J Intensive Care. 2015 May 29;3(1):25. doi: 10.1186/s40560-015-0091-6. eCollection 2015.
Acute respiratory distress syndrome (ARDS) has been intensively and continuously studied in various settings, but its mortality is still as high as 30-40 %. For the last 20 years, lung protective strategy has become a standard care for ARDS, but we still do not know the best way to ventilate patients with ARDS. Tidal volume itself does not seem to have an important role to develop ventilator-induced lung injury (VILI), but the driving pressure, which is inspiratory plateau pressure-PEEP, is the most important to predict and affect the outcome of ARDS, though there is no safe limit for the driving pressure. There is so much controversy regarding what the best PEEP is, whether collapsed lung should be recruited, and what parameters should be measured and evaluated to improve the outcome of ARDS. Since the mechanical ventilation for patients with respiratory failure, including ARDS, is a standard care, we need more dynamic and regional information of ventilation and pulmonary circulation in the injured lungs to evaluate the efficacy of new type of treatment strategy. In addition to the CT scanning of the lung as the gold standard of evaluation, the electrical impedance tomography (EIT) of the lung has been clinically available to provide such information non-invasively and at the bedside. Various parameters have been tested to evaluate the homogeneity of regional ventilation, and EIT could provide us with the information of ventilator settings to minimize VILI.
Trials. 2015 May 24;16:226. doi: 10.1186/s13063-015-0759-1.
BACKGROUND: It is uncertain whether lung-protective mechanical ventilation using low tidal volumes should be used in all critically ill patients, irrespective of the presence of the acute respiratory distress syndrome (ARDS). A low tidal volume strategy includes use of higher respiratory rates, which could be associated with increased sedation needs, a higher incidence of delirium, and an increased risk of patient-ventilator asynchrony and ICU-acquired weakness. Another alleged side-effect of low tidal volume ventilation is the risk of atelectasis. All of these could offset the beneficial effects of low tidal volume ventilation as found in patients with ARDS. METHODS/DESIGN: PReVENT is a national multicenter randomized controlled trial in invasively ventilated ICU patients without ARDS with an anticipated duration of ventilation of longer than 24 hours in 5 ICUs in The Netherlands. Consecutive patients are randomly assigned to a low tidal volume strategy using tidal volumes from 4 to 6 ml/kg predicted body weight (PBW) or a high tidal volume ventilation strategy using tidal volumes from 8 to 10 ml/kg PBW. The primary endpoint is the number of ventilator-free days and alive at day 28. Secondary endpoints include ICU and hospital length of stay (LOS), ICU and hospital mortality, the incidence of pulmonary complications, including ARDS, pneumonia, atelectasis, and pneumothorax, the cumulative use and duration of sedatives and neuromuscular blocking agents, incidence of ICU delirium, and the need for decreasing of instrumental dead space. DISCUSSION: PReVENT is the first randomized controlled trial comparing a low tidal volume strategy with a high tidal volume strategy, in patients without ARDS at onset of ventilation, that recruits a sufficient number of patients to test the hypothesis that a low tidal volume strategy benefits patients without ARDS with regard to a clinically relevant endpoint.
TRIAL REGISTRATION: The trial is registered at www.clinicaltrials.gov under reference number NCT02153294 on 23 May 2014.