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.
· Nose: choanal atresia, stenosis
· Oropharynx: tonsillar hypertrophy
· Tongue: glossomegaly
· Pharynx: peritonsillar abscess, retropharyngeal abscess, diphtheria
· Larynx: vocal cord dysfunction, laryngomalacia, papilloma, haemangioma, croup
· Epiglottis: epiglottitis, foreign body
· Trachea: tracheitis, tracheobronchomalacia, foreign body, pulmonary artery sling
· Bronchi: bronchitis, bronchomalacia
· Bronchioles: asthma, bronchiolitis, pertussis
· 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, spinal muscle 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 on your 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, or manometry to assess maximum inspiratory force <–20mmHg.