ASV & ABGS: Adjusting %Min Vol Based on Arterial Blood Gases

Adjust %Min Vol setting during ASV in regards to ABG analysis

I often get asked how do I adjust my settings during Adaptive Support Ventilation based on my arterial blood gas (ABG) results.

 Above is a snap shot of a flow chart from my new ASV guide I'm currently working on. 

This chart provides a brief overview of adjusting the percent minute volume setting based on ABG results, the guide will provide more details. 

RELATED LINKS

Adaptive Support Ventilation Book

The ASV Target Point

Incorporating Proportional Assist into Ventilator Protocols

Image 1: PAV+ Work of Breathing bar. 

PAV+ may be used for the initial mode of ventilation during the acute phase of mechanical ventilation. However, from my experience I have had the most success and efficiency with PAV+ utilizing the mode to rest patients after a failed spontaneous breathing trial. After reviewing the literature it is still unclear the best way to wean or liberate a patient from PAV+. However, a traditional T-piece trail has been supported by many peer reviewed journals, so at my institution we still use a 30 minute to one hour T-Piece trial to screen patients for extubation.

How to incorporate PAV+

Why is this patient on mechanical ventilation TODAY?

Photo from: http://theprogressivepatient.wordpress.com/2012/04/22/6/

It is very frustrating when I meet with the ICU staff Respiratory Therapist and ask why is this patient on the ventilator today and I get the following response “they had surgery”, “they coded”, “they had ventilatory failure”, “they have ARDS”, etc. Yet, these events happened hours, days, or even weeks ago, and they are not in the acute stages of their illness anymore.  There is a huge difference between initial indications for mechanical ventilation (MV) versus current goals for MV.

ZEEP Trial

Zero End-Expiratory Pressure "ZEEP" trial is an alternative to a standard SBT with minimal ventilator settings and/or trach collar or T-piece trials. See video for more information.

RELATED POST/ LINKS

Tobin: minimal PEEP & pressure support during SBT kills some patients

Myth Buster:ventilator weaning should be done on minimal settings (no T-Piece)

Is the T-piece trial futile?

Performing a T-piece trial through the ventilator.

The intrinsic diaphragmatic frequency. 

Why Aren't Your Patients Weaning? Don't Blame Nursing

http://respiratorytherapycave.blogspot.com/

The successful weaning and extubation of ventilated patients decreases hospital length of stay and reduces morbidity and mortality. One tool utilized to facilitate this process is “wean predictors” incorporated into RCP driven protocols to determine whether a patient may advance to a spontaneous breathing trial (SBT).

In a previous post [1] I mentioned that the level of sedation was the foremost reason why patients did not progress to a spontaneous breathing trial with a prevalence of 48%. 

This is concerning since it is a standard of care to provide ventilator patients with a daily "sedation vacation" or a interruption or decrease in sedation to assess neurological status and wean readiness.

This poses many questions:

The Importance of Identifying Patient Ventilator Asynchrony

There are many factors that increase the risks for prolonged mechanical ventilation (PMV). So It is imperative that the practitioner is able to identify factors that they can proactively emend.

One factor associated with PMV is inappropriate ventilator settings. The below abstract reinforces how ventilator asynchrony increases the likelihood of  PMV. 

Electrolyte Imbalances During Mechanical Ventilation

Numerous factors contribute to ventilator dependence. However, one should focus on identifying factors that are potentially reversible. Electrolyte imbalances have a direct relationship to weaning from mechanical ventilation. 

Below is a summary of different electrolytes and how their imbalances may prolong mechanical ventilation. 

Performing a T-Piece Trial with the Ventilator

Utilizing the Pressure/Volume Loop to determine the appropriate pressure support level during  a simulated T-piece trial.

Many institutions perform spontaneous breathing trials with the ventilator using a small amount of PEEP (~ 5 cmH2O) and automatic tube compensation or a small amount of pressure support (~ 5 to 10 cmH2O). However, occasionally a traditional T-Piece trial may prove to be more beneficial [1].

Utilizing pressure support during a spontaneous breathing trial to off-set the work of breathing related to the artificial airway may lead to false positives, due to over compensation.

Why is this?

Is the T-Piece Trial Futile? 3 Cases that Justify a T-Piece Trial.

In a current Blog posting “No More T-Piece” author Rick Frea states that at his facility T-piece trials are pretty much non-existent.

I don’t remember the last time I have preformed a T-piece trial on a patient with an E.T. Tube? It is very popular these days to perform the Spontaneous Breathing Trial (SBT) inline with the mechanical ventilator, due to the advance physiological monitoring and the extra alarm capabilities.

Most institutions I’m familiar with use a small amount of pressure support (~5 cmH2O) or Automatic Tube Compensation (a.k.a. Tube Comp, ATC, or Tube Resistance Compensation) if it is available on the machine to overcome the resistance of the artificial airway.

Even though the t-piece method is rarely used I believe it can be beneficial and more diagnostic in some cases to prevent false positives created by spontaneous breathing augmented with pressure support & PEEP.

3 examples:

TRENDS ASSOCIATED WITH FAILED WEANING INDICES

This Abstract was originally presented at the AARC 2007 Open Forum

Background:
The Successful wean & extubation of ventilated patients decreases hospital length of stay and reduces morbidity and mortality. One tool utilized to facilitate this process is “wean predictors” incorporated into RCP driven protocols to determine whether a patient may advance to a spontaneous breathing trial (SBT).
Hypothesis: Patients are less probable to be placed on a SBT due to weaning predictors that are not within the RCP’s scope of practice vs. predictors, which can be manipulated/controlled, by the RCP.
Design: Single center, nonrandomized, prospective, convenience cohort.
Setting- 18 bed general ICU. Patients- 91 adult patients requiring mechanical ventilation > 24 hours, admitted to the ICU between June 2006 and March 2007.