• Rosanna Vaschetto, Gianmaria Cammarota, Davide Colombo, Federico Longhini, Francesca Grossi, Andrea Giovanniello, Francesco Della Corte, and Paolo Navalesi.
• 1Anesthesia and Intensive Care, "Maggiore Della Carità" Hospital, Novara, Italy. 2Anesthesia and Intensive Care, Department of Translational Medicine, Eastern Piedmont University "A. Avogadro," Novara, Italy. 3Anesthesia and Intensive Care, Sant'Andrea Hospital, ASL VC, Vercelli, Italy. 4CRRF Mons. L. Novarese, Moncrivello (VC), Vercelli, Italy.
• Crit. Care Med.. 2014 Jan 1;42(1):74-82.

ObjectivesEvaluating the physiologic effects of varying depths of propofol sedation on patient-ventilator interaction and synchrony during pressure support ventilation and neurally adjusted ventilatory assist.DesignProspective crossover randomized controlled trial.SettingUniversity hospital ICU.PatientsFourteen intubated patients mechanically ventilated for acute respiratory failure.InterventionsSix 25-minute trials randomly performed applying both pressure support ventilation and neurally adjusted ventilatory assist during wakefulness and with two doses of propofol, administered by Target Control Infusion, determining light (1.26 ± 0.35 μg/mL) and deep (2.52 ± 0.71 μg/mL) sedation, as defined by the bispectral index and Ramsay Sedation Scale.Measurements And Main ResultsWe measured electrical activity of the diaphragm to assess neural drive and calculated its integral over time during 1 minute (∫electrical activity of the diaphragm/min) to estimate diaphragm energy expenditure (effort), arterial blood gases, airway pressure, tidal volume and its coefficient of variation, respiratory rate, neural timing components, and calculated the ineffective triggering index. Increasing the depth of sedation did not cause significant modifications of respiratory timing, while determined a progressive significant decrease in neural drive (with both modes) and effort (in pressure support ventilation only). In pressure support ventilation, the difference in ineffective triggering index between wakefulness and light sedation was negligible (from 5.9% to 7.6%, p = 0.97); with deep sedation, however, ineffective triggering index increased up to 21.8% (p < 0.0001, compared to both wakefulness and light sedation). With neurally adjusted ventilatory assist, ineffective triggering index fell to 0%, regardless of the depth of sedation. With both modes, deep sedation caused a significant increase in PaCO2, which resulted, however, from different breathing patterns and patient-ventilator interactions.ConclusionsIn pressure support ventilation, deep propofol sedation increased asynchronies, while light sedation did not. Propofol reduced the respiratory drive, while breathing timing was not significantly affected. Gas exchange and breathing pattern were also influenced by propofol infusion to an extent that varied with the depth of sedation and the mode of ventilation.

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