🔧 Chapter 27: Mechanical Ventilation — Troubleshooting

Patient-ventilator asynchrony · Triggering issues (ineffective, double, auto-triggering) · Flow asynchrony · High/low pressure alarms · ETT problems · PIP vs Pplat analysis · Air leaks · Alarm management

🔍 Core Concepts: Ventilator Troubleshooting

🚨 First Principles
On alarm: assess patient ABCs first, not machine. If patient deteriorating, disconnect and bag. Never mute alarm without finding cause. Never sedate/paralyse an agitated patient on ventilator without evaluation.
⚠️ Patient-Ventilator Asynchrony
Trigger phase: ineffective triggering (sensitivity too low), double triggering (Ti too short), auto-triggering (sensitivity too high). Flow phase: flow starvation (scooped pressure curve). Cycle phase: premature or delayed cycling.
📊 PIP vs Pplat Analysis
High PIP + normal Pplat = increased airway resistance (bronchospasm, secretions, kinked tube). High PIP + high Pplat = decreased compliance (ARDS, pneumothorax, mainstem intubation). Low PIP + low Pplat = leak/disconnection.
🫁 ETT Problems
Kinked/twisted → reposition head. Obstructed → suction. Dislodged → reintubate. Biting → bite block + sedation. Carinal impingement → pull back ETT.
🔊 Common Alarms
High pressure: coughing, biting, secretions, bronchospasm, pneumothorax. Low pressure: cuff leak, circuit disconnect. Apnoea: no trigger in set time. High exhaled volume: improved compliance, in-line nebuliser.
📉 Acute Deterioration Approach
Check ETT position, circuit connections, ventilator settings, patient position. Assess breath sounds, SpO2, ETCO2. Obtain CXR if pneumothorax suspected. Ventilator graphics guide diagnosis.

🛠️ Stepwise Approach: Ventilator Troubleshooting

1
Assess patient first (ABCs)
Ventilator alarm → check patient's airway, breathing, consciousness. If unstable, disconnect ventilator and bag with 100% O2. Do not delay patient assessment to investigate machine.
2
Check ETT and circuit
Rule out dislodgement (listen over stomach, EtCO2), obstruction (pass suction catheter), kinking (reposition head), cuff leak (check cuff pressure).
3
Analyse PIP and Pplat (Volume Control)
High PIP + normal Pplat → airway resistance (bronchospasm, secretions, ETT kink). High PIP + high Pplat → decreased compliance (ARDS, pneumothorax, mainstem intubation, abdominal distension). Low pressures → leak or disconnect.
4
Identify asynchrony using graphics
Ineffective triggering → increase sensitivity (less negative). Double triggering → increase inspiratory time. Flow starvation (scooped pressure) → increase flow. Auto-PEEP (flow not returning) → decrease rate, increase expiratory time, set external PEEP.
5
Respond to specific alarms
High pressure: suction, bronchodilators, sedation, check for pneumothorax. Low pressure: tighten connections, reinflate cuff, check for circuit disconnect. Apnoea: check trigger sensitivity, ensure patient not oversedated, set backup rate.
6
Obtain diagnostics
CXR to confirm ETT position, rule out pneumothorax, assess lung volumes. ABG to check ventilation/oxygenation. Ventilator graphics to assess for auto-PEEP, asynchrony, obstruction.