To recognize auto-peep look at the flow wave form to see if the expiratory cycle fails to return to baseline prior to the new inspiratory cycle
The flow waveform is purple at the start of inspiration when a patient triggering a breath
Volume Waveform
To identify a leak, look at the volume waveform where the waveform doesn’t return to baseline, instead it cuts off early
Pressure Waveform
You can recognize obstructing on the pressure waveform, specifically in NIV, when there are double arches like the McDonalds sign, representing an interruption in flow
During the exhalation phase after peak expiratory flow there a dip in the pressure wave form because the expiratory valve opens allowing the circuit to decompress
Auto-Cycle
Typically occurs because of:
A leak anywhere in the system starting from the ventilator, up to the patient’s lungs
Leaks in the circuit
ET tube cuff leak
Lungs (pneumothorax)
May also result from condensation in the circuit sloshing around and causing false triggers
How to recognize auto cycling
The respiratory rate increases suddenly without any patient input
The exhaled tidal volume will be lower than the set parameters and this may set off a ventilator alarm for low exhaled tidal volume, low minute ventilation, circuit disconnect or rapid respiratory
Auto-Peep and Trapping
To determine auto peep, amount do an expiratory hold
How to measure termination of peak expiratory flow in BI level and look for trapping
Save the waveforms
Review the waveform and using the cursor on the monitor find the most negative point on expiratory phase of the waveform (PEFR)
Find the last negative number on the expiratory waveform until the inspiratory phase begins
Divide the last negative number of the expiratory phase by the most negative number and multiply that number by 100 to get the percentage of volume trapped in the lungs when expiration ends, and inspiration begins