Strategies to reduce ventilator-associated lung injury (VALI)

Ferroptosis plays a crucial role in lung cell damage caused by ventilation stretch

Mechanical ventilation is an essential respiratory support in acute respiratory distress syndrome and intensive care cases. However, it is possible to cause ventilator-induced lung damage (VILI). In this work, we used a microfluidic device to provide a mechanical ventilation with cyclic stretch (30% total area change rate and 15 cycles per min) and oxygen (air) flux applied by a controlled pressured airflow. Compared to static control, the ventilation stretch resulted in significant death of A549 cells accompanied by increased lipid peroxidation, mitochondrial reactive oxygen species (ROS) production, and ferrous ion accumulation, while by decreased protein expression of solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) proteins, as well as ratio of reduced-to-oxidized glutathione. The resulted A549 cell death could be alleviated by two ferroptosis inhibitors, deferoxamine and ferrostatin-1. These similar phenomena also occurred in other three types of human lung cells, such as primary alveolar type II epithelial cells, primary alveolar microvascular endothelial cells, and bronchial epithelial cell line. From the A549 RNA sequence analysis, the gene ontology (GO) based on 85 ferroptosis-related genes (FRGs) indicated that several iron homeostasis-related biological processes and molecular functions were involved in the ventilation-stretch-induced cell death, while the gene set enrichment analysis (GSEA) based on 2901 differentially expressed genes (DEGs) showed that glutathione metabolism was significantly suppressed. Finally, solute carrier family 39 member 14 (SLC39A14), a transporter of uptake extracellular divalent metal ion, was selected to be knocked down to verify its role in the ventilation-stretch-induced death of A549. Our results suggest that ferroptosis may be an alternative pathway for VILI, but it needs to be confirmed by further animal experiments and clinical data.

Guidelines on the management of acute respiratory distress syndrome

The Faculty of Intensive Care Medicine and Intensive Care Society Guideline Development Group have used GRADE methodology to make the following recommendations for the management of adult patients with acute respiratory distress syndrome (ARDS). The British Thoracic Society supports the recommendations in this guideline. Where mechanical ventilation is required, the use of low tidal volumes (<6 ml/kg ideal body weight) and airway pressures (plateau pressure <30 cmH2O) was recommended. For patients with moderate/severe ARDS (PF ratio<20 kPa), prone positioning was recommended for at least 12 hours per day. By contrast, high frequency oscillation was not recommended and it was suggested that inhaled nitric oxide is not used. The use of a conservative fluid management strategy was suggested for all patients, whereas mechanical ventilation with high positive end-expiratory pressure and the use of the neuromuscular blocking agent cisatracurium for 48 hours was suggested for patients with ARDS with ratio of arterial oxygen partial pressure to fractional inspired oxygen (PF) ratios less than or equal to 27 and 20 kPa, respectively. Extracorporeal membrane oxygenation was suggested as an adjunct to protective mechanical ventilation for patients with very severe ARDS. In the absence of adequate evidence, research recommendations were made for the use of corticosteroids and extracorporeal carbon dioxide removal.

The abbreviated burn severity index as a predictor of acute respiratory distress syndrome in young individuals with severe flammable starch-based powder burn

Here, we investigated whether the abbreviated burn severity index (ABSI) scoring system predicts acute respiratory distress syndrome (ARDS) in a retrospective analysis of a severe flammable starch-based powder burn population. Demographics, total body surface area (TBSA) burn, the presence of mouth and nose burn, ABSI, inhalation injury, and clinical outcomes for each patient were analysed for association with inpatient ARDS based on the Berlin definition. We treated 53 patients (64% male, 36% female) and observed no fatalities. The median age, TBSA burn, and the ABSI were 22.2±3.6, 42.2±21, and 7.8±2.8, respectively. Inhalation injury was present in 56.6% of the cases, and mouth and nose burn was present in 30.2%. ARDS was prevalent at 30%. The mean abbreviated burn severity index (ABSI) was 10.6±1.5 in the ARDS group and 6.6±2.3 in the non-ARDS (P<0.001) group. The mean TBSA burn percentage for ARDS and the non-ARDS groups were 61.4±13.9% and 34±18%, respectively (P<0.001). The area under the curve of the receiver operating characteristic curves for an ABSI≥9 was 0.905. Our results show that the ABSI is effective for predicting ARDS in young individuals with severe starch-based powder burn.

Acute respiratory distress syndrome

Acute respiratory distress syndrome is a common cause of acute respiratory failure that is underdiagnosed both inside and outside of intensive care units. Progression to the most severe forms of the syndrome confers a mortality rate greater than 40% and is associated with often severe functional disability and psychological sequelae in survivors. While there are no disease-modifying pharmacotherapies for the syndrome, this progression may be prevented through the institution of quality improvement measures that minimise iatrogenic injury associated with acute severe illness.

Update on traumatic acute spinal cord injury. Part 2

The aim of treatment in acute traumatic spinal cord injury is to preserve residual neurologic function, avoid secondary injury, and restore spinal alignment and stability. In this second part of the review, we describe the management of spinal cord injury focusing on issues related to short-term respiratory management, where the preservation of diaphragmatic function is a priority, with prediction of the duration of mechanical ventilation and the need for tracheostomy. Surgical assessment of spinal injuries based on updated criteria is discussed, taking into account that although the type of intervention depends on the surgical team, nowadays treatment should afford early spinal decompression and stabilization. Within a comprehensive strategy in spinal cord injury, it is essential to identify and properly treat patient anxiety and pain associated to spinal cord injury, as well as to prevent and ensure the early diagnosis of complications secondary to spinal cord injury (thromboembolic disease, gastrointestinal and urinary disorders, pressure ulcers).

Acute respiratory distress syndrome

Acute respiratory distress syndrome is a common cause of acute respiratory failure that is underdiagnosed both inside and outside of intensive care units. Progression to the most severe forms of the syndrome confers a mortality rate greater than 40% and is associated with often severe functional disability and psychological sequelae in survivors. While there are no disease-modifying pharmacotherapies for the syndrome, this progression may be prevented through the institution of quality improvement measures that minimise iatrogenic injury associated with acute severe illness.

Efficacy of a Low-Tidal Volume Ventilation Strategy to Prevent Reperfusion Lung Injury after Pulmonary Thromboendarterectomy

RATIONALE

Reperfusion lung injury is a postoperative complication of pulmonary thromboendarterectomy that can significantly affect morbidity and mortality. Studies in other postoperative patient populations have demonstrated a reduction in acute lung injury with the use of a low-tidal volume (Vt) ventilation strategy. Whether this approach benefits patients undergoing thromboendarterectomy is unknown.

OBJECTIVES

We sought to determine if low-Vt ventilation reduces reperfusion lung injury in patients with chronic thromboembolic pulmonary hypertension undergoing thromboendarterectomy.

METHODS

Patients undergoing thromboendarterectomy at one center were randomized to receive either low (6 ml/kg predicted body weight) or usual care Vts (10 ml/kg) from the initiation of mechanical ventilation in the operating room through Postoperative Day 3. The primary endpoint was the onset of reperfusion lung injury. Secondary outcomes included severity of hypoxemia, days on mechanical ventilation, and intensive care unit and hospital lengths of stay.

MEASUREMENTS AND MAIN RESULTS

A total of 128 patients were enrolled and included in the analysis; 63 were randomized to the low-Vt group and 65 were randomized to the usual care group. There was no statistically significant difference in the incidence of reperfusion lung injury between groups (32%, n=20 in the low-Vt group vs. 23%, n=15 in the usual care group; P=0.367). Although differences were noted in plateau pressures (17.9 cm H2O vs. 20.1 cm H2O, P<0.001) and peak inspiratory pressures (20.4 cm H2O vs. 23.0 cm H2O, P<0.001) between the low-Vt and usual care groups, respectively, mean airway pressures, PaO2/FiO2, days on mechanical ventilation, and ICU and hospital lengths of stay were all similar between groups.

CONCLUSIONS

In patients with chronic thromboembolic pulmonary hypertension undergoing pulmonary thromboendarterectomy, intra- and postoperative ventilation using low Vts (6 mg/kg) compared with usual care Vts (10 mg/kg) does not reduce the incidence of reperfusion lung injury or improve clinical outcomes. Clinical trial registered with www.clinicaltrials.gov (NCT00747045).

Bronchoconstriction and airway biology: potential impact and therapeutic opportunities

Recent work has demonstrated that mechanical forces occurring in the airway as a consequence of bronchoconstriction are sufficient to not only induce symptoms but also influence airway biology. Animal and human in vitro and in vivo work demonstrates that the airways are structurally and functionally altered by mechanical stress induced by bronchoconstriction. Compression of the airway epithelium and mechanosensing by the airway smooth muscle trigger the activation and release of growth factors, causing cell proliferation, extracellular matrix protein accumulation, and goblet cell differentiation. These effects of bronchoconstriction are of major importance to asthma pathophysiology and appear sufficient to induce remodeling independent of the inflammatory response. We review these findings in detail and discuss previous studies in light of this new evidence regarding the influence of mechanical forces in the airways. Furthermore, we highlight potential impacts of therapies influencing mechanical forces on airway structure and function in asthma.

Redox Changes Induced by General Anesthesia in Critically Ill Patients with Multiple Traumas

The critically ill polytrauma patient is a constant challenge for the trauma team due to the complexity of the complications presented. Intense inflammatory response and infections, as well as multiple organ dysfunctions, significantly increase the rate of morbidity and mortality in these patients. Moreover, due to the physiological and biochemical imbalances present in this type of patients, the bioproduction of free radicals is significantly accelerated, thus installing the oxidative stress. In the therapeutic management of such patients, multiple surgical interventions are required and therefore they are being subjected to repeated general anesthesia. In this paper, we want to present the pathophysiological implications of oxidative stress in critically ill patients with multiple traumas and the implications of general anesthesia on the redox mechanisms of the cell. We also want to summarize the antioxidant treatments able to reduce the intensity of oxidative stress by modulating the biochemical activity of some cellular mechanisms.

Comparison of the Berlin definition with the American European consensus definition for acute respiratory distress syndrome in burn patients

OBJECTIVE

Acute respiratory distress syndrome (ARDS) is a leading cause of mortality in burn patients. Smoke inhalation, pneumonia and inflammation process are the major causes of ARDS in burn patients. The American European Consensus Conference (AECC) definition proposed in 1994 has recently been revised by the Berlin definition. Our objective was to describe the epidemiology of ARDS comparing the Berlin definition with the AECC definition in a retrospective cohort of burn patients.

METHODS

We reviewed admitted burn adult patients for a two year period, and investigated patient who received mechanical ventilation for more than 48 h and in whom pneumonia was diagnosed.

RESULTS

40 patients were analyzed. According to the AECC definition, 11 patients met criteria for ALI (27.5%), and 29 patients for ARDS (72.5%). According to the Berlin definition, all patients met criteria for ARDS: 4 (10%) for a severe ARDS, 25 (62.5%) for a moderate ARDS, 11 (27.5%) for a mild ARDS. Inhalation injury was diagnosed in 10 patients (25%). Categorizing patients with the Berlin definition showed statistically significative difference of mortality within the three groups, but not with the AECC definition.

CONCLUSION

The Berlin definition seems to be more accurate than the AECC definition to assess the severity of ARDS in term of outcome in burn patients. This definition may facilitate prompt recognition of ARDS in burn patients, and promote protective ventilation strategy to a larger number of patients.

Respiratory management in the patient with spinal cord injury

Spinal cord injuries (SCIs) often lead to impairment of the respiratory system and, consequently, restrictive respiratory changes. Paresis or paralysis of the respiratory muscles can lead to respiratory insufficiency, which is dependent on the level and completeness of the injury. Respiratory complications include hypoventilation, a reduction in surfactant production, mucus plugging, atelectasis, and pneumonia. Vital capacity (VC) is an indicator of overall pulmonary function; patients with severely impaired VC may require assisted ventilation. It is best to proceed with intubation under controlled circumstances rather than waiting until the condition becomes an emergency. Mechanical ventilation can adversely affect the structure and function of the diaphragm. Early tracheostomy following short orotracheal intubation is probably beneficial in selected patients. Weaning should start as soon as possible, and the best modality is progressive ventilator-free breathing (PVFB). Appropriate candidates can sometimes be freed from mechanical ventilation by electrical stimulation. Respiratory muscle training regimens may improve patients' inspiratory function following a SCI.