Mechanical ventilation principles in children — branching viva

Station opening

Examiner: "Define mechanical ventilation in children and tell me how a volume-controlled breath differs from a pressure-controlled one." [10]

Strong candidate (must-hit)

• Defines mechanical ventilation as the delivery of positive-pressure breaths through an endotracheal tube when a child's oxygenation, ventilation or respiratory effort has failed; explains that a volume-controlled breath guarantees a set tidal volume and lets the pressure vary with compliance, whereas a pressure-controlled breath fixes the inspiratory pressure and lets the delivered tidal volume vary; adds that the variable that is not guaranteed is the one to watch, because a worsening compliance shows as a rising pressure in volume control and a falling volume in pressure control. [10] [3]

Weak candidate

• "It is just a breathing machine; volume and pressure modes are basically the same." [10]

Branch A — Severe paediatric acute respiratory distress syndrome and lung-protective settings

Examiner: "An 8-year-old with severe pneumonia now has paediatric acute respiratory distress syndrome. What lung-protective settings do you choose and why?" [2]

Strong

• Chooses a low tidal volume near 6 to 8 millilitres per kilogram predicted body weight, reduced toward 4 to 6 in severe disease, because the injured lung is a small baby lung that overdistends easily; holds the inspiratory plateau pressure at or below 28 centimetres of water; titrates positive end-expiratory pressure to recruit the lung and prevent atelectrauma while avoiding overdistension; accepts permissive hypercapnia with a pH above about 7.20; and cites the Wong trial showing that a structured protocol built on these targets improved survival. [2] [5]

Weak

• "Give 10 millilitres per kilogram and push the oxygen up to keep the saturation at 100 percent." [2]

Branch B — The ventilated child who suddenly deteriorates

Examiner: "A ventilated child acutely desaturates with a rising peak pressure. Walk me through your assessment." [10]

Strong

• Approaches the child as machine then patient, working through airway and circuit causes first (blocked, kinked or displaced tube, disconnected circuit, plugged endotracheal tube), then lung causes (right mainstem intubation, pneumothorax, atelectasis, consolidation), then patient and machine causes (agitation, inadequate sedation, machine fault); notes that rising peak pressure with unchanged volume in volume control signals a stiffer lung or obstructed tube and is an alarm demanding an immediate answer rather than a silenced setting; uses bag ventilation and auscultation to localise the problem. [10] [3]

Weak

• "Turn the alarm off and increase the inspired oxygen until the saturation improves." [10]

Branch C — Liberation and post-extubation support in an infant

Examiner: "A 3-month-old former premature infant is recovering from bronchiolitis. How do you assess readiness and what do you plan for after extubation?" [4]

Strong

• Assesses readiness daily by weaning positive end-expiratory pressure and inspired oxygen, moving to pressure support and lightening sedation, then performs a spontaneous awakening and breathing trial as the screening step and a formal extubation readiness test on low pressure support; because the infant is predicted to fail, plans post-extubation non-invasive support, citing Iyer that high-flow nasal cannula, continuous positive airway pressure and bilevel all reduce extubation failure compared with conventional oxygen, with non-invasive ventilation the strongest. [4] [11]

Weak

• "Extubate straight to room air once the fever settles and see how he goes." [4]

Branch D — Preventing ventilator-associated pneumonia

Examiner: "A child is likely to be ventilated for several days. How do you reduce the risk of ventilator-associated pneumonia?" [9]

Strong

• Applies a prevention bundle: elevating the head of the bed, maintaining oral hygiene, using closed suction and subglottic secretion management, reviewing sedation daily to permit a liberation attempt, and liberating from the ventilator promptly, because the endotracheal tube is the gateway to the infection and minimising its time in place is central; adds that routine prophylactic antibiotics are not part of prevention and early enteral nutrition is generally continued. [9] [3]

Weak

• "Start broad-spectrum antibiotics for the whole ventilation course and keep the child flat." [9]

Closing

Examiner: "What did the RESTORE and SANDWICH trials teach us about translating adult sedation and liberation protocols to children?" [8]

Strong

• States that both large multicentre trials found, in their primary analysis, that protocolised sedation and ventilator-liberation strategies did not shorten the duration of mechanical ventilation in children; concludes that adult protocols do not translate directly, and liberation in children remains guided by the tested pathway of daily awakening and breathing trials and extubation readiness testing. [7] [8]

Weak

• "They proved that standardising care halves the ventilation time, just like in adults." [8]