Bronchopulmonary dysplasia (BPD)
Definition: Chronic pulmonary disease characterized by need for supplemental oxygen for at least 28 days after birth and/or oxygen requirement at 36 weeks’ postmenstrual age (PMA).
Incidence: Approximately 30% for infants with birthweight <1000 g, 20% for infants born at <1500 g, and estimated gestational age <30 weeks. May be as high as 70% in the tiniest infants.
Pathophysiology
Old: primarily seen prior to the advent of surfactant replacement therapy; characterized by airway injury, inflammation, parenchymal fibrosis
New: found in extremely low birthweight infants; an arrest in lung development with fewer and larger alveoli, decreased pulmonary microvascular development
Risk factors
Prematurity: Incidence increases with decreasing estimated gestational age (EGA) and birthweight.
Chorioamnionitis/sepsis: Increased incidence in infants born with exposure to infection/inflammation.
Prolonged mechanical ventilation: Injury primarily due to tidal volumes that overdistend airways and cause volutrauma/barotrauma.
Patent ductus arteriosus (PDA): Due to pulmonary overcirculation.
Oxygen: Toxicity due to hyperoxia and inadequate levels of antioxidants that leads to cellular damage.
Genetic contribution: Genetic factors largely contribute to the development of BPD in preterm infants.
Poor nutrition: Growth and optimal nutritional status contribute to healing and maturation of lung tissue.
Clinical presentation
Signs and symptoms
Respiratory insufficiency: Need for supplemental oxygen or distending pressure via continuous positive airway pressure (CPAP) or high flow nasal cannula (HFNC).
Pulmonary edema: Increased microvascular pressure causes fluid filtration into the perivascular interstitium.
Tachypnea.
Increased work of breathing.
Condition variability
Mild BPD: management with medications, on room air
Moderate BPD: oxygen requirement up to 30%
Severe BPD: oxygen requirement >30%, ventilator/CPAP dependent, or pulmonary hypertension
Diagnosis
Oxygen dependence for at least 28 days after birth.
Oxygen requirement continuing at 36 weeks’ PMA for infants born at <32 weeks’ EGA or at 56 days of life for infants born >32 weeks.
Chest radiographic findings may include haziness due to pulmonary edema and/or atelectasis and low lung volumes. Findings in severe BPD include hyperinflation, cystic areas, and patchy atelectasis.
Physical examination: Tachypnea is the major finding; may be accompanied by retractions, rales, or wheezing.
Management
Medical
Respiratory Support
Mechanical ventilation: Severe BPD.
Oxygen: Saturations >94% may be necessary to prevent/treat pulmonary hypertension in the infant with established BPD and to promote growth.
Nitric oxide: Acts to reduce pulmonary vascular tone; may prevent BPD in some infants or treat pulmonary hypertension. Used in the acute setting.
Medications
Diuretics (for dosing, see the Convalescent Care section later): Treats associated pulmonary edema.
Corticosteroids: Due to associated negative impacts on long-term neurodevelopmental outcomes and growth, systemic steroids should be reserved for severe cases of BPD. Dexamethasone course is most common.
Inhaled medications (for dosing, see the Convalescent Care section later)
Bronchodilators: β-Agonists (albuterol or Xopenex) or anticholinergics (ipratropium bromide) can be used to treat airway hyperactivity/bronchospasm.
Steroids (budesonide/Pulmicort) reduce airway inflammation and may be used over a prolonged period (1 to 4 weeks) to achieve reduced inflammation similar to systemic corticosteroids without the adverse effects.
Vitamin A: Shown to reduce BPD in ELBW infants.
Surgical
Bronchoscopy: Tracheobronchomalacia may complicate BPD due to airway collapse during expiration. Rigid bronchoscopy can be used to assess this as a contributing factor in moderate to severe disease.
Tracheostomy: May be required for infants with severe lung disease or obstructive upper airway disease who remain ventilator dependent.
Early developmental/therapeutic interventions
Maximizing nutrition: Infants with BPD may need modest fluid restriction while requiring 120 to 150 kcal/kg/d. This can be accomplished by feeding MBM with additives to provide 27 kcal/oz feedings and 3.5 to 4 g/kg/d of protein. Alternatively, preterm and transitional formulas of 27 to 30 kcal/oz are also available in the absence of MBM.
Minimizing infection/inflammation due to the possibility of ongoing lung injury.
Therapy services: Very preterm infants with BPD are often hypotonic and may have difficulty transitioning to oral feeding. Early involvement of physical, occupational, and speech therapy services should be considered.
Prognosis
Early predictors
Chorioamnionitis/early onset sepsis increase the risk of BPD.
Severity of respiratory distress syndrome/length of mechanical ventilation correlate with the development of BPD.
Estimated gestational age: The incidence of BPD is highest for the most premature infants.
Birthweight: The incidence of BPD increases incrementally with decreasing birthweight.
Outcomes
Long-term obstructive/reactive airway disease: May persist into adulthood depending on severity of BPD.
Pulmonary hypertension: Develops in 25% to 35% of infants with BPD.
Impact on initiation of oral feeding: Prolonged ventilation or CPAP prohibits introduction of oral feeding and lack of pulmonary reserve prevents many infants with BPD from progressing to full oral feeds.
Chronic lung disease of infancy
Definition: BPD accounts for the vast majority of cases. Many very preterm infants may not meet strict definition for BPD (ie, O2 requirement at 36 weeks’ PCA); however, they may have clinical evidence of chronic lung disease based on need for medical treatment (diuretics, inhaled medications) and/or radiographic findings.
Incidence: In addition to the 20% of VLBW infants who develop BPD, term infants requiring prolonged mechanical ventilation or significant respiratory support due to primary respiratory diseases of infancy (meconium aspiration, congenital pneumonia, etc), congenital heart defects, or gastrointestinal disease (gastroschisis) may develop CLD.
Pathophysiology: Lung parenchymal changes, including large alveolar spaces with decreased septation, decreased vascularization, and decreased surface area.
Risk factors
Extreme prematurity
Oxygen (oxidative stress)
Increased respiratory support (positive pressure)
Infection
Aspiration
Poor nutrition
Clinical presentation
Signs and symptoms
Tachypnea
Increased work of breathing
Hypoxia
Fatigue with oral feeding
Poor growth
Diagnosis
“Physiologic definition of BPD” and “oxygen challenge test”
At 36 weeks’ PMA, infants on positive pressure or >30% supplemental oxygen, then diagnosed with BPD.
At 36 weeks’ PMA, infants on <30% supplemental oxygen undergo a stepwise reduction in O2 until on room air. If O2 saturations drop below 88% over 60 minutes, then diagnosed with BPD.
Clinical diagnosis
Ongoing signs and symptoms of CLD and/or on medical management necessary to relieve the symptoms.
Radiographic diagnosis
Streaky interstitial markings, patchy atelectasis, cystic areas, and hyperinflation.
Management
Medical
In general, weaning off medical treatments for CLD in the convalescent phase should follow the same pattern: first, wean off supplemental oxygen, then diuretic therapy, then inhaled medications.
Oxygen: via NC
High flow: 1 to 3 lpm at 21% FiO2 (may act as CPAP, but allows for development of early oral motor skills).
Low flow: 0.1 to 0.5 lpm at 100% FiO2.
May wean NC as respiratory status improves.
If concern for pulmonary hypertension, recommend to continue oxygen for treatment. Target SaO2 is >94% for >90% of the time.
When and how to wean off oxygen
Criteria for weaning O2 include adequate growth, O2 saturations >94%, normal work of breathing.
If on HFNC, wean flow by 0.5 lpm every 2 to 3 days.
If on low flow NC O2, wean flow by 0.1 lpm, keeping at 100%, until down to 0.1 lpm. Then gradually blend down O2 concentration until on room air and remove cannula.
Diuretics
Lasix (furosemide, loop of Henle): begin at 2 mg/kg/dose PO q12h and titrate to effect up to 4 mg/kg/dose PO q6h
Diuril (chlorothiazide, distal convoluted tubule): begin at 10 mg/kg/dose PO q12h and titrate to effect up to 20 mg/kg/dose PO q12h
Aldactone (spironolactone, aldosterone antagonist): used for its potassium-sparing effects with Diuril or Lasix; has poor diuretic effect; begin at 1 mg/kg/dose PO q12h and titrate as Diuril or Lasix dosing increases to 2 mg/kg/dose PO q12h
When and how to wean off diuretics
Criteria for weaning diuretics include tolerating full feeds, adequate growth, no increased work of breathing, and adequate oxygenation for age on room air.
Wean last added diuretic off first, no more frequent than every 3 days.
Check electrolytes at least weekly. If requiring electrolyte supplements, check more often during wean.
Inhaled medications: via nebulizer
Inhaled steroid (budesonide/Pulmicort): begin at 0.25 mg q12h, may increase to 0.5 mg q12h in bigger babies
Bronchodilators
β-agonists: albuterol 2.5 mg or Xopenex 0.63 mg—start at q12h and increase to q6h as needed
Anticholinergic: ipratropium bromide (Atrovent) 250 μg—start at q12h and increase to q6h as needed
Alternating a β-agonist with anticholinergic q6h may result in a synergistic effect, improving bronchodilation greater than either agent given alone.
When and how to wean off inhaled medications
Criteria for weaning inhaled medications include tolerating full feeds, adequate growth, no increased work of breathing, and adequate oxygenation for age on room air.
Wean off bronchodilator first, then inhaled steroid.
Consider maintaining inhaled steroid treatment through discharge, especially during the winter months.
Laboratory monitoring
Blood gases may demonstrate carbon dioxide (CO2) retention with a compensated respiratory acidosis.
Electrolyte imbalances include increased serum bicarbonate due to CO2 retention, hyponatremia, hypokalemia, and hypochloremia due to diuretic therapy and elevated BUN due to fluid restriction/diuretic use.
Supplementation with NaCl and/or KCl may be necessary to maintain normal electrolytes during diuretic therapy. Serum electrolytes should be obtained 1 to 2 days after a change in diuretics or supplementation.
Nutrition
Infants with CLD may require up to 150 kcal/kg/d provided by fortified MBM or transitional formulas of 24 to 27 kcal/oz.
Ongoing tachypnea and poor pulmonary reserve limit many infants with BPD from progressing to full oral feeding, necessitating home supplemental gavage feeding or gastrostomy tube placement to meet ongoing caloric demands.
Pulmonary function testing
Assesses response to bronchodilator due to reactive airways component of BPD.
IPFTs are indicated when an infant exhibits persistent tachypnea without evidence of pulmonary edema or audible wheezing.
Management of gastroesophageal reflux disease: May lessen ongoing lung injury from microaspiration.
Pulmonary hypertension: Monthly echocardiograms, while hospitalized, for assessment and monitoring in cases of severe BPD.
Renal ultrasonography: Infants on long-term diuretic therapy are at risk of developing nephrocalcinosis/nephrolithiasis.
Immunizations
RSV prophylaxis (Table 7-1)
Palivizumab is a monoclonal antibody against respiratory syncytial virus), which should be given to all infants with CLD during their first RSV season. Infants still on oxygen or pulmonary medications within 6 months of their second season may still qualify to receive.
Influenza vaccine
Should be administered to all infants >6 months and their caregivers when it becomes available for the season.
Discharge issues
Discharging home on supplemental oxygen
Up to 60% of infants with moderate to severe BPD will be discharged on oxygen and medications.
Equipment: see Appendix B
Teaching
Parents should be instructed on the purpose of oxygen therapy, tips for securing the NC, hours of usage (continuous vs room-air trials), who to call for equipment failure, etc.
All caregivers should be instructed in infant cardiorespiratory resuscitation (CPR).
Monitoring
Generally discharged home on home apnea monitor or pulse oximeter. Pulse oximeter, when compared to standard transthoracic impedance home apnea monitor, generates fewer false alarms and allows titrating to meet true oxygen need or assist in weaning from O2 in the home environment.
Safety
No smoking around an infant with BPD should be stressed, especially if the child is going home on supplemental oxygen.
An emergency plan should be established, instructing the parents on what to do (increase O2 flow, give nebulizer treatment, call 911, etc) and what medical facility to bring the child to if he/she becomes hypoxic or increased work of breathing.
Discharging home on diuretics
Wide center variation exists in discharging infants home with diuretic therapy; however, discharge home on oxygen is associated with increased diuretic use at discharge and a longer taper in the outpatient setting.
Teaching
Parents should be instructed on the purpose of diuretic therapy, and electrolyte supplements if needed, as well as how to store, prepare, and give medications to their baby.
Planning to weight adjust the dose of diuretics for the first month postdischarge may assist with the transition to home.
Diuretics should not be abruptly discontinued postdischarge, but a gradual taper or allowing the infant to outgrow the therapeutic dosing may be better tolerated.
Monitoring
Serum electrolytes should be monitored 1 week postdischarge and then within 1 week of making changes in diuretic therapy or electrolyte supplements.
Safety
Concern for dehydration should be discussed with the parents when an infant is discharged home on diuretics so that they can monitor for symptoms in the event of an acute febrile or GI illness, especially if the child is on highly concentrated formula.
Discharging home with a tracheostomy
Equipment: see Appendix B
Teaching
Parents should be instructed on the purpose of a tracheostomy, as well as all aspects of care.
Each caregiver at home should have the opportunity to change the trach several times in the hospital setting with the support of a nurse or respiratory therapist prior to discharge.
All caregivers should be instructed in infant CPR and manual ventilation.
Monitoring
Generally discharged home on home apnea monitor or pulse oximeter.
An emergency plan should be established in the event of the tracheostomy tube becoming dislodged, plugged, or infection around the stoma.
Consider skilled nursing home visits or private duty nursing for at least the first month postdischarge.
Discharging home on a ventilator
Equipment: see Appendix B
Teaching
Parents should be instructed on the purpose of the ventilator and need for oxygen therapy, tips for usage, hours of usage (continuous vs nighttime, etc), who to call for equipment failure, etc.
All caregivers should be instructed in infant CPR and manual ventilation.
Monitoring
Generally discharged home on home apnea monitor or pulse oximeter. Pulse oximeter, when compared to standard transthoracic impedance home apnea monitor, generates fewer false alarms and allows titrating to meet true oxygen need.
Safety
No smoking around an infant with BPD should be stressed, especially if the child is going home on a ventilator and supplemental oxygen.
An emergency plan should be established, instructing the parents on what to do (increase O2 delivery, increase vent settings, give nebulizer treatment, call 911, etc) and what medical facility to bring the child to if he/she becomes hypoxic or increased work of breathing.
Private duty nursing to assist with monitoring respiratory status, cares, transportation, and transition to the home setting is essential. A core group of skilled pediatric home health nurses should be established long before discharge, due to limited availability in most communities. Ideally, they should meet the child and family before discharge.
Local emergency medical personnel and utility companies should be notified that the child will be going home on a ventilator.
A disability parking permit should be recommended to assist the family with parking at future follow-up appointments.
Car seat safety test
All infants with BPD/CLD should undergo car seat safety challenge for duration of at least 90 minutes or the duration of the car ride home, if longer.
If the infant is going home on supplemental oxygen, the car seat test should be on the same amount of oxygen flow that is being prescribed for discharge.
Oxygen saturations should remain greater than 90% (no more than 20-second dips below) for the duration of the test and without apnea (greater than 20 seconds) or bradycardia (definition based on gestational age).
Infant may need a car bed for transport if fails the car seat challenge.
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