Authors: David Tuxen, Carol Hodgson, Steve Philpot
Reviewer: Chris Nickson
The Eighth Alfred Advanced Mechanical Ventilation Conference (AAMV) was held on July 18th 2014 and featured Professor Marcelo Amato from Sao Paulo, Brazil and Associate Professor Eddy Fan from Toronto, Canada as brilliant international keynote speakers. The theme was ‘Recent Advances in Mechanical Ventilation’.
Read on for some of the key learning points from this event, many of which precede the published literature (i.e. coming to a journal near you soon!)
1. Pay attention to ‘driving pressure’!
From the largest meta-analysis done on the mechanical ventilation of patients with acute respiratory distress syndrome (ARDS), driving pressure (Pplat – PEEP) is a more important factor in patient survival than PEEP, Pplat and tidal volume. A driving pressure <13 cmH2O is recommended.
2. HFOV: down, but not quite out (if you’re a researcher!)
Following the 2 recent large trials (RCTs) of high frequency oscillation (HFOV) in adults with ARDS, one of which showed no benefit (OSCAR) and the other was stopped early because of a significantly increased mortality in the HFOV group (OSCILLATE), a keynote speaker from one of the trial centres stated that HFOV research will continue to better define the group of patients who benefit from HFOV and the best settings in ARDS, but it can no longer be recommended for routine use or as a rescue therapy in ARDS.
3. Electrical impedance tomography (EIT) is here!
Electrical impedance tomography (EIT) is an emerging technology for mechanically ventilated patients. From a series of electrodes around the chest, real time images of lung impedance (which directly correlates to lung volume) can show regional distribution of ventilation and the effects if changes in tidal volume and PEEP. Some devices can also show perfusion. This has the potential to identify problems not otherwise detectable at the bedside and provide better endpoints for changes in PEEP.
4. Spontaneously triggered breaths may cause hidden lung injury in ventilated patients
Recent work using EIT has shown that some inflated lung regions may be transiently over inflated early during a spontaneously triggered breath (with potential for lung injury) before adjacent collapsed regions expand towards the end of the breath deflating these over expanded regions leading to the misleading impression of a safe Pplat at the end of the breath. This is why the use of neuromuscular blockers early in ARDS may be useful, to reduce early spontaneous breaths that have a dangerously high Pplat (that cannot be measured by the ventilator).
5. Less sedation and early mobilisation may help survivors of critical illness and ARDS
It is now becoming well recognised that survivors of severe critical illness (e.g. ARDS) commonly have significantly impaired functional states 6-12 months later including reduced cognition, depression, post traumatic stress, reduced exercise capacity and inability to return to work. Emerging information suggests that less sedation and more active mobilisation including ambulation during mechanical ventilation may not only reduce length of stay but may also improve these longterm problems.
6. Don’t forget APRV for ARDS
Airway Pressure Release Ventilation (APRV) was used in mechanically ventilated patients with ARDS during the H1N1 Influenza epidemic in a major teaching hospital in Perth. The use of APRV was associated with significant improvements in oxygenation and the avoidance of the need for ECMO support in their case series.
Keep an eye on The Alfred ICU Courses page for announcements about next year’s conference.