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682 S P E C I A LT Y P R A C T I C E I N C R I T I C A L C A R E

2 mL/kg/hr, with 1 mL/kg/hr in children and 0.5–1 mL/
kg/hr in adolescents. Other indirect evidence of poor
systemic perfusion in infants may include: 15
l feeding difficulties
l abdominal distension
l fluid imbalances
l temperature instability
l hypoglycaemia
l hypocalcaemia
l apnoea.
Indirect evidence of poor systemic perfusion in children
is irritability, then disorientation or lethargy. Clinical
signs of reduced cardiac output, typically seen in shock,
are similar to adults. 16
RESPIRATORY SYSTEM

The child’s respiratory system, including airways, contin-
ues to mature until at least eight years of age, therefore
the paediatric airway is described and managed differ-
ently from the adult’s. Structural and mechanical differ-
ences predispose infants and young children to respiratory
compromise. Respiratory compromise leading to apnoeas
and even respiratory arrest, is a relatively common occur-
rence in the paediatric population, although specific inci-
dences of occurrence have not been determined. FIGURE 25.1 Adult airway (Courtesy Australian College of Critical Care
Nurses).
The newborn’s larynx is just one-third of the diameter of
17
the adult larynx. Narrow nasal passages, in combination
with being obligatory nose-breathers up to 5–6 months
of age, means that infants may experience respiratory
distress if nasal passages become oedematous or contain
secretions such as mucus or blood. With the airway of an
infant measuring around 6 mm in diameter at the level
of the cricoid, obstruction is more likely. The paediatric
airway is characterised and differentiated from an adult
airway by the following features: 13,17
l short maxilla and mandible
l large tongue
l floppy epiglottis
l shorter trachea
l more acute angle of airway, particularly notable when
attempting to visualise with a laryngoscope
l a more cephalad larynx that moves distally as the neck
grows
l the cricoid ring is the narrowest portion of the airway
l smaller lower airways, less developed with fewer
alveoli
l true alveoli not present until 2 months, with full
complement developed by around eight years of age
l little smooth muscle present in airways
l little collateral ventilation in airways, as the pores of
Kohn are not fully developed until about eight years
of age (see Figures 25.1 and 25.2).

Paediatric Respiratory Assessment
Newborn infants have a respiratory rate of approximately FIGURE 25.2 Paediatric airway (Courtesy Australian College of Critical
40 breaths/min, generating an average tidal volume of Care Nurses).
18
16 mL/kg and minute volume of 0.64 L/min. The tho-
racic cavity of infants and children is characterised by a
thin chest wall that is highly compliant, with poorly