Regional Assessment of the Risk of Lung Injury in Ventilated Patients

Regional Assessment of the Risk of Lung Injury in Ventilated Patients With Similar Lung Load

Specific characteristics of the lung, such as its functional capacity, heterogeneity, and recruitment potential, can influence the development of ventilator-induced lung injury even under safe ventilation conditions. Objective: To evaluate the risk of ventilator-induced lung injury at the regional level in patients with acute respiratory distress syndrome ventilated with similar tidal volumes and inspiratory pressures.

Mechanical ventilation constitutes a crucial resource serving as a bridge to pulmonary recovery in acute respiratory distress syndrome. However, like any medical intervention, it carries risks of adverse effects, both at the pulmonary and systemic levels. Mechanisms involved in the development of ventilator-induced lung injury include excessive stretching and deformation of lung tissues (stress/strain), cyclic opening and closing of alveoli causing shear stress (atelectrauma injury), and the resulting biological response to tissue damage (biotrauma).

To prevent and/or minimize the risk of ventilator-induced lung injury, monitoring of ventilatory mechanics seeks to understand the effects of the ventilatory cycle on the diseased lung. Factors such as tidal volume, plateau pressure, driving pressure, inspiratory flow, respiratory rate, excessive inspiratory effort, and occasionally positive end-expiratory pressure have been directly associated with the mechanism of damage. From an integrative perspective, the concept of mechanical power seeks to encompass most of these factors within a measurable unit thus expressing the energy repeatedly applied to the respiratory system over a unit of time. Mechanical power provides a more comprehensive view of the burden imposed on the lung and can assist in the identification and management of potential risks associated with mechanical ventilation.

However, mechanical power is not the only factor involved in the development of VILI, as factors such as the duration of mechanical ventilation and the conditions specific to the diseased lung also play a role.ventilator-induced lung injury results from the relationship between the load imposed by the ventilator and the inability of the lung parenchyma to tolerate it. Factors such as reduced lung functional capacity, heterogeneity of aeration loss, and instability of collapsed alveoli, among others, can modulate the lung's tolerance to mechanical injury and influence the development of ventilator-induced lung injury . Finally, different regional lung conditions may give rise to the coexistence of different injury mechanisms in the same lung.

Objective: To evaluate different mechanisms of ventilator-induced lung injury at the regional level in patients with acute respiratory distress syndrome ventilated in the supine position with similar lung load.

Inclusion Criteria: ARDS patients

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Exclusion Criteria:Patients with any of the following criteria were excluded:

• History of emphysema, asthma, pneumothorax, or active bronchopulmonary fistula.
• Severe instability at the time of the study defined by at least one of the following indicators: SaO2 ≤ 90%, shock requiring > 0.5 γ/kg/min of noradrenaline, complex arrhythmia, myocardial ischemia, intracranial hypertension refractory despite first-line measures.
• Esophageal pathology contraindicating esophageal balloon placement (esophageal varices, stenosis, trauma or esophageal surgery, tumor) and/or hematemesis.
• Severe coagulopathy (platelet count <20,000/mm3 or INR >4.
• Inability to undergo computed tomography: morbid obesity (>170 kg) or abdominal circumference >200 cm.
• Patients with do-not-resuscitate orders and pregnant women.
• Participation in another research study in the last 30 days.