WikiSysop at 19:00, 3 February 2025

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	''Originally from Update in Anaesthesia \| www.wfsahq.org/resources/update-in-anaesthesia''		''Originally from Update in Anaesthesia \| www.wfsahq.org/resources/update-in-anaesthesia''

			Large airway obstruction in children
			Reprinted with revisions from Update in Anaesthesia, (2004)18:44-49. Originally Royal College of
			Anaesthetists Newsletter 1999; Issue 47: 159-162, reused with permission.
			N S Morton
			Correspondence Email: neilmorton@mac.com
			part 1: caUSES and ASSESSment
			Opening and maintaining the airway is fundamental
			to the treatment of all emergency situations in
			paediatrics, as in adults. All resuscitation algorithms
			start with ABC (Airway, Breathing, Circulation) and
			must be qualified in trauma to include cervical spine
			control. The commonest cause of paediatric airway
			obstruction is still the child with depressed conscious
			level who is not positioned properly or whose airway
			is not opened adequately by Basic Life Support
			manoeuvres. Airway foreign bodies are also common
			and may need rapid intervention. The pattern of
			infective causes of airway obstruction has changed
			since the introduction of vaccination programmes
			against Haemophilus influenzae type B. There has been a
			marked reduction in the incidence of epiglottitis, with a
			relative predominance now of viral croup and bacterial
			tracheitis, usually caused by Staphylococcus aureus.
			Why are children at increased risk from airway
			obstruction?
			There are anatomical, physiological and developmental
			reasons for children to be particularly susceptible to
			airway obstruction.
			The nares, upper and lower airways are smaller in
			absolute terms in children. Resistance to air-flow (and
			thus the work of breathing) increases during quiet,
			laminar flow breathing in inverse proportion to the
			fourth power of the radius. A small decrease in radius
			of the airway increases markedly the resistance to
			breathing. This is even more noticeable during crying
			when air-flow is turbulent as resistance is then related
			to the fifth power of the radius. An example of this
			amplification effect in the upset child is to compare the
			increase in airway resistance when the airway narrows
			from 4mm to 2mm: in the quiet child the airway
			resistance increases 16-fold but when the child cries
			the increase is 32-fold.
			The infant has a relatively large tongue and the
			larynx is situated relatively high in the neck, with the
			epiglottis at the level of C1 at birth, C3 in the infant
			and C6 from puberty. The laryngeal inlet appears to
			lie more anteriorly because of its high position. In
			the infant, the epiglottis is long and omega shaped
			and angled away from the long axis of the trachea.
			The larynx is funnel shaped and is narrowest at the
			level of the cricoid ring compared with the cylindrical
			adult conformation, which is narrowest at the level of
			the vocal cords. The airway is more compressible as
			cartilage support components are less well developed.
			Thus, extrinsic pressure from haematomas, neoplasms,
			vessels or enlarged heart chambers may more readily
			compress the airway. The collapse of the laryngeal
			inlet during inspiration is a feature of laryngomalacia
			and the collapse of the trachea and/or bronchi during
			expiration occurs in tracheo-bronchomalacia. If the
			intrathoracic airways are narrowed from whatever
			cause, the extra work of inspiration and of expiration
			leads to large swings in intrathoracic pressure and the
			potential for gas trapping and hyperinflation behind
			the obstructed airway causing further compression of
			small airways. During forced expiration efforts, the
			intrathoracic airways may collapse down exacerbating
			the gas trapping effect.
			Hyperinflation and gas trapping also impair the
			function of the diaphragm which is unable to contract
			so efficiently from its optimal length. In infants the
			diaphragm has a smaller proportion of contractile
			elements and fewer fatigue resistant muscle fibres. The
			rib cage is cartilaginous and more compliant, so the
			diaphragm anchor points are more mobile, leading
			to wasted inspiratory work and the clinical sign of
			recession of the chest wall. The chest wall shape in
			cross-section is circular in the infant compared with the
			eliptical shape in the older child and the ribs are attached
			perpendicular to the vertebral column compared with
			the acute angle of attachment in the older child. This
			means that the contribution of the “bucket-handle”
			movement of the rib cage to inspiration is minimal
			in small infants and also the elastic recoil effect is
			much less during expiration. The intercostal muscles
			and accessory muscles of inspiration are also less well
			developed. Thus, the small infant is very reliant on the
			diaphragm’s contribution to inspiration and thus has
			few reserves when work of breathing has to increase.
			This is on top of the already high basal demands placed
			on the infant respiratory system by the higher rate of
			metabolism in early life.
			The small absolute size of airways in children means
			that secretions, small airway constriction, oedema or

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Large airway obstruction in children - Revision history

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