Variation in Viscoelastic Properties of Pulmonary Mucus in Patients Undergoing Mechanical Ventilation

Ventilator-associated pneumonia (VAP) is defined as an infection of the lung parenchyma in patients undergoing invasive mechanical ventilation for at least 48 hours. It is one of the types of pneumonia acquired in intensive care units (ICUs) and is one of the most common infections in this population, representing a major complication. The diagnosis of VAP is based on three main criteria: clinical suspicion, adiological imaging, and microbiological cultures of the lower respiratory tract. However, these elements have significant limitations. New rapid diagnostic techniques, such as multiplex polymerase chain reaction (PCR), can quickly identify pathogens and resistance mechanisms in just a few hours. These promising tools could reduce the time to initiate targeted treatment while limiting the excessive use of antibiotics. However, no single tool is currently accurate enough to diagnose VAP, and diagnosis is based on a combination of factors. Today, scores exist that can be used to assess the probability of PAVM, such as the CIPS. These are useful tools but lack specificity. The clinical, biological and radiological criteria used to calculate the score can also be observed in other pathologies. Thus, although they are sensitive to the detection of PAVM, they are often insufficient to establish a definitive diagnosis. They must be supplemented by other diagnostic approaches, such as microbiological cultures and more detailed imaging examinations, to obtain a more accurate assessment. It is also essential to mention the importance of gaining a better understanding of the lung microbiome. Indeed, it appears to play a central role not only in the pathophysiology of MVAP, but also in its diagnosis and management. The work of Fromentin et al. shows that it is possible to observe dysbiosis associated with a loss of microbial diversity and the onset of certain pulmonary infections. Thus, structural variations in mucus could reflect changes in the pulmonary microbiome. It is therefore essential to remember that mucus plays an essential protective role in the respiratory tract by trapping particles, bacteria and pathogens, while facilitating their transport thanks to its viscoelastic properties. However, in mechanically ventilated patients, these mucociliary clearance mechanisms are often impaired, promoting the accumulation of secretions, bacterial proliferation and, ultimately, the onset of MVAP. The work of Patarin and Giovanna and al. suggests that biochemical and microbiological changes in mucus could be a criterion for initiating treatment in recurrent pulmonary infections in patients with chronic obstructive pulmonary disease (COPD) or cystic fibrosis. These observations suggest the potential value of early characterisation of mucus in ventilated patients in order to detect additional diagnostic clues that would enable rapid and appropriate treatment.