Saturday, June 25, 2011

4 Reasons Not to Use APRV

Over Inflated

Airway Pressure Release Ventilation is a modality of ventilation that has been in use for greater than 20 years. Some practitioners' believe APRV is the panacea of mechanical ventilation and utilize the mode on every ventilated patient. Before initiating APRV one should consider 4 arguments against its use.

1.      Patient Outcomes- this is the strongest argument, stating that APRV has no greater patient outcomes over traditional mechanical ventilation strategies in the treatment of Acute Respiratory Distress Syndrome (ARDS net low tidal volume strategy).

2.      Release Volume & the risk of Ventilator Induced Lung Injury- this is one of my favorites. You have a physician that is very strict insuring tidal volumes remain in the 4-6-cc/kg/IDBW ranges during traditional mechanical ventilation. Conversely, when on APRV the release volumes are > 10-to-12 cc/kg/IDBW. Why would these large tidal volumes be less of concern with APRV? This is usually the same practitioner which is apprehensive of using PEEP > 8 cmH2O in ARDS patients, nevertheless has no issues with generating a mean airway pressure > 20 cmH2O with APRV.

3.       Minute Ventilation Support- APRV is not ideal for the patient that is hypercapnic. If the patient is severely hypercapnic APRV will make the situation worse. I have witnessed practitioners initiating APRV for ventilation issues (thinking its cure-all), which in turn created pneumothoraces.

4.      Patient Ventilator Synchrony- Proponents will argue that APRV is very synchronous due to the floating exhalation valve, allowing for unhindered spontaneous ventilation. Studies, which evaluated synchrony, compared APRV to inverse ratio ventilation, ventilators without active/ floating exhalation valves (not a great comparison). What about the dramatic release phase, I would think this would cruelly interfere with the patients' neural timing versus the ventilators timing. Additionally, when classifying APRV based on breathing pattern it is basically an IMV (intermittent Mandatory Ventilation) mode. Many esophageal balloon studies   evaluating IMV modes proved that IMV provided very little patient ventilator synchrony. The mode interfered with the patient's neural timing versus the ventilators timing. During the assisted/mandatory breaths the patient's diaphragm still contracted (basically the diaphragm never rested).

[1]. Kallet, R. (2011). Patient-Ventilator Interaction During Acute Lung Injury, and the Role of Spontaneous Breathing: Part 2: Airway Pressure Release Ventilation. Respiratory Care. 56 (2): 190-196.