Effects of Neurally Adjusted Ventilatory Assist (NAVA) levels in non-invasive ventilated patients: titrating NAVA levels with electric diaphragmatic activity and tidal volume matching

Yeong Shiong Chiew, J. Geoffrey Chase, Bernard Lambermont, Jean Roeseler, Christopher Pretty, Emilie Bialais, Thierry Sottiaux, Thomas Desaive

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Abstract

Background: Neurally adjusted ventilatory assist (NAVA) delivers pressure in proportion to diaphragm electrical activity (Eadi). However, each patient responds differently to NAVA levels. This study aims to examine the matching between tidal volume (Vt) and patients' inspiratory demand (Eadi), and to investigate patient-specific response to various NAVA levels in non-invasively ventilated patients.Methods: 12 patients were ventilated non-invasively with NAVA using three different NAVA levels. NAVA100 was set according to the manufacturer's recommendation to have similar peak airway pressure as during pressure support. NAVA level was then adjusted ±50% (NAVA50, NAVA150). Airway pressure, flow and Eadi were recorded for 15 minutes at each NAVA level. The matching of Vt and integral of Eadi (sh{phonetic}Eadi) were assessed at the different NAVA levels. A metric, Range90, was defined as the 5-95% range of Vt/sh{phonetic}Eadi ratio to assess matching for each NAVA level. Smaller Range90 values indicated better matching of supply to demand.Results: Patients ventilated at NAVA50 had the lowest Range90 with median 25.6 uVs/ml [Interquartile range (IQR): 15.4-70.4], suggesting that, globally, NAVA50 provided better matching between sh{phonetic}Eadi and Vt than NAVA100 and NAVA150. However, on a per-patient basis, 4 patients had the lowest Range90 values in NAVA100, 1 patient at NAVA150 and 7 patients at NAVA50. Robust coefficient of variation for sh{phonetic}Eadi and Vt were not different between NAVA levels.Conclusions: The patient-specific matching between sh{phonetic}Eadi and Vt was variable, indicating that to obtain the best possible matching, NAVA level setting should be patient specific. The Range90 concept presented to evaluate Vt/sh{phonetic}Eadi is a physiologic metric that could help in individual titration of NAVA level.

Original languageEnglish
Article number61
JournalBioMedical Engineering Online
Volume12
Issue number1
DOIs
Publication statusPublished - 2 Jul 2013
Externally publishedYes

Keywords

  • Matching
  • Mechanical ventilation
  • NAVA
  • Non-invasive ventilation
  • Patient-ventilator interaction

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