Efficacy and safety of recruitment maneuvers in acute respiratory distress syndrome

Incremental Application of Positive End-Expiratory Pressure for the Evaluation of Atelectasis During RP-EBUS and Bronchoscopy (I-APPEAR)

BACKGROUND

CT-to-body divergence-described as the difference between preprocedural CT scans and intraprocedural lung architecture-is a significant barrier to improving diagnostic yield during navigational bronchoscopy. A major proposed contributor to CT-to-body divergence is the development of atelectasis, which can confound visualization of peripheral lung lesions via radial probe endobronchial ultrasound (RP-EBUS). High positive end-expiratory pressure (PEEP) ventilatory strategies have been used to decrease atelectasis, allowing the lesion to re-APPEAR on intraprocedure imaging. However, standardized PEEP levels may not be appropriate for all patients due to hemodynamic and ventilatory impacts.

METHODS

We performed a multicenter, prospective observational study in which patients were imaged with RP-EBUS under general anesthesia to determine if subsegmental atelectasis would resolve as incremental increases in PEEP were applied. Resolution of atelectasis was based on the transition from a non-aerated pattern to an aerated appearance on RP-EBUS. RP-EBUS images were reviewed by 3 experienced operators to determine correlation.

RESULTS

Forty-three patients underwent RP-EBUS examination following navigational bronchoscopy. Thirty-seven patients underwent incremental PEEP application and subsequent RP-EBUS imaging. Atelectasis was determined to have resolved in 33 patients (88.2%) following increased PEEP. The intraclass correlation coefficient between reviewers was 0.76. A recruitment maneuver was performed in 7 (16.3%) patients after atelectasis persisted at maximal PEEP. Atelectasis was not identified in the examined subsegments in 6 (10.8%) patients despite zero PEEP.

CONCLUSION

RP-EBUS is an effective tool to monitor what pressure atelectasis within a lung segment has resolved with increasing levels of PEEP.

Translational medicine for acute lung injury

Acute lung injury (ALI) is a complex disease with numerous causes. This review begins with a discussion of disease development from direct or indirect pulmonary insults, as well as varied pathogenesis. The heterogeneous nature of ALI is then elaborated upon, including its epidemiology, clinical manifestations, potential biomarkers, and genetic contributions. Although no medication is currently approved for this devastating illness, supportive care and pharmacological intervention for ALI treatment are summarized, followed by an assessment of the pathophysiological gap between human ALI and animal models. Lastly, current research progress on advanced nanomedicines for ALI therapeutics in preclinical and clinical settings is reviewed, demonstrating new opportunities towards developing an effective treatment for ALI.

Risk factors and long-term prognosis for postoperative hypoxemia in patients with acute type A aortic dissection: A retrospective observational study

Hypoxemia is 1 of the most common complications in the patients with acute Type A aortic dissection (ATAAD). This study aimed to summarize the risk factors, management strategies and long-term prognosis for postoperative hypoxemia in ATAAD patients. Baseline characteristics and clinical data of all the patients were collected. Patients were divided into 2 groups according to the PaO2/FiO2 after surgery: Hypoxemia group (n = 142) and Non-hypoxemia group (n = 68). The differences in gender, age, body mass index, operation time, cardiopulmonary bypass (CPB) time, aortic cross-clamping time, deep hypothermic circulatory arrest time, preoperative PaO2/FiO2, postoperative PaO2/FiO2, PaO2/FiO2 before extubating, time of mechanical ventilation, length of intensive care unit stay, length of hospital stay, in-hospital mortality, and overall mortality were compared between the 2 groups. The incidence of postoperative hypoxemia in this study was 67.6% (142/210). body mass index (26.4 ± 3.8 vs 24.4 ± 3.3kg/m2, P < .001) in the hypoxemia group were markedly higher and CPB time (196.3 ± 41.0 vs 181.0 ± 37.3 minutes, P = .010) in the hypoxemia group were significantly longer than those in the non-hypoxemia group. While preoperative PaO2/FiO2 (229.7 ± 91.4 vs 299.7 ± 101.2mmHg, P < .001) was significantly lower than those in the non-hypoxemia group. In the hypoxemia group, PaO2/FiO2 before extubating was significantly higher than that after operation, and the difference was significant. Logistic regression analysis showed that overweight (odds ratio [OR]: 1.113, P = .030), CPB time (OR: 1.009, P = .043) and preoperative PaO2/FiO2 (OR: 0.994, P = .001) were independent risk factors for postoperative hypoxemia. Further follow-up results showed no significant difference in long-term mortality between the 2 groups. Logistic regression analysis revealed that PaO2/FiO2 before extubating (OR: 0.985, P < .001), paraplegia (OR: 10.994, P = .019), acute renal failure (OR: 12.590, P < .001), re-operation (OR: 4.721, P = .014) and re-admission to intensive care unit (OR: 13.727, P = .001) were independent risk factors for long-term mortality. Our results showed that overweight and prolonged CPB time were risk factors for postoperative hypoxemia in ATAAD patients. While PaO2/FiO2 before extubating were independent risk factors for long-term mortality, indicating that active correction of hypoxemia and maintain a higher PaO2/FiO2 before extubating may help to improve the prognosis of the ATAAD patients.

A novel Vascular Leak Index identifies sepsis patients with a higher risk for in-hospital death and fluid accumulation

Purpose

Sepsis is a leading cause of morbidity and mortality worldwide and is characterized by vascular leak. Treatment for sepsis, specifically intravenous fluids, may worsen deterioration in the context of vascular leak. We therefore sought to quantify vascular leak in sepsis patients to guide fluid resuscitation.

Methods

We performed a retrospective cohort study of sepsis patients in four ICU databases in North America, Europe, and Asia. We developed an intuitive vascular leak index (VLI) and explored the relationship between VLI and in-hospital death and fluid balance using generalized additive models (GAM).

Results

Using a GAM, we found that increased VLI is associated with an increased risk of in-hospital death. Patients with a VLI in the highest quartile (Q4), across the four datasets, had a 1.61–2.31 times increased odds of dying in the hospital compared to patients with a VLI in the lowest quartile (Q1). VLI Q2 and Q3 were also associated with increased odds of dying. The relationship between VLI, treated as a continuous variable, and in-hospital death and fluid balance was statistically significant in the three datasets with large sample sizes. Specifically, we observed that as VLI increased, there was increase in the risk for in-hospital death and 36–84 h fluid balance.

Conclusions

Our VLI identifies groups of patients who may be at higher risk for in-hospital death or for fluid accumulation. This relationship persisted in models developed to control for severity of illness and chronic comorbidities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-03968-4.

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.

Unsuccessful and Successful Clinical Trials in Acute Respiratory Distress Syndrome: Addressing Physiology-Based Gaps

The acute respiratory distress syndrome (ARDS) is a severe form of acute hypoxemic respiratory failure caused by an insult to the alveolar-capillary membrane, resulting in a marked reduction of aerated alveoli, increased vascular permeability and subsequent interstitial and alveolar pulmonary edema, reduced lung compliance, increase of physiological dead space, and hypoxemia. Most ARDS patients improve their systemic oxygenation, as assessed by the ratio between arterial partial pressure of oxygen and inspired oxygen fraction, with conventional intensive care and the application of moderate-to-high levels of positive end-expiratory pressure. However, in some patients hypoxemia persisted because the lungs are markedly injured, remaining unresponsive to increasing the inspiratory fraction of oxygen and positive end-expiratory pressure. For decades, mechanical ventilation was the only standard support technique to provide acceptable oxygenation and carbon dioxide removal. Mechanical ventilation provides time for the specific therapy to reverse the disease-causing lung injury and for the recovery of the respiratory function. The adverse effects of mechanical ventilation are direct consequences of the changes in pulmonary airway pressures and intrathoracic volume changes induced by the repetitive mechanical cycles in a diseased lung. In this article, we review 14 major successful and unsuccessful randomized controlled trials conducted in patients with ARDS on a series of techniques to improve oxygenation and ventilation published since 2010. Those trials tested the effects of adjunctive therapies (neuromuscular blocking agents, prone positioning), methods for selecting the optimum positive end-expiratory pressure (after recruitment maneuvers, or guided by esophageal pressure), high-frequency oscillatory ventilation, extracorporeal oxygenation, and pharmacologic immune modulators of the pulmonary and systemic inflammatory responses in patients affected by ARDS. We will briefly comment physiology-based gaps of negative trials and highlight the possible needs to address in future clinical trials in ARDS.

Respiratory care for the critical patients with 2019 novel coronavirus

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted through respiratory droplets, aerosols and close contact. Cross infections occur because viruses spread rapidly among humans. Nineteen percent (19%) of the infected patients developed severe pneumonia and acute respiratory distress syndrome (ARDS). Hypoxemia usually occurs and patients may require oxygen therapy or mechanical ventilation (MV) support. In this article, recently published clinical experience and observational studies were reviewed. Corresponding respiratory therapy regarding different stages of infection is proposed. Infection control principles and respiratory strategies including oxygen therapy, non-invasive respiratory support (NIRS), intubation evaluation, equipment preparation, ventilator settings, special maneuvers comprise of the prone position (PP), recruitment maneuver (RM), extracorporeal membrane oxygenation (ECMO), weaning and extubation are summarized. Respiratory equipment and device disinfection recommendations are worked up. We expect this review article could be used as a reference by healthcare workers in patient care while minimizing the risk of environmental contamination.

BD, Salazar Gutierrez G, Gómez González JF, Echeverry Piedrahita DR, Galvis JC, Aguirre-Flórez M. Mechanical ventilation in SARS-CoV-2 patients: state of art

COVID-19-associated infection leads to a pathology of yet unknown clinical behavior, confronting the clinician with various challenges. An extensive search was conducted based on review articles on SARS-CoV-2 infection and studies including mechanical ventilation management strategies in order to complete this narrative review. Evidenced-based treatment for SARS-CoV2 infection is still in the works. We have some tools from our knowledge from past experiences indicating that a step-wise management approach should be used, without neglecting other joint therapeutic measures for improved clinical outcomes of a condition with a high mortality. The current recommendations indicate that patients with severe acute respiratory failure due to SARS-CoV-2 should be managed with protective mechanical ventilation measures. No strong evidence is yet available on the individualization of mechanical ventilation therapy according to phenotypes.

Emergency Department Management of Severe Hypoxemic Respiratory Failure in Adults With COVID-19

Background

While emergency physicians are familiar with the management of hypoxemic respiratory failure, management of mechanical ventilation and advanced therapies for oxygenation in the emergency department have become essential during the coronavirus disease 2019 (COVID-19) pandemic.

Objective

We review the current evidence on hypoxemia in COVID-19 and place it in the context of known evidence-based management of hypoxemic respiratory failure in the emergency department.

Discussion

COVID-19 causes mortality primarily through the development of acute respiratory distress syndrome (ARDS), with hypoxemia arising from shunt, a mismatch of ventilation and perfusion. Management of patients developing ARDS should focus on mitigating derecruitment and avoiding volutrauma or barotrauma.

Conclusions

High flow nasal cannula and noninvasive positive pressure ventilation have a more limited role in COVID-19 because of the risk of aerosolization and minimal benefit in severe cases, but can be considered. Stable patients who can tolerate repositioning should be placed in a prone position while awake. Once intubated, patients should be managed with ventilation strategies appropriate for ARDS, including targeting lung-protective volumes and low pressures. Increasing positive end-expiratory pressure can be beneficial. Inhaled pulmonary vasodilators do not decrease mortality but may be given to improve refractory hypoxemia. Prone positioning of intubated patients is associated with a mortality reduction in ARDS and can be considered for patients with persistent hypoxemia. Neuromuscular blockade should also be administered in patients who remain dyssynchronous with the ventilator despite adequate sedation. Finally, patients with refractory severe hypoxemic respiratory failure in COVID-19 should be considered for venovenous extracorporeal membrane oxygenation.

Tolerable Maximum Positive End Expiratory Pressure in Mechanically Ventilated Patients and Its Impact on Blood Flow across Cardiac Valves: Index Case Report of a Physiology Study

<b><i>Introduction:</i></b> Positive end expiratory pressure (PEEP) exerts variable effects on preload, pulmonary vascular flow, and afterload. Lung recruitment with gradual increase in PEEP improves oxygenation, but it may have variable cardiovascular effects. <b><i>Method:</i></b> A patient with respiratory failure from tetanus was recruited after informed consent. The sedated and paralyzed patient was subjected to sequential increase in PEEP with measurement of hemodynamics, ventilator parameters, and echocardiographic parameters (Doppler flow across tricuspid, pulmonic, and mitral valves at end inspiration and end expiration, in addition to blood volume flowing across RVOT and mitral valve). <b><i>Results:</i></b> We observed an initial rise in pulmonic and mitral blood flows, followed by a decline back to baseline around PEEP of 20, with an eventual decline associated with a drop in mean MAP &#x3c;60 torr above PEEP of 29. Similar effects were also observed on blood volume flowing across RVOT and mitral valve. PEEP of 5 was associated with best blood flow parameters. <b><i>Conclusion:</i></b> Although systemic pressure was maintained at PEEP of 29, pulmonary blood flow started to be compromised at PEEP of 20. Best pulmonary perfusion parameters were achieved at PEEP of 5.

Managing Persistent Hypoxemia: what is new?

Mechanical ventilation is the standard life-support technique for patients with severe acute respiratory failure. However, some patients develop persistent and refractory hypoxemia because their lungs are so severely damaged that they are unable to respond to the application of high inspired oxygen concentration and high levels of positive end-expiratory pressure. In this article, we review current knowledge on managing persistent hypoxemia in patients with injured lungs.

Effect of Lung Recruitment and Titrated Positive End-Expiratory Pressure (PEEP) vs Low PEEP on Mortality in Patients With Acute Respiratory Distress Syndrome: A Randomized Clinical Trial

IMPORTANCE

The effects of recruitment maneuvers and positive end-expiratory pressure (PEEP) titration on clinical outcomes in patients with acute respiratory distress syndrome (ARDS) remain uncertain.

OBJECTIVE

To determine if lung recruitment associated with PEEP titration according to the best respiratory-system compliance decreases 28-day mortality of patients with moderate to severe ARDS compared with a conventional low-PEEP strategy.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, randomized trial conducted at 120 intensive care units (ICUs) from 9 countries from November 17, 2011, through April 25, 2017, enrolling adults with moderate to severe ARDS.

INTERVENTIONS

An experimental strategy with a lung recruitment maneuver and PEEP titration according to the best respiratory-system compliance (n = 501; experimental group) or a control strategy of low PEEP (n = 509). All patients received volume-assist control mode until weaning.

MAIN OUTCOMES AND MEASURES

The primary outcome was all-cause mortality until 28 days. Secondary outcomes were length of ICU and hospital stay; ventilator-free days through day 28; pneumothorax requiring drainage within 7 days; barotrauma within 7 days; and ICU, in-hospital, and 6-month mortality.

RESULTS

A total of 1010 patients (37.5% female; mean [SD] age, 50.9 [17.4] years) were enrolled and followed up. At 28 days, 277 of 501 patients (55.3%) in the experimental group and 251 of 509 patients (49.3%) in the control group had died (hazard ratio [HR], 1.20; 95% CI, 1.01 to 1.42; P = .041). Compared with the control group, the experimental group strategy increased 6-month mortality (65.3% vs 59.9%; HR, 1.18; 95% CI, 1.01 to 1.38; P = .04), decreased the number of mean ventilator-free days (5.3 vs 6.4; difference, -1.1; 95% CI, -2.1 to -0.1; P = .03), increased the risk of pneumothorax requiring drainage (3.2% vs 1.2%; difference, 2.0%; 95% CI, 0.0% to 4.0%; P = .03), and the risk of barotrauma (5.6% vs 1.6%; difference, 4.0%; 95% CI, 1.5% to 6.5%; P = .001). There were no significant differences in the length of ICU stay, length of hospital stay, ICU mortality, and in-hospital mortality.

CONCLUSIONS AND RELEVANCE

In patients with moderate to severe ARDS, a strategy with lung recruitment and titrated PEEP compared with low PEEP increased 28-day all-cause mortality. These findings do not support the routine use of lung recruitment maneuver and PEEP titration in these patients.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01374022.

Alveolar recruitment maneuver attenuates extravascular lung water in acute respiratory distress syndrome

BACKGROUND

The alveolar recruitment maneuver (RM) has been reported to improve oxygenation in acute respiratory distress syndrome (ARDS) and may be related to reduced extravascular lung water (EVLW) in animals. This study was designed to investigate the effects of RM on EVLW in patients with ARDS.

METHODS

An open label, prospective, randomized controlled trial including patients with ARDS was conducted in hospitals in North Taiwan between 2010 and 2016. The patients were divided into 2 groups (with and without RM). The primary endpoint was the comparison of the EVLW index between the 2 groups.

RESULTS

Twenty-four patients with ARDS on mechanical ventilator support were randomized to receive ventilator treatment with RM (RM group, n = 12) or without RM (non-RM group, n = 12). Baseline demographic characteristics were similar between the 2 groups. After recruitment, the day 3 extravascular lung water index (EVLWI) (25.3 ± 9.3 vs 15.5 ± 7.3 mL/kg, P = .008) and the arterial oxygen tension/fractional inspired oxygen ratio (PaO2/FiO2) (132.3 ± 43.5 vs 185.6 ± 38.8 mL/kg, P = .003) both improved over that of day 1. However, both EVLWI and PaO2/FiO2 did not significantly change from day 1 to 3 in the non-RM group.

CONCLUSION

RM is a feasible method for improving oxygenation and the EVLW index in patients with ARDS, as well as for decreasing ventilator days and intensive care unit stay duration.

Incidence and outcomes of acute lung injury in the surgical intensive care unit of a tertiary care hospital in Bangkok, Thailand

Background

Although the pathophysiology and treatment of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are well established, the incidence and outcomes of ALI have not been extensively reported. Variations in healthcare systems, demographics, socioeconomics, and levels of intensive care units (ICU) may explain remarkable differences in outcomes reported.

Objectives

To evaluate the incidence and outcomes of ALI/ARDS at the surgical ICU (SICU) at Siriraj Hospital of Mahidol University, Bangkok.

Methods

We included patients aged ≥18 years admitted to the general SICU between June 1, 2010 and May 31, 2013 in this prospective, cohort observational study. All patients required ≥24 h of ventilatory support. The study outcomes were the incidence of ALI/ARDS, SICU length of stay, and mortality rate.

Results

Of 2523 patients admitted to the SICU, 495 (20%) required ≥24 h ventilatory support, and 15 (3%) developed ALI/ARDS. ALI/ARDS occurred on day 2 of ventilatory support. ARDS was caused by sepsis and pneumonia. The patients who developed ALI/ARDS had a higher APACHE II score (P = 0.001) and end-stage renal disease (P = 0.01). Pneumonia and acute kidney injury were more severe in patients with ALI and ARDS (40% vs 9%, P = 0.002; 33% vs 10%, P = 0.02, respectively). Ventilatory support duration, SICU lengths of stay and hospital mortality were higher in the ALI/ARDS group.

Conclusions

The incidence of ALI/ARDS in the SICU was low, but the mortality rate was high. A larger sample size is necessary to identify independent risk factors for ALI/ARDS.

Acute respiratory distress syndrome

Acute respiratory distress syndrome presents as hypoxia and bilateral pulmonary infiltrates on chest imaging in the absence of heart failure sufficient to account for this clinical state. Management is largely supportive, and is focused on protective mechanical ventilation and the avoidance of fluid overload. Patients with severe hypoxaemia can be managed with early short-term use of neuromuscular blockade, prone position ventilation, or extracorporeal membrane oxygenation. The use of inhaled nitric oxide is rarely indicated and both β2 agonists and late corticosteroids should be avoided. Mortality remains at approximately 30%.

Regenerative potential of human airway stem cells in lung epithelial engineering

Bio-engineered organs for transplantation may ultimately provide a personalized solution for end-stage organ failure, without the risk of rejection. Building upon the process of whole organ perfusion decellularization, we aimed to develop novel, translational methods for the recellularization and regeneration of transplantable lung constructs. We first isolated a proliferative KRT5(+)TP63(+) basal epithelial stem cell population from human lung tissue and demonstrated expansion capacity in conventional 2D culture. We then repopulated acellular rat scaffolds in ex vivo whole organ culture and observed continued cell proliferation, in combination with primary pulmonary endothelial cells. To show clinical scalability, and to test the regenerative capacity of the basal cell population in a human context, we then recellularized and cultured isolated human lung scaffolds under biomimetic conditions. Analysis of the regenerated tissue constructs confirmed cell viability and sustained metabolic activity over 7 days of culture. Tissue analysis revealed extensive recellularization with organized tissue architecture and morphology, and preserved basal epithelial cell phenotype. The recellularized lung constructs displayed dynamic compliance and rudimentary gas exchange capacity. Our results underline the regenerative potential of patient-derived human airway stem cells in lung tissue engineering. We anticipate these advances to have clinically relevant implications for whole lung bioengineering and ex vivo organ repair.

Acute Lung Injury Causes Asynchronous Alveolar Ventilation That Can Be Corrected by Individual Sighs

RATIONALE

Improved ventilation strategies have been the mainstay for reducing mortality in acute respiratory distress syndrome. Their unique clinical effectiveness is, however, unmatched by our understanding of the underlying mechanobiology, and their impact on alveolar dynamics and gas exchange remains largely speculative.

OBJECTIVES

To assess changes in alveolar dynamics and associated effects on local gas exchange in experimental models of acute lung injury (ALI) and their responsiveness to sighs.

METHODS

Alveolar dynamics and local gas exchange were studied in vivo by darkfield microscopy and multispectral oximetry in experimental murine models of ALI induced by hydrochloric acid, Tween instillation, or in antibody-mediated transfusion-related ALI.

MEASUREMENTS AND MAIN RESULTS

Independent of injury mode, ALI resulted in asynchronous alveolar ventilation characteristic of alveolar pendelluft, which either spontaneously resolved or progressed to a complete cessation or even inversion of alveolar ventilation. The functional relevance of the latter phenomena was evident as impaired blood oxygenation in juxtaposed lung capillaries. Individual sighs (2 × 10 s at inspiratory plateau pressure of 30 cm H2O) largely restored normal alveolar dynamics and gas exchange in acid-induced ALI, yet not in Tween-induced surfactant depletion.

CONCLUSIONS

We describe for the first time in detail the different forms and temporal sequence of impaired alveolar dynamics in the acutely injured lung and report the first direct visualization of alveolar pendelluft. Moreover, we identify individual sighs as an effective strategy to restore intact alveolar ventilation by a mechanism independent of alveolar collapse and reopening.

Exogenous surfactant and alveolar recruitment in the treatment of the acute respiratory distress syndrome

OBJECTIVE

To investigate the effect of alveolar recruitment combined with surfactant administration on children with acute respiratory distress syndrome (ARDS).

MATERIAL AND METHODS

A prospective, randomized, controlled and sequential study was carried out. Group A (16 children) was treated with both the alveolar recruitment manoeuvres (ARM) and the administration of the surfactant every 8 h for 3 days; group B (15) received the usual treatment only. The alveolar recruitment was carried out by increasing positive end-expiratory pressure 2 by 2 cm H₂ O to improve the transcutaneous oxygen saturation values up to 88% and 90%. Demographic data, gasometric and ventilator parameters, chest radiography and 28-day mortality were evaluated.

RESULTS

There were no significant differences in baseline characteristics between groups. An hour after treatment, significant differences (P < 0.001) were observed in transcutaneous oxygen saturation (SaO₂ ; Group A: 94.1%, Group B: 89.9%), PaO₂ /FiO₂ (212.7 and 126.4) and oxygenation index (OI; 11.4 and 18.5). After 8 h, the differences in SaO₂ (Group A: 94.6%, Group B: 90.3%), PaO₂ /FiO₂ (225.8 and 126.9) and OI (10.8 and 18.4) were also significant (P < 0.001). From the fifth dose of the surfactant, the static compliance (P = 0.0034) and radiological images (P = 0.002) were more greatly improved in group A than in group B. Survival was significantly higher in group A (81.3%) than in group B (26.7%) (P = 0.006).

CONCLUSIONS

The combined treatment of surfactant administration and ARM resulted in a better oxygenation and survival in children with ARDS than when only recruitment was used.

Role of extracorporeal membrane oxygenation in adult respiratory failure: an overview

Extracorporeal membrane oxygenation (ECMO) provides complete or partial support of the heart and lungs. Ever since its inception in the 1960s, it has been used across all age groups in the management of refractory respiratory failure and cardiogenic shock. While it has gained widespread acceptance in the neonatal and pediatric physician community, ECMO remains a controversial therapy for Acute Respiratory Distress Syndrome (ARDS) in adults. Its popularity was revived during the swine flu (H1N1) pandemic and advancements in technology have contributed to its increasing usage. ARDS continues to be a potentially devastating condition with significant mortality rates. Despite gaining more insights into this entity over the years, mechanical ventilation remains the only life-saving, yet potentially harmful intervention available for ARDS. ECMO shows promise in this regard by offering less dependence on mechanical ventilation, thereby potentially reducing ventilator-induced injury. However, the lack of rigorous clinical data has prevented ECMO from becoming the standard of care in the management of ARDS. Therefore, the results of two large ongoing randomized trials, which will hopefully throw more light on the role of ECMO in the management of this disease entity, are keenly awaited. In this article we will provide a basic overview of the development of ECMO, the types of ECMO, the pathogenesis of ARDS, different ventilation strategies for ARDS, the role of ECMO in ARDS and the role of ECMO as a bridge to lung transplantation.

Cardiorespiratory effects of recruitment maneuvers and positive end expiratory pressure in an experimental context of acute lung injury and pulmonary hypertension

Background

Recruitment maneuvers (RM) and positive end expiratory pressure (PEEP) are the cornerstone of the open lung strategy during ventilation, particularly during acute lung injury (ALI). However, these interventions may impact the pulmonary circulation and induce hemodynamic and respiratory effects, which in turn may be critical in case of pulmonary hypertension (PHT). We aimed to establish how ALI and PHT influence the cardiorespiratory effects of RM and PEEP.

Methods

Rabbits control or with monocrotaline-induced PHT were used. Forced oscillatory airway and tissue mechanics, effective lung volume (ELV), systemic and right ventricular hemodynamics and blood gas were assessed before and after RM, during baseline and following surfactant depletion by whole lung lavage.

Results

RM was more efficient in improving respiratory elastance and ELV in the surfactant-depleted lungs when PHT was concomitantly present. Moreover, the adverse changes in respiratory mechanics and ELV following ALI were lessened in the animals suffering from PHT.

Conclusions

During ventilation with open lung strategy, the role of PHT in conferring protection from the adverse respiratory consequences of ALI was evidenced. This finding advocates the safety of RM and PEEP in improving elastance and advancing lung reopening in the simultaneous presence of PHT and ALI.

Effect of Repeated Recruitment Manoeuvres on Patients with Severe Acute Respiratory Distress Syndrome

OBJECTIVE

The study aimed to evaluate the influence of repeated recruitment manoeuvres (RRMs) on lung injury in patients with acute respiratory distress syndrome (ARDS).

METHODS

Forty-one ventilated patients with severe ARDS were selected for this study. Recruitment manoeuvres (RMs) were conducted with continuous positive airway pressure (CPAP; 30 cm H2O for 40 seconds). Recruitment manoeuvres were repeated every two hours for all three groups. Changes in haemodynamics, pulmonary compliance, gas exchange and extravascular lung water index (EVLWI) were monitored before RM (pre-RM), 10 minutes after each RM, and four hours after RM3 (4 hours post-RRM). Pulmonary inflammatory factors (tumour necrosis factor-alpha [TNF-α] and interleukin [IL]-6 and -10) were also analysed.

RESULTS

Compared with those in pre-RM, pulmonary compliance, oxygenation index (ratio of partial pressure of arterial oxygen to fraction of inspired oxygen [PaO2/FiO2]) and EVLWI remarkably improved in RM1, RM2, RM3 and 4 hours post-RRM (p < 0.05). The PaO2/FiO2 ratio increased significantly in RM1 and RM3 (p < 0.05). Extravascular lung water index decreased significantly in RM1 compared with that in RM3 and 4 hours post-RRM (p < 0.05). There was no significant difference in cytokines.

CONCLUSION

Repeated recruitment manoeuvres during lung-protected ventilation can improve pulmonary compliance and oxygenation and significantly decrease extravascular lung water in ARDS patients. Lung injury was not worsened by RRMs in patients with severe ARDS.

Ultrashort echo time MRI of pulmonary water content: assessment in a sponge phantom at 1.5 and 3.0 Tesla

PURPOSE

We aimed to develop a predictive model for lung water content using ultrashort echo time (UTE) magnetic resonance imaging (MRI) and a sponge phantom.

MATERIALS AND METHODS

Image quality was preliminarily optimized, and the signal-to-noise ratio (SNR) of UTE was compared with that obtained from a three-dimensional fast gradient echo (FGRE) sequence. Four predetermined volumes of water (3.5, 3.0, 2.5, and 2.0 mL) were soaked in cellulose foam sponges 1.8 cm3 in size and were imaged with UTE-MRI at 1.5 and 3.0 Tesla (T). A multiple echo time experiment (range, 0.1-9.6 ms) was conducted, and the T2 signal decay curve was determined at each volume of water. A three-parameter equation was fitted to the measured signal, allowing for the calculation of proton density and T2*. The calculation error of proton density was determined as a function of echo time. The constants that allowed for the determination of unknown volumes of water from the measured proton density were calculated using linear regression.

RESULTS

UTE-MRI provided excellent image quality for the four phantoms and showed a higher SNR, compared to that of FGRE. Proton density decreased proportionally with the decreases in both lung water and field strength (from 3.5 to 2.0 mL; proton density range at 1.5 T, 30.5-17.3; at 3.0 T, 84.2-41.5). Minimum echo time less than 0.6 ms at 1.5 T and 1 ms at 3.0 T maintained calculation errors for proton density within the range of 0%-10%. The slopes of the lines for determining the unknown volumes of water with UTE-MRI were 0.12±0.003 at 1.5 T and 0.05±0.002 at 3.0 T (P < 0.0001).

CONCLUSION

In a sponge phantom imaged at 1.5 and 3.0 T, unknown volumes of water can be predicted with high accuracy using UTE-MRI.

Feasibility of titrating PEEP to minimum elastance for mechanically ventilated patients

Background

Selecting positive end-expiratory pressure (PEEP) during mechanical ventilation is important, as it can influence disease progression and outcome of acute respiratory distress syndrome (ARDS) patients. However, there are no well-established methods for optimizing PEEP selection due to the heterogeneity of ARDS. This research investigates the viability of titrating PEEP to minimum elastance for mechanically ventilated ARDS patients.

Methods

Ten mechanically ventilated ARDS patients from the Christchurch Hospital Intensive Care Unit were included in this study. Each patient underwent a stepwise PEEP recruitment manoeuvre. Airway pressure and flow data were recorded using a pneumotachometer. Patient-specific respiratory elastance (E_rs) and dynamic functional residual capacity (dFRC) at each PEEP level were calculated and compared. Optimal PEEP for each patient was identified by finding the minima of the PEEP-E_rs profile.

Results

Median E_rs and dFRC over all patients and PEEP values were 32.2 cmH₂O/l [interquartile range (IQR) 25.0–45.9] and 0.42 l [IQR 0.11–0.87]. These wide ranges reflect patient heterogeneity and variable response to PEEP. The level of PEEP associated with minimum E_rs corresponds to a high change of functional residual capacity, representing the balance between recruitment and minimizing the risk of overdistension.

Conclusions

Monitoring patient-specific E_rs can provide clinical insight to patient-specific condition and response to PEEP settings. The level of PEEP associated with minimum-E_rs can be identified for each patient using a stepwise PEEP recruitment manoeuvre. This ‘minimum elastance PEEP’ may represent a patient-specific optimal setting during mechanical ventilation.

Trial registration

Australian New Zealand Clinical Trials Registry: ACTRN12611001179921.

Electronic supplementary material

The online version of this article (doi:10.1186/s40814-015-0006-2) contains supplementary material, which is available to authorized users.

Evaluation of lung recruitment maneuvers in acute respiratory distress syndrome using computer simulation

Introduction

Direct comparison of the relative efficacy of different recruitment maneuvers (RMs) for patients with acute respiratory distress syndrome (ARDS) via clinical trials is difficult, due to the heterogeneity of patient populations and disease states, as well as a variety of practical issues. There is also significant uncertainty regarding the minimum values of positive end-expiratory pressure (PEEP) required to ensure maintenance of effective lung recruitment using RMs. We used patient-specific computational simulation to analyze how three different RMs act to improve physiological responses, and investigate how different levels of PEEP contribute to maintaining effective lung recruitment.

Methods

We conducted experiments on five ‘virtual’ ARDS patients using a computational simulator that reproduces static and dynamic features of a multivariable clinical dataset on the responses of individual ARDS patients to a range of ventilator inputs. Three recruitment maneuvers (sustained inflation (SI), maximal recruitment strategy (MRS) followed by a titrated PEEP, and prolonged recruitment maneuver (PRM)) were implemented and evaluated for a range of different pressure settings.

Results

All maneuvers demonstrated improvements in gas exchange, but the extent and duration of improvement varied significantly, as did the observed mechanism of operation. Maintaining adequate post-RM levels of PEEP was seen to be crucial in avoiding cliff-edge type re-collapse of alveolar units for all maneuvers. For all five patients, the MRS exhibited the most prolonged improvement in oxygenation, and we found that a PEEP setting of 35 cm H₂O with a fixed driving pressure of 15 cm H₂O (above PEEP) was sufficient to achieve 95% recruitment. Subsequently, we found that PEEP titrated to a value of 16 cm H₂O was able to maintain 95% recruitment in all five patients.

Conclusions

There appears to be significant scope for reducing the peak levels of PEEP originally specified in the MRS and hence to avoid exposing the lung to unnecessarily high pressures. More generally, our study highlights the huge potential of computer simulation to assist in evaluating the efficacy of different recruitment maneuvers, in understanding their modes of operation, in optimizing RMs for individual patients, and in supporting clinicians in the rational design of improved treatment strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0723-6) contains supplementary material, which is available to authorized users.

Compliance versus dead space for optimum positive end expiratory pressure determination in acute respiratory distress syndrome

Objective:

To Compare compliance versus dead space (Vd) targeted positive end-expiratory pressure (PEEP) as regard its effect on lung mechanics and oxygenation.

Materials and Methods:

This study was carried out on 30 adult acute respiratory distress syndrome patients. The ventilator was initially set on volume controlled with tidal volume (Vt) 7 mL/kg predicted body weight (PBW), inspiratory plateau pressure (Ppl) <30 cm H₂ O. If the Ppl was >30 cm H₂ O with a TV of 6 mL/kg PBW, a step-wise Vt reduction of 1 mL/kg PBW to as low as 4 mL/kg/PBW was allowed. Respiratory rate adjusted to maintain pH 7.30-7.45. FiO₂ start at 100%. Best PEEP determined at 2 points, one by titrating PEEP until reaching the highest static compliance (Cst) (PEEP Cst) and the other one is at the lowest Vd/Vt (PEEP Vd/Vt). The following data measured before and 30 min after setting PEEP Cst and PEEP Vd/Vt. Cst, PaCO₂ - PetCO₂, Vd/Vt, PaO₂ /FiO₂, Ppl, heart rate, mean arterial pressure and oxygen saturation.

Results:

optimum PEEP determined by Vd/Vt was significantly (P < 0.05) lower than the optimum PEEP determined by Cst. Best PEEP Vd/Vt showed a significant decrease (P < 0.05) in Cst, PaCO₂ - PetCO₂, Vd/Vt and Ppl in comparison with best PEEP Cst. The PaO₂ /FiO₂ showed a significant increase (P < 0.05) with best PEEP Vd/Vt in comparison with best PEEP Cst.

Conclusion:

Vd guided PEEP improved compliance and oxygenation with less Ppl. Hence, its use as a guide for best PEEP determination may be useful.

Effects of sigh during pressure control and pressure support ventilation in pulmonary and extrapulmonary mild acute lung injury

INTRODUCTION

Sigh improves oxygenation and lung mechanics during pressure control ventilation (PCV) and pressure support ventilation (PSV) in patients with acute respiratory distress syndrome. However, so far, no study has evaluated the biological impact of sigh during PCV or PSV on the lung and distal organs in experimental pulmonary (p) and extrapulmonary (exp) mild acute lung injury (ALI).

METHODS

In 48 Wistar rats, ALI was induced by Escherichia coli lipopolysaccharide either intratracheally (ALIp) or intraperitoneally (ALIexp). After 24 hours, animals were anesthetized and mechanically ventilated with PCV or PSV with a tidal volume of 6 mL/kg, FiO2 = 0.4, and PEEP = 5 cmH2O for 1 hour. Both ventilator strategies were then randomly assigned to receive periodic sighs (10 sighs/hour, Sigh) or not (non-Sigh, NS). Ventilatory and mechanical parameters, arterial blood gases, lung histology, interleukin (IL)-1β, IL-6, caspase-3, and type III procollagen (PCIII) mRNA expression in lung tissue, and number of apoptotic cells in lung, liver, and kidney specimens were analyzed.

RESULTS

In both ALI etiologies: (1) PCV-Sigh and PSV-Sigh reduced transpulmonary pressure, and (2) PSV-Sigh reduced the respiratory drive compared to PSV-NS. In ALIp: (1) PCV-Sigh and PSV-Sigh decreased alveolar collapse as well as IL-1β, IL-6, caspase-3, and PCIII expressions in lung tissue, (2) PCV-Sigh increased alveolar-capillary membrane and endothelial cell damage, and (3) abnormal myofibril with Z-disk edema was greater in PCV-NS than PSV-NS. In ALIexp: (1) PSV-Sigh reduced alveolar collapse, but led to damage to alveolar-capillary membrane, as well as type II epithelial and endothelial cells, (2) PCV-Sigh and PSV-Sigh increased IL-1β, IL-6, caspase-3, and PCIII expressions, and (3) PCV-Sigh increased the number of apoptotic cells in the lung compared to PCV-NS.

CONCLUSIONS

In these models of mild ALIp and ALIexp, sigh reduced alveolar collapse and transpulmonary pressures during both PCV and PSV; however, improved lung protection only during PSV in ALIp.

Efficacy of recruitment maneuver for improving the brain dead marginal lungs to ideal

BACKGROUND

Because of the shortage of lungs for transplantation, finding the suitable lungs in brain-dead donors is an important issue. Recruitment maneuver is a strategy aimed at re-expanding collapsed and edematous lung tissue. The aim of this study was to assess the efficacy of this maneuver on improving marginal lungs for transplantation.

METHODS

From 127 brain-dead potential donor which were evaluated for lung donation in Masih Daneshvari Organ Procurement Unit of Tehran, Iran, 31 (25%) had marginal lungs for transplantation. These donors had normal chest X ray or bilateral infiltration and had PaO2 200-300 mm Hg with FIO2 100%. The recruitment maneuver was performed and arterial blood gas was obtained before and after maneuver. The maneuver lasts for 2 hours with continuous check of O2 saturation and patient's hemodynamic during. Finally, patients with normal bronchoscopy and PaO2/FIO2 >300 mm Hg were considered good candidates for lung transplantation. The frequency (%) and mean ± SD were used for description of variables and the Wilcoxon test was used for comparison between pre- and post-maneuver PaO2 with FIO2 100%.

RESULTS

The mean ± SD of PaO2/FIO2 with 100% FIO2 of patients before and after recruitment were 239 ± 62 and 269 ± 91, respectively. Recruitment maneuver could convert 10 marginal lungs (32%) to appropriate ones (PaO2 > 300) and finally 8 lungs were transplanted.

CONCLUSIONS

Findings of this study showed that recruitment maneuver could convert inappropriate lungs to appropriate ones in one third of brain-dead patients who had marginal lung condition. So, it is recommended that this maneuver is considered in the assessment protocol of lungs for donation.

Respiratory and hemodynamic effects of a stepwise lung recruitment maneuver in pediatric ARDS: a feasibility study

BACKGROUND

Little is known about the efficacy and safety of recruitment maneuvers (RMs) in pediatric patients with acute respiratory distress syndrome (ARDS). We therefore assessed the effects on gas exchange and lung mechanics and the possible detrimental effects of a sequential lung RMs and decremental positive end-expiratory pressure (PEEP) titration in pediatric ARDS patients.

METHODS

We enrolled patients <15 years of age with ARDS, progressive hypoxemia, <72 hr of mechanical ventilation, and hemodynamic stability. A step-wise RM and decremental PEEP trial were performed. Safety was evaluated as the occurrence of hypotension and low pulse oxymeter oxygen saturation during the maneuver and development of airleaks after. Efficacy was evaluated as changes in lung compliance (Cdyn ) and gas exchange 1, 12, and 24 hr after the RM.

RESULTS

We included 25 patients, of median age 5 (1-16) months, median weight 7.0 (4.1-9.2) kg, median PaO2 /FIO2 117 (96-139), and median Cdyn 0.48 (0.41-0.68) ml/cmH2 O/kg at baseline. Thirty RM were performed, with all completed successfully. No airleaks developed. Mild hypotension was detected during four procedures. Following RM, Cdyn , and PaO2 /FIO2 increased significantly (P < 0.01 each), without changes in PaCO2 (P = 0.4). A >25% improvement in lung function (Cdyn or PaO2 /FIO2 ) was observed after 90% of the RM procedures. Gas exchange worsening over the next 24 hr resulted in HFOV use in 36% of patients, while the remaining subjects sustained improvements in oxygenation at 12 and 24 hr. The 28-day mortality rate was 16%.

CONCLUSIONS

Sequential RMs were safe and well tolerated in hemodynamically stable children with ARDS. RMs and a decremental PEEP trial may improve lung function in pediatric patients with ARDS and severe hypoxemia.

Evaluation of effects of repetitive recruitment maneuvers

Introduction:

acute respiratory failure is manifested clinically as patient with variable degrees of respiratory distress, but characteristically an abnormal arterial blood partial pressure of oxygen or carbon dioxide. The application of mechanical ventilation in this setting can be life saving.

Goals:

The aim of this study is to evaluate the effects of two recruitment maneuvers not only on oxygenation, but on aeration of the lung as well. For that purpose chest x ray and thoracic computed tomography scan (CT) of the lung were used as safe and objective methods for evaluation the impact of recruitment maneuvers on aeration of the lung. CT scan and chest x ray were performed before recruitment maneuvers as confirmation of diagnose and one day after the last recruitment maneuvers.

Material and methods:

Sixty patients who met ar DS criteria of the american european consensus conference were included in this study. This study was conducted in iCU in our hospital between november 2009 and December 2011. Patients were orally intubated, sedated with 0, 2-0, 4 μg/kg /min and midazolam 4 mg/h, and ventilated with evita 2 Dura ventilator (Dragger germany). According to the recom-mendation of the Consensus Conference of the american College of Chest physician all patients had an arterial catheter and cen-tral venous catheter. Hemodynamic data were collected from Data Ohmeda monitors. Gas analyses were mesured from blood samples taken from arteria radialis. Partial pressure of oxygen of mixed blood was messured from blood sample taken from v jugularis interior. We used arterial blood colection syringe Bd preset, and blood samples were analyzed with aVl 995HB blood gas analiser.

Results:

Hemodynamic changes: there wasn’t any differences in heart rate, and mean arterial blood pressure before the recruitment five minutes and sixty minutes after the recruitment in both groups. respiratory mechanics: Highest values of the compliance are achived during the recruitment manouver in both groups. There was better improvment in compliance during the e sigh recruitment maneouver, then in Cpap recruitment maneouver. There was improvement in chest X ray in both groups. 93,4% of patients in the Cpap group and 96,7% in e sigh group. CT scan: in Cpap group there were 8 patients with focal changes and 22 patients with diffusse changes. in e sigh group 29 patients had diffuse changes of the lung and one patient had focal changes. We noticed that there was better improvment in aeration in patients with diffuse changes of the lung 96.7% in e sigh group and 73,3% in Cpapgroup. In patient with focal changes there was improvment in 26,7% in e sigh group and 3,3% in Cpap group. We noticed that there was better improvmnet in aeration in patients with diffuse changes than in patients with focal changes. E sigh maneuver had better impact on aeration of the lung then Cpap recruitment maneuver.

Conclusion:

In our study we proved that e sigh recruitment maneuvers better improved oxygenation in arterial blood than Cpap recruitment maneuver. Repetative e sigh manouvers proved to be essential for arDS patients. They reopened collapsed alveolli and improved aeration of the lung which was confirmed by X ray and CT scan as an objective methods for verification of lung condition.

Recruitment manoeuvres in acute respiratory distress syndrome: Little evidence for routine use

The use of alveolar recruitment manoeuvres for the treatment of acute respiratory distress syndrome is a topic of uncertainty in current critical care practice. Acute respiratory distress syndrome leads to inflammatory atelectasis, which challenges the gas exchange properties of the lung. Recruitment of atelectatic lung tissue requires elevation of transpulmonary pressure. Transpulmonary pressure can be suppressed at a given airway pressure when pleural pressures are elevated. The present review discusses recruitment of lung tissue in detail, highlighting the key research in the field. Differing techniques for recruiting lung tissue, as well as various outcome measures to determine efficacy, are analyzed and critiqued. The commonly used sustained inflation manoeuvre is perhaps regarded as the only strategy to recruit the lung, explaining its prevalence. Staircase recruitment with positive end-expiratory pressure titration is shown to be an equally - if not more - effective therapy that devotes attention to the maintenance of lung recruitment.

Increased extravascular lung water reduces the efficacy of alveolar recruitment maneuver in acute respiratory distress syndrome

Introduction. In acute respiratory distress syndrome (ARDS) the recruitment maneuver (RM) is used to reexpand atelectatic areas of the lungs aiming to improve arterial oxygenation. The goal of our paper was to evaluate the response to RM, as assessed by measurements of extravascular lung water index (EVLWI) in ARDS patients. Materials and Methods. Seventeen adult ARDS patients were enrolled into a prospective study. Patients received protective ventilation. The RM was performed by applying a continuous positive airway pressure of 40 cm H₂O for 40 sec. The efficacy of the RM was assessed 5 min later. Patients were identified as responders if PaO₂/FiO₂ increased by >20% above the baseline. EVLWI was assessed by transpulmonary thermodilution before the RM, and patients were divided into groups of low EVLWI (<10 mL/kg) and high EVLWI (≥10 mL/kg). Results. EVLWI was increased in 12 patients. Following RM, PaO₂/FiO₂ increased by 33 (4–65) % in the patients with low EVLWI, whereas those in the high EVLWI group experienced a change by only −1((−13)–(+5)) % (P = 0.035). Conclusion. In ARDS, the response to a recruitment maneuver might be related to the severity of pulmonary edema. In patients with incresed EVLWI, the recruitment maneuver is less effective.