Rationale and study design of ViPS - variable pressure support for weaning from mechanical ventilation: study protocol for an international multicenter randomized controlled open trial

Effects of Different Levels of Variability and Pressure Support Ventilation on Lung Function in Patients With Mild-Moderate Acute Respiratory Distress Syndrome

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 (ΔP_S) 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 ΔP_S level. In the first block, the effects of three levels of variability were tested at constant ΔP_S: 0% (PSV_0%, conventional PSV), 15% (vPSV_15%), and 30% (vPSV_30%). In the second block, two levels of variability (0% and variability set to achieve ±5 cmH₂O variability) were tested at two ΔP_S levels (baseline ΔP_S and ΔP_S reduced by 5 cmH₂O from baseline). The following four ventilation strategies were tested in the second block: PSV with baseline ΔP_S and 0% variability (PSV_BL) or ±5 cmH₂O variability (vPSV_BL), PSV with ΔP_S 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 vPSV_15% and vPSV_30% compared with PSV_0%. The variability of tidal volume (V_T) was higher with vPSV_15% and vPSV_30% compared with PSV_0%. The incidence of asynchronies and the variability of transpulmonary pressure (P_L) were higher with vPSV_30% compared with PSV_0%. In the second block of interventions, different levels of pressure support with and without variability did not change oxygenation. The variability of V_T and P_L was higher with vPSV₋₅ compared with PSV₋₅, but not with vPSV_BL compared with PSV_BL.

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.

Reduction of ventilatory time using the multidisciplinary disconnection protocol. Pilot study

Objective:

compare ventilatory time between patients with the application of a disconnection protocol, managed in a coordinated way between doctor and nurse, with patients managed exclusively by the doctor.

Method:

experimental pilot study before and after. Twenty-five patients requiring invasive mechanical ventilation for 24 hours or more were included, and the protocol-guided group was compared with the protocol-free group managed according to usual practice.

Results:

by means of the multidisciplinary protocol, the time of invasive mechanical ventilation was reduced (141.94 ± 114.50 vs 113.18 ± 55.14; overall decrease of almost 29 hours), the time spent on weaning (24 hours vs 7.40 hours) and the numbers of reintubation (13% vs 0%) in comparison with the group in which the nurse did not participate. The time to weaning was shorter in the retrospective cohort (2 days vs. 5 days), as was the hospital stay (7 days vs. 9 days).

Conclusion:

the use of a multidisciplinary protocol reduces the duration of weaning, the total time of invasive mechanical ventilation and reintubations. The more active role of the nurse is a fundamental tool to obtain better results.

Variable mechanical ventilation

Objective

To review the literature on the use of variable mechanical ventilation and the main outcomes of this technique.

Methods

Search, selection, and analysis of all original articles on variable ventilation, without restriction on the period of publication and language, available in the electronic databases LILACS, MEDLINE^®, and PubMed, by searching the terms "variable ventilation" OR "noisy ventilation" OR "biologically variable ventilation".

Results

A total of 36 studies were selected. Of these, 24 were original studies, including 21 experimental studies and three clinical studies.

Conclusion

Several experimental studies reported the beneficial effects of distinct variable ventilation strategies on lung function using different models of lung injury and healthy lungs. Variable ventilation seems to be a viable strategy for improving gas exchange and respiratory mechanics and preventing lung injury associated with mechanical ventilation. However, further clinical studies are necessary to assess the potential of variable ventilation strategies for the clinical improvement of patients undergoing mechanical ventilation.

Inhaled AP301 for treatment of pulmonary edema in mechanically ventilated patients with acute respiratory distress syndrome: a phase IIa randomized placebo-controlled trial

Background

High-permeability pulmonary edema is a hallmark of acute respiratory distress syndrome (ARDS) and is frequently accompanied by impaired alveolar fluid clearance (AFC). AP301 enhances AFC by activating epithelial sodium channels (ENaCs) on alveolar epithelial cells, and we investigated its effect on extravascular lung water index (EVLWI) in mechanically ventilated patients with ARDS.

Methods

Forty adult mechanically ventilated patients with ARDS were included in a randomized, double-blind, placebo-controlled trial for proof of concept. Patients were treated with inhaled AP301 (n = 20) or placebo (0.9% NaCl; n = 20) twice daily for 7 days. EVLWI was measured by thermodilution (PiCCO®), and treatment groups were compared using the nonparametric Mann–Whitney U test.

Results

AP301 inhalation was well tolerated. No differences in mean baseline-adjusted change in EVLWI from screening to day 7 were found between the AP301 and placebo group (p = 0.196). There was no difference in the PaO₂/FiO₂ ratio, ventilation pressures, Murray lung injury score, or 28-day mortality between the treatment groups. An exploratory subgroup analysis according to severity of illness showed reductions in EVLWI (p = 0.04) and ventilation pressures (p < 0.05) over 7 days in patients with initial sequential organ failure assessment (SOFA) scores ≥11 inhaling AP301 versus placebo, but not in patients with SOFA scores ≤10.

Conclusions

There was no difference in mean baseline-adjusted EVLWI between the AP301 and placebo group. An exploratory post-hoc subgroup analysis indicated reduced EVLWI in patients with SOFA scores ≥11 receiving AP301. These results suggest further confirmation in future clinical trials of inhaled AP301 for treatment of pulmonary edema in patients with ARDS.

Trial registration

The study was prospectively registered at clinicaltrials.gov, NCT01627613. Registered 20 June 2012.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1795-x) contains supplementary material, which is available to authorized users.

Variable ventilation from bench to bedside

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency medicine 2016. Other selected articles can be found online at http://www.biomedcentral.com/collections/annualupdate2016. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Approaches to ventilation in intensive care

BACKGROUND

Mechanical ventilation is a common and often life-saving intervention in intensive care medicine. About 35% of all patients in intensive care are mechanically ventilated; about 15% of these patients develop a ventilation-associated pneumonia. The goal of ventilation therapy is to lessen the work of respiration and pulmonary gas exchange and thereby maintain or restore an adequate oxygen supply to the body's tissues. Mechanical ventilation can be carried out in many different modes; the avoidance of ventilation-induced lung damage through protective ventilation strategies is currently a major focus of clinical interest.

METHOD

This review is based on pertinent articles retrieved by a selective literature search.

RESULTS

Compared to conventional lung-protecting modes of mechanical ventilation, the modern modes of ventilation presented here are further developments that optimize lung protection while improving pulmonary function and the synchrony of the patient with the ventilator. In high-frequency ventilation, tidal volumes of 1-2 mL/kgBW (body weight) are given, at a respiratory rate of up to 12 Hz. Assisted forms of spontaneous respiration are also in use, such as proportional assist ventilation (PAV), neurally adjusted ventilatory assist (NAVA), and variable pressure-support ventilation. Computer-guided closed-loop ventilation systems enable automated ventilation; according to a recent meta-analysis, they shorten weaning times by 32% .

CONCLUSION

The currently available scientific evidence with respect to clinically relevant endpoints is inadequate for all of these newer modes of ventilation. It appears, however, that they can lower both the invasiveness and the duration of mechanical ventilation, and thus improve the care of patients who need ventilation. Randomized trials with clinically relevant endpoints must be carried out before any final judgments can be made.

Low tidal volume pressure support versus controlled ventilation in early experimental sepsis in pigs

Background

In moderate acute respiratory distress syndrome (ARDS) several studies support the usage of assisted spontaneous breathing modes. Only limited data, however, focus on the application in systemic sepsis and developing lung injury. The present study examines the effects of immediate initiation of pressure support ventilation (PSV) in a model of sepsis-induced ARDS.

Methods

18 anesthetized pigs received a two-staged continuous lipopolysaccharide infusion to induce lung injury. The animals were randomly assigned to PSV or volume controlled (VCV) lung protective ventilation (tidal volume each 6 ml kg^-1, n = 2x9) over six hours. Gas exchange parameters, hemodynamics, systemic inflammation, and ventilation distribution by multiple inert gas elimination and electrical impedance tomography were assessed. The post mortem analysis included histopathological scoring, wet to dry ratio, and alveolar protein content.

Results

Within six hours both groups developed a mild to moderate ARDS with comparable systemic inflammatory response and without signs of improving gas exchange parameters during PSV. The PSV group showed signs of more homogenous ventilation distribution by electrical impedance tomography, but only slightly less hyperinflated lung compartments by multiple inert gas elimination. Post mortem and histopathological assessment yielded no significant intergroup differences.

Conclusions

In a porcine model of sepsis-induced mild ARDS immediate PSV was not superior to VCV. This contrasts with several experimental studies from non-septic mild to moderate ARDS. The present study therefore assumes that not only severity, but also etiology of lung injury considerably influences the response to early initiation of PSV.