Topic Progress:

First, they notice there is a patient-ventilator dyssyncrhony. Can you tell which one your patient has among the following possible types of dyssynchrony?


Dyssynchrony occurs when the ventilator settings don’t match the patient’s requirements

  • Can cause
    • Increased work of breathing and muscle fatigue
    • Increased oxygen requirements
  • Often requires increased sedation and can prolong duration of ventilation
  • Requires adjustment of ventilator settings or transition to a different or spontaneous breathing mode


Types of Dyssynchrony

 [az_accordion_section] [accordion title=”Trigger dyssynchrony” id=”acc-1″]

o Mandatory mode with no ability to trigger spontaneous breaths

o Trigger set too high

§ A weak patient will be unable to initiate a spontaneous breath as they won’t sufficiently change the flow or pressure in the circuit

§ Hint: negative inflections on the PAW curve often due to intrinsic PEEP too high to overcome, so signs of high intrinsic PEEP might be present

o Trigger set too low

§ Other actions for example hiccups will trigger a breath

§ Hint: usually fast RR without physiologic explanation extra breaths matching the external triggering event (hiccups..) [/accordion] [accordion title=”Flow dyssynchrony” id=”acc-2″]

o Flow set too low

§ results in insufficient TV being delivered and the patient may appear to be sucking or gasping

§ Hint: “pull down” on PAW curve upstroke during inspiration

o Flow set too high

§ results in either an excessively large breath or the patient tries to initiate expiration early and works against the ventilator

§ Hint: most likely you won’t see it…but patient will be uncomfortable [/accordion] [accordion title=”Cycle dyssynchrony” id=”acc-3″]

o Ti set too short

§ Prematurely ends inspiration and can result in inadequate TV

§ Patient discomfort as still trying to inspire when expiration begins

§ Hint: since still wanting more air, patient will sometimes be able to trigger a second breath right at the end of the ventilators breath. It will look like 2 stacked breaths

o Ti set too long

§ Can result in excessive TV

§ In obstructive lung disease the resulting lack of expiratory time can result in gas trapping

§ Hint: most likely you won’t see it…but patient will be uncomfortable signs of gas trapping if patient at risk and TE too short[/accordion] [/az_accordion_section]

[az_toggle_section] [toggle title=”What dyssynchrony does your patient have?” id=”tgl-1″] Looks like a trigger dyssynchrony. Patient tries to trigger a breath (negative inflections in PAW curve), but can’t seem to reach the set trigger to start a breath. Would be suprising for your patient to have become too weak to breathe in just 1 night, so it must be that the effort he needs to generate to reach the set trigger is too high…

[/toggle] [/az_toggle_section]

[az_toggle_section] [toggle title=”What other problem is seen on the ventilator curves?” id=”tgl-1″] Expiration phase of the flow curve doesn’t go back to zero before the next inspiration begins. This can put your patient at risk of building high intrinsic PEEP…and maybe that’s why he can’t trigger a breath.. [/toggle] [/az_toggle_section]

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