Assessment of @entity1 -ventilator breath contribution during neurally adjusted ventilatory assist in XXXX with @entity1576 .

@entity1 @entity22922 @entity1576
INTRODUCTION: We previously showed in animals that the ratio of inspired tidal volume (Vtinsp) to inspiratory peak electrical activity of the diaphragm (EAdipk) can be used to quantify the respective @entity1 and ventilator breath contributions (PVBCs) during neurally adjusted ventilatory assist (NAVA). The PVBC index has not been tested clinically. METHODS: We studied 12 intubated and mechanically ventilated @entity1 with @entity1576 and measured EAdipk, airway (Paw) and inspiratory esophageal pressure (Pes) and Vtinsp. We applied 11 different NAVA levels, increasing them every 3  minutes in steps of 0.3  cm H2O/ V from 0 to 3.0 cmH2O/ V. At each NAVA level, one breath was non-assisted (NAVA level 0). PVBC indices were calculated by relating Vtinsp/EAdipk of the non-assisted breath to Vtinsp/EAdipk of the assisted breath(s) using one ((N1)PVBC) or the mean value of five preceding assisted breaths ((X5)PVBC). During assisted breaths, inspiratory changes in Pes (   Pes) and transpulmonary (  @entity22922 ) pressures were used to calculate the relative contribution of @entity1 to total inspiratory lung-distending pressures (  Pes/  @entity22922 ). Matching of respiratory drive indices and squaring of the PVBC was evaluated for their effect on the correlation between PVBC and   Pes/  @entity22922 . Linear regression analysis and Bland-Altman analysis were applied to compare indices. RESULTS: Using an average of five assisted breaths prior to the non-assisted breath and squaring the PVBC ((X5)PVBC(2)) improved determination coefficients (P <0.05), adjusted the regression slope and intercept between PVBC and   Pes/  @entity22922 toward identity (P <0.05) and reduced bias (P <0.05). Matching EAdipk between non-assisted and assisted breaths within the range of 0.77 to 1.30 improved the relationship between (X5)PVBC(2) and   Pes/  @entity22922 (P <0.05) and abolished the need for EAdi normalization in the PVBC calculation (R (2)   =   0.96; bias   =   0.16        0.06; precision   =   0.33        0.08 (mean and 95% confidence interval)). CONCLUSIONS: This clinical study confirms previous experimental results showing that the PVBC(2) predicts the contribution of the inspiratory muscles versus that of the ventilator during NAVA, when differences in effort (EAdi) between non-assisted and assisted breaths are limited. PVBC could help to quantify and standardize the adjustment of the level of assist, and hence reduce the risks of excessive ventilatory assist in @entity1 . TRIAL REGISTRATION: ClinicalTrials.gov NCT01663480 . Registered 9 August 2012.
