Lung Surfactant Deficiency in Severe Respiratory Failure: A Potential Biomarker for Clinical Assessment

Background/Objectives: Critical lung infection affects alveolar cells and probably also their ability to perform surfactant procedures, but bedside tools for monitoring lung surfactants are lacking. In this descriptive exploratory study, we aimed to evaluate lung surfactant levels in bronchial aspirate (BA) from patients admitted to the intensive care unit due to severe respiratory failure. Methods: Bronchial aspirates were collected from nine patients (median age: 72 years, range: 52-85) who required orotracheal intubation. Samples were obtained within 24 h of mechanical ventilation initiation (T1), after three days on a ventilator (T2), and on day seven (T3) for four patients. The concentration of dipalmitoylphosphatidylcholine (DPPC), a key surfactant component, was assessed in the lamellar body precipitate. Results: Across the nine patients at T1, the DPPC level was 12 µM (range: 3-20 µM). By T2, the DPPC level declined to 8 µM (range: 2-22 µM), with a statistically significant decrease from T1 (p = 0.0039). At T3, the DPPC level in four patients ranged from 2 to 5 µM, though the difference from T2 was not statistically significant. A surfactant biomarker would assist clinical decision-making when dealing with patients in severe respiratory failure where exogenous surfactant therapy may be considered. Conclusions: DPPC levels obtained from bronchial aspirate can be measured in patients with severe respiratory failure and may serve as a useful biomarker for lung surfactant status, which suggests the potential for bedside assessment in clinical practice with a dedicated test device.