CHRISTY L. CUMMINGS, MD

RESPIRATORY DISTRESS IN THE FULL TERM NEONATE

OBJECTIVES

1. Informal case-based learning2. Differentiate between cardiac and respiratory

causes of cyanosis3. Describe the primary parenchymal diseases that

can cause respiratory distress in the term neonate

4. Describe the primary developmental lung abnormalities that can cause respiratory distress in the term (or near-term) neonate

RULE OUT CARDIAC DISEASE

• Pulse Oximetry Test• Determines whether formal hyperoxia test is useful• Cyanosis without marked respiratory distress and O2 sat <

85% in room air and 100% oxygen suggests intracardiac shunt

• If O2 sat increases to > 85% on 100% oxygen, a full hyperoxia test should be performed

• Hyperoxia Test• Obtain baseline right radial (preductal) arterial blood gas

measurement with baby breathing room air and 100% O2

• A PaO2 > 300 mm Hg on 100% O2 is normal, 150-300 mm Hg suggests pulmonary disease, and 50 -150 mm Hg suggests cardiac disease (or severe pulmonary hypertension)

• ECHO

HINTS ON CHEST RADIOGRAPH

• RDS• Mostly premies, but seen in term (rare) and near-term• Reticular granular pattern and air bronchograms

• MAS• Patchy areas of atelectasis due to complete airway

obstruction, interspersed with areas of air trapping due to partial obstruction and a one-way valve phenomenon

• White out, and/or air leak syndrome

• Neonatal pneumonia• Classical patchy infiltrates, but the findings also may be

indistinguishable from RDS• Pleural effusion supports diagnosis of PNA, seen 67%

HINTS ON CHEST RADIOGRAPH

• TTN• Diffuse parenchymal infiltrates, a “wet silhouette” around

heart, or accumulation of fluid in various intralobar spaces (fissure)

• Indicate increased pulmonary interstitial, alveolar, or pleural water content

• CHD• Cardiac enlargement, unusual silhouette (snowman, boot)

• Congenital lymphangiectasia• Lungs may appear normal, overinflated or exhibit a coarse

interstitial infiltrate due to distended, abnormal lymphatics• Effusion (chylous)

POSSIBLE DIAGNOSIS RELATED TO RADIOGRAPHIC FEATURES

CASE

• 1 hour old FT baby boy with tachypnea (RR 70s) born via C/S, GBS neg• PE:• Moderate retractions• O2 sat 88% on RA• O2 sat 100% on 100%

TRANSIENT TACHYPNEA OF THE NEWBORN (TTN)

• Relatively benign, self-limited disease • 11:1000 births, M>F• Increased risk:• M, C/S, perinatal asphyxia, cord prolapse, IDM, maternal

asthma or anesthesia during labor

• Tachypnea (>60bpm) shortly after birth, lasts 1-5d• Unclear etiology:• Delayed resorption of fetal lung fluid related to elevated

CVP, delayed clearance of pulmonary liquid by lymphatics• Mild asphyxia resulting in mild pulmonary capillary leak

and to myocardial dysfunction with elevated filling pressure

• Almost never requires mechanical ventilation

RESORPTION OF ALVEOLAR FLUID AT BIRTH: CELLULAR MECHANISMS

CASE

• 1 hour old FT baby boy born via NSVD who required PPV in DR, increasing WOB, retractions, required intubation

RDS IN TERM INFANT: SP-B DEFICIENCY

• Congenital abnormalities of surfactant proteins• Most common is deficiency of surfactant protein B (SP-B)• Autosomal recessive, frame-shift mutation chromosome 2,

• Severe respiratory distress after birth• CXR identical to RDS• Continued distress despite mechanical ventilation,

oxygen, repeated surfactant, corticosteroids• Prognosis is poor, most die within 1-6 months• Only effective therapy (although neither available

for nor consented to by all) is lung transplantation

CASE

• 1 hour old FT baby girl born via NSVD, meconium, who emerged limp, was suctioned below cords x1• Now with grunting, retractions, desats, requiring

intubation

MECONIUM ASPIRATION SYNDROME

• Incidence: • 13% of all live births complicated by meconium-stained

amniotic fluid, and of these, 4% to 5% develop MAS

• Mechanism• Direct toxicity of the meconium chemical pneumonitis• Inactivation of surfactant• Activation of complement• Vasoconstriction• Partial/complete airway obstruction by thick meconium• Secondary pulmonary hypertension

MECONIUM ASPIRATION SYNDROME

• Management• NRP guidelines, endotracheal suction below cords if limp• Intubation, mechanical ventilation• Surfactant• RCTs shown that surfactant reduces need for ECMO

• iNO• Since the approval of iNO by the US FDA in 2001, there has

been a steady decrease in the use of ECMO for neonates with MAS

• HFOV +/-• Reduction in complications from air-leak syndromes (PTX)

CASE

• FT baby girl born via NSVD, GBS+, treated with PCN x1 2 hours PTD• Increased WOB, desats• Requires PPV

PNEUMONIA

• Early onset <7d, late onset >7d• In utero• Rubella, CMV, HSV, mumps, adenovirus, Toxo, T. pallidum,

M. tuberculosis, Listeria monocytogenes, VZV, HIV

• During delivery/perinatally• GBS, Escherichia coli, Klebsiella sp, Chlamydia trachomatis

• Postnatally• Respiratory viruses (adenovirus, RSV), gram-positive

bacteria(groups A, B, and G streptococci or S. aureus), and gram-negative enteric bacteria (Klebsiella sp, Proteus sp, Pseudomonas aeruginosa, flavobacteria, Serratia marcescens, and E coli)

PULMONARY CAUSES FOR RESPIRATORY DISTRESS

Parenchymal conditions:•Transient tachypnea of the newborn•Meconium aspiration syndrome, other aspirations•Respiratory distress syndrome•Pneumonia•Pulmonary edema•Pulmonary hemorrhage•Pulmonary lymphangiectasia

CASE

• FT baby boy born via repeat C/S with increased WOB, retractions• Requires intubation• Transillumination neg

CONGENITAL LOBAR EMPHYSEMA

• Accounts for 50% of structural lesions causing respiratory distress in the newborn

• M:F 2:1, associated anomalies 14-40% (often CHD)• Air trapping and overdistention of segments and

lobes of the lungs• Prenatal diagnosis via high-res U/S, MRI or CT• Clinical signs/sx include respiratory distress,

mediastinal shift, wheezing• Upper lobes afftected 90% time• Symptomatic lesions need surgical resection• Asymptomatic lesions may be watched carefully

CASE

• FT baby girl born via repeat C/S• Respiratory distress• Intubated• CXR appears ok, but on close inspection reveals small dense mass LLL• CT with contrast shown

PULMONARY SEQUESTRATION

• Abnormal lung tissue with no connection to normal tracheobronchial tree• Receives arterial blood supply from systemic

circulation, usually branch of the aorta• Mutation in Homeobox gene Hoxb-5, crucial for normal

airway branching/development• Intralobar vs extralobar

PULMONARY SEQUESTRATION

• Intralobar – lesion within lobe without separate pleura• 3x more common than extralobar• May be acquired (recurrent infection due to lack of pleura)• Lower lobe (95%), and in 55% of cases is on the left side• M=F

• Extralobar - discrete mass of pulmonary parenchyma outside pleural investment of lung• In 66% of the cases, left side, proximal to esophagus and

between lower lobe and diaphragm• M:F 3-4:1• >65% associated with anomalies (CDH, TAPVR, CHD, CCAM)

• Resection for both types necessary

CASE

• 1 day old FT female born via NSVD, GBS neg, with respiratory distress

CCAM/CPAM

• Multicystic mass of dilated bronchiolarlike spaces that proliferate at the expense of alveoli• Large lesions may obstruct venous return to heart,

causing fetal hydrops• Abnormal signaling/conjugation between developing

terminal bronchioles and alveolar mesenchyme• Mesenchymal & plt-derived GF

CCAM/CPAM

• M=F, usually affects right side one lobe• Solid lesions worse prognosis than large cysts• Type 1 (75%) – small # of large cysts, 2-10cm, mucin• Type 2 - small cysts (<2cm), assoc anomalies, poor

outcomes• Type 3 – microscopic cysts, rare, appears solid on gross

exam• (Type 4 – acinar epithelium)

• Surgical resection for all types• 100% survival with surgery (without hydrops

fetalis)

CASE

• FT baby boy delivered via repeat C/S, prenatal L:H ratio 0.8 and + liver• Intubated immediately

CONGENITAL DIAPHRAGMATIC HERNIA (CDH)

Herniation of intestinal contents into thoracic cavityResults in pulmonary hypoplasia leading to respiratory distress

• 95% occur through posterior foramen of Bochdalek (lies posteriorly and lateral to spine); of these, 80% are on left side

1 : 4,000 birthsSigns/symptoms:

Cyanosis, severe respiratory distress, scaphoid abdomen

Usually seen during routine prenatal U/SL:H ratio, presence of liver or other organs in chest

Post delivery xray reveals intestinal loops in chest cavityImmediate intubation and gastric decompression is essential

to higher survival rates Intubation should be performed by most experienced team member

CONGENITAL DIAPHRAGMATIC HERNIA

PULMONARY CAUSES FOR RESPIRATORY DISTRESS

Developmental abnormalities:•Lobar emphysema•Pulmonary sequestration•Cystic adenomatoid malformation•Congenital diaphragmatic hernia•Tracheoesophageal fistula•Pulmonary hypoplasia

CASE

• 3 hour old FT baby girl with respiratory distress while eating, improves with crying. CXR WNL.• ENT consulted, CT ordered

CHOANAL ATRESIA

• Congenital anomaly, back of the nasal passage (choana) is blocked, usually by abnormal bony or soft tissue formed during fetal development

• 0.82 cases per 10,000 individuals, F>>M• Unilateral (R) and 2:1, B/L • CHARGE syndrome• 6% with chromosomal anomalies• Cyanosis• Worse with feeds or pacifier• Improves with crying

• Surgical correction, stent, revisions

CHOANAL ATRESIA: CHARGE

• C – Coloboma of the eye, CNS anomalies• H - Heart defects• A - Atresia of the choanae• R - Retardation of growth and/or development• G - Genital and/or urinary defects

(Hypogonadism)• E - Ear anomalies and/or deafness

CASE

• FT baby boy with respiratory distress, hoarse cry• Intubated for worsening respiratory status• CXR WNL• ENT consulted

LARYNGEAL WEB

• Incomplete recanalization of the laryngotracheal tube during 3rd month of gestation (atresia – stenosis)

• Most commonly at level of vocal folds anteriorly• Sx: Mild dysphonia to significant airway obstruction• 30% associated airway anomalies (subglottic stenosis), 22q11

• Diagnosis – rigid laryngoscopy/bronchoscophy• Management• Ranges from observation to emergent tracheotomy• Lysis endoscopically using cold knife or laser• Endoscopic suturing of the cut edges or placement of a keel may

prevent restenosis in these cases• Thicker webs may require laryngofissure approach, with

postoperative stenting of the airway

PULMONARY CAUSES FOR RESPIRATORY DISTRESS

Airway abnormalities:•Choanal atresia/stenosis•Laryngeal web•Laryngotracheomalacia or bronchomalacia•Subglottic stenosis

CASE

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RIB CAGE ABNORMALITIESJEUNE SYNDROME

• Asphyxiated Thoracic Displasia (Jeune syndrome)• Autosomal recessive• Clinical signs/sx:• Bone dysplasia – rhizomelic brachymelia• Thoracic anomalies – bell shaped rib cage, short ribs• Renal and hepatic malformations• Pulmonary hypoplasia

• Radiologic changes often seen by 16-18wk gestation• Usually death in the newborn period from severe

pulmonary hypoplasia

CASE

• FT baby girl born via NSVD, worsening respiratory distress, increasing O2• Required intubation and intervention

PNEUMOTHORAX/MEDIASTINUM

• Air collection: pleura and chest cavity or mediastinum• Neonatal pneumomediastium 2.5:1000 live births• Assoc with mechanical ventilation, PNA, RDS, mec• Often asymptomatic• May require intervention

CASE

• 3 day old FT baby boy born via NSVD, worsening respiratory distress

CHYLOTHORAX

• Pleural effusion from lymphatic fluid (chyle)• Leakage from thoracic duct or branch• M:F is 2:1and R>L side• 50% occur within 24hr of life, 70% by 1st week of life• Composition: milky, chylomicrons, TGs, lymphs• Treatment: • Thoracentesis, CT to allow drainage• D/c FFAs in diet; formula high in medium chain TGs (Portagen) bypasses lymphatic system via direct absorption into blood stream• Surgical ligation of thoracic duct• Chemical or surgical pleurodesis• Octreotide for several weeks

PULMONARY CAUSES FOR RESPIRATORY DISTRESS

Mechanical abnormalities:•Rib cage anomalies (eg, Jeune syndrome)•Pneumothorax•Pneumomediastinum•Pleural effusion•Chylothorax

QUESTIONS?

References:

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