Head retraction and respiratory disorders in infancy.

Head retraction in infancy is a physical sign that is usually associated with central nervous system pathology. It is not generally recognised that head retraction can occur as a consequence of respiratory system abnormality, particularly in younger infants. Head retraction may be seen in any respiratory condition where decreased lung compliance or airway obstruction causes increased work of breathing. Mechanisms by which head retraction can reduce work of breathing include: (1) increasing the efficiency of accessory muscles of respiration and (2) reducing resistance in large airways by: (a) 'splinting' the airway and (b) preventing upper airway obstruction. (1) Increasing the efficiency of accessory muscles of respiration The efficiency of accessory muscles of respiration can be maximised by fixing their origin as rigidly as possible. In the case of sternocleidomastoid and scalene muscles this means holding the mastoid process and the cervical spine rigid. This is best achieved by anchoring the head in hyper-extension. The resulting muscle action expands the rib cage along its anteroposterior and transverse diameters.' The efficacy of this mechanism can be demonstrated in older ventilator dependent quadriplegic children where 'neck' breathing can be life saving.2 Maximising the efficienoy of these accessory muscles becomes essential in infants with respiratory fatigue in order to help intercostal muscles stabilise and expand a pliable chest wall.3 Therefore head retraction may be seen in primary or secondary lung disease-for example, pulmonary infection, aspiration syndromes, chronic lung disease of prematurity, or pulmonary oedema. We have recently observed a premature infant whose appreciable head retraction coincided with the onset offlorid signs ofcardiac decompensation secondary to a patent ductus arteriosus. Head retraction dramatically improved after duct ligation. (2) Reducing resistance in large airways The trachea and main bronchi in neonates are readily collapsible4 probably because of deficient cartilagenous support. Extension of the neck by stretching these floppy airways provides a splinting action allowing a more even airflow, lower airway resistance, and decreased work of breathing. Upper airway obstruction causing apnoea in the preterm infant would be expected to occur in association with the muscle hypotonia of active (rapid eye movement) sleep; recent studies however, do not support a particular sleep phase.5 Inhibition of muscle tone interferes with the vital role of the genioglossus and geniohyoid muscles in maintaining upper airway patency.6 Extension of the head and neck increases resting muscle tone thus preventing the tongue from occluding the lower pharvnx. In artificially ventilated infants, head …