Noninvasive NAVA

Technology Trends

A recent study demonstrated that 43 percent of the patients placed on noninvasive ventilation (n=60) presented with an asynchrony index of greater than 10 percent.² Patients who had an asynchrony index less than 10 percent demonstrated a higher patient comfort scale. Information retrieved for diagnosing the asynchrony index in the study was achieved via visual inspection and clinical observation of pneumatic waveforms along with surface electromyography or electromyography of the diaphragm.

In cardiac medicine, it would be difficult to accept a balloon pump designed to synchronize with the cardiac cycle of the patient and provide coronary vessel perfusion if it was unreliable 43 percent of the time. Why do we accept this from the ventilation side when machines that are pneumatically delivering support are unable to tolerate the varying interface fit or the leakage variability during noninvasive application?

The ability to apply noninvasive ventilation is available with improved patient device interaction with a modality called NIV NAVA. NIV NAVA is an option of noninvasive support that allows the patient and device to harmonize by utilizing the diaphragm activity or electrical activity of the diaphragm (Edi) as the controller of support for flow and pressure delivered during therapy. This capability allows patients to control the pneumatic delivery of support based on their breathing efforts in real time, thus improving patient device interaction as well as comfort.

Significant strides have been made to improve the sensing of patient effort to minimize the level of asynchrony during conventional NIV. Yet the pneumatic technologies are not directly correlated to the physiologic effort of the patient, which leads to a potentially increased amount of asynchrony associated with
pneumatic triggering and cycling off limitations. (See Diagram.)

Click to view larger graphic.

The level of leakage during therapy also plays a major role in generating patient ventilator asynchrony and discomfort. NIV NAVA’s use of Edi allows the technology to be less dependent on leakage around the interface and opens the opportunity for continuity of delivered support with different interfaces.

A recent study showed that utilizing NAVA technology during invasive ventilation helped avoid patient-ventilator asynchrony when compared to conventional pressure support.³ Utilization of the Edi or diaphragm signal for NIV application seems like the natural and obvious transition to help reduce the reported 43 percent of asynchrony during conventional NIV.

The benefits of using NIV ventilation are well documented for various patient ranges and pathologies as a solution to reduce hospital length of stay. In the future, it will be interesting to see the results of studies that will compare asynchronous NIV vs. synchronized to determine if there are any improvements in mortality and morbidity. Nonetheless, the availability of technology that would allow breathing to feel more natural based on timing and effort should not be foregone but rather should be considered as a standard of care for the patient’s comfort.

References

1. Plant P, Owen J, Parrott S, Elliot M. Cost effectiveness of ward based noninvasive ventilation for acute exacerbations of chronic obstructive pulmonary disease: economic analysis of randomized controlled trial. BMJ. 2003;326:1-5.

2. Vignaux L, Vargas F, Roeseler J, Tassaux D, Thille A, Kossowsky M, Brochard L, Jolliet P. Patient-ventilator asynchrony during noninvasive ventilation for acute respiratory failure: a multicenter study. Intensive Care Medicine. 2009:35:840-6.

3. Columbo D, Cammarota G, Bergamaschi V, De Lucia M, Della Corte F, Navalesi P. Physiologic response to varying levels of pressure support and neutrally adjusted ventilatory assist in patients with acute respiratory failure. Intensive Care Medicine. 2008:34:2010-8.

Louis Fuentes, RRT, is clinical marketing specialist for Maquet Inc., Wayne, N.J. He is also an Industry Advisory Board member for ADVANCE.