartilage.
• Usually caused by the parainfluenza virus — the most common airway obstruction in children 6 months to 6 years old. Bacterial infections (S. aureus, group A Streptococcus pyogenes, H. influenzae) may worsen it.
• Clinical: starts as nasal congestion, fever, and cough; progresses to stridor and a barking seal cough, sometimes dyspnea, cyanosis, and exhaustion/agitation.
• Treatment: only given with signs of severe RDS with cyanosis. Cool mist for mild-to-moderate cases; corticosteroids and epinephrine for severe cases; heliox may help overcome the obstruction.

Croup — the "steeple sign" of subglottic narrowing on an A-P neck X-ray. Source: Wikimedia Commons.

Epiglottitis

• An acute, often life-threatening infection causing severe supraglottic swelling and upper-airway obstruction. The most common cause is Haemophilus influenzae (others: S. pneumoniae, S. aureus, Klebsiella pneumoniae, beta-hemolytic streptococci).
• Clinical: labored breathing, fever, sore throat, difficulty swallowing, and stridor — much like croup. On a lateral neck x-ray, the swollen epiglottis produces a "thumbs up" (thumbprint) sign (vs. croup's steeple sign).
• Treatment: the danger is that further inflaming the airway causes complete obstruction — only staff familiar with emergency intubation should care for these patients. Treat with antibiotics, corticosteroids, racemic epinephrine, and heliox to bypass airway resistance.

Epiglottitis — the "thumb sign" of a swollen epiglottis on a lateral neck X-ray. Source: Wikimedia Commons.

---

Cystic Fibrosis

One of the most common genetic diseases among whites in the U.S. — an autosomal recessive trait affecting approximately 30,000 people.

• Pathophysiology: a genetic mutation of the gene coding for CFTR (cystic fibrosis transmembrane conductance regulator). CFTR regulates the movement of chloride ions through the cell membrane, vital to the secretion of mucus and fluid transport throughout the body. With ~1,000 CFTR variants, there are varying levels of CF impact.
• Clinical: CF affects all exocrine functions — skin sweat glands, pancreas, and lungs. Patients cannot reabsorb salt effectively, giving sweat a salty taste (basis of the sweat chloride test / iontophoresis) and causing vulnerability to dehydration in hot weather. Exocrine dysfunction → pancreatic insufficiency (decreased digestive enzymes).
• Lung disease is the primary cause of death. Mucus buildup and recurrent infections cause recurrent bronchiolitis and bronchiectasis, atelectasis, pneumonia, and lung abscesses; as it progresses it may cause cor pulmonale with marked hypoxemia.
• Diagnosis: suspected with clinical manifestations or close family history; recurrent pulmonary infections early in life plus the sweat chloride test (iontophoresis).
• Treatment (complicated because CF is progressive): pancreatic enzymes, antibiotics, anti-inflammatories, bronchodilators, and lung-clearance therapies like chest physiotherapy to prolong the time between hospital treatments.