Recognising ventilator problems

Core idea: patient first, ventilator second

• If the patient is deteriorating, prioritise oxygenation and ventilation rather than “fixing the machine”.
• Always look at the patient: chest movement, colour, work of breathing (if not paralysed), pulse oximetry (SpO2), blood pressure and heart rate.
• If in doubt: disconnect from the ventilator and ventilate with a self-inflating bag (with 100% oxygen) while you troubleshoot.
• Call for help early if oxygenation/ventilation is not rapidly improving.

What to monitor (and what it means)

• SpO2: falling suggests oxygenation problem (but may lag behind acute events).
• End-tidal CO2 (EtCO2): sudden drop suggests disconnection, major leak, circuit problem, severe hypotension/PEA, or pulmonary embolism; rising suggests hypoventilation, rebreathing, increased CO2 production, or obstructed expiration.
• Airway pressures: peak pressure (Ppeak) rises with resistance (kinked tube, bronchospasm, secretions); plateau pressure (Pplat) rises with poor compliance (atelectasis, pneumothorax, pulmonary oedema, abdominal insufflation).
• Tidal volume (Vt) and minute ventilation: low values suggest leak/disconnection or inadequate settings; high values may occur if patient is over-breathing or settings too aggressive.
• Alarms are prompts to assess; they are not diagnoses.

Common ventilator alarms and first responses

• High airway pressure alarm: check patient and tube first (biting, kink, obstruction, bronchospasm); ensure adequate anaesthesia/relaxation; suction; consider pneumothorax if sudden and severe.
• Low airway pressure / low exhaled tidal volume alarm: think disconnection or leak (circuit, filter, catheter mount, cuff leak); check connections from patient to machine.
• Apnoea / low minute ventilation alarm: check patient effort (if spontaneous), sedation/opiates, neuromuscular blockade; check trigger sensitivity and circuit integrity.
• High EtCO2 alarm: check ventilation adequacy, circuit rebreathing (CO2 absorber, one-way valves), increased metabolic CO2 (fever, shivering), and expiratory obstruction.
• Low EtCO2 alarm: check disconnection/leak, sampling line, severe hypotension/low cardiac output, or pulmonary embolism.

A simple troubleshooting sequence (new-starter friendly)

• 1) Look at the patient: chest rise, SpO2, EtCO2 trace shape, haemodynamics.
• 2) Give 100% oxygen; increase FiO2 immediately if unstable.
• 3) If severe problem: disconnect and bag-ventilate; this separates “patient/lung” from “ventilator/circuit”.
• 4) Check the airway: tube position (depth, markings), patency (suction), cuff pressure/leak, biting/kinking, water/secretions in HME/filter.
• 5) Check the circuit: connections, filter, catheter mount, sampling line, water in tubing, ventilator valves if suspected.
• 6) Check settings: mode, set Vt/pressure, respiratory rate, PEEP, inspiratory time, pressure limits, trigger sensitivity.
• 7) Reassess: SpO2, EtCO2, pressures, and clinical exam; consider ABG if ongoing concern.

Recognising patterns: resistance vs compliance

• Increased resistance (problem with flow): high Ppeak with relatively normal Pplat; wheeze, prolonged expiration, “shark-fin” capnogram (bronchospasm), thick secretions, kinked/bitten tube.
• Reduced compliance (stiff lungs/chest): both Ppeak and Pplat rise; reduced chest movement; causes include atelectasis, pneumothorax, pulmonary oedema, ARDS, laparoscopic insufflation, tight strapping, obesity.
• If you can’t measure plateau pressure, use clinical clues: sudden severe difficulty ventilating + haemodynamic compromise = treat as pneumothorax until proven otherwise.

Capnography clues (quick pattern recognition)

• Flat trace or sudden loss: disconnection, oesophageal intubation, sampling line off/blocked, cardiac arrest/very low output.
• Gradual rise in EtCO2: hypoventilation, increased CO2 production, rebreathing.
• Shark-fin (slanted upstroke): bronchospasm or expiratory obstruction (including kinked tube/secretions).
• Baseline not returning to zero: rebreathing (faulty valves, exhausted CO2 absorber, inadequate fresh gas flow in circle system).

First-time scenarios in theatre/ICU and what to do

• Sudden high pressure after turning the patient: check tube kink, circuit traction, endobronchial intubation (listen, check depth), pneumothorax if abrupt and severe.
• Low volume alarm after moving the bed: likely disconnection at catheter mount/filter/circuit; reconnect and reassess EtCO2 and chest rise.
• Poor ventilation after induction: consider laryngospasm/bronchospasm, biting on tube, inadequate depth, or oesophageal intubation; check capnography and chest movement.
• High EtCO2 with normal pressures: check respiratory rate/Vt, CO2 absorber, one-way valves, and whether patient is shivering/pyrexial.
• Difficulty triggering breaths (patient “fighting” ventilator): check sedation/analgesia, trigger sensitivity, auto-PEEP (especially COPD/asthma), and consider changing mode.

When to switch to manual ventilation

• Immediate manual ventilation if: rapidly falling SpO2, sudden loss of EtCO2, very high pressures with poor chest rise, or haemodynamic collapse.
• Manual ventilation helps you feel compliance/resistance and confirms whether the problem is the ventilator/circuit.
• If manual ventilation is also difficult: think patient/lung problem (tube obstruction, bronchospasm, pneumothorax, severe atelectasis) and treat urgently.

Safety essentials

• Ensure alarms are on and appropriately set (pressure limits, low minute volume, apnoea, FiO2).
• Always confirm tracheal tube position with continuous capnography in intubated patients.
• After any intervention, reassess and document: SpO2, EtCO2, pressures, settings, and clinical findings.
• Escalate early: senior help, ICU outreach, or anaesthetic consultant if instability persists.