Ventilator Basics for EMS: Settings, Alarms, and Troubleshooting

Transport ventilators are increasingly standard on ALS units and critical care transfers. You do not need to be a respiratory therapist, but you do need to set four numbers correctly and recognize a deteriorating patient fast.

The four settings you touch

• Tidal volume: 6–8 mL/kg of ideal body weight, based on height, not actual weight.
• Rate: 10–12 breaths per minute for most adults; titrate to an EtCO2 of 35–45 mmHg.
• PEEP: start at 5 cm H2O; increase for refractory hypoxemia, cautiously if hypotensive.
• FiO2: start high, then titrate down to keep SpO2 92–96%.

Modes in plain language

Assist-Control (AC/CMV) delivers a set breath and a full breath whenever the patient triggers — the default for a sedated, paralyzed patient. SIMV synchronizes mandatory breaths and lets spontaneous breaths be smaller. Pressure support assists spontaneous breaths only and is not appropriate for an apneic patient.

Special populations

• Asthma or COPD: slower rate, longer expiratory time, watch for breath stacking and auto-PEEP.
• ARDS: low tidal volume 6 mL/kg, higher PEEP, accept permissive hypercapnia.
• Head injury: keep EtCO2 at 35–40 mmHg; do not prophylactically hyperventilate.
• Cardiac arrest with an advanced airway: 10 breaths per minute, avoid excessive pressure.

When the patient crashes: DOPE

1. Displacement — has the tube moved or come out? Recheck depth and capnography.
2. Obstruction — kinked tube, mucus plug, biting. Suction and reposition.
3. Pneumothorax — unilateral silence with rising pressures and hypotension; decompress.
4. Equipment — disconnect, oxygen source, circuit leak, dead battery. Take them off the vent and bag.

Alarms mean something

High pressure alarms point to obstruction, bronchospasm, pneumothorax, or a poorly compliant lung. Low pressure or low volume alarms point to a leak or disconnect. Never silence an alarm without finding the cause.