Analysis of kinetics of phosphatidylcholine and specific surfactant proteins, total body water and water turnover in patients with acute respiratory distress syndrome (ARDS) and in intensive care unit (ICU) patients by using non radioactive isotopes as deuterium and Carbon-13.

Patients with adult respiratory distress syndrome (ARDS) have low concentrations of disaturated-phosphatidylcholine and surfactant protein-B and C in bronchoalveolar lavage fluid and altered fluid metabolism.

Injection of stable isotopes such as 13 Carbon Leucine and deuterated water allows the analysis of disaturated-phosphatidylcholine and surfactant protein-B and C kinetics, total body water and water turnover in patients with ARDS and in human adults with normal lungs (controls).

Inclusion Criteria:

Inclusion criteria were:

• adult patients older than 18 years
• expected intensive care unit (ICU) length of stay greater than 120 hours from the onset of acute respiratory failure, defined according to the acute respiratory syndrome (ARDS) Berlin criteria or patients admitted for acute neurological failure defined as Glasgow coma scale < 8.
• All patients with ARDS also had sepsis syndrome or septic shock according to the surviving sepsis campaign criteria at the admission to the ICU, while no patients with acute neurological failure was septic.

At the start of the study, patients with ARDS/sepsis fulfilled also the following criteria:

• start of the study within 72 hours from the onset of the respiratory failure;
• stable hemodynamic conditions, defined as no need of fluid boluses for at least 6 hours before the start of the study;
• serum urea and creatinine within the normal ranges.

Patients with acute neurological failure fulfilled the following inclusion criteria:

• normal chest radiograph;
• arterial partial pressure of oxygen / fraction of inspired oxygen (PaO2/FiO2) >300;
• no evidence of sepsis, according to body temperature, C reactive protein, white cell count and differential count within normal ranges;
• intubation and mechanical ventilation started within 72 h before the beginning of the study.

Exclusion Criteria:

Exclusion criteria for all study subjects were:

• presence of liver failure or renal failure (transaminases > 3 and creatinine > 2 times the normal values),
• burns > 30% of body surface bone marrow or lung transplantation,
• need of fluid boluses to maintain hemodynamic conditions during the study or extracorporeal circulatory support.