Page 717 - ACCCN's Critical Care Nursing

694 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

applied negative pressure, as too much can result in Non-invasive Ventilation
atelectasis. Non-invasive ventilation (NIV) refers to ventilatory
l Restraints may be required to limit the movement of support without an artificial airway in the trachea (see
the child, with the aim of preventing accidental extu- Chapter 15). In critically ill children with respiratory
bation rather than maintaining the child in an immo- failure, NIV may be used to reduce the need for intuba-
bile state. Restraints may be physical, such as arm tion. However, the evidence for its use in children is
boards or hand ties; or chemical, such as sedation. weak 152 and often extrapolated from adults. 153 Some
Accidental extubation is a medical emergency.
studies showed that NIV decreases the rate of ventilator-
MODES OF VENTILATION associated pneumonia and reduces oxygen requirement
in children with lower airway diseases when compared to
There are many modes of ventilation (see Chapter 15 for conventional ventilation 140,154 and may be recommended
more details). This section includes information specifi- as the first line ventilation strategy. 142
cally related to paediatric ventilation. As with adults, arte-
rial blood gases should be taken about 15–20 minutes High-frequency Oscillatory Ventilation
after initiating mechanical ventilation.
High-frequency oscillatory ventilation (HFOV) uses
Volume Ventilation of Children supra-physiological ventilatory rates and tidal volumes
Typically, volume ventilation is not used in infants under less than anatomical dead space to accomplish gas
exchange. Typical ventilator rates are 3–15 Hz or 180–
5 kg due to the small tidal volumes, which risk being 600 breaths/min (1 Hz = 60 breaths). HFOV is primarily
lost in the distensible tubing and leaking around the used in managing infants and children with diffuse alveo-
ETT. In addition, most volume ventilators do not have lar or interstitial disease requiring high peak distending
a constant fresh gas flow, so the infant has to work pressures. Goals include maximising alveolar recruit-
harder to trigger a breath. Some of the newer models of ment, minimising barotrauma and providing adequate
ventilator have attempted to overcome these problems. alveolar gas exchange.
Steps in beginning volume ventilation for a child are as
follows: 150 HFOV is delivered primarily by the Sensor Medics 3100A
(Mayo Healthcare Australia). This ventilator uses a dia-
1. Set the tidal volume at <8 mL/kg. This is a protec- phragm piston unit to actively move gas into and out of
tive lung strategy approach and can be increased the lung, and requires a non-compliant breathing circuit.
151
if needed. A major difference between HFOV and other forms of
2. Set the rate at 20 breaths/min. This is lower than ventilation is that there is active expiration with oscilla-
physiological norm for infants, but the slightly tion versus passive expiration for conventional ventila-
larger tidal volumes will compensate. tion. 150,155 Unlike conventional ventilation, which uses
3. Set the FiO 2 at <0.6 and titrate according to oxygen bulk flow to deliver gas to the lungs, using smaller-than-
saturation and blood gases. dead-space tidal volumes utilises the mechanisms of pen-
4. Set the PEEP at 5 cm. This is slightly higher than delluft, Taylor dispersion, asymmetrical velocity profiles,
physiological norm. cardiogenic mixing and, to a very limited extent, bulk
5. Set the trigger sensitive enough to allow the infant flow. 155 These are all terms used to describe the distribu-
or child to trigger a breath without working too tion of gas when rapid rates and tiny volumes are used.
hard. If a continuous fresh gas flow is available,
then this is preferable. If autocycling occurs, gradu- Ventilation is dependent on amplitude (a determinant of
ally decrease the trigger-setting sensitivity until the tidal volume) much more than rate. With the Sensor
autocycling stops. Medics oscillator, paradoxically lowering frequency (Hz)
improves CO 2 removal. This is thought to occur because
Pressure Ventilation of Children the oscillating diaphragm is able to move through a
The pressure ventilation mode is most commonly used greater distance, thus increasing tidal volume by provid-
ing more inspiratory time and a longer expiratory time.
155
in infants weighing under 5 kg or with children who have
a large leak around the ETT. Steps in beginning pressure The principal determinants of oxygenation are the same
ventilation for a child are as follows and should be based as those for conventional ventilation. Therefore, as with
on arterial blood gases: 150 conventional ventilation, the alveoli must be opened and
prevented from collapsing if hypoxaemia is to be cor-
1. Set the peak inspiratory pressure (PIP) at rected. HFOV achieves this through delivering a high
18–20 cmH 2 O. mean airway pressure without imposing a large tidal
2. Set the positive end expiratory pressure (PEEP) at volume. It thus avoids overdistension and the risk of
150
5 cmH 2 O. barotrauma.
3. Set the rate at 20 breaths/min.
4. Set the FiO 2 at <0.6 and titrate according to oxygen
saturation and blood gases. Extracorporeal Membrane Oxygenation
5. Set the trigger sensitive enough to trigger a breath. Extracorporeal membrane oxygenation (ECMO) is an
Most pressure ventilators have a constant fresh gas alternative method of providing ventilatory and/or
flow, which allows the child to breathe spontane- cardiac support. When used to support ventilation,
ously without increased effort. ECMO allows the lungs to rest and heal.