Continuous axial rotation and pulmonary fluid balance in acute lung injury

The Impact of Sample Size Misestimations on the Interpretation of ARDS Trials: Systematic Review and Meta-analysis

BACKGROUND

Indeterminate randomized controlled trials (RCTs) in ARDS may arise from sample size misspecification, leading to abandonment of efficacious therapies.

RESEARCH QUESTIONS

If evidence exists for sample size misspecification in ARDS RCTs, has this led to rejection of potentially beneficial therapies? Does evidence exist for prognostic enrichment in RCTs using mortality as a primary outcome?

STUDY DESIGN AND METHODS

We identified 150 ARDS RCTs commencing recruitment after the 1994 American European Consensus Conference ARDS definition and published before October 31, 2020. We examined predicted-observed sample size, predicted-observed control event rate (CER), predicted-observed average treatment effect (ATE), and the relationship between observed CER and observed ATE for RCTs with mortality and nonmortality primary outcome measures. To quantify the strength of evidence, we used Bayesian-averaged meta-analysis, trial sequential analysis, and Bayes factors.

RESULTS

Only 84 of 150 RCTs (56.0%) reported sample size estimations. In RCTs with mortality as the primary outcome, CER was overestimated in 16 of 28 RCTs (57.1%). To achieve predicted ATE, interventions needed to prevent 40.8% of all deaths, compared with the original prediction of 29.3%. Absolute reduction in mortality ≥ 10% was observed in 5 of 28 RCTs (17.9%), but predicted in 21 of 28 RCTs (75%). For RCTs with mortality as the primary outcome, no association was found between observed CER and observed ATE (pooled OR: β = -0.04; 95% credible interval, -0.18 to 0.09). We identified three interventions that are not currently standard of care with a Bayesian-averaged effect size of > 0.20 and moderate strength of existing evidence: corticosteroids, airway pressure release ventilation, and noninvasive ventilation.

INTERPRETATION

Reporting of sample size estimations was inconsistent in ARDS RCTs, and misspecification of CER and ATE was common. Prognostic enrichment strategies in ARDS RCTs based on all-cause mortality are unlikely to be successful. Bayesian methods can be used to prioritize interventions for future effectiveness RCTs.

Impact of differences in acute respiratory distress syndrome randomised controlled trial inclusion and exclusion criteria: systematic review and meta-analysis

BACKGROUND

Control-arm mortality varies between acute respiratory distress syndrome (ARDS) RCTs.

METHODS

We systematically reviewed ARDS RCTs that commenced recruitment after publication of the American-European Consensus (AECC) definition (MEDLINE, Embase, and Cochrane central register of controlled trials; January 1994 to October 2020). We assessed concordance of RCT inclusion criteria to ARDS consensus definitions and whether exclusion criteria are strongly or poorly justified. We estimated the proportion of between-trial difference in control-arm 28-day mortality explained by the inclusion criteria and RCT design characteristics using meta-regression.

RESULTS

A literature search identified 43 709 records. One hundred and fifty ARDS RCTs were included; 146/150 (97.3%) RCTs defined ARDS inclusion criteria using AECC/Berlin definitions. Deviations from consensus definitions, primarily aimed at improving ARDS diagnostic certainty, frequently related to duration of hypoxaemia (117/146; 80.1%). Exclusion criteria could be grouped by rationale for selection into strongly or poorly justified criteria. Common poorly justified exclusions included pregnancy related, age, and comorbidities (infectious/immunosuppression, hepatic, renal, and human immunodeficiency virus/acquired immunodeficiency syndrome). Control-arm 28-day mortality varied between ARDS RCTs (mean: 29.8% [95% confidence interval: 27.0-32.7%; I2=88.8%; τ2=0.02; P<0.01]), and differed significantly between RCTs with different Pao2:FiO2 ratio inclusion thresholds (26.6-39.9 kPa vs <26.6 kPa; P<0.01). In a meta-regression model, inclusion criteria and RCT design characteristics accounted for 30.6% of between-trial difference (P<0.01).

CONCLUSIONS

In most ARDS RCTs, consensus definitions are modified to use as inclusion criteria. Between-RCT mortality differences are mostly explained by the Pao2:FiO2 ratio threshold within the consensus definitions. An exclusion criteria framework can be applied when designing and reporting exclusion criteria in future ARDS RCTs.

[Short version S2e guidelines: "Positioning therapy and early mobilization for prophylaxis or therapy of pulmonary function disorders"]

The German Society of Anesthesiology and Intensive Care Medicine (DGAI) commissioned a revision of the S2 guidelines on "positioning therapy for prophylaxis or therapy of pulmonary function disorders" from 2008. Because of the increasing clinical and scientific relevance the guidelines were extended to include the issue of "early mobilization" and the following main topics are therefore included: use of positioning therapy and early mobilization for prophylaxis and therapy of pulmonary function disorders, undesired effects and complications of positioning therapy and early mobilization as well as practical aspects of the use of positioning therapy and early mobilization. These guidelines are the result of a systematic literature search and the subsequent critical evaluation of the evidence with scientific methods. The methodological approach for the process of development of the guidelines followed the requirements of evidence-based medicine, as defined as the standard by the Association of the Scientific Medical Societies in Germany. Recently published articles after 2005 were examined with respect to positioning therapy and the recently accepted aspect of early mobilization incorporates all literature published up to June 2014.

S2e guideline: positioning and early mobilisation in prophylaxis or therapy of pulmonary disorders : Revision 2015: S2e guideline of the German Society of Anaesthesiology and Intensive Care Medicine (DGAI)

The German Society of Anesthesiology and Intensive Care Medicine (DGAI) commissioneda revision of the S2 guidelines on "positioning therapy for prophylaxis or therapy of pulmonary function disorders" from 2008. Because of the increasing clinical and scientificrelevance the guidelines were extended to include the issue of "early mobilization"and the following main topics are therefore included: use of positioning therapy and earlymobilization for prophylaxis and therapy of pulmonary function disorders, undesired effects and complications of positioning therapy and early mobilization as well as practical aspects of the use of positioning therapy and early mobilization. These guidelines are the result of a systematic literature search and the subsequent critical evaluation of the evidence with scientific methods. The methodological approach for the process of development of the guidelines followed the requirements of evidence-based medicine, as defined as the standard by the Association of the Scientific Medical Societies in Germany. Recently published articles after 2005 were examined with respect to positioning therapy and the recently accepted aspect of early mobilization incorporates all literature published up to June 2014.

[Positioning of patients with acute respiratory failure]

The collapse of lung tissue, edema and intrapulmonary shunt are the main symptoms in patients with acute respiratory insufficiency. The techniques of ventilation in a prone position and continuous lateral rotational therapy (CLRT) are based on these pathophysiological changes. Ventilation in a prone position was found to improve ventilation and perfusion relationships and reduction in the pleural pressure gradient. In hypoxemic lung failure (PaO(2)/FIO(2) <100) a prone position was found to improve oxygenation as a rescue measure and to improve survival. In contrast CLRT is considered to be an early therapeutic or prophylactic measure aimed at prevention of ventilation-associated complications. In trauma patients these beneficial effects were demonstrated in several studies. Positioning therapy can be accompanied by potentially serious complications (e.g. face and skin ulceration, accidental loss of tubes and catheters and cardiac arrhythmias) and its use requires routine management and exact knowledge of indications and risks.

Continuous lateral rotation therapy to prevent ventilator-associated pneumonia

OBJECTIVE

To investigate the impact of prophylactic continuous lateral rotation therapy on the prevalence of ventilator-associated pneumonia, duration of mechanical ventilation, length of stay, and mortality in critically ill medical patients.

DESIGN

Prospective, randomized, clinical study.

SETTING

Three medical intensive care units of an university tertiary care hospital.

PATIENTS

Patients were randomized to continuous lateral rotation therapy or standard care if they were mechanically ventilated for <48 hrs and free from pneumonia. Primary study end point was development of ventilator-associated pneumonia. Ventilator-associated pneumonia was defined as infiltrate on the chest radiograph plus newly developed purulent tracheal secretion plus increasing signs of inflammation. The diagnosis had to be confirmed microbiologically and required the growth of a pathogen >10(4) colony-forming units/mL in bronchoalveolar lavage. Radiologists were blinded to randomization whereas clinical outcome assessors were not.

INTERVENTIONS

Rotation therapy was performed continuously in a specially designed bed over an arc of 90 degrees. Additional measures to prevent ventilator-associated pneumonia were equally standardized in both groups including semirecumbent position.

MEASUREMENTS AND MAIN RESULTS

Ventilator-associated pneumonia frequency during the intensive care unit stay was 11% in the rotation group and 23% in the control group (p = .048), respectively. Duration of ventilation (8 +/- 5 vs. 14 +/- 23 days, p = .02) and length of stay (25 +/- 22 days vs. 39 +/- 45 days, p = .01) were significantly shorter in the rotation group. In a forward stepwise logistic regression model including the continuous lateral rotation therapy, gender, Lung Injury Score, and Simplified Acute Physiology Score II, continuous lateral rotation therapy just failed to reach statistical significance with respect to development of ventilator-associated pneumonia (p = .08). Intolerance to continuous lateral rotation therapy during the weaning phase was observed in 29 patients (39%). Mortality was comparable in both groups.

CONCLUSIONS

Ventilator-associated pneumonia prevalence was significantly reduced by continuous lateral rotation therapy. Continuous lateral rotation therapy led to shorter ventilation time and length of stay. Continuous lateral rotation therapy should be considered in ventilated patients at risk for ventilator-associated pneumonia as a feasible method exerting additive effects to other preventive measures.

Prolonged lateral steep position impairs respiratory mechanics during continuous lateral rotation therapy in respiratory failure

OBJECTIVE

To establish whether prolonged lateral steep position during continuous rotation therapy leads to improvement on pulmonary gas exchange, respiratory mechanics and hemodynamics.

DESIGN

Prospective observational study.

SETTING

Intensive care unit of a university hospital.

PATIENTS

Twelve consecutive patients suffering from acute lung injury or adult respiratory distress syndrome undergoing continuous rotation therapy.

INTERVENTIONS

Blood gas analysis, static lung compliance, blood pressure, cardiac index and pulmonary shunt fraction were measured in supine as well as in left and right lateral steep position at 62 degrees during continuous rotation therapy (phase I). Rotation was then stopped for 30 min with the patients in supine position, left and right lateral steep position, and the same measurements were performed every 10 min (phase II).

MEASUREMENTS AND RESULTS

Phase I and II revealed no significant changes in PaO(2)/FiO(2) ratio, mean arterial blood pressure, pulmonary shunt fraction, or cardiac index. Significantly lower static compliance was observed in lateral steep position than in supine position (p<0.001). Concomitantly, PaCO(2) was significantly lower in supine position than in left and right lateral steep position (p<0.01).

CONCLUSIONS

Lateral steep positioning impairs the compliance of the respiratory system. Prolonged lateral steep position does not lead to benefits with respect to oxygenation or hemodynamics. Individual response to the different positions is unpredictable. The pauses in "extreme" positions should be as short as possible.