Probably the most relevant is knowing the "Anatomical and physiological changes... from neonate to older child in relation to the conduct of anaesthesia".
Examiner feedback
There has not yet been a CRQ dedicated to paediatric ventilation, but it features within related questions.
In the February 2025 paediatric mediastinal mass question, marks were dropped on patient positioning and mode of ventilation, which examiners felt reflected limited clinical experience.
Lung-protective ventilation (LPV) is standard practice in adults, but there is a lack of paediatric perioperative data
Most paediatric evidence comes from PICU and NICU; ventilating a critically ill child with ARDS differs significantly from ventilating healthy lungs under GA
Observational data show wide variation in practice, often ventilating children with higher tidal volumes and higher energy than recommended
Contrary to general perception, postoperative pulmonary complications (PPCs) are common in children; they prolong hospital stay and increase costs
Relevant paediatric respiratory physiology
High closing capacity relative to FRC: small airways close during tidal breathing
High oxygen demand per kg: rapid desaturation if gas exchange is impaired
General anaesthesia significantly reduces end-expiratory lung volume (EELV)
Together these predispose to:
Intraoperative atelectasis
Tidal derecruitment: cyclical collapse and reopening of alveoli with each breath, which impairs gas exchange and may cause lung injury over time
These problems are more marked the younger the child
Ventilator-induced lung injury (VILI)
Volutrauma: overdistension from excessive tidal volume
Barotrauma: excessive airway pressure
Atelectrauma: shear stress from repetitive alveolar opening and closing
The aim of LPV is to minimise lung stress and strain, and thereby reduce VILI and PPCs
Setting
Suggested approach in children
Tidal volume
6–10 ml/kg; avoid >10 ml/kg
PEEP
Individualised (PEMVECC suggests 3–5 cmH2O)
Recruitment manoeuvres
Lowest effective pressure, shortest time, fewest insufflations
FiO2
Lowest that achieves target saturations; avoid hyperoxaemia
Driving pressure
As low as possible; no paediatric perioperative target
Tidal volume
Adult intraoperative lung-protective ventilation is typically defined as Vt 6–8 ml/kg and this is often extrapolated to children
There's no clear association between Vt and pulmonary complications has yet been found in children and the 'ideal' Vt remains debated
PEMVECC recommends avoiding Vt >10 ml/kg to prevent volutrauma
Lower Vt (5 ml/kg) combined with higher PEEP (10 cmH2O) has produced the most favourable compliance profiles
Overall, intraoperative ventilation can be safely performed with Vt 6–10 ml/kg
PEEP
Imaging studies show PEEP prevents anaesthesia-induced atelectasis in healthy children yet despite this, children often receive less PEEP than adults
PEEP 5 cmH2O improves respiratory mechanics, reducing driving pressure and intrinsic PEEP
However, PEEP up to 8 cmH2O may still not prevent tidal derecruitment, while high PEEP risks overdistension
A fixed PEEP is therefore unlikely to suit every child; individualised PEEP after a recruitment manoeuvre is the preferred approach
Recruitment manoeuvres
Reduce the risk of anaesthesia-induced atelectasis in children
Options include a single sustained insufflation or repeated short insufflations
To limit lung stress use the shortest effective time, lowest effective pressure and fewest number of insufflations
Should be followed by adequate PEEP to keep recruited lung open
Oxygenation
FiO2 is often increased in response to hypoxaemia, but this treats the number rather than the cause (atelectasis)
Up to 90% of children experience intraoperative hyperoxaemia, which has its own potential adverse effects
FiO2 has no significant impact on development of atelectasis in ventilated children
Driving pressure (ΔP)
ΔP = plateau pressure − PEEP
It reflects the tidal volume relative to the compliance of the aerated lung, so it is a surrogate for lung stress and strain
In adults under GA, ΔP rather than PEEP or Vt alone is associated with POPCs
In critically ill children, ΔP >15 cmH2O is independently associated with prolonged time to extubation and increased 28 day mortality
Reduced by lowering Vt, increasing respiratory rate and optimising PEEP
Paediatric perioperative data are scarce, so no specific target can be recommended
Mechanical power (MP)
The energy delivered to the lungs per minute during mechanical ventilation
A composite variable incorporating Vt, respiratory rate and pressures
High MP is associated with higher mortality in paediatric and adult ARDS
In adults under GA, MP >12 J/min is associated with a greater risk of PPCs
The trade-off
The settings that lower ΔP and MP pull in opposite directions; reducing ΔP by lowering Vt and raising the rate may push MP too high, and vice versa
Ventilator change
Effect on ΔP
Effect on MP
↓ Vt and ↑ RR
↓
May ↑
↑ Vt and ↓ RR
↑
↓
Optimised PEEP
↓
Variable
Aims
To ensure adequate gas exchange: CO2 clearance and O2 delivery
Ventilator adjustments directly alter PaCO2 and PaO2, so these need continuous monitoring throughout GA
Methods
Arterial blood gas: the gold standard for PaCO2 and PaO2
Pulse oximetry
End-tidal CO2:
Relies on a tracheal tube to measure the inspired and expired CO2 difference
Unreliable during shared airway procedures and with high-frequency ventilation
Transcutaneous CO2:
Has returned to use in theatre, particularly for shared airway procedures
Shows reliable agreement with PaCO2
Ventilator mechanics: plateau pressure, PEEP and ΔP, compliance and intrinsic PEEP
Principles
An alternative to conventional mechanical ventilation (CMV) designed to reduce VILI
Optimises lung expansion while delivering Vt at or below anatomical dead space
Widely used in NICU, often as rescue therapy when CMV has failed (e.g. congenital diaphragmatic hernia)
Increasingly used in theatre, especially for shared airway procedures
HFOV
HFJV
Breaths
Oscillating pressure swings at 300–900/min
Rapid, small, high-velocity jets; conventional ventilator provides PEEP
Expiration
Active
Passive
Mean airway pressure
Constant and higher; holds the lung open
Lower
Main uses
NICU; thoracic surgery such as TOF repair for CO2 elimination
Shared airway surgery (supraglottic jetting via suspension laryngoscope); restrictive lungs
High-frequency oscillatory ventilation (HFOV)
The most studied mode in children
As an elective strategy in extreme preterm infants it reduces VILI and chronic lung disease
No mortality benefit over CMV if chosen as the initial mode and no mortality benefit in hypoxaemic respiratory failure
Can improve hypercapnia when lung-protective ventilation has failed
No clear postoperative benefit over CMV when used in theatre
High-frequency jet ventilation (HFJV)
Effective ventilation and oxygenation at low airway pressures
Appears equivalent to CMV during cardiac surgery and congenital diaphragmatic hernia repair
Lower mean airway pressure than HFOV, so may be better for restrictive lungs to reduce adverse cardiac effects
Complications
HFJV: barotrauma and intrinsic PEEP because exhalation is passive; particular caution with catheter jetting or any obstruction to expiratory outflow
Unreliable end-tidal CO2 monitoring
Unlikely to benefit severe established BPD, as high airway resistance reduces gas delivery and exchange
Advantages
Disadvantages
Small Vt minimises volutrauma
Limited perioperative evidence of benefit
Unobstructed surgical field in shared airway surgery
Barotrauma and gas trapping (HFJV)
Good CO2 elimination
End-tidal CO2 unreliable
Rescue option when CMV fails
Specialist equipment and experience required
Setting
Asthma (poorly controlled)
ARDS
BPD
Vt (ml/kg)
5–8
6–8 (4–6 if needed to meet pressure limits)
5–8
Respiratory rate
Near or below physiological
Increase to allow lower Vt
Near or below physiological
Pressures (cmH2O)
PIP <40
Pplat <28 (<32 if poor chest wall compliance)
PIP 20–30
PEEP (cmH2O)
3–5
Titrated to oxygen delivery
4–8
I:E ratio
1:3–1:4
–
1:2–1:3
ΔP (cmH2O)
<30
<15
–
Asthma
Well controlled with no perioperative bronchospasm: ventilate as for any other child
Poorly controlled: LPV approach aiming to prolong expiratory time, minimising gas trapping, intrinsic PEEP and barotrauma
Low Vt, low inspiratory pressures and a slow rate; accept permissive hypercapnia
ARDS
Commonly secondary to pneumonia or sepsis in children
Higher ΔP is associated with increased mortality, morbidity and prolonged time to extubation
Minimise ΔP by reducing Vt and increasing rate and PEEP
High MP and high PEEP are associated with mortality, although this may reflect illness severity rather than direct harm
Bronchopulmonary dysplasia (BPD)
Chronic lung disease of prematurity, partly caused by the mechanical ventilation used to treat infant respiratory distress syndrome
Mainly a small airways disease, but prolonged intubation may also cause tracheomalacia and bronchomalacia
Often V/Q mismatch with a compensated respiratory acidosis
Optimise PEEP to prevent airway collapse, obstruction and atelectasis
Reduced lung volumes may require Vt below physiological values
Increase CO2 elimination by increasing rate rather than PIP, as higher PIP risks volutrauma
Permissive hypercapnia accepted if pH >7.25
Incidence
8–35% after paediatric surgery, depending on population and procedure
LPV reduces pulmonary complications
Complications
Bronchospasm
Atelectasis
Hypoxaemia
Pneumonia
Respiratory failure
Pleural effusion
Pneumothorax
Risk factors
Patient:
Lower gestational age
Higher comorbidity scores
Preoperative pneumonia
Preoperative mechanical ventilation
Surgical:
Abdominal and spinal surgery
Duration >60 minutes
Anaesthetic:
High Vt (>8 ml/kg), although in 1–3 year olds a higher Vt was linked to fewer PPCs
Intraoperative albumin infusion
Prevention
Individualised ventilation aiming for the lowest ΔP and MP compatible with adequate gas exchange
Vt 6–10 ml/kg
Recruitment manoeuvre followed by individualised PEEP
Avoid unnecessary hyperoxaemia
Optimise pre-existing lung disease such as asthma before elective surgery