Respiratory disorders

BY : DR . SANJEEV

Intercostal recession

Subcostal retraction

• Fig :

Causes of Accessory muscle use

• Respiratory distress syndrome • Airway obstruction • Asthma • Emphysema • Pneumonia• Postoperative respiratory failure• Pulmonary edema • Pulmonary embolism • Spinal cord injury • Suffocation

Approach to a neonate with respiratory distress:

Consists of any two of the following signs : • Tachypnoea ( RR more than 60 / min )• Chest retractions and • Grunting • Cyanosis may or may not be present

Severity of distress can be assessed by using the respiratory distress score : -

Downes’ score Score Respiratory Cyanosis Air Grunt Retraction Score Respiratory Cyanosis Air Grunt Retraction

rate entryrate entry 0 <60/min Nil Normal None Nil

1 60- 80/min In room Mild ? Ausc Mild air with stethoscope

2 >80/min present Marked ? Audible Moderate with naked ear• Mild: 0-3, moderate: 4-6 , severe: 7-10• A score of >6 is indicative of impending respiratory failure.

Silverman Anderson retraction score

• Score Upper Lower Xiphoid Nasal Grunt• chest chest retraction dilatation• retraction retraction

• 0 Synch None None None None

• 1 Lag on Just Just Minimal Stethoscope

• inspiration visible visible only

• 2 See-Saw Marked Marked Marked Naked ear

• A score of >6 is indicative of impending respiratory failure.

Preterm newborn with RDS exhibiting substernal and intercostal retractions, nasal flaring, and circumoral

cyanosis.

common causes of respiratory distress in the neonate are : -

1. Hyaline Membrane Disease (HMD)

2. Meconium Aspiration Syndrome (MAS)

3. Transient Tachypnoea of the Newborn (TTNB)

4. Congenital or acquired pneumonia

5. Persistent Pulmonary Hypertension of the Newborn

(PPHN)

6. Air leaks

Cont.. 7. Congenital anomalies of upper airway (choanal

atresia), gut (tracheoesophageal fistula, congenital

diaphragmatic hernia) or lungs (lobar emphysema,

cysts)

8. Cardiac shock or Congenital Heart Disease (CHD).

9. Haematological causes (severe anaemia,

polycythaemia)

10. Neurological ( seizures )

11. Metabolic causes- metabolic acidosis

Clinical Examination Clues to the likely aetiology on examination of the

neonate : 1. A preterm baby weighing <1500 gms with retractions and grunt is likely to have HMD.2. A term baby born through meconium stained amniotic fluid with an increase in the anteriorposterior diameter of the chest (full chest) is likely to be suffering from MAS.3. A depressed baby with poor circulation is likely to have neonatal sepsis with or without congenital pneumonia.4. A near term baby with no risk factors and mild distress may have TTNB.5. An asphyxiated baby may have PPHN.

Cont..

6. A growth retarded baby with a plethoric look may have polycythaemia.7. A baby with respiratory distress should be checked for an air leak by placing a cold light source over the chest wall in a darkened room.8. A baby presenting with tachypnoea and a cardiac murmur may have a congenital heart disease.9. Inability to pass catheter through the nostril of a term baby is suggestive of choanal atresia.

Cont..

For babies presenting later with distress ask for :

a) Is the distress associated with feed refusal and lethargy? (sepsis, pneumonia)

b) Is there a family history of early neonatal deaths?

(CHD).

Respiratory Distress Syndrome (RDS)Synonym: hyaline membrane disease

• Caused by the inadequate production of surfactant in the lungs. • produced by type II pneumocytes (reduce surface tension). • surfactant is produced after 30 weeks gestation.• Inadequate surfactant production causes air sacs to collapse

on expiration and greatly increases the energy required for breathing.

• The development of interstitial oedema makes the lung less compliant. This leads to hypoxia and retention of carbon dioxide.

• Right-to-left shunting occurs: - - in collapsed lung (intrapulmonary) or, - if pulmonary hypertension is severe, across the ductus arteries

and the foramen ovale (extrapulmonary).

.Neonatal Respiratory Distress Syndrome - NRDS (Hyaline membrane disease) is characterized by collapsed alveoli alternating with hyperaerated alveoli, vascular congestion and hyaline membranes (resulted from fibrin, cellular debris, red blood cells). Hyaline membranes appear like an eosinophilic, lining or filling the alveolar spaces and blocking the gases exchange.

Epidemiology

• The incidence and severity are related inversely to the gestational age of the infant.

• Affects approximately one half of infants born at 28-32 weeks' gestation.

Risk factors

• Premature delivery • Infants delivered via caesarian section

without maternal labour. • Hypothermia • Perinatal asphyxia • Multiple pregnancy • Family history of RD

Clinical features . Usually preterm delivery.

- tachypnoea,

- expiratory grunting,

- subcostal and intercostal retractions

- diminished breath sounds,

- cyanosis and

- nasal flaring.

• May rapidly progress to fatigue, apnoea and hypoxia

Investigations • Blood gases: respiratory and metabolic acidosis

along with hypoxia. • Pulse oximetry should be maintained at 90-95%. • Chest x-ray (ground glass opacity )• Monitor full blood count, electrolytes, renal and liver

function • Echocardiogram • diagnosing PDA• determine the direction and degree of shunting, • Cultures to rule out sepsis

Diffuse ground-glass appearance

Imaging findings : • Typically, diffuse “ground-glass” opacification of

both lungs with air bronchograms and hypoaeration

• Hypoaeration from loss of lung volume• Fine granular pattern • Prominent air bronchograms • Bilateral and symmetrical distribution• Whiteout lung in severe disease

Diffuse ground-glass appearance to both lungs with a left-sided

tension pneumothorax and pneumomediastinum

a radiographic presentation of bone in fibrous dysplasia in which the bone is of uniform increased radiodensity, with the lesions appearing radiolucent, "milky" or hazy.. Frequently this pattern is seen in the tubular bones and vertebrae.

Prenatal diagnosis

• Lecithin and sphingomyelin ratio in the amniotic fluid, if ratio is more than 2 indicates adequate lung maturity

• Shake test : - • Done on the amniotic fluid or gastric aspirate • Mixed with absolute alcohol and shaken for 15

seconds and allow to settle.• Copious bubbles are formed - indicates

adequate surfactant

Management• Surfactant replacement therapy (endotracheal

tube).

• Oxygen: infants with mild RDS.

• Continuous positive airway pressure (CPAP).

• CPAP may be administered via an endotracheal tube, nasal prongs, or nasopharyngeal tubes.

• Assisted ventilation at fast rates (more than 40 breaths per minute)

Supportive therapy includes the following : .

. Temperature regulation:

prevent hypothermia. • Fluids, metabolism, and nutrition:

monitor and maintain blood glucose, electrolytes, acid balance, renal function, and hydration.

• Once the infant is stable, intravenous nutrition with amino acids and lipid.

• After the respiratory status is stable, initiate small volume gastric feeds (preferably breast milk) via a tube to initially stimulate gut development.

Cont..

• Circulation and anaemia: monitor heart rate, peripheral perfusion, and blood

pressure. Blood or volume expanders may be required. • Antibiotics: start antibiotics in all infants who present with

respiratory distress at birth after obtaining blood cultures. Discontinue antibiotics after three to five days if blood cultures are negative.

• Support of parents and family: keep the parents well informed. Encourage parents to

frequently visit and stay with their baby.

. Dosage recommendations for commonly used

exogenous surfactants : -

• Product Dosage Additional doses

• • Calfactant 3 mL/kg of birth weight May berepeated every 12 hours

for up to three subsequent doses at 12-hour intervals, if indicated

• Beractant 4 mL/kg of birth weight May be repeated after at least 6 hours, up to a total of four doses within 48 hours of birth

Colfosceril 5 mL/kg of birth weight given over a 4-minute period. May be repeated after 12 hours and 24 hours, if indicated

• Porcine 2.5 mL/kg of birth weight Two subsequent 1.25-mL/kg doses given at 12-hour intervals, if indicated

Prenatal corticosteroids in preterm labour : Benefits : • 50% reduction in the incidence of RDS• 50% reduction in the incidence of

intraventricular hemorrhage (IVH)• 40% reduction in mortality Indication : • All mother at risk of preterm delivery between

24 and 34 weeks of gestation • Cases of preterm premature rupture of

membrane at less than 32 weeks of gestation

Treatment schedule

• Inj. Betamethasone 12 mg IM every 24 hours , 2 doses

• Inj. Dexamethasone 6 mg IM every 12hours , 4 doses

Timing of effect :

• Opitimal effect occurs after 24 hours of initiating treatment

• Effect of one course lasts for 7 days.

Prevention

• Antenatal corticosteroids (dexamethasone) accelerate foetal surfactant production and lung maturation. They have been shown to reduce respiratory distress syndrome, intraventricular haemorrhage and mortality by 40%.

• Delaying premature birth. Tocolytics, e.g.nifedipine or ritodrine, may delay delivery by 48 hours and therefore enable time for antenatal corticosteroids to be given.

• Avoid hypothermia in the neonate.

Prognosis

• improved in recent years with the increased use of antenatal steroids to improve pulmonary maturity, early postnatal surfactant therapy to replace surfactant deficiency, and gentler techniques of ventilation to minimize damage to the immature lungs.

• The prognosis is much better for babies weighing over 1500g.

Differential Diagnosis of Respiratory Distress in the Newborn

Most common causes *• Transient tachypnea of the newborn• Respiratory distress syndrome (hyaline membrane disease)• Meconium aspiration syndrome Less common but significant causes• Infection (e.g., pneumonia, sepsis)• Nonpulmonary causes (e.g., anemia, congenital heart

disease, congenital malformation, medications, neurologic or metabolic abnormalities, polycythemia, upper airway obstruction)

• Persistent pulmonary hypertension of the newborn• Pneumothorax * -Listed in order of incidence.

Differential diagnosis . - Pulmonary air leaks (e.g., pneumothorax, interstitial

emphysema, pneumomediastinum, pneumopericardium).

.- Pneumonia. - Aspiration of amniotic fluid, blood, or meconium may

occur (seen in term or postmature infants.) - Transient tachypnoea of the newborn usually occurs in

term or near-term infants and usually after caesarean delivery.

- Congenital anomalies of the lungs (e.g., diaphragmatic hernia, chylothorax, lobar emphysema, bronchogenic cyst,).

- Metabolic problems (e.g. hypothermia, hypoglycaemia). - Haematological problems (e.g. anaemia, polycythaemia)

Complications

Acute complications :– Complications related to procedures, e.g. trauma to vocal

cords from tracheal intubation; infection, – Alveolar rupture: pneumothorax, pneumomediastinum,

pneumopericardium, interstitial emphysema. – Intracranial haemorrhage: the risk is increased in those who

require mechanical ventilation. – Pulmonary haemorrhage increases in very premature

infants, especially following surfactant therapy. – Hospital acquired infection. – Necrotizing enterocolitis and/or gastrointestinal perforation.

Chronic complications include the following

• Chronic lung disease :- - it is due to lung injury from

mechanical ventilation and the risk increases with decreasing gestational age, small for dates, severity of respiratory distress syndrome and duration of mechanical ventilation.

• Neurological impairment is related to the gestational age, the presence of hypoxia, and the presence of infections.