Mechanical Ventilation Alarms: High Airway Pressure
Before you make changes to the ventilator, recall the variables that affect airway pressures. These can be divided into two categories; resistance and compliance. Resistance (∆ Pressure/Flow) is a measurement of air flow from the ventilator through the airways. Compliance (∆ Volume/ ∆ Pressure) describes the degree to which the lung and chest wall can stretch. The more pressure required to inflate the lung and expand the chest wall, the lower the compliance. A high airway pressure alarm is signaling a problem with resistance or compliance.
The first thing to do is turn up the upper limit on the alarm parameter to stop the alarm and ensure that the patient receives the set breath from the ventilator. Now the ventilator is not alarming, allowing you to see the peak inspiratory pressure is 45 cm H2O (normal <30 cm H2O).
Two things can be happening when the peak inspiratory pressure is high
- Peak pressure is high with a normal plateau pressure, indicating a problem with resistance
- Peak pressure is high with an elevated plateau pressure (normal < 25 cm H2O) demonstrating that there is a problem with lung and/or chest wall compliance
Do an inspiratory hold to determine your plateau pressure. Once you have your peak pressure and plateau pressure you can determine a differential diagnosis.
Resistance problems (high peak pressure with normal plateau pressure)
- Kink in the circuit
- Fluid pooling in the circuit
- Biting the ETT
- A small ETT with biofilm forming
- High flow rate or tidal volume
- Ventilatory asynchrony
- Mucous plugging
- Foreign body
Compliance problems (high peak pressures and high plateau pressures)
- ETT in right mainstem
- Pulmonary edema
- Air trapping (Auto PEEP)
- Pulmonary fibrosis, ILD
- Abdominal compartment syndrome
Special thanks to Dr. Emily Damuth and Dr. Jason Bartock for their workshop on troubleshooting mechanical ventilation at ResusX on October 1, 2019.