Short-term effects of noisy pressure support ventilation in patients with acute hypoxemic respiratory failure

Abstract

IntroductionThis study aims at comparing the very short-term effects of conventional and noisy (variable) pressure support ventilation (PSV) in mechanically ventilated patients with acute hypoxemic respiratory failure.MethodsThirteen mechanically ventilated patients with acute hypoxemic respiratory failure were enrolled in this monocentric, randomized crossover study. Patients were mechanically ventilated with conventional and noisy PSV, for one hour each, in random sequence. Pressure support was titrated to reach tidal volumes approximately 8 mL/kg in both modes. The level of positive end-expiratory pressure and fraction of inspired oxygen were kept unchanged in both modes. The coefficient of variation of pressure support during noisy PSV was set at 30%. Gas exchange, hemodynamics, lung functional parameters, distribution of ventilation by electrical impedance tomography, breathing patterns and patient-ventilator synchrony were analyzed.ResultsNoisy PSV was not associated with any adverse event, and was well tolerated by all patients. Gas exchange, hemodynamics, respiratory mechanics and spatial distribution of ventilation did not differ significantly between conventional and noisy PSV. Noisy PSV increased the variability of tidal volume (24.4 ± 7.8% vs. 13.7 ± 9.1%, P <0.05) and was associated with a reduced number of asynchrony events compared to conventional PSV (5 (0 to 15)/30 min vs. 10 (1 to 37)/30 min, P <0.05).ConclusionsIn the very short term, noisy PSV proved safe and feasible in patients with acute hypoxemic respiratory failure. Compared to conventional PSV, noisy PSV increased the variability of tidal volumes, and was associated with improved patient-ventilator synchrony, at comparable levels of gas exchange.Trial registrationClinicialTrials.gov, NCT00786292

Effects of Different Levels of Pressure Support on Intra-Individual Breath-to-Breath Variability

“…In agreement with our results, a recent study reported the same level of intrinsic BBV, with a coefficient of variation of V T of 13.7 Ϯ 9.1% (mean Ϯ SD), in critically ill patients ventilated with the PS mode. Interestingly, even intra-individual BBV in the present study was similar to that reported by Spieth et al 21 Increased variability in V T in critically ill patients has been associated with successful weaning from mechanical ventilation, 18,22 and the coefficient of variation of V T has been proposed as a predictor for extubation outcome. 18 In this context, our results suggest that such a prediction is not influenced by the PS level and that very low PS levels can be avoided for this assessment, reducing the occurrence of fatigue and distress in the patient.…”

Should we breathe quiet or noisy?

“…Noisy PSV was associated with higher V T variability and a lower number of asynchrony events. In contrast to experimental findings, cardio-pulmonary function and spatial distribution of ventilation were comparable between conventional and noisy PSV [1]. During conventional and noisy PSV, however, V T significantly higher than 8 ml/kg predicted body weight was frequently noticed.…”

“…In Critical Care , Spieth and colleagues [1] report for the first time the use of noisy pressure support ventilation (PSV) in patients with acute hypoxemic respiratory failure.…”

Variable Ventilation from Bench to Bedside

“…The reported increase in tidal volume variability (24.4 ± 7.8 % vs. 13.7 ± 9.1 %) during variable PSV was associated with improved patient-ventilator synchrony. The externally increased tidal volume variability mimics the intrinsic healthy variability more closely than can be achieved by the patient through simple on/off triggering during conventional PSV, which may explain the improved patientventilator synchrony [48].…”