Paediatrics: Respiratory distress
Respiratory distress is defined as increased work of breathing that causes a sense of altered well-being.
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
- 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
- Hyperventilation: psychogenic, brainstem tumour
- Hypoventilation: apnoea, drugs
- Respiratory muscle weakness: Duchenne muscular dystrophy, spinalmuscle atrophy, central nervous system (CNS) depression
- Pleural: pneumothorax, chylothorax, haemothorax, pleural effusion,empyema
- Chest wall: flail chest, rib fractures
Broadly, we can define the two major causes of respiratory distress as follows.
- Hypoxaemia despite high FiO2: arterial 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.
- 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.