Mechanical ventilation principles in children — structured clinical encounter

Station brief (candidate)

You are the paediatric registrar in the paediatric intensive care unit. An 8-year-old has just been intubated for severe pneumonia and is now diagnosed with paediatric acute respiratory distress syndrome. The team asks you to confirm the airway is safe, set the lung-protective ventilator strategy and justify it, describe how you will monitor the child, and outline the plan for eventual liberation. You have 12 minutes with the team and 5 minutes for examiner discussion. [2]

Information available on request

• Intubated for rising work of breathing and refractory hypoxaemia; cuffed endotracheal tube secured. [3]
• Chest radiograph (on request): bilateral diffuse infiltrates consistent with acute respiratory distress; tube tip in satisfactory position, no pneumothorax. [1]
• Bedside confirmation (on request): bilateral air entry, chest rise, and continuous waveform capnography with a steady end-tidal carbon dioxide trace. [3]
• Initial arterial blood gas (on request): low arterial oxygen partial pressure on a high inspired oxygen fraction, confirming a high oxygenation index. [1]
• Current ventilator (on request): volume-control mode with a conventional tidal volume, high positive end-expiratory pressure and a high inspired oxygen fraction. [2]

Tasks

1. State how you confirm the endotracheal tube is correctly placed and patent. [3]
2. Give the lung-protective ventilator settings you would set and the targets behind them. [2]
3. Describe how you monitor the child over the first hours, including the plateau pressure and the oxygenation index. [2] [1]
4. Outline the evidence for a structured lung-protective protocol and your plan for liberation. [5] [4]

Marking anchors

Must-hit

• Confirms tube placement with bilateral air entry, symmetric chest rise and continuous waveform capnography, and excludes right mainstem intubation and pneumothorax on imaging. [3]
• Sets a low tidal volume near 6 to 8 millilitres per kilogram predicted body weight, reduced toward 4 to 6 in severe disease, holds the inspiratory plateau pressure at or below 28 centimetres of water, titrates positive end-expiratory pressure to recruit the lung, and accepts permissive hypercapnia with a pH above about 7.20. [2] [1]
• Monitors the plateau pressure (not just the peak) as the compliance marker that governs protection, and uses the oxygenation index, mean airway pressure times inspired oxygen fraction divided by arterial oxygen partial pressure, to grade severity and trend the response. [2]

Merit

• Cites the Wong controlled trial showing that a structured lung-protective protocol built on these targets improved survival, and outlines a daily liberation pathway of a spontaneous awakening and breathing trial followed by an extubation readiness test, with planned post-extubation non-invasive support for the child predicted to fail. [5] [4]

Fail

• Continues a conventional high tidal volume to keep the carbon dioxide normal and chases 100 percent saturation with rising pressure, ignoring the risk of ventilator-induced lung injury. [1] [2]
• Fails to confirm tube placement with capnography and imaging, or sets no plan for daily readiness assessment or post-extubation support. [3] [4]