Check out this study.


Critical Care Medicine:
February 2010 - Volume 38 - Issue 2 - pp 518-526
doi: 10.1097/CCM.0b013e3181cb0d7b
Clinical Investigations
Patient-ventilator interaction during pressure support ventilation and neurally adjusted ventilatory assist

Pressure support was compared to NAVA....

BUT....

Reading the Materials and Methods section...

it seems that they used a Servo 300 and NOT a ServoI for both wings of this study. (ServoI comes with NAVA built in).

The Servo 300 has a default and non-adjustable breath termination criteria of 5% of the peak flow. With the Servoi this can be adjusted from 0-40%.

For the PAV/NAVA group a Servo 300 was outfitted to respond to cycle off when a decrease to 80% of peak diaphragm signal.

Read Neil McIntyre's editorial in the same issue.

I don't think this was a fair comparison. To use a ventilator renowned for causing problems with it's PS flow termination criteria...(see references)for comparison with neural triggered (triggering and cycling) seems to have a built in bias for NAVA.

Parthasarathy S, Jubran A, Tobin MJ: Cycling of inspiratory and expiratory muscle groups with the ventilator in airflow limitation. Am J Respir Crit Care Med 1998; 158:1471–1478

Branson RD, Johannigman JA: Innovations in mechanical ventilation. Respir Care 2009; 54:933–947

There needs to be some corrections to your statements. It is correct the Servo300 had a built in default of 5% of peak during PS or VS. The Servoi is adjustable from 1 to 70% of peak in these modes. The default is 30% and generally it is left there by most RT's. The current version of NAVA terminates at 70% of peak Edi. The data collection on this study is a bit old and hence why it was done on the prototype of NAVA with the servo300. Tells you how long it takes from the time researchers do the work until it hits the masses.
I would like to know how much experience Mr. Mcintyre has with the mode. However this is another comment he makes in his editorial

Neil Mcyntire wrote......Despite my concerns, I am intrigued with an approach to interactive ventilatory support that senses directly neural
drive and provides flow and pressure in
accordance with that drive.


You can also check out the AARC poster presentation from Univ of Virgina. They found that 25% of patients had significant degree of asynchrony just as Thille in 2006 and de witt in 2009 found (the latter two studies were not done on the Servo)

DIAPHRAGMATIC ELECTRICAL ACTIVITY MONITORING UNMASKS BREATH-CYCLE ASYNCHRONY
DURING CONVENTIONAL MECHANCIAL VENTILATION
Daniel D. Rowley, B.S., RRT-NPS, RPFT, FAARC,1Stuart M. Lowson, M.D.2, Frank J. Caruso, B.S., RRT1
Pulmonary Diagnostics & Respiratory Therapy Services1
Department of Anesthesiology2
University of Virginia Medical Center, Charlottesville, Virginia, U.S.A.


If you would like to look at more recent data check out this article and editorial from Ped Critical Care 2010.

A prospective crossover comparison of neurally adjusted ventilatory assist and pressure-support ventilation in a pediatric
and neonatal intensive care unit population*
Cormac Breatnach, MRCPI;1 Niamh P. Conlon, FCARCSI;1 Maria Stack, MRCPI; Martina Healy, FFARCSI;
Brendan P. O’Hare, MRCPI, FFARCSI

Editorial from John Arnold at Boston Kids.

Synchronizing ventilatory support with the neural signal to breathe*