Ventilator alarms, auto-PEEP and the DOPE approach

What it is

A ventilator alarm, or a sudden fall in oxygen saturation or blood pressure in a ventilated patient, is a possible emergency. The first rule is to look at the patient, not the screen: if the patient is in distress, disconnect from the ventilator and ventilate by hand with a self-inflating bag and pure oxygen. This removes the machine from the problem and lets you feel how easy the lungs are to inflate. The DOPE mnemonic organises the causes: Displacement of the tube (into the oesophagus, out of the trachea or down a main bronchus), Obstruction (secretions, blood, kinking, biting, bronchospasm), Pneumothorax (often tension, especially with high pressures) and Equipment failure (disconnection, leak, gas supply, ventilator fault). Many teams add S for stacked breaths: auto-PEEP from gas trapping, typical of asthma and COPD, where too little expiratory time leaves gas in the lungs, raises intrathoracic pressure and can cause hypotension or even pulseless electrical activity. Pressure alarms help locate the problem: on volume control, a high peak with a normal plateau points to the airway or tube, a high peak with a high plateau points to the lung, pleura, chest wall or trapped gas, and low pressure with low volumes points to a leak or disconnection. Capnography confirms the tube is still in the trachea. Once the patient is safe, the cause is fixed and the ventilator settings are reviewed.

How to recognise it

• Falling SpO2, rising heart rate, falling blood pressure or agitation in a ventilated patient.
• High-pressure alarm with low delivered volume, or low-pressure alarm with a loss of returned volume.
• Change or loss of the end-tidal CO2 waveform; a «shark-fin» shape suggests bronchospasm.
• Unequal chest movement or breath sounds, surgical emphysema, tracheal shift or raised neck veins.
• Expiratory flow that does not return to zero before the next breath (gas trapping).

Why it happens

• Displacement: head movement, transfer or loose ties move the tube out of the trachea or into one bronchus.
• Obstruction: thick secretions, blood clots, kinks or a bitten tube raise resistance and cut ventilation.
• Pneumothorax: positive pressure drives air through a ruptured alveolus; under pressure it compresses lung and heart.
• Auto-PEEP: in obstructive disease or at high rates, expiration is incomplete, so each breath adds trapped gas and pressure.

What to do at once

1. Look at the patient and call for help — the alarm is a symptom; the patient's state sets the urgency.
2. Disconnect and ventilate by hand with a bag and pure oxygen — removes the machine and lets you feel lung compliance.
3. Check the tube: depth at the teeth, capnography trace, cuff, kinks or biting — displacement is the first killer to exclude.
4. Pass a suction catheter down the tube — if it will not pass, the tube is blocked: clear it or replace it.
5. Examine the chest for pneumothorax; decompress a tension pneumothorax at once, then insert a chest drain.
6. If hypotension improves when disconnected, suspect auto-PEEP — allow full exhalation, then reduce rate and lengthen expiration.
7. Treat bronchospasm with inhaled bronchodilators and deeper sedation if needed — it raises resistance and trapping.
8. Check the equipment: circuit connections, leaks, humidifier, filter and gas supply — then reconnect and review settings.

DOPE(S): causes, clues and first actions

Costly mistakes

• Silencing the alarm or adjusting the ventilator before looking at the patient.
• Increasing sedation or paralysing an agitated patient before excluding a blocked or displaced tube.
• Missing a tension pneumothorax because a chest X-ray was awaited in an unstable patient.
• Treating hypotension from auto-PEEP with more fluids or vasopressors instead of letting the trapped gas out.
• Forgetting that a blocked filter or heat-moisture exchanger can mimic airway obstruction.

Next step

• After stabilising, obtain a blood gas and chest X-ray or lung ultrasound to confirm tube position and exclude pneumothorax.
• Call a senior or anaesthetist at once for a suspected displaced or blocked tube, or a difficult re-intubation.
• Review settings: tidal volume, rate, expiratory time and PEEP; measure plateau pressure and intrinsic PEEP.
• Secure the tube, document its depth, check cuff pressure and keep a bag, suction and airway kit at the bedside.
• Report the event and debrief: alarm limits, tube securing and transfer practice.

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Elsewhere in DurgiPedia

• Bag-mask ventilation
• Chest drain insertion and care
• Airway suctioning: oral, nasal and artificial airways
• Tracheostomy care
• Mechanics of breathing: pressures and muscles

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Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: Invasive Mechanical Ventilation (StatPearls (NCBI Bookshelf), 2024).

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