Bedside tip - How to diagnose and avoid ineffective efforts

08.07.2019
Author: David Grooms, Reviewer: Jean-Michel Arnal

An ineffective effort is defined as a patient effort that is unable to trigger the delivery of a mechanical breath.

​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
Figure 1: Waveform characteristics indicating an ineffective effort

 

 

 

 

 

 

 

 

 

Resolution

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 (Figures 2 and 3)
Figure 2: Ineffective effort with ETS set at 25%

 

 

 

 

 

 

 

 

 

 

Figure 3: ETS increased to 50% at the red line, resulting in elimination of ineffective efforts

 

 

 

 

 

 

 

 

 

Related Articles

Ineffective effort, trigger threshold, waveforms, autoPEEP, pressure support, expiratory trigger sensitivity, ETS
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Date of Printing: 25.08.2019
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