In last months article “Effects of Implementing Adaptive Support Ventilation in a Medical Intensive Care Unit” in the Respiratory Care Journal [1], Chew & colleagues discovered that ASV provided a quicker time to extubation readiness then their standard ventilation protocol.
These results are not surprising, especially after reviewing their standard way of managing ventilator patients. This study was a poor comparison of practitioner guided ventilator management versus an automated ventilator mode.
Let’s compare & contrast the differences in the ASV study group versus the traditional ventilator management there are three (3) main areas to investigate.
Issue 1: Initial Ventilator Mode
Traditional Protocol- Uses VC-CMV or PC-CMV
ASV- Start at 100% (VE %), if no spontaneous efforts decrease to 80% (VE %).
Comments- The ASV model allows for spontaneous breaths, if the patient meets the set percent minute ventilation then the ventilator will allow for all breaths to be spontaneous. Thus allows for one, better synchrony and two decrease chance of ventilator induced diaphragmatic dysfunction (VIDD).
The traditional protocol has the patient on a control mode of ventilation, it does not state if the patient is spontaneous breathing, or how much off-loading is present. To prevent VIDD passive mechanical ventilation should be avoided, and the mandatory rate should be adjusted to assure the patient triggers breaths [2].
At this facility the respiratory practitioner only assesses the ventilator patients twice per day and is not available at night. So how can one adequately titrate the settings to meet the patients’ demands and allow for spontaneous breathing?
Advantage- ASV
Issue 2: Partial Support Modes
Partial support mode is used after patient is out of the initial respiratory failure phase & meets criteria.
Traditional Protocol- Uses Pressure Support Ventilation or SIMV
ASV- Stays at 100% or 80% no transition needed.
Comments- With ASV it does not need practitioner interaction to switch to a partial support mode. As previously mentioned during ASV if the patient meets the % VE setting the ventilator immediately switches to a partial support mode.
The traditional protocol uses SIMV as a choice for a partial support mode; however use of SIMV has been shown to increase the time it takes for ventilation liberation. Additionally, based on esophageal monitoring studies SIMV has been associated with fatigue and increased patient ventilator asynchrony.
Furthermore, the respiratory practitioner only assesses the patients twice per day.
Advantage- ASV
Issue 3: The Spontaneous Breathing Trial
Traditional Protocol- If the patient meets criteria then a max of twice per day, no weaning at night due to staffing.
ASV- If patient meets criteria (VE %), then continuously.
Comments- ASV allows for quicker transition to minimal support or an SBT.
Advantage- ASV
Summary
This is what I take from this study:
If you have staffing issues, only assess your patients twice per day, and/ or a poor ventilator management protocol in place, ASV may prove to provide a quicker time to extubation readiness.
Reference
[1]. Chew, CW et. al. (2011). Effects of Implementing Adaptive Support Ventilation in a Medical Intensive Care Unit. Respiratory Care. 56 (7): 976-982.
[2]. Kallet, R. (2011). Patient-Ventilator Interaction During Acute Lung Injury, and the Role of Spontaneous Breathing Part 1: Respiratory Muscle Function During Critical Illness. Respiratory Care. 56 (2): 181
