Respiratory Distress in the Newborn
The general clinical features are described and then the causes obvious on external examination. There are sections on respiratory distress relieved by crying (choanal atresia), the frothy baby (oesophageal atresia), severe or progressive respiratory and respiratory distress that occurs suddenly (pneumothorax).
KeywordsRespiratory Distress Diaphragmatic Hernia Congenital Diaphragmatic Hernia Tension Pneumothorax Oesophageal Atresia
Oxygenation of the fetus is achieved through gas exchange in the placenta. At birth, this connection with the placenta is lost, and the infant becomes dependent on the lungs which, within seconds of birth, fill with air and pulmonary blood flow increases. Respiratory distress in the newborn occurs if (1) the lungs are unable to expand because of obstruction of the upper airways, (2) there is inadequate room within the thoracic cage for lung expansion to occur or (3) the infant cannot produce sufficient negative intrathoracic pressure to inflate the lungs.
In the premature infant, lack of surfactant allows the alveoli to collapse and leads to respiratory distress (hyaline membrane disease); this condition will worsen significantly the respiratory difficulties experienced by the newborn with a coexisting anomaly which interferes with respiration. When respiratory distress is recognized in the newborn, its cause must be established promptly by careful examination and a chest x-ray.
Occasionally, antenatal ultrasound examination detects major congenital anomalies which cause respiratory insufficiency at birth. For example, the presence of bowel in the thorax with mediastinal shift is indicative of congenital diaphragmatic hernia, and, in such a case, the mother should be transported to a major institution for the birth of her child. As soon as the child is born, the diagnosis can be confirmed and immediate resuscitation instituted.
Signs of respiratory distress in the neonate
3. Increased respiratory effort with sternal retraction
Progression of respiratory distress results in respiratory failure and, subsequently, cardiovascular collapse. The signs of respiratory distress are not specific for the cause. In some situations, the underlying abnormality is immediately apparent, although a chest x-ray may be required to make a diagnosis.
Cause Obvious on External Examination
Respiratory Distress Relieved by Crying
Unilateral choanal atresia does not cause respiratory distress in the newborn and is detected in later years because of a persistent discharge from the obstructed nostril. It must be distinguished from a nasal foreign body which usually produces a purulent discharge.
A rare but potentially lethal cause of upper airway obstruction is a pedunculated hamartoma of the nasopharynx. It causes intermittent obstruction according to the posture of the infant and may be seen at the back of the mouth as it prolapses into the oropharynx. Early diagnosis permits surgical removal before asphyxia occurs.
The Frothy Baby in Respiratory Distress
Oesophageal atresia is a relatively common congenital anomaly where there is interruption of the continuity of the oesophagus, associated in 85 % with a fistulous communication between the lower trachea and distal oesophageal segment. The trachea and the oesophagus both form from the foregut tube, and the fistula represents persistence of this embryological connection.
Oesophageal atresia often (50 %) is associated with other congenital anomalies, particularly cardiac, renal, anorectal, vertebral, radial and digital (i.e. ‘VACTERL’ association). The infant must be examined carefully for the presence of these anomalies. Oesophageal atresia is seen also in association with chromosomal trisomies, of which 13, 18 and 21 are the most common.
A chest x-ray should be obtained in every case. This will often show the dilated upper ‘pouch’ of the oesophagus, and presence of air below the diaphragm suggests a distal tracheo-oesophageal fistula. A lateral film may show the lower oesophagus filled with air from the trachea. Absence of gas in the abdomen is indicative of the rare defects of atresia without fistula or of atresia in association with a proximal tracheo-oesophageal fistula. Overflow of saliva, or reflux of gastric juice up the fistula into the trachea, may produce radiological signs of aspiration pneumonia. The vertebral column should be inspected for hemivertebrae or other anomalies. A contrast study is not needed to make the diagnosis of oesophageal atresia and should be avoided because of the high risk of aspiration.
Onset of Severe or Progressive Respiratory Distress
Respiratory insufficiency shortly after birth in the absence of other conditions suggests a diagnosis of congenital diaphragmatic hernia. Development of the transverse septum between the chest and abdomen is defective, leaving a hole in the diaphragm – usually on the left side – through which the abdominal viscera herniate into the chest. This occurs before birth and inhibits pulmonary development by compressing the lung buds, which are hypoplastic. At birth, this produces respiratory distress because of (1) pulmonary hypoplasia and (2) occupation of much of the thoracic volume by abdominal contents. The degree of hypoplasia of the lungs is the ultimate determinant of survival.
Often, there is rapid development of respiratory distress with cyanosis. The rapidity of onset and severity of symptoms vary with the degree of hypoplasia and the extent of interference with ventilation. In the most severe cases, poor peripheral perfusion and cardiovascular collapse occur within minutes of birth. Apgar scores remain low, and, without immediate resuscitation, these infants die quickly. Lesser degrees of lung compression produce a less dramatic clinical picture, and a few children have no symptoms for days or months.
Loops of bowel in the chest on the side of the defect
Hemidiaphragm not visible
Mediastinal shift to the contralateral side
Abnormal distribution of bowel gas within the abdomen
There are a number of uncommon conditions which can have a similar radiological appearance to diaphragmatic hernia, for example, cystic lung disease, lobar emphysema, staphylococcal pneumonia with pneumatocele and other diaphragmatic defects, but these conditions are rarely a cause of such severe respiratory symptoms in the first few hours after birth.
Sudden Onset of Respiratory Distress
The sudden onset of severe and progressive symptoms of respiratory distress in an infant who has been asymptomatic or is stable following endotracheal intubation suggests the development of a pneumothorax. The respiratory rate increases with marked sternal retraction, diminished air entry on auscultation and increased resonance on percussion on the side of the pneumothorax. Shift of the mediastinum is difficult to detect in this condition. The diagnosis should always be considered in infants with a pre-existing condition known to predispose to the development of a pneumothorax. The most critical of these is diaphragmatic hernia, but a pneumothorax may also occur following a difficult delivery or in an infant with hyaline membrane disease, lung cyst and lobar emphysema. A plain radiograph of the chest confirms the diagnosis.
The development of a tension pneumothorax is particularly hazardous to the infant and is suggested by continued progression of symptoms as a result of further mediastinal shift, contralateral lung compression and interference of venous return. Cyanosis and cardiovascular collapse are later signs. The diagnosis of tension pneumothorax is confirmed on chest x-ray, but in some cases, needle aspiration or tube thoracostomy are required as life-saving measures before an x-ray can be obtained. The best position in which to insert a chest drain is through the fourth or fifth intercostal spaces in the anterior axillary line.
Prevent excessive swallowed air in respiratory distress as it interferes with diaphragmatic breathing.
Nasal obstruction is serious in neonates, who have difficulty breathing through the mouth.
Cyanosis relieved by crying indicates nasal obstruction (e.g. choanal atresia).
A big tongue or small jaw may cause obstruction of the pharynx.
Excessive salivation in the neonate suggests inability to swallow saliva because of oesophageal atresia.
Gas in the stomach in association with oesophageal atresia confirms the presence of a distal tracheo-oesophageal fistula.
Oesophageal atresia is confirmed by gentle passage of a stiff 10-French catheter through the mouth: The catheter is arrested at about 10 cm from the gums.
An infant with oesophageal atresia requires careful examination for other anomalies.
Diaphragmatic hernia or pneumothorax should be suspected where respiratory distress occurs soon after birth.
Diaphragmatic hernia is the only common cause of respiratory distress where the abdomen is scaphoid (the bowel is in the thorax).