Table 1 Main available clinical studies
From: Clinical review: Update on neurally adjusted ventilatory assist - report of a round-table conference
Study | Diagnosis (number of patients) | Design | Duration | Major findings |
|---|---|---|---|---|
Colombo and colleagues, 2008 [21] | Acute respiratory failure (unselected) (n = 14) | Crossover - PSV set to obtain VT 6 to 8 ml/kg predicted body weight; NAVA vs. PSV increased or decreased by 50%. Effects of modification of assist level | 20 minutes ×3 | NAVA averted the risk of overassistance and improved synchrony |
Wu and colleagues, 2009 [19] | ARDS (n = 18) | PSV vs. NAVA - randomized study. Incremental PSV and NAVA run randomly in four steps. The PSV level was gradually increased by 5 cmH2O every 5 minutes from 5 to 20 cmH2O. Incremental NAVA was individually set in steps of 0.2 to 1.0 cmH2O/μV every 5 minutes to determine the NAVA level providing an airway pressure in each step equivalent to that with PSV. Evaluation of patient-ventilator synchrony (trigger delay, ineffective effort); effect of assist level | 5 minutes ×4 | Improved synchrony with NAVA |
Brander and colleagues, 2009 [20] | Acute respiratory failure (unselected) (n = 15) | NAVA level increased progressively. Method for titrating the NAVA level | 30 minutes + 3 hours | Progressive implementation of NAVA may be a method for determining the adequate level - downregulation of EAdi confirmed |
Schmidt and colleagues, 2010 [23] | Mainly acute lung injury (n = 12) | Longitudinal observational study - PSV set to obtain VT 6 to 8 ml/kg predicted body weight; NAVA vs. PSV with increasing assist. Breath-by-breath variability of flow and EAdi-related variables quantified by the coefficient of variation and autocorrelation analysis | 10 minutes ×4 = 40 minutes | NAVA increases breathing pattern variability |
Coisel and colleagues, 2010 [27] | Postoperative patients (n = 15) | Crossover randomized - PSV set to obtain VT 6 to 8 ml/kg predicted body weight; NAVA vs. PSV. Effects on breathing pattern, gas exchange, and variability of respiratory cycles (evaluated by coefficient of variation) | 24 hours | Variability of, tidal volume and minute ventilation were significantly higher with NAVA than with PSV. Variability of electrical diaphragmatic activity was significantly lower with NAVA than with PSV. Oxygenation increased during NAVA |
Terzi and colleagues, 2010 [25] | ARDS (n = 11) | Crossover randomized - PSV set to obtain VT 6 to 8 ml/kg predicted body weight; NAVA vs. PSV. Effect of neural trigger vs. flow trigger. Assist level was randomized to be 20%, 40%, or 60% over the basal level. Assessment of the physiological response to varying PSV and NAVA levels in selected ARDS patients and the effect of neural triggering | 5 minutes ×4 × 3 = 60 minutes | Compared with PSV, NAVA limited the risk of overassistance, prevented patient-ventilator asynchrony, and improved overall patient-ventilator interactions. Compared with the pneumatic trigger, the neural trigger (from NAVA) considerably decreased patient-ventilator asynchrony |
Spahija and colleagues, 2010 [22] | COPD (14) | Prospective, comparative crossover - PSV set to obtain VT 6 to 8 ml/kg predicted body weight; NAVA vs. PSV. Patients were ventilated for 10-minute periods, using two PSV levels (lowest tolerable and 7 cmH2O higher) and two NAVA levels (same peak pressures and external PEEP as with PSV), delivered in random order | 10 minutes ×2 | NAVA improved patient-ventilator synchrony by reducing the triggering and cycling delays, especially at higher levels of assist, while preserving breathing and maintaining blood gas exchange |
Passath and colleagues, 2010 [28] | Unselected patients (n = 20) | Longitudinal observational study. Evaluation of effects of PEP on breathing pattern and neuroventilatory efficiency during NAVA. Adequate NAVA level was determined as the NAVA level early after the transition from an initial steep increase in Paw and VT to a less steep increase or even plateau of Paw and VT, as described by Brander and colleagues. PEEP was set at 20 cmH2O then decreased to 1 cmH2O. VT/EAdi was evaluated as an indicator of neuroventilatory efficiency | 20 minutes ×3 | During adequate-assist NAVA, increasing PEEP reduces respiratory drive. Patients adapt their neuroventilatory efficiency such that the individual ventilatory pattern is preserved over a wide range of PEEP levels. Monitoring VT/EAdi during PEEP changes allows identification of a PEEP level at which tidal breathing occurs at minimal EAdi cost |
Piquilloud and colleagues, 2011 [26] | Unselected patients (n = 22; COPD n = 8/22) | Prospective interventional study - three consecutive periods of ventilation: PSV-NAVA-PSV. Airway pressure, flow, and transesophageal diaphragmatic electromyography were recorded continuously. To determine whether, compared with PSV, NAVA reduced trigger delay, inspiratory time excess, and the number of patient-ventilator asynchrony events | 20 minutes ×3 | NAVA reduces trigger delay, improves expiratory synchrony (inspiratory time excess was reduced) and reduces total asynchrony events |
Rozé and colleagues, 2011 [24] | Unselected patients (n = 15) | To determine the feasibility of daily titration of the NAVA level in relation to the maximal diaphragmatic electrical activity (EAdimaxSBT) measured during a SBT during PSV. EAdimaxSBT was determined daily during a SBT using PSV with 7 cmH2O inspiratory pressure and no PEEP. If the SBT was unsuccessful, NAVA was used and the level was then adjusted to obtain an EAdi of 60% of the EAdimaxSBT. Arterial blood gas analyses were performed 20 minutes after each change in NAVA level | Until extubation | Daily titration of NAVA level with an electrical goal of 60% EAdimaxSBT is feasible and well tolerated |