Paediatrics: Respiratory distress

2021-03-10 12:00 AM

Respiratory distress is defined as increased work of breathing that causes a sense of altered well-being.

Respiratory distress

Respiratory distress is defined as increased work of breathing that causes a sense of altered well-being. The hallmarks are use of accessory muscles and tachypnoea. Distress can be caused by disorders of gas exchange (O2 absorption, or CO2 elimination), respiratory drive, neuromuscular disease, and infection.

Box 5.1 Differential diagnosis of respiratory distress

Nasopharynx

  • Nose: choanal atresia, stenosis
  • Oropharynx: tonsillar hypertrophy
  • Tongue: glossomegaly
  • Pharynx: peritonsillar abscess, retropharyngeal abscess, diphtheria

Upper airway obstruction

  • Larynx: vocal cord dysfunction, laryngomalacia, papilloma,haemangioma, croup
  • Epiglottis: epiglottitis, foreign body

Lower airway disorder

  • Trachea: tracheitis, tracheobronchomalacia, foreign body, pulmonaryartery sling
  • Bronchi: bronchitis, bronchomalacia
  • Bronchioles: asthma, bronchiolitis, pertussis

Disordered gas exchange

  • Haemoglobin: carbon monoxide poisoning, methaemoglobinaemia,acidosis
  • Shunt: pulmonary oedema, haemorrhage, atelectasis, or embolism
  • Dead space ventilation: asthma, bronchiolitis, pulmonary hypertension
  • Other: sickle chest syndrome, pneumonia, pneumothorax

Respiratory drive

  • Hyperventilation: psychogenic, brainstem tumour
  • Hypoventilation: apnoea, drugs

Neuromuscular

  • Respiratory muscle weakness: Duchenne muscular dystrophy, spinalmuscle atrophy, central nervous system (CNS) depression

Other

  • Pleural: pneumothorax, chylothorax, haemothorax, pleural effusion,empyema
  • Chest wall: flail chest, rib fractures

Definitions

Broadly, we can define the two major causes of respiratory distress as follows.

Respiratory failure

  • Hypoxaemia despite high FiO2arterial oxygen tension (PaO2) <8kPa in previously well child.
  • Acidosis: pH <7.25; no specific arterial carbon dioxide tension (PaCO2)since the child may have a chronic ‘compensated’ problem.
  • Increasing fatigue,or absence of improvement with therapy: based onyour observations on child’s breathing and mental state.

Neuromuscular weakness

  • Clinical: bulbar dysfunction with poor or absent cough, gag, swallow,or chest wall weakness of neurological or muscular origin.
  • Physiological: use spirometry to assess vital capacity <12mL/kg, ormanometry to assess maximum inspiratory force <–20mmHg.