How to diagnose and avoid ineffective efforts

The most common causes are:

• Trigger threshold set too high
• Pressure support too high
• Set frequency and/or inspiratory time too high (in controlled/assisted modes)
• Tidal volume set too high
• Presence of AutoPEEP
• Low respiratory drive
• Weak inspiratory effort
• Sedation

Several waveform characteristics can assist in the diagnosis (see Figure 1):

• The pressure/time scalar waveform will show a decrease in baseline airway pressure not followed by ventilator support
• The flow/time scalar waveform will reveal an abrupt change in the steepness of the waveform (decrease in expiratory flow or increase in inspiratory flow not followed by ventilator support)
• The esophageal pressure/time scalar waveform will display a decrease in pleural pressure not followed by ventilator support

The most practical adjustments that can be made on the ventilator to reduce ineffective efforts are as follows:

• Minimize AutoPEEP by reducing minute ventilation
• Reduce pressure support and/or tidal volume
• Adjust the expiratory trigger sensitivity (ETS) to make it more sensitive to the patient's activity (see Figures 2 and 3)