This study will look at a protein called Interleukin (IL)-17A and how it relates to health markers in patients with a serious lung condition known as Acute Respiratory Distress Syndrome (ARDS). IL-17A is part of the immune system and helps the body fight infections, but too much of it can lead to inflammation, which can be harmful.

The researchers want to find out if the levels of IL-17A in the blood are connected to important health outcomes for patients, such as whether they survive in the Intensive Care Unit (ICU), after 30 days, and after 60 days. They will also check how long patients can stay off a ventilator and how many days they need to use a mechanical ventilator. A ventilator is a machine that helps people breathe when their lungs are not working well.

In addition to the main goal, the researchers will study how IL-17A relates to a severe form of ARDS called the hyperinflammatory sub-phenotype. They will also look at how IL-17A connects with other health markers, including IL-6, soluble tumor necrosis factor receptor (sTNFR), IL8, Tumor Necrosis Factor (TNF)a, IL1beta, and IL23. These markers can give information about inflammation and how the body is responding to illness.

To compare results, the researchers will include a control group of patients who had Acute Respiratory Failure (ARF) but did not have ARDS. This control group will help them understand the differences between the two conditions.

This research will use data from the FROG-ICU Registry, which gathers information on patients in intensive care units across Europe. The registry tracks patients' health after they leave the ICU, focusing on the risk factors for death in the year following their discharge. The data comes from 28 different ICUs in 19 hospitals.

The researchers will create two groups of patients based on their diagnoses: one group with ARDS and another with ARF. By studying these groups, they hope to learn more about the role of IL-17A in ARDS and its potential impact on patient outcomes.

Inclusion Criteria:

• invasive mechanical ventilation support for at least 24 h and/or treatment with a positive inotropic agent (except dopamine) for more than 24 h

• ARDS patients:

  o Diagnosis of ARDS at the time of study inclusion and within 24-48 hours of bio sample collection

• ARF patients o Diagnosis of Acute respiratory Failure (ARF) who do not have sepsis at the time of study inclusion and within 24-48 hours of bio sample collection

Exclusion Criteria:

o Patients with ARF who later develop ARDS after the 24-48 hour bio sample draw time period will be excluded as they will not have had baseline bio samples drawn in relation to onset of ARDS.

• Patients less than 18 years old
• severe head injury (initial Glasgow Coma Scale < 8) or brain death or a persistent vegetative state
• pregnancy or breastfeeding
• transplantation in the past 12 months; not expected to survive or to leave the hospital
• no social security coverage

Using the data from FROG ICU registry, we will create two cohorts of patients using diagnosis codes:

Acute Respiratory Distress Syndrome (ARDS) Acute Respiratory Failure (ARF) The FROG ICU registry is a completed, prospective, observational, multicenter cohort study, designed to assess the incidence and to identify the risk factors of all-cause mortality during the year following discharge from the ICU. Our study will retrospectively analyze this prospectively collected data.

The evaluation of each patient is performed through a comprehensive clinical assessment, instrumental tests (electrocardiogram, echocardiogram) and biological parameters. All the data are collected at admission, during the stay as well as at discharge and in addition these patients are followed up for long-term outcomes after ICU discharge. This allows us to evaluate the effect of different biomarkers as well as level of care in the ICU on long-term outcomes.

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