Abstract
Background: Variable pressure support ventilation (vPSV) is an assisted ventilation mode that varies the level of pressure support on a breath-by-breath basis to restore the physiological variability of breathing activity. We aimed to compare the effects of vPSV at different levels of variability and pressure support (ΔPS) in patients with acute respiratory distress syndrome (ARDS).Methods: This study was a crossover randomized clinical trial. We included patients with mild to moderate ARDS already ventilated in conventional pressure support ventilation (PSV). The study consisted of two blocks of interventions, and variability during vPSV was set as the coefficient of variation of the ΔPS level. In the first block, the effects of three levels of variability were tested at constant ΔPS: 0% (PSV0%, conventional PSV), 15% (vPSV15%), and 30% (vPSV30%). In the second block, two levels of variability (0% and variability set to achieve ±5 cmH2O variability) were tested at two ΔPS levels (baseline ΔPS and ΔPS reduced by 5 cmH2O from baseline). The following four ventilation strategies were tested in the second block: PSV with baseline ΔPS and 0% variability (PSVBL) or ±5 cmH2O variability (vPSVBL), PSV with ΔPS reduced by 5 cmH2O and 0% variability (PSV−5) or ±5 cmH2O variability (vPSV−5). Outcomes included gas exchange, respiratory mechanics, and patient-ventilator asynchronies.Results: The study enrolled 20 patients. In the first block of interventions, oxygenation and respiratory mechanics parameters did not differ between vPSV15% and vPSV30% compared with PSV0%. The variability of tidal volume (VT) was higher with vPSV15% and vPSV30% compared with PSV0%. The incidence of asynchronies and the variability of transpulmonary pressure (PL) were higher with vPSV30% compared with PSV0%. In the second block of interventions, different levels of pressure support with and without variability did not change oxygenation. The variability of VT and PL was higher with vPSV−5 compared with PSV−5, but not with vPSVBL compared with PSVBL.Conclusion: In patients with mild-moderate ARDS, the addition of variability did not improve oxygenation at different pressure support levels. Moreover, high variability levels were associated with worse patient-ventilator synchrony.Clinical Trial Registration: www.clinicaltrials.gov, identifier: NCT01683669.
Highlights
Pressure support ventilation (PSV) is an assisted ventilation mode commonly used in critically ill patients (Esteban et al, 2013)
The FiO2 and positive end-expiratory pressure (PEEP) were kept constant during the study in all patients; one patient required pressure support level (PS) reduction between ventilation block 1 and block 2 according to the treating clinician decision for reasons unrelated to the study procedures
PSVBL, pressure support ventilation with no variability and baseline PS as per clinical indication; vPSVBL, variable pressure support with variability set to achieve ±5 cmH2O and baseline PS as per clinical indication; PSV−5, pressure support ventilation with no variability and PS reduced by 5 cmH2O from the baseline value; Variable pressure support ventilation (vPSV)−5, variable pressure support ventilation with variability set to achieve ±5 cmH2O and PS reduced by 5 cmH2O from the baseline value; CV, coefficient of variation; PEEP, positive end-expiratory pressure; PBW, predicted body weight; PS, pressure support; VT, tidal volume; esophageal pressuretime product (PTP), esophageal pressure-time product; Pes, esophageal pressure swings; PL, peak transpulmonary pressure
Summary
Pressure support ventilation (PSV) is an assisted ventilation mode commonly used in critically ill patients (Esteban et al, 2013). Variable pressure support ventilation (vPSV), compared with conventional PSV, improved oxygenation in the experimental models of ARDS (Gama de Abreu et al, 2008) and ventilatorpatient synchrony in a small pilot study in critically ill patients with acute respiratory failure (Spieth et al, 2013). These effects could be mediated by an amelioration of the ventilationperfusion matching (Huhle et al, 2016), as well as a recruitment effect due to the repetitive delivery of breaths with a higher tidal volume, which might result in a reduction of lung inhomogeneity (Mauri et al, 2017). We aimed to compare the effects of vPSV at different levels of variability and pressure support ( PS) in patients with acute respiratory distress syndrome (ARDS)
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