Clinical Research Directory

A Study of the Determinants of Neurological Outcomes in Patients With Acute Respiratory Distress Syndrome

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.

Personalized Ventilator Settings for Patients on ECMO

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.

EIT-Guided Ventilator Settings in AHRF

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.