Ventilator Induced Lung Injury

This study investigates how different breathing machine (ventilator) settings affect the energy delivered to the lungs during surgery. Mechanical power is a measure of this energy, and high levels can sometimes lead to lung irritation. In clinical practice, a mode called Pressure-Regulated Volume Control (PRVC) is often used because it lowers the "peak" pressure in the airways, which is generally thought to be safer. However, doctors have noticed that even though the peak pressure goes down in PRVC mode, the total mechanical power displayed on the monitor might actually increase compared to the standard Volume-Controlled Ventilation (VCV) mode. In this study, patients undergoing gallbladder surgery will be monitored using both ventilation modes in a random order. The researchers will compare the machine-calculated mechanical power for both modes to see if the perceived benefit of lower peak pressure in PRVC actually results in lower overall energy transfer to the lungs.

While mechanical ventilation can be used to sustain life in those with lung injury, it, can further worsen lung injury or prevent lung healing resulting in high morbidity and mortality as seen in Acute Respiratory Distress Syndrome (ARDS). Using extracorporeal membrane oxygenation (ECMO), the highest level of life support also known as the heart-lung machine, investigators may minimize injury from mechanical ventilation to allow the lungs to heal; however, the optimal ventilator strategies while on ECMO are unknown. This study will evaluate personalized ventilator strategy compared to standard of care ventilation.

Acute respiratory distress syndrome (ARDS) is characterized by pathological pulmonary edema caused by direct or indirect damage to the alveolar-capillary membrane. Its management relies on etiological treatment, invasive mechanical ventilation, and the use of sedatives and neuromuscular blockers, depending on the patient's condition. Improvements in patient care have led to an improved prognosis. However, in-hospital mortality remains high (between 35% and 45%). Notably, morbidity among surviving patients is very high and is largely dominated by neuropsychological sequelae. Attention and executive function disorders, confusion, disorientation, or memory impairment are thus found in 70 to 100% of patients following ARDS. These disorders are still present in 46 to 80% of surviving patients one year after ARDS and in 20% of them five years later. Although essential to treatment, mechanical ventilation carries a risk of significant complications. Beyond the risk of infection and complications related to sedation and neuromuscular blockade, the use of mechanical ventilation is associated with a risk of ventilator-induced lung injury (VILI). The use of so-called protective ventilation reduces the risk of VILI and improves patient outcomes. However, analysis of relevant physiological parameters shows that the risk of VILI may still exist even when ventilator settings comply with recommendations and the concept of protective ventilation. Driving pressure (which represents Strain) is a good marker of VILI; it represents the distension of the lung with each breath relative to the initial lung volume. Values above 14 cmH₂O are associated with high mortality in patients with ARDS. Inspiratory transpulmonary pressure represents Stress-that is, the pressure that distends the alveoli at the end of inspiration-and is also associated with the risk of VILI. Finally, mechanical power represents the amount of energy delivered to the lung by the ventilator and has been validated as a marker of VILI. The advantage of mechanical power over the other indices described is that it incorporates all components that can lead to VILI. Among the various sources of neurological damage during ARDS, inflammatory processes appear to play a major role. Numerous inflammatory mediators (TNF-α, IL-6, IL-8, IL-1β) are secreted during ARDS, and animal studies have demonstrated a link between inflammation and hippocampal damage. Furthermore, cerebral ischemic lesions, exacerbated by systemic inflammation and endothelial activation leading to coagulation activation with thrombus formation, may also contribute to the development of cognitive impairments. In addition to the inflammatory processes associated with ARDS, mechanical ventilation itself may have a significant impact on neuroinflammatory damage. Recently, the term "ventilator-associated brain injury" (VABI) has been proposed to describe these secondary neurological lesions induced by mechanical ventilation. Studies in mouse and pig models have demonstrated a relationship between the dose and duration of VILI, apoptosis, neuroinflammation, and neuronal damage. An animal study in mice also showed an association between the duration of mechanical ventilation and the onset of cognitive impairments. During brain injury, proteins and neurotransmitters are released and serve as biomarkers of brain damage. Elevated plasma levels of S100B protein indicate astrocyte damage caused by traumatic, anoxic-ischemic, or inflammatory mechanisms. It correlates with neurological prognosis following cardiac arrest, in ischemic or hemorrhagic strokes, in neurodegenerative diseases, and in patients with traumatic brain injury. Clinical studies have shown a negative correlation between elevated S100B protein levels, the MoCA (Montreal Cognitive Assessment) score, and the MMSE (Mini-mental state evaluation ) in patients with OSA (Obstructive Sleep Apnea) or COPD (chronic obstructive pulmonary disease), respectively, indicating an association between this protein and cognitive impairment. The investigators therefore hypothesize that mechanical ventilation associated with high mechanical power is linked to a significant risk of brain injury, reflected by elevated serum S100B protein levels and the presence of neurocognitive disorders long after ARDS.

Acute respiratory distress syndrome is characterized by heterogeneous lung injury, with dependent regions often collapsed and non-dependent regions relatively well-aerated, forming the so called "baby lung." Mechanical ventilation, while essential, can induce additional lung injury (VILI) via overdistension (baro/volutrauma) or repetitive alveolar collapse (atelectrauma). Protective ventilation strategies with low tidal volumes (VT 6-8 mL/kg predicted body weight, PBW) reduce mortality, but their efficacy relies on accurate PBW estimation, which is derived from patient height. In critical care, height measurement is often challenging, and common methods such as visual estimation or tape measurement can be inaccurate, leading to inappropriate VT settings and increased risk of lung stress and VILI. Alternative methods, including heel-to-knee distance and laser measurement, may offer more precise PBW estimation, yet their impact on lung mechanics in ARDS remains unexplored. This study addresses the knowledge gap by evaluating whether differences in height measurement methods significantly affect lung stress, tidal volume distribution, and ventilatory mechanics in ARDS patients. Patients' heights will be measured using five methods (stadiometer, visual, tape, laser, heel-to knee). Corresponding PBW and tidal volumes (VT = 6 mL/kg PBW) will be calculated and applied in randomized order, each for 30 minutes. Lung stress, ventilatory mechanics, gas exchange, and regional ventilation distribution will be assessed for each VT setting, preceded by a short alveolar recruitment maneuver. During the study, continuous monitoring of hemodynamics and oxygenation will be performed. Ventilatory parameters including plateau pressure, driving pressure, and transpulmonary pressures will be recorded. Electrical impedance tomography will assess regional tidal volume distribution. Each patient's participation is limited to approximately two hours with no further follow-up.

Previous clinical trials in adults with acute respiratory distress syndrome (ARDS) have demonstrated that ventilator management choices can improve Intensive Care Unit (ICU) mortality and shorten time on mechanical ventilation. This study seeks to scale an established Clinical Decision Support (CDS) tool to facilitate dissemination and implementation of evidence-based research in mechanical ventilation of infants and children with pediatric ARDS (PARDS). This will be accomplished by using CDS tools developed and deployed in Children's Hospital Los Angeles (CHLA) which are based on the best available pediatric evidence, and are currently being used in an NHLBI funded single center randomized controlled trial (NCT03266016, PI: Khemani). Without CDS, there is significant variability in ventilator management of PARDS patients both between and within Pediatric ICUs (PICUs), but clinicians are willing to accept CDS recommendations. The CDS tool will be deployed in multiple PICUs, targeting enrollment of up to 180 children with PARDS. Study hypotheses: 1. The CDS tool in will be implementable in nearly all participating sites 2. There will be \> 80% compliance with CDS recommendations and 3. The investigators can implement automatic data capture and entry in many of the ICUs Once feasibility of this CDS tool is demonstrated, a multi-center validation study will be designed, which seeks to determine whether the CDS can result in a significant reduction in length of mechanical ventilation (LMV).

Background: In patients with acute hypoxemic respiratory failure or ARDS, mechanical ventilation is often required. Two common strategies are pressure support ventilation (PSV), which allows spontaneous breathing, and volume-controlled ventilation (VCV), which delivers fixed tidal volumes. Although PSV can improve comfort, strong inspiratory efforts may cause excessive lung inflation and increase the risk of ventilator-induced lung injury (VILI). In contrast, VCV with muscle paralysis ensures full control over tidal volume and driving pressure, potentially offering better lung protection. Hypothesis: The study will help determine whether a controlled ventilation strategy - with or without volume adjustments and with or without muscle paralysis - provides superior lung protection compared to PSV in hypoxemic patients with intense inspiratory effort. Methods: This prospective physiological study will be performed in the ICU of Fondazione Policlinico Universitario A. Gemelli (Rome, Italy) and will include 20 moderate to severe ARDS patients. Each patient will undergo four 30-minute ventilation phases: PSV with clinical PEEP; VCV at 6 ml/kg predicted body weight (PBW); VCV with muscle paralysis and Vt equal to PSV; VCV with muscle paralysis and Vt adjusted to keep driving pressure ≤14 cmH₂O. During each phase, data on gas exchange, respiratory mechanics, inspiratory effort, and regional ventilation (via electrical impedance tomography) will be collected. Endpoints: Primary: Regional tidal volume distribution during VCV vs. PSV. Secondary: Transpulmonary driving pressure, dorsal ventilation fraction, and pendelluft occurrence. Expected Impact: By comparing assisted and controlled ventilation under different conditions, the study aims to clarify which strategy better balances patient comfort, effective ventilation, and lung protection in ARDS patients with high respiratory drive.

The Inspiratory effort-Targeted Pressure Support Ventilation (IT-PSV) is a cluster randomized controlled trial. Its main aim is to determine whether an inspiratory effort-targeted pressure support setting strategy, compared to the traditional tidal volume and respiratory rate target, can improve clinical outcomes in adult participants undergoing pressure support ventilation. The investigators propose a physiological-oriented assisted ventilation management that, if found effective, could potentially change the clinical practice for mechanical ventilation.

Perioperative respiratory complications are a major source of morbidity and mortality. Postoperative atelectasis plays a central role in their development. Protective "open lung" mechanical ventilation aims to minimize the occurrence of atelectasis during the perioperative period. Randomized controlled studies have been performed comparing various "open lung" ventilation protocols, but these studies report varying and conflicting effects. The interpretation of these studies is complicated by the absence of imagery supporting the pulmonary impact associated with the use of different ventilation strategies. Imaging studies suggest that the gain in pulmonary gas content in "open lung" ventilation regimens disappears within minutes after the extubation. Thus, the potential benefits of open-lung ventilation appear to be lost if, at the time of extubation, no measures are used to keep the lungs well aerated. Recent expert recommendations on good mechanical ventilation practices in the operating room conclude that there is actually no quality study on extubation. Extubation is a very common practice for anesthesiologists as part of their daily clinical practice. It is therefore imperative to generate evidence on good clinical practice during anesthetic emergence in order to potentially identify an effective extubation strategy to reduce postoperative pulmonary complications.

The primary objective of the study is to create a small dataset of regional pulmonary strain values in patients suffering from pulmonary diseases under mechanical ventilation in an intensive care setting. Hypothesis: The analysis of lung ultrasonographic sequences using speckle-tracking allows the determination of local pleural strain in 4 predetermined pulmonary areas in mechanically ventilated patients suffering from pulmonary diseases.

Protective ventilatory strategy should be applied to reduce ventilator-induced lung injury (VILI) after Lung Transplantation (LTx) or in case of acute respiratory failure requiring invasive mechanical ventilation. Neurally Adjusted Ventilatory Assist (NAVA) is an assisted ventilation mode in which respiratory support is coordinated by the electrical activity of the diaphragm (EAdi). Aim of the study is to assess the physiological relationship between neural respiratory drive, as assessed by EAdi, and tidal volume, driving pressure, and mechanical power, at different levels of ventilatory assist, in the absence of pulmonary vagal afferent feedback or during acute respiratory failure. Additional parameters will be collected: Pmus, Pocc, transpulmonary pressure etc.

Critically ill patients who (1) are not able to maintain their airway, (2) cannot breathe on their own, or (3) both, are ones who often require tracheal intubation and support from a breathing machine (mechanical ventilator). When the patient is ready to be liberated from the mechanical ventilator because the initial insult for intubation has been resolved, the patient is screened using the readiness to wean test in preparation for extubation. As the patient passes this screening, a spontaneous breathing test (SBT) is initiated. Currently, there are many debates surrounding which SBT technique is most favorable. At Toronto General Hospital, the clinical team uses a zero-end expiratory pressure (ZEEP) trial. Once the patient successfully passes their SBT they are then extubated. The patient will undergo a spontaneous breathing trial of continuous positive airway pressure (CPAP) of 5 cmH2O and ZEEP, in which time the investigators will be using a new technology called electrical impedance tomography (EIT), to study and compare the end expiratory lung volume (EELV); investigators will use an esophageal catheter to measure and monitor pressures in the lung, and also assess the patient's work of breathing. This will be repeated once the patient has been extubated safely.

This multicenter, prospective, observational study aims to develop and validate an EIT-based prognostic model for ARDS. By focusing on the pathophysiological characteristics of ARDS and the causes of ventilator-induced lung injury, the investigators intend to establish a prognostic model that reveals lung injury and heterogeneity, enabling risk stratification and guiding individualized treatment.

This exploratory study aims to investigate the effect of Electrical Impedance Tomography (EIT)-guided ventilator settings on mechanical power in patients with acute hypoxemic respiratory failure (AHRF), including both ARDS and non-ARDS conditions. Mechanical power, a key factor associated with ventilator-induced lung injury (VILI), will be measured before and after EIT-guided PEEP titration. The study will evaluate feasibility and changes in lung mechanics, gas exchange, and EIT parameters. A total of 17 patients requiring invasive mechanical ventilation will be enrolled at Siriraj Hospital, Mahidol University.

Little is known about how lung mechanics are affected during the very early phase after starting mechanical ventilation. Since the conventional method of measuring esophageal pressure is complicated, hard to interpret and expensive, there are no studies on lung mechanics on intensive care patients directly after intubation, during the first hours of ventilator treatment and forward until the ventilator treatment is withdrawn. Published studies have collected data using the standard methods from day 1 to 3 of ventilator treatment for respiratory system mechanics, i.e. the combined mechanics of lung and chest wall. Consequently, information on lung mechanical properties during the first critical hours of ventilator treatment is missing and individualization of ventilator care done on the basis of respiratory system mechanics, which are not representative of lung mechanics on an individual patient basis. We have developed a PEEP-step method based on a change of PEEP up and down in one or two steps, where the change in end-expiratory lung volume ΔEELV) is determined and lung compliance calculated as ΔEELV divided by ΔPEEP (CL = ΔEELV/ΔPEEP). This simple non-invasive method for separating lung and chest wall mechanics provides an opportunity to enhance the knowledge of lung compliance and the transpulmonary pressure. After the two-PEEP-step procedure, the PEEP level where transpulmonary driving pressure is lowest can be calculated for any chosen tidal volume. The aim of the present study in the ICU is to survey lung mechanics from start of mechanical ventilation until extubation and to determine PEEP level with lowest (least injurious) transpulmonary driving pressure during ventilator treatment. The aim of the study during anesthesia in the OR, is to survey lung mechanics in lung healthy and identify patients with lung conditions before anesthesia, which may have an increased risk of postoperative complications.

The Continuous Tracheal Gas Insufflation (CTGI) is a ventilation option of conventional mechanical ventilation that is used to reduce or even eliminate the dead space caused by respiratory prostheses. This objective is of particular interest in the smallest preterm infants, where the volume of anatomical dead space due to prostheses is little different from the tidal volume. The principle of this option is to continuously blow an additional flow of 0.2 L/minute at the tip of the endotracheal tube to purge expired CO2 trapped in the prostheses, to have a CO2-free volume of gas available for subsequent insufflation. The goal of this clinical trial is to learn if Continuous Tracheal Gas Insufflation (CTGI) works to reduce ventilatory dependence in preterm infants after mechanical ventilation. It will also learn about the safety of CTGI. The main questions it aims to answer are: * Does Continuous Tracheal Gas Insufflation (CTGI) reduce the number of days of non-invasive ventilation in extremely preterm infants who needed mechanical ventilation? * Does Continuous Tracheal Gas Insufflation (CTGI) reduce the age at the weaning of any ventilatory support and/or oxygen supplementation. Researchers will compare the clinical outcome of patients mechanically ventilated with the CTGI-device to the outcome of patients ventilated without the CTGI device, to see if the CTGI ventilation works to reduce ventilation dependence. Participants will: • Be mechanically ventilated using CTGI (if randomly assigned in the CTGI-group), for the entire endotracheal ventilation period during their stay in the neonatal intensive care unit.

Reduced diaphragmatic activity during mechanical ventilation can lead to diaphragmatic disuse atrophy, atelectasis, increased lung stress and strain, and hemodynamic impairment. This, in turn, may prolong the duration of mechanical ventilation, make weaning more difficult, and even increase mortality. Synchronizing phrenic nerve stimulation to promote diaphragmatic activity may prevent ventilator-induced lung injury and ventilator-induced diaphragm dysfunction, thereby improving patient outcomes. Surgically implanted phrenic nerve stimulation has been used in certain neurological disorders, but the effects of percutaneous non-invasive synchronized phrenic nerve stimulation in patients with ARDS undergoing mechanical ventilation remain unclear and require further investigation.

1. We collect lung tissues from patients with different ages and confirm that KLK8 expression is positively correlated with age. 2. We collect peripheral blood from patients with different ages and duration of mechanical ventilation to explore the correlation between the degree of endothelial/epithelial damage, age and duration of mechanical ventilation.