Understanding recruitment maneuvers

A stepwise lung recruitment maneuver using I-gel can improve respiratory parameters: A prospective observational study

I-gel has been used in various clinical situations. The study investigated alterations in respiratory parameters following a stepwise lung recruitment maneuver (LRM) using the i-gel. The research involved 60 patients classified as American Society of Anesthesiologists class I-II, aged 30 to 75 years, undergoing elective urologic surgery. Various respiratory parameters, including lung compliance, airway resistance, leak volume, airway pressure, and oxygen reserve index, were recorded at different time points: before LRM, immediately after LRM, and at 5, 15, and 30 minutes after LRM, as well as at the end of the surgery. The primary outcome was to assess an improvement in lung compliance. Dynamic lung compliance (mean ± SD) was significantly increased from 49.2 ± 1.8 to 70.15 ± 3.2 mL/cmH2O (P < .05) after LRM. Static lung compliance (mean ± SD) was increased considerably from 52.4 ± 1.7 to 65.0 ± 2.5 mL/cmH2O (P < .05) after the LRM. Both parameters maintained a statistically significant increased status for a certain period compared to baseline despite a decreased degree of increment. Airway resistance (mean ± SD) was significantly reduced after the LRM from 12.05 ± 0.56 to 10.41 ± 0.64 L/cmH2O/s (P < .05). Stepwise LRM using i-gel may improve lung compliance and airway resistance. Repeated procedures could lead to prolonged improvements in respiratory parameters.

Prediction of hypotension during the alveolar recruitment maneuver in spine surgery: a prospective observational study

BACKGROUND

Atelectasis can occur in many clinical practices. One way to prevent this complication is through the alveolar recruitment maneuver (ARM). However, hemodynamic compromise can accompany ARM. This study aims to predict ARM-induced hypotension using a non-invasive method.

METHODS

94 American Society of Anesthesiologists physical status I-II patients aged 19 to 75 with scheduled spinal surgery were enrolled. After anesthesia, we performed a stepwise ARM. Data on perfusion index, mean arterial pressure, heart rate, pleth variability index, cardiac index, and stroke volume variation was collected before induction of anesthesia (T0), just before ARM (T1), at the start of ARM (T2), 0.5 min (T3), 1 min (T4), 1.5 min (T5, end of ARM), and 2 min after the beginning of ARM (T6). Hypotension was defined as when the mean arterial pressure at T5 decreased by 20% or more compared to the baseline. The primary endpoint is that the perfusion index measuring before induction of anesthesia, which reflects the patients' own vascular tone, was correlated with hypotension during ARM.

RESULTS

Seventy-five patients (79.8%) patients developed hypotension during ARM. The pre-induction persufion index (Pi) (95% confidence interval) was 1.7(1.4-3.1) in the non-hypotension group and 3.4(2.4-3.9) in the hypotension group. (p < 0.004) The hypotension group showed considerably higher Pi than the non-hypotension group before induction. The decrease of Pi (%) [IQR] in the non-hypotensive group (52.8% [33.3-74.7]) was more significant than in the hypotensive group. (36% [17.6-53.7]) (p < 0.05) The area under the receiver operating characteristic curve of Pi for predicting hypotension during ARM was 0.718 (95% CI 0.615-0.806; p = 0.004), and the threshold value of the Pi was 2.4.

CONCLUSION

A higher perfusion index value measuring before induction of anesthesia can be used to predict the development of hypotension during ARM. Prophylactic management of the following hypotension during ARM could be considered in high baseline Pi patients.

Management of refractory hypoxemia using recruitment maneuvers and rescue therapies: A comprehensive review

Refractory hypoxemia in patients with acute respiratory distress syndrome treated with mechanical ventilation is one of the most challenging conditions in human and veterinary intensive care units. When a conventional lung protective approach fails to restore adequate oxygenation to the patient, the use of recruitment maneuvers and positive end-expiratory pressure to maximize alveolar recruitment, improve gas exchange and respiratory mechanics, while reducing the risk of ventilator-induced lung injury has been suggested in people as the open lung approach. Although the proposed physiological rationale of opening and keeping open previously collapsed or obstructed airways is sound, the technique for doing so, as well as the potential benefits regarding patient outcome are highly controversial in light of recent randomized controlled trials. Moreover, a variety of alternative therapies that provide even less robust evidence have been investigated, including prone positioning, neuromuscular blockade, inhaled pulmonary vasodilators, extracorporeal membrane oxygenation, and unconventional ventilatory modes such as airway pressure release ventilation. With the exception of prone positioning, these modalities are limited by their own balance of risks and benefits, which can be significantly influenced by the practitioner's experience. This review explores the rationale, evidence, advantages and disadvantages of each of these therapies as well as available methods to identify suitable candidates for recruitment maneuvers, with a summary on their application in veterinary medicine. Undoubtedly, the heterogeneous and evolving nature of acute respiratory distress syndrome and individual lung phenotypes call for a personalized approach using new non-invasive bedside assessment tools, such as electrical impedance tomography, lung ultrasound, and the recruitment-to-inflation ratio to assess lung recruitability. Data available in human medicine provide valuable insights that could, and should, be used to improve the management of veterinary patients with severe respiratory failure with respect to their intrinsic anatomy and physiology.

Effects of two alveolar recruitment maneuvers in an “open-lung” approach during laparoscopy in dogs

Objectives

The aim of this study was to compare the effects of a sustained inflation alveolar recruiting maneuver (ARM) followed by 5 cmH₂O of PEEP and a stepwise ARM, in dogs undergoing laparoscopic surgery.

Materials and methods

Twenty adult dogs were enrolled in this prospective randomized clinical study. Dogs were premedicated with methadone intramuscularly (IM); anesthesia was induced with propofol intravenously (IV) and maintained with inhaled isoflurane in pure oxygen. The baseline ventilatory setting (BVS) was as follows: tidal volume of 15 mL/kg, inspiratory pause of 25%, inspiratory to expiratory ratio of 1:2, and the respiratory rate to maintain the end-tidal carbon dioxide between 45 and 55 mmHg. 10 min after pneumoperitoneum, randomly, 10 dogs underwent sustained inflation ARM followed by 5 cmH₂O of PEEP (ARMi), while 10 dogs underwent a stepwise recruitment maneuver followed by the setting of the “best PEEP” (ARMc). Gas exchange, respiratory system mechanics, and hemodynamic were evaluated before the pneumoperitoneum induction (BASE), 10 min after the pneumoperitoneum (PP), 10 min after the recruitment (ARM), and 10 min after the pneumoperitoneum resolution (PostPP). Statistical analysis was performed with the ANOVA test (p < 0.05).

Results

Static compliance decreased in both groups at PP (ARMc = 1.35 ± 0.21; ARMi = 1.16 ± 0.26 mL/cmH₂O/kg) compared to BASE (ARMc = 1.78 ± 0.60; ARMi = 1.66 ± 0.66 mL/cmH₂O/kg) and at ARM (ARMc = 1.71 ± 0.41; ARMi = 1.44 ± 0.84 mL/cmH₂O/kg) and PostPP (ARMc = 1.75 ± 0.45; ARMi = 1.89 ± 0.59 mL/cmH₂O/kg), and it was higher compared to PP and similar to BASE. The PaO₂/FiO₂, in both groups, was higher at ARM (ARMc = 455.11 ± 85.90; ARMi = 505.40 ± 31.70) and PostPP (ARMc = 521.30 ± 66.20; ARMi = 450.90 ± 70.60) compared to PP (ARMc = 369.53 ± 49.31; ARMi = 394.32 ± 37.72).

Conclusion and clinical relevance

The two ARMs improve lung function in dogs undergoing laparoscopic surgery similarly. Application of PEEP at the end of the ARMs prolonged the effects of the open-lung strategy.

The impact of ultrasound-guided recruitment maneuvers on the risk of postoperative pulmonary complications in patients undergoing general anesthesia

Introduction

Postoperative pulmonary complications are among the most frequent problems in perioperative care. The risk of their development depends not only on the parameters associated with the patient’s initial clinical condition, but also on the employed anesthesia technique, the method of mechanical ventilation, and the type and technique of the surgical procedure. Atelectasis is the most common complication, affecting nearly 90% of the patients undergoing general anesthesia.

Aim

The aim of this study was to determine whether it was possible to positively impact the postoperative period and reduce the frequency of postoperative pulmonary complications via patient-based intraoperative ultrasound-guided recruitment maneuvers.

Methodology

The course of the postoperative period was analyzed in two groups of patients. One of them comprised 100 patients in whom no recruitment maneuvers were performed during general anesthesia. The other group (100 patients) consisted of patients in whom patient-based ultrasound-guided pulmonary recruitment maneuvers were performed.

Results

In the recruitment group, the postoperative hospitalization was statistically significantly shorter (p = 0.003) and the risk of intensive care treatment significantly lower. Additionally, the need for prolonged postoperative mechanical ventilation was reduced, as was the risk of respiratory tract infections.

Conclusions

Intraoperative ultrasound-guided recruitment maneuvers reduce the frequency of postoperative pulmonary complications.

Intraoperative Protective Mechanical Ventilation in Dogs: A Randomized Clinical Trial

Objective

To evaluate gas exchange, respiratory mechanics, and hemodynamic impact of mechanical ventilation with low tidal volume (V_T) in dogs with the use of positive end-expiratory pressure (PEEP) or preceded by alveolar recruitment maneuver (ARM).

Study Design

Prospective randomized clinical trial.

Animals

Twenty-one healthy client-owned mesocephalic healthy dogs, 1-7 years old, weighing 10-20 kg, and body condition scores 4-6/9 admitted for periodontal treatment.

Methods

Isoflurane-anesthetized dogs in dorsal recumbency were ventilated until 1 h with a volume-controlled ventilation mode using 8 mL kg^-1 of V_T. The dogs were distributed in 2 groups: in the ARM group, PEEP starts in 0 cmH₂O, increasing gradually 5 cmH₂O every 3 min, until reach 15 cmH₂O and decreasing in the same steps until 5 cmH₂O, maintaining this value until the end; and PEEP group, in which the pressure 5 cmH₂O was instituted from the beginning of anesthesia and maintained the same level up to the end of the anesthesia. Cardiopulmonary, metabolic, oxygenation parameters, and respiratory mechanics were recorded after the anesthesia induction (baseline-BL), 15, 45, and 75 min after BL and during the recovery.

Results

The ARM increased the static compliance (C_st) (15 min after baseline) when compared with baseline moment (24.9 ± 5.8 mL cmH₂0^-1 vs. 20.7 ± 5.4 mL cmH₂0^-1-p = 0.0364), oxygenation index (PaO₂/FIO₂) (505.6 ± 59.2 mmHg vs. 461.2 ± 41.0 mmHg-p = 0.0453) and reduced the shunt fraction (3.4 ± 2.4% vs. 5.5 ± 1.6%-p = 0.062). In the PEEP group, no statistical differences were observed concerning the variables evaluated. At the beginning of the evaluation, the driving pressure (DP) before ARM was significantly greater than all other evaluation time points (6.9 ± 1.8 cmH₂0).

Conclusions and Clinical Relevance

The use of 8 mL kg^-1 of V_T and 5 cmH₂0 PEEP without ARM maintain adequate oxygenation and mechanical ventilation in dental surgeries for up to 1 h. The use of ARM slightly improved compliance and oxygenation during the maneuver.

Antioxidants as Therapeutic Agents in Acute Respiratory Distress Syndrome (ARDS) Treatment-From Mice to Men

Acute respiratory distress syndrome (ARDS) is a major cause of patient mortality in intensive care units (ICUs) worldwide. Considering that no causative treatment but only symptomatic care is available, it is obvious that there is a high unmet medical need for a new therapeutic concept. One reason for a missing etiologic therapy strategy is the multifactorial origin of ARDS, which leads to a large heterogeneity of patients. This review summarizes the various kinds of ARDS onset with a special focus on the role of reactive oxygen species (ROS), which are generally linked to ARDS development and progression. Taking a closer look at the data which already have been established in mouse models, this review finally proposes the translation of these results on successful antioxidant use in a personalized approach to the ICU patient as a potential adjuvant to standard ARDS treatment.

Optimizing Mechanical Ventilation in Refractory ARDS

Mechanical ventilation in patients with refractory acute respiratory distress syndrome (ARDS) must provide lung protection. This is achieved by limiting tidal volume (VT) and plateau pressure (Pplat). With the current evidence available VT should be initially set around 6 mL per kg predicted body weight and PPlat maintained below 30 cmH₂O and monitored. Positive end-expiratory pressure (PEEP), which also contributes to lung protection, should be set > 12 cmH₂O, provided oxygenation gets improved, with same Pplat target. Recruitment maneuvers should be used with caution avoiding higher PEEP. Neuromuscular blockade should be started and prone position performed for sessions longer than 16 h. High frequency oscillation ventilation should be used in expert centers only if previous management failed to improve oxygenation.

Electrical Impedance Tomography Analysis Between Two Similar Respiratory System Compliance During Decremetal PEEP Titration in ARDS Patients

Purpose

The positive end-expiratory pressure (PEEP) level with best respiratory system compliance (Crs) is frequently used for PEEP selection in acute respiratory distress syndrome (ARDS) patients. On occasion, two similar best Crs (where the difference between the Crs of two PEEP levels is < 1 ml/cm H₂O) may be identified during decremental PEEP titration. Selecting PEEP under such conditions is challenging. The aim of this study was to provide supplementary rationale for PEEP selection by assessing the global and regional ventilation distributions between two PEEP levels in this situation.

Methods

Eight ARDS cases with similar best Crs at two different PEEP levels were analyzed using examination-specific electrical impedance tomography (EIT) measures and airway stress index (SIaw). Five Crs were measured at PEEP values of 25 cm H₂O (PEEP₂₅), 20 cm H₂O (PEEP₂₀), 15 cm H₂O (PEEP_H), 11 cm H₂O (PEEP_I), and 7 cm H₂O (PEEP_L). The higher PEEP value of the two PEEPs with similar best Crs was designated as PEEP_upper, while the lower designated as PEEP_lower.

Results

PEEP_H and PEEP_I shared the best Crs in two cases, while similar Crs was found at PEEP_I and PEEP_L in the remaining six cases. SIaw was higher with PEEP_upper as compared to PEEP_lower (1.06 ± 0.10 versus 0.99 ± 0.09, p = 0.05). Proportion of lung hyperdistension was significantly higher with PEEP_upper than PEEP_lower (7.0 ± 5.1% versus 0.3 ± 0.5%, p = 0.0002). In contrast, proportion of recruitable lung collapse was higher with PEEP_lower than PEEP_upper (18.6 ± 4.4% versus 5.9 ± 3.7%, p < 0.0001). Cyclic alveolar collapse and reopening during tidal breathing was higher at PEEP_lower than PEEP_upper (34.4 ± 19.3% versus 16.0 ± 9.1%, p = 0.046). The intratidal gas distribution (ITV) index was also significantly higher at PEEP_lower than PEEP_upper (2.6 ± 1.3 versus 1.8 ± 0.7, p = 0.042).

Conclusions

PEEP_upper is a rational selection in ARDS cases with two similar best Crs. EIT provides additional information for the selection of PEEP in such circumstances.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40846-021-00668-2.

Aggressive alveolar recruitment in ARDS: More shadows than lights

Alveolar recruitment in acute respiratory distress syndrome (ARDS) is defined as the penetration of gas into previously unventilated areas or poorly ventilated areas. Alveolar recruitment during recruitment maneuvering (RM) depends on the duration of the maneuver, the recruitable lung tissue, and the balance between the recruitment of collapsed areas and over-insufflation of the ventilated areas. Alveolar recruitment is estimated using computed tomography of the lung and, at the patient bedside, through assessment of the recruited volume using pressure-volume curves and assessing lung morphology with pulmonary ultrasound and/or impedance tomography. The scientific evidence on RM in patients with ARDS remains subject to controversy. Randomized studies on ARDS have shown no benefit or have even reflected an increase in mortality. The routine use of RM is therefore not recommended.

Lung Ultrasonography in the Monitoring of Intraoperative Recruitment Maneuvers

Introduction: Postoperative respiratory failure is a serious problem in patients who undergo general anesthesia. Approximately 90% of mechanically ventilated patients during the surgery may develop atelectasis that leads to perioperative complications. Aim: The aim of this study is to determine whether it is possible to optimize recruitment maneuvers with the use of chest ultrasonography, thus limiting the risk of respiratory complications in patients who undergo general anesthesia. Methodology: The method of incremental increases in positive end-expiratory pressure (PEEP) values with simultaneous continuous ultrasound assessments was employed in mechanically ventilated patients. Results: The study group comprised 100 patients. The employed method allowed for atelectasis reduction in 91.9% of patients. The PEEP necessary to reverse areas of atelectasis averaged 17cmH₂O, with an average peak pressure of 29cmH₂O. The average PEEP that prevented repeat atelectasis was 9cmH₂O. A significant improvement in lung compliance and saturation was obtained. Conclusions: Ultrasound-guided recruitment maneuvers facilitate the patient-based adjustment of the process. Consequently, the reduction in ventilation pressures necessary to aerate intraoperative atelectasis is possible, with the simultaneous reduction in the risk of procedure-related complications.

Management of ARDS - What Works and What Does Not

Acute respiratory distress syndrome (ARDS) is a clinically and biologically heterogeneous disorder associated with a variety of disease processes that lead to acute lung injury with increased non-hydrostatic extravascular lung water, reduced compliance, and severe hypoxemia. Despite significant advances, mortality associated with this syndrome remains high. Mechanical ventilation remains the most important aspect of managing patients with ARDS. An in-depth knowledge of lung protective ventilation, optimal PEEP strategies, modes of ventilation and recruitment maneuvers are essential for ventilatory management of ARDS. Although, the management of ARDS is constantly evolving as new studies are published and guidelines being updated; we present a detailed review of the literature including the most up-to-date studies and guidelines in the management of ARDS. We believe this review is particularly helpful in the current times where more than half of the acute care hospitals lack in-house intensivists and the burden of ARDS is at large.

Improvement in Lung Insufflation in Spontaneously Breathing Tracheostomized Patients by Using a New Pulmonary Expansion Device: A Pilot Study

Lung expansion techniques (LETs) are a key component of pulmonary rehabilitation. Nevertheless, these can be limited in tracheostomized patients because of the infraglottic position of tracheostomy cannulas. We propose a novel pulmonary expansion device (PED) that allows deep inspiration with a postinspiratory pause for a few seconds by means of a unidirectional valve and an occlusion/flow release cap. It is equipped with a relief valve that opens at 60 cm H2O in cases in which this threshold is attained. We aimed to evaluate the impact on lung volume and pressure in spontaneously breathing tracheostomized patients subjected to LETs. A single-arm pilot interventional study was conducted in an adult intensive care unit (ICU), including spontaneously breathing tracheostomized patients. 80 treatments were performed on 10 patients with tracheostomies with PED over a period of 3 months. The maximal inspiratory volume (MIV) was significantly increased by using PED (MIV-PED) at both day 1 (725 (600–820) mL versus 1550 (1250–1700) mL, P &lt; 0.001) and day 3 (870 (750–950) mL versus 1662 (1550–1900) mL, P &lt; 0.001). Inspiratory pause pressure (PIP-PED) did not significantly change from day 1 to day 3 (18 (14–20) cm H2O versus 14 (12–22) cm H2O, P = 0.36). The use of the PED in tracheostomy patients acted as an artificial glottis by performing a novel pulmonary re-expansion maneuver, and increased volumes and intrapulmonary pressure with prolongation of maximum inspiration were achieved.

Lung protective ventilation in infants undergoing cardiopulmonary bypass surgery for congenital heart disease: A prospective randomized controlled trial

BACKGROUND

Lung protective ventilation (LPV) has been applied to surgical adults with normal pulmonary function for optimizing mechanical ventilation and reducing postoperative pulmonary complications. Few studies have reported the use of LPV in infants undergoing cardiac surgery with cardiopulmonary bypass (CPB).

AIMS

To explore safety and effectiveness of LPV in infants undergoing CPB surgery for congenital heart disease (CHD).

METHODS

Included in this study were 77 infants who underwent CPB surgery for CHD from November 2017 to September 2018. They were randomized into the LPV group and conventional ventilation (CV) group. In the LPV group, small-tidal-volume (6-8 ml/kg) ventilation, lung recruitment by PEEP increment to the maximum level of 15 cm H₂ O after CPB, and individualized optimal PEEP titration were applied. In the CV group, traditional tidal volume (10-12 ml/kg with zero PEEP) was applied. The primary outcome was the ratio of arterial partial pressure of oxygen to inspiratory oxygen fraction (PaO₂ /FiO₂ ). The secondary outcomes were respiratory dynamic parameters, hypoxemia, prognostic indexes, and postoperative pulmonary complications.

RESULTS

PaO₂ /FiO₂ in the LPV group (416.86, 95%CI: 381.60-452.12) was significantly higher than that in the CV group (263.37, 95%CI: 227.65-299.09) after intervention (P < .001). There was a significant difference in the trend of change in dynamic compliance, alveolar-arterial oxygen difference, arterial-end-expired carbon dioxide difference, driving pressure, and respiratory index between the two groups at different time points from weaning from CPB to 2 hours after operation. There was no significant difference in PaO₂ /FiO₂ , alveolar-arterial oxygen difference, respiratory index, and dynamic compliance 2 hours postoperative and in the incidence of postoperative pulmonary complications, prognostic indexes between the two groups.

CONCLUSIONS

LPV could be used safely in infants undergoing CPB in that it can improve oxygenation, alveolar aeration, and dynamic compliance, and reduce driving pressure, pulmonary shunting, and dead space. Its effect on oxygenation, pulmonary gas exchange, and pulmonary compliance was relatively short, and had less impact on postoperative pulmonary complications and prognosis.

Effect of lung recruitment and titrated positive end-expiratory pressure (PEEP) versus low PEEP on patients with moderate-severe acute respiratory distress syndrome: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Setting a positive end-expiratory pressure (PEEP) on patients with acute respiratory distress syndrome (ARDS) receiving mechanical ventilation has been an issue of great contention. Therefore, we aimed to determine effects of lung recruitment maneuver (RM) and titrated PEEP versus low PEEP on adult patients with moderate-severe ARDS.

METHODS

Data sources and study selection proceeded as follows: PubMed, Ovid, EBSCO, and Cochrane Library databases were searched from 2003 to May 2018. Original clinical randomized controlled trials which met the eligibility criteria were included. To compare the prognosis between the titrated PEEP and low PEEP groups on patients with moderate-severe ARDS (PaO2/FiO2 < 200 mmHg). Heterogeneity was quantified through the I2 statistic. Egger's test and funnel plots were used to assess publication bias.

RESULTS

No difference was found in 28-day mortality and ICU mortality (OR = 0.97, 95% CI (0.61-1.52), p = 0.88; OR = 1.14, 95% CI (0.91-1.43), p = 0.26, respectively). Only ventilator-free days, length of stay in the ICU, length of stay in hospital, and incidence of barotrauma could be systematically reviewed owing to bias and extensive heterogeneity.

CONCLUSION

No difference was observed in the RM between the titrated PEEP and the low PEEP in 28-day mortality and ICU mortality on patients with moderate-severe ARDS.

Acute life-threatening hypoxemia during mechanical ventilation

PURPOSE OF REVIEW

To describe current evidence-based practice in the management of acute life-threatening hypoxemia in mechanically ventilated patients and some of the methods used to individualize the care of the patient.

RECENT FINDINGS

Patients with acute life-threatening hypoxemia will often meet criteria for severe ARDS, for which there are only a few treatment strategies that have been shown to improve survival outcomes. Recent findings have increased our knowledge of the physiological effects of spontaneous breathing and the application of PEEP. Additionally, the use of advanced bedside monitoring has a promising future in the management of hypoxemic patients to fine-tune the ventilator and to evaluate the individual patient response to therapy.

SUMMARY

Treating the patient with acute life-threatening hypoxemia during mechanical ventilation should begin with an evidence-based approach, with the goal of improving oxygenation and minimizing the harmful effects of mechanical ventilation. The use of advanced monitoring and the application of simple maneuvers at the bedside may assist clinicians to better individualize treatment and improve clinical outcomes.

Mechanical Ventilation in Adults with Acute Respiratory Distress Syndrome. Summary of the Experimental Evidence for the Clinical Practice Guideline

RATIONALE

The American Thoracic Society/European Society for Intensive Care Medicine/Society of Critical Care Medicine guidelines on mechanical ventilation in adult patients with acute respiratory distress syndrome (ARDS) provide treatment recommendations derived from a thorough analysis of the clinical evidence on six clinical interventions. However, each of the recommendations contains areas of uncertainty and controversy, which may affect their appropriate clinical application.

OBJECTIVES

To provide a critical review of the experimental evidence surrounding the pathophysiology of ventilator-induced lung injury and to help clinicians apply the clinical recommendations to individual patients.

METHODS

We conducted a literature search and narrative review.

RESULTS

A large number of experimental studies have been performed with the aim of improving understanding of the pathophysiological effects of mechanical ventilation. These studies have formed the basis for the design of many clinical trials. Translational research has fundamentally advanced understanding of the mechanisms of ventilator-induced lung injury, thus informing the design of interventions that improve survival in patients with ARDS.

CONCLUSIONS

Because daily management of patients with ARDS presents the challenge of competing considerations, clinicians should consider the mechanism of ventilator-induced lung injury, as well as the rationale for interventions designed to mitigate it, when applying evidence-based recommendations at the bedside.

Statistical analysis plan for the Alveolar Recruitment for Acute Respiratory Distress Syndrome Trial (ART). A randomized controlled trial

BACKGROUND

The Alveolar Recruitment for Acute Respiratory Distress Syndrome Trial (ART) is an international multicenter randomized pragmatic controlled trial with allocation concealment involving 120 intensive care units in Brazil, Argentina, Colombia, Italy, Poland, Portugal, Malaysia, Spain, and Uruguay. The primary objective of ART is to determine whether maximum stepwise alveolar recruitment associated with PEEP titration, adjusted according to the static compliance of the respiratory system (ART strategy), is able to increase 28-day survival in patients with acute respiratory distress syndrome compared to conventional treatment (ARDSNet strategy).

OBJECTIVE

To describe the data management process and statistical analysis plan.

METHODS

The statistical analysis plan was designed by the trial executive committee and reviewed and approved by the trial steering committee. We provide an overview of the trial design with a special focus on describing the primary (28-day survival) and secondary outcomes. We describe our data management process, data monitoring committee, interim analyses, and sample size calculation. We describe our planned statistical analyses for primary and secondary outcomes as well as pre-specified subgroup analyses. We also provide details for presenting results, including mock tables for baseline characteristics, adherence to the protocol and effect on clinical outcomes.

CONCLUSION

According to best trial practice, we report our statistical analysis plan and data management plan prior to locking the database and beginning analyses. We anticipate that this document will prevent analysis bias and enhance the utility of the reported results.

TRIAL REGISTRATION

ClinicalTrials.gov number, NCT01374022.

Update in Management of Severe Hypoxemic Respiratory Failure

Mortality related to severe-moderate and severe ARDS remains high. We searched the literature to update this topic. We defined severe hypoxemic respiratory failure as Pao₂/Fio₂ < 150 mm Hg (ie, severe-moderate and severe ARDS). For these patients, we support setting the ventilator to a tidal volume of 4 to 8 mL/kg predicted body weight (PBW), with plateau pressure (Pplat) ≤ 30 cm H₂O, and initial positive end-expiratory pressure (PEEP) of 10 to 12 cm H₂O. To promote alveolar recruitment, we propose increasing PEEP in increments of 2 to 3 cm provided that Pplat remains ≤ 30 cm H₂O and driving pressure does not increase. A fluid-restricted strategy is recommended, and nonrespiratory causes of hypoxemia should be considered. For patients who remain hypoxemic after PEEP optimization, neuromuscular blockade and prone positioning should be considered. Profound refractory hypoxemia (Pao₂/Fio₂ < 80 mm Hg) after PEEP titration is an indication to consider extracorporeal life support. This may necessitate early transfer to a center with expertise in these techniques. Inhaled vasodilators and nontraditional ventilator modes may improve oxygenation, but evidence for improved outcomes is weak.