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Assessment of patient-ventilator breath contribution during neurally adjusted ventilatory assist.
MedLine Citation:
PMID:  22584798     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
PURPOSE: During neurally adjusted ventilatory assist (NAVA), it is difficult to quantify the relative contribution of the patient versus the ventilator to the inspiratory tidal volume (Vt(insp)). To solve this problem, we developed an index, the "patient-ventilator breath contribution" (PVBC), using the inspiratory deflection of the diaphragmatic electrical activity (∆EAdi) and Vt(insp) during assisted and non-assisted breaths. This study evaluated the PVBC index in an experimental setup. METHOD: Nine intubated and sedated rabbits were studied during repeated ramp increases of the NAVA level. One breath was non-assisted at each NAVA level. The PVBC index was evaluated during resistive loading and after acute lung injury. PVBC was calculated by relating Vt(insp)/∆EAdi of a non-assisted breath to that of the preceding assisted breath. The PVBC was compared to the relative contribution of esophageal pressure (∆Pes) to transpulmonary pressure deflections (∆P (L,dyn)). RESULTS: The relationship between PVBC and ∆Pes/∆P (L,dyn) was slightly curvilinear with an intercept different from zero (y = -1x (2 )+ 1.64x + 0.21) and a determination coefficient (R (2)) of 0.95. Squaring the PVBC values resulted in a near perfect linear relationship (y = 1.02x + 0.05) between PVBC(2) and ∆Pes/∆P (L,dyn) with an R (2) of 0.97. CONCLUSION: This study shows that Vt(insp) and EAdi can be used to predict the contribution of the inspiratory muscles versus that of the ventilator during NAVA. If clinically applicable, this could serve to quantify and standardize the adjustment of the level of assist, and hence reduce the risks of excessive ventilatory assist. Further studies are required to evaluate if this method is clinically applicable.
Authors:
Giacomo Grasselli; Jennifer Beck; Lucia Mirabella; Antonio Pesenti; Arthur S Slutsky; Christer Sinderby
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-5-15
Journal Detail:
Title:  Intensive care medicine     Volume:  -     ISSN:  1432-1238     ISO Abbreviation:  -     Publication Date:  2012 May 
Date Detail:
Created Date:  2012-5-15     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7704851     Medline TA:  Intensive Care Med     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Department of Experimental Medicine, Azienda Ospedaliera San Gerardo, University of Milano-Bicocca, via Cadore 48, 20900, Monza, MB, Italy.
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